Mesenchymal stem cells in knee osteoarthritis treatment: A systematic review and meta-analysis

Efficiently directing differentiation and homing of mesenchymal stem cells to boost cartilage repair in osteoarthritis via a nanoparticle and peptide dual-engineering strategy

Mesenchymal stem cells (MSCs) are expected to be useful therapeutics in osteoarthritis (OA), the most common joint disorder characterized by cartilage degradation. However, evidence is limited with regard to cartilage repair in clinical trials because of the uncontrolled differentiation and weak cartilage-targeting ability of MSCs after injection. To overcome these drawbacks, here we synthesized CuO@MSN nanoparticles (NPs) to deliver Sox9 plasmid DNA (favoring chondrogenesis) and recombinant protein Bmp7 (inhibiting hypertrophy). After taking up CuO@MSN/Sox9/Bmp7 (CSB NPs), the expressions of chondrogenic markers were enhanced while hypertrophic markers were decreased in response to these CSB-engineered MSCs. Moreover, a cartilage-targeted peptide (designated as peptide W) was conjugated onto the surface of MSCs via a click chemistry reaction, thereby prolonging the residence time of MSCs in both the knee joint cavity of mice and human-derived cartilage. In a surgery-induced OA mouse model, the NP and peptide dual-modified W-CSB-MSCs showed an enhancing therapeutic effect on cartilage repair in knee joints compared with other engineered MSCs after intra-articular injection. Most importantly, W-CSB-MSCs accelerated cartilage regeneration in damaged cartilage explants derived from OA patients. Thus, this new peptide and NPs dual engineering strategy shows potential for clinical applications to boost cartilage repair in OA using MSC therapy.

Ultrasound-targeted microbubble destruction facilitates cartilage repair through increased the migration of mesenchymal stem cells via HIF-1α-mediated glycolysis pathway in rats

OBJECTIVE

Mesenchymal stem cells (MSCs) can treat osteoarthritis (OA), but their therapeutic efficacy is poor to date due to low migration efficiency. This study aimed to determine whether ultrasound-targeted microbubble destruction (UTMD) could ameliorate cartilage repair efficiency through facilitating the migration of MSCs via hypoxia-inducible factor-1α (HIF-1α)-mediated glycolysis regulatory pathway in OA model rats.

METHODS

OA rats were treated with MSCs alone or in combination with UTMD, respectively, for 4 weeks. Cartilage histopathology, MSCs migration efficiency, von Frey fiber thresholds, and the expression levels of collagen II and MMP-13 were measured. Further, MSCs were extracted from the bone marrow of rats, cocultured with osteoarthritic chondrocytes, transfected to siRNA-HIF-1α, and subjected to UTMD for 4 days. Glucose consumption, lactate production, and cell migration efficiency were assessed. The protein expression levels of HIF-1α, HK2, PKM2, and GLUT1 were measured, respectively.

RESULTS

In OA rat model, NC-MSCs + UTMD improved migration efficiency, increased collagen II expression, decreased MMP-13 expression, and delayed osteoarthritis progression. Silencing HIF-1α attenuated the effects induced by UTMD. In vitro, UTMD led to increases in MSC activity and migration, glucose consumption, lactate production, and the protein expression of HIF-1α, HK2, PKM2, and GLUT1 expression, all of which were reversed upon HIF-1α silencing.

CONCLUSION

UTMD enhances MSCs migration and improves cartilage repair efficiency through the HIF-1α-mediated glycolytic regulatory pathway, providing a novel therapy strategy for knee osteoarthritis.

Interplay Between Skeletal and Hematopoietic Cells in the Bone Marrow Microenvironment in Homeostasis and Aging

PURPOSE OF THE REVIEW

In this review, we discuss the most recent scientific advances on the reciprocal regulatory interactions between the skeletal and hematopoietic stem cell niche, focusing on immunomodulation and its interplay with the cell's mitochondrial function, and how this impacts osteoimmune health during aging and disease.

RECENT FINDINGS

Osteoimmunology investigates interactions between cells that make up the skeletal stem cell niche and immune system. Much work has investigated the complexity of the bone marrow microenvironment with respect to the skeletal and hematopoietic stem cells that regulate skeletal formation and immune health respectively. It has now become clear that these cellular components cooperate to maintain homeostasis and that dysfunction in their interaction can lead to aging and disease. Having a deeper, mechanistic appreciation for osteoimmune regulation will lead to better research perspective and therapeutics with the potential to improve the aging process, skeletal and hematologic regeneration, and disease targeting.

Transplantation of three mesenchymal stem cells for knee osteoarthritis, which cell and type are more beneficial? a systematic review and network meta-analysis

BACKGROUND

In knee osteoarthritis (KOA), treatments involving knee injections of bone marrow-derived mesenchymal stem cells (BM-MSC), adipose tissue-derived mesenchymal stem cells (AD-MSC), or umbilical cord-derived mesenchymal stem cells (UC-MSC) have shown promise in alleviating symptoms. However, which types of mesenchymal stem cells (MSCs) have the best therapeutic outcomes remain uncertain.

METHOD

We systematically searched PubMed, OVID, Web of Science, and the Cochrane Library until January 1, 2024. The study evaluated five endpoints: Visual Analog Score (VAS) for Pain, Range of Motion (ROM), Whole-Organ Magnetic Resonance Imaging Score (WORMS), Western Ontario McMaster Universities Osteoarthritis Index (WOMAC), and adverse events (ADs). Standard meta-analysis and network meta-analysis were performed using Stata 16.0.

RESULTS

Fifteen studies involving 585 patients were included in the meta-analysis. Standard meta-analysis revealed significant improvements with MSCs in VAS score (P < 0.001), knee ROM (P < 0.001), and WOMAC (P < 0.016) compared to traditional therapy. In the network meta-analysis, autologous MSCs significantly improved VAS score [SMD = 2.94, 95% CI (1.90, 4.56)] and knee ROM [SMD = 0.26, 95% CI (0.08, 0.82)] compared to traditional therapy. Similarly, BM-MSC significantly improved VAS score [SMD = 0.31, 95% CI (0.11, 0.91)] and knee ROM [SMD = 0.26, 95% CI (0.08, 0.82)] compared to hyaluronic acid. However, compared with traditional therapy, autologous or allogeneic MSCs were associated with more adverse reactions [SMD = 0.11, 95% CI (0.02, 0.59)], [SMD = 0.13, 95% CI (0.002, 0.72)]. Based on the surface under the cumulative ranking results, autologous BM-MSC showed the most improvement in ROM and pain relief in KOA patients, UC-MSC (SUCRA 94.1%) were most effective for positive WORMS, and AD-MSC (SUCRA 70.6%) were most effective for WOMAC-positive patients.

CONCLUSION

MSCs transplantation effectively treats KOA patients, with autologous BM-MSC potentially offering more excellent benefits.

What is the rationale for mesenchymal stromal cells based therapies in the management of hemophilic arthropathies?

Hemophilia A and B are rare X-linked genetic bleeding disorders due to a complete or partial deficiency in the coagulation factors VIII or IX, respectively. The main treatment for hemophilia is prophylactic and based on coagulation factor replacement therapies. These treatments have significantly reduced bleeding and improved the patients' quality of life. Nevertheless, repeated joint bleedings (hemarthroses), even subclinical hemarthroses, can lead to hemophilic arthropathy (HA). This disabling condition is characterized by chronic pain due to synovial inflammation, cartilage and bone destruction requiring ultimately joint replacement. HA resembles to rheumatoid arthritis because of synovitis but HA is considered as having similarities with osteoarthritis as illustrated by the migration of immune cells, production of inflammatory cytokines, synovial hypertrophy and cartilage damage. Various drugs have been evaluated for the management of HA with limited success. The objective of the review is to discuss new therapeutic approaches with a special focus on the studies that have investigated the potential of using mesenchymal stromal cells (MSCs) in the management of HA. A systematic review of the literature has been made. Most of the studies have focused on the interest of MSCs for the delivery of missing factors VIII or IX but in some studies, more insight on the effect of MSC injection on synovial inflammation or cartilage structure were provided and put in perspective for possible clinical applications.

Extracellular vesicles from senescent mesenchymal stromal cells are defective and cannot prevent osteoarthritis

Age is the most important risk factor in degenerative diseases such as osteoarthritis (OA), which is associated with the accumulation of senescent cells in the joints. Here, we aimed to assess the impact of senescence on the therapeutic properties of extracellular vesicles (EVs) from human fat mesenchymal stromal cells (ASCs) in OA. We generated a model of DNA damage-induced senescence in ASCs using etoposide and characterized EVs isolated from their conditioned medium (CM). Senescent ASCs (S-ASCs) produced 3-fold more EVs (S-EVs) with a slightly bigger size and that contain 2-fold less total RNA. Coculture experiments showed that S-ASCs were as efficient as healthy ASCs (H-ASCs) in improving the phenotype of OA chondrocytes cultured in resting conditions but were defective when chondrocytes were proliferating. S-EVs were also impaired in their capacity to polarize synovial macrophages towards an anti-inflammatory phenotype. A differential protein cargo mainly related to inflammation and senescence was detected in S-EVs and H-EVs. Using the collagenase-induced OA model, we found that contrary to H-EVs, S-EVs could not protect mice from cartilage damage and joint calcifications, and were less efficient in protecting subchondral bone degradation. In addition, S-EVs induced a pro-catabolic and pro-inflammatory gene signature in the joints of mice shortly after injection, while H-EVs decreased hypertrophic, catabolic and inflammatory pathways. In conclusion, S-EVs are functionally impaired and cannot protect mice from developing OA.

Immunomodulatory Strategies for Cartilage Regeneration in Osteoarthritis

Osteoarthritis (OA) is the most prevalent musculoskeletal disorder and a leading cause of disability globally. Although many efforts have been made to treat this condition, current tissue engineering (TE) and regenerative medicine strategies fail to address the inflammatory tissue environment that leads to the rapid progression of the disease and prevents cartilage tissue formation. First, this review addresses in detail the current anti-inflammatory therapies for OA with a special emphasis on pharmacological approaches, gene therapy, and mesenchymal stromal cell (MSC) intra-articular administration, and discusses the reasons behind the limited clinical success of these approaches at enabling cartilage regeneration. Then, we analyze the state-of-the-art TE strategies and how they can be improved by incorporating immunomodulatory capabilities such as the optimization of biomaterial composition, porosity and geometry, and the loading of anti-inflammatory molecules within an engineered structure. Finally, the review discusses the future directions for the new generation of TE strategies for OA treatment, specifically focusing on the spatiotemporal modulation of anti-inflammatory agent presentation to allow for tailored patient-specific therapies. Impact statement Osteoarthritis (OA) is a prevalent and debilitating musculoskeletal disorder affecting millions worldwide. Despite significant advancements in regenerative medicine and tissue engineering (TE), mitigating inflammation while simultaneously promoting cartilage tissue regeneration in OA remains elusive. In this review article, we discuss current anti-inflammatory therapies and explore their potential synergy with cutting-edge cartilage TE strategies, with a special focus on novel spatiotemporal and patient-specific anti-inflammatory strategies.

Infra-patellar fat pad-derived mesenchymal stem cells maintain their chondrogenic differentiation potential after arthroscopic harvest with blood-product supplementation

PURPOSE

Mesenchymal stem cells/medicinal signaling cells (MSCs) possess therapeutic potential and are used in regenerative orthopaedics. The infra-patellar fat pad (IFP) is partially resected during knee arthroscopy (KASC) and contains MSCs. Heat, irrigation, and mechanical stress during KASC may decrease MSC's therapeutic potential. This study assessed MSCs' regenerative potential after arthroscopic IFP harvest and potential effects of two blood products (BP) (platelet-rich plasma (PRP), hyperacute serum (HAS)) on MSCs' viability and chondrogenic differentiation capacity.

METHODS

IFP was arthroscopically harvested, isolated, and counted (n = 5). Flow cytometry was used to assess cell viability via staining with annexin V/7-AAD and stemness markers via staining for CD90, CD73, and CD105. MSCs were incubated with blood products, and metabolic activity was determined via an XTT assay. Deposition of cartilage extracellular matrix was determined in histologic sections of chondrogenically differentiated 3D pellet cultures via staining with Alcian Blue. Expression of cartilage-specific genes (SOX9, MMP3/13, ACAN, COL1/2) was analyzed via quantitative PCR.

RESULTS

MSC isolation from IFP yielded 2.66*106 ± 1.49*106 viable cells from 2.7 (0.748) g of tissue. MSC markers (CD 90/105/73) were successfully detected and annexin V staining showed 81.5% viable cells. XTT showed increased metabolic activity. Within the BP groups, this increase was significant (days 0-14, p < 0.05). PCR showed expression of cartilage-specific genes in each group. COL2 (p < 0.01) as well as ACAN (p < 0.001) expression levels were significantly higher in the HAS group. Histology showed successful differentiation.

CONCLUSION

Arthroscopic harvest of IFP-MSCs yields sufficient cells with maintained regenerative potential and viability. Blood products further enhance MSCs' viability.

Mesenchymal stem cell implantation provides short-term clinical improvement and satisfactory cartilage restoration in patients with knee osteoarthritis but the evidence is limited: a systematic review performed by the early-osteoarthritis group of ESSKA-European knee associates section

PURPOSE

Implantation of mesenchymal stem cells (MSCs) is a potential cell-based modality for cartilage repair. Currently, its clinical use largely surrounds focal cartilage defect repair and intra-articular injections in knee osteoarthritis. The MSCs' implantation efficacy as a treatment option for osteoarthritis remains contentious. This systematic review aims to evaluate studies that focused on MSCs implantation in patients with knee OA to provide a summary of this treatment option outcomes.

METHODS

A systematic search was performed in PubMed (Medline), Scopus, Cinahl, and the Cochrane Library. Original studies investigating outcomes of MSCs implantations in patients with knee OA were included. Data on clinical outcomes using subjective scores, radiological outcomes, and second-look arthroscopy gradings were extracted.

RESULTS

Nine studies were included in this review. In all included studies, clinical outcome scores revealed significantly improved functionality and better postoperative pain scores at 2-3 years follow-up. Improved cartilage volume and quality at the lesion site was observed in five studies that included a postoperative magnetic resonance imaging assessment and studies that performed second-look arthroscopy. No major complications or tumorigenesis occurred. Outcomes were consistent in both single MSCs implantation and concurrent HTO with MSCs implantation in cases with excessive varus deformity.

CONCLUSION

According to the available literature, MSCs implantation in patients with mild to moderate knee osteoarthritis is safe and provides short-term clinical improvement and satisfactory cartilage restoration, either as a standalone procedure or combined with HTO in cases with axial deformity. However, the evidence is limited due to the high heterogeneity among studies and the insufficient number of studies including a control group and mid-term outcomes.

LEVEL OF EVIDENCE

IV.

Stem cells for the treatment of early to moderate osteoarthritis of the knee: a systematic review

PURPOSE

Mesenchymal stem cells (MSCs) present a valuable treatment option for knee osteoarthritis with promising results. The purpose of the present study was to systematically review the clinical and functional outcomes following mesenchymal stem cell application focusing on early to moderate knee osteoarthritis.

METHODS

A systematic search was done using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines in Pubmed, Scopus, Web of Science, and Cochrane Library databases. All Studies published between 2017 and March 2023 on patients treated with single mesenchymal stem cell injection for Kellgren-Lawrence grade I-III knee osteoarthritis reported on clinical and functional outcomes were included.

RESULTS

Twelve articles comprising 539 patients and 576 knees treated with a single intraarticular injection of MSCs for knee osteoarthritis were included in the current systematic review. In eligible studies, the reported outcomes were improved concerning patient-reported outcomes measures, knee function, pain relief, and quality of patient's life.

CONCLUSION

Based on high-level evidence studies, single intraarticular injection of MSCs is a safe, reliable, and effective treatment option for Kellgren-Lawrence grade I-III knee osteoarthritis. However, the lack of homogeneity in the included studies and the variance in MSCs sources and preparations should be noted.

LEVEL OF EVIDENCE

III.

Chinese guidelines for the rehabilitation treatment of knee osteoarthritis: An CSPMR evidence-based practice guideline

BACKGROUND

Knee osteoarthritis (KOA) is the most common degenerative joint disease in China, causing a huge economic burden on patients, families, and society. Standardized KOA rehabilitation treatment is an important means to prevent and treat the disease and promote the development of high-quality medical services. This guideline is updated on the basis of the 2016 and 2019 editions.

METHODS

Clinical questions regarding rehabilitation assessment and treatment were selected through clinical questions screening and deconstruction, and multiple rounds of Delphi questionnaire consultation. The International Classification of Functioning, Disability and Health (ICF) was used as the theoretical framework, and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method was used to grade the quality of evidence and recommendations.

RESULTS

The reporting of this guideline followed the standard of Reporting Items for Practice Guidelines in Healthcare (RIGHT). Taking into account patients' preferences and values and the needs of Chinese clinical practice, a total of 11 clinical questions and 28 recommendations were established. The clinical questions were grouped into two categories: KOA assessment (body function, body structure, activity and participation, quality of life, and environmental factors and clinical outcomes assessment, resulting in 9 recommendations) and KOA treatment (health education, therapeutic exercise, therapeutic modalities, occupational therapy, assistive devices, and regenerative rehabilitation approaches, resulting in 19 recommendations).

CONCLUSION

This is the first evidence-based guideline for KOA rehabilitation in China utilizing the ICF framework. This guideline provides key guidance for developing systematic, standardized, and precise rehabilitation protocols for KOA across various healthcare settings.

MATN3 delivered by exosome from synovial mesenchymal stem cells relieves knee osteoarthritis: Evidence from in vitro and in vivo studies

Background

Synovial mesenchymal stem cell (SMSC) exerts chondroprotective effects in osteoarthritis (OA) clinical models. However, the regulatory potentials of SMSC-derived exosomes (SMSC-Exo) in OA still need to be discovered, which attracted our attention.

Methods

The destabilization of the medial meniscus surgery was performed on the knee joints of a mouse OA model, followed by injection of SMSC-Exo. In addition, SMSC-Exo was administrated to mouse chondrocytes to observe the functional and molecular alterations.

Results

Both of SMSC-Exo and overexpression of Matrilin-3 (MATN3) alleviated cartilage destruction and suppressed degradation of extracellular matrix (ECM) in the OA rat model. In addition, assays concerning the in vitro OA model induced by IL-1β showed that SMSC-Exo could promote chondrocyte viability and inhibit autophagy defects. Furthermore, SMSC-Exo achieved the chondroprotective effects through the delivery of MATN3/IL-17A, and MATN3 could suppress the activation of PI3K/AKT/mTOR signaling through IL-17A.

Conclusion

SMSC-Exo exerts beneficial therapeutic effects on OA by preventing ECM degradation and autophagy defects by delivering MATN3/IL-17A.

The Translational Potential of this Article

The translational potential of this study is not only limited to the treatment of knee osteoarthritis but also provides new insights for the treatment of other joint diseases by exploring the mechanism of MATN3. In addition, SMSCExo, as a novel drug carrier, has great potential for treating and diagnosing other diseases. With further research, these findings will provide new directions for developing personalized and innovative treatment options.

Evaluation of expanded peripheral blood derived CD34+ cells for the treatment of moderate knee osteoarthritis

Knee osteoarthritis (OA) is a degenerative joint disease of the knee that results from the progressive loss of articular cartilage. It is most common in the elderly and affects millions of people worldwide, leading to a continuous increase in the number of total knee replacement surgeries. These surgeries improve the patient's physical mobility, but can lead to late infection, loosening of the prosthesis, and persistent pain. We would like to investigate if cell-based therapies can avoid or delay such surgeries in patients with moderate OA by injecting expanded autologous peripheral blood derived CD34+ cells (ProtheraCytes^®) into the articular joint. In this study we evaluated the survival of ProtheraCytes^® when exposed to synovial fluid and their performance in vitro with a model consisting of their co-culture with human OA chondrocytes in separate layers of Transwells and in vivo with a murine model of OA. Here we show that ProtheraCytes^® maintain high viability (>95%) when exposed for up to 96 hours to synovial fluid from OA patients. Additionally, when co-cultured with OA chondrocytes, ProtheraCytes^® can modulate the expression of some chondrogenic (collagen II and Sox9) and inflammatory/degrading (IL1β, TNF, and MMP-13) markers at gene or protein levels. Finally, ProtheraCytes^® survive after injection into the knee of a collagenase-induced osteoarthritis mouse model, engrafting mainly in the synovial membrane, probably due to the fact that ProtheraCytes^® express CD44, a receptor of hyaluronic acid, which is abundantly present in the synovial membrane. This report provides preliminary evidence of the therapeutic potential of CD34+ cells on OA chondrocytes in vitro and their survival after in vivo implantation in the knee of mice and merits further investigation in future preclinical studies in OA models.

Mechanism of mesenchymal stem cells and exosomes in the treatment of age-related diseases

Mesenchymal stem cells (MSCs) from multiple tissues have the capability of multidirectional differentiation and self-renewal. Many reports indicated that MSCs exert curative effects on a variety of age-related diseases through regeneration and repair of aging cells and organs. However, as research has progressed, it has become clear that it is the MSCs derived exosomes (MSC-Exos) that may have a real role to play, and that they can be modified to achieve better therapeutic results, making them even more advantageous than MSCs for treating disease. This review generalizes the biological characteristics of MSCs and exosomes and their mechanisms in treating age-related diseases, for example, MSCs and their exosomes can treat age-related diseases through mechanisms such as oxidative stress (OS), Wnt/β-catenin signaling pathway, mitogen-activated protein kinases (MAPK) signaling pathway, and so on. In addition, current in vivo and in vitro trials are described, and ongoing clinical trials are discussed, as well as the prospects and challenges for the future use of exosomes in disease treatment. This review will provide references for using exosomes to treat age-related diseases.

Mesenchymal stem cells in osteoarthritis: The need for translation into clinical therapy

Widely used for cell-based therapy in various medical fields, mesenchymal stem cells (MSCs) show capacity for anti-inflammatory effects, anti-apoptotic activity, immunomodulation, and tissue repair and regeneration. As such, they can potentially be used to treat osteoarthritis (OA). However, MSCs from different sources have distinct advantages and disadvantages, and various animal models and clinical trials using different sources of MSCs are being conducted in OA regenerative medicine. It is now widely believed that the primary tissue regeneration impact of MSCs is via paracrine effects, rather than direct differentiation and replacement. Cytokines and molecules produced by MSCs, including extracellular vesicles with mRNAs, microRNAs, and bioactive substances, play a significant role in OA repair. This chapter outlines the properties of MSCs and recent animal models and clinical trials involving MSCs-based OA therapy, as well as how the paracrine effect of MSCs acts in OA cartilage repair. Additionally, it discusses challenges and controversies in MSCs-based OA therapy. Despite its limits and unanticipated hazards, MSCs have the potential to be translated into therapeutic therapy for future OA treatment.

circRNA-ZCCHC14 affects the chondrogenic differentiation ability of peripheral blood-derived mesenchymal stem cells by regulating GREM1 through miR-181a

circRNAs play an important role in the progression of osteoarthritis (OA). Therefore, we aimed to reveal the mechanism of action of circRNA-ZCCHC14 in OA. OA animal and cell models were constructed, and clinical samples were collected. The expression of circRNA-ZCCHC14 and miR-181a was detected by RT‒qPCR. The chondrogenic differentiation ability of peripheral blood-derived mesenchymal stem cells (PBMSCs) was detected by Alcian blue staining. The expression of chondrogenic differentiation-related proteins was detected by Western blotting. Double fluorescein experiments verified the targeting relationship of miR-181a with circRNA-ZCCHC14 and GREM1. Upregulation of circRNA-ZCCHC14 was observed in blood, in BMP-2- and TGF-β3-treated PBMSCs from OA patients and in animal models. Knockdown of circRNA-ZCCHC14 promoted the chondrogenic differentiation ability of PBMSCs. circRNA-ZCCHC14 was found to bind to miR-181a and negatively regulate miR-181a expression. Inhibition of miR-181a reversed the promoting effect of circRNA-ZCCHC14 knockdown on the chondrogenic differentiation ability of PBMSCs. GREM1 was identified as a target of miR-181a. Overexpression and knockdown of GREM1 regulated the expression of BMP2, which in turn affected the chondrogenic differentiation ability of PBMSCs, indicating that GREM1 and BMP2 have antagonistic effects and that they jointly regulate the chondrogenic differentiation of PBMSCs. circRNA-ZCCHC14 may promote the chondrogenic differentiation ability of PBMSCs by regulating miR-181a and inhibiting the expression of GREM1.

Challenges in osteoarthritis treatment

Osteoarthritis (OA) is the most common form of arthritis and a degenerative joint cartilage disease that is the most common cause of disability in the world among the elderly. It leads to social, psychological, and economic costs with financial consequences. The principles of OA treatment are to reduce pain and stiffness as well as maintain function. In recent years, due to a better understanding of the underlying pathophysiology of OA, a number of potential therapeutic advances have been made, which include tissue engineering, immune system manipulation, surgical technique, pharmacological, and non-pharmacological treatments. Despite this, there is still no certain cure for OA, and different OA treatments are usually considered in relation to the stage of the disease. The purpose of the present review is to summarize and discuss the latest results of new treatments for OA and potential targets for future research.

Clinical and Radiological Comparison of Single and Double Intra-articular Injection of Adipose-Derived Stromal Vascular Fraction for Knee Osteoarthritis

The aim of the article is to compare the clinical and radiological outcomes between single and double stromal vascular fraction (SVF) cell injections in patients with knee osteoarthritis (OA). We included 54 patients treated for varus knee OA with intra-articular SVF cell injection. They were divided into two groups: those who received one injection and those who received two. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, knee range of motion, and knee muscle force were assessed at baseline and 3, 6, 12, and 24 months after the first injection. The preoperative hip-knee-ankle (HKA) angle was evaluated using plain radiographs, and T2 mapping values were assessed. The total WOMAC score improved significantly in the single injection group from 3 to 24 months, but the total WOMAC score in the double injection group improved significantly at 24 months. The T2 mapping values in both the groups improved, with a significant difference at 12 months. The preoperative mean HKA angle and the correlation coefficients between the HKA angle and the total WOMAC score and between the HKA angle and the T2 mapping value of the medial femur were significant. In conclusion, double injections may provide more satisfactory treatment outcomes in patients with severe varus knee alignment. This clinical trial is registered in the Japanese Ministry of Health, Labour and Welfare (URL: https://saiseiiryo.mhlw.go.jp/published_plan/index/2) with the registration name "Cell transplantation therapy for osteoarthritis using autologous subcutaneous adipose tissue-derived regenerative (stem) cells (ADRCs)," and the registration number was "PB5160012."

Extracellular Vesicle Isolation and Characterization for Applications in Cartilage Tissue Engineering and Osteoarthritis Therapy

Extracellular vesicles (EVs) have the capacity for use in cartilage tissue engineering by stimulating tissue repair and microenvironmental reprogramming. This makes them ideal candidates for treating focal cartilage defects and cartilage degeneration in osteoarthritis (OA). Observational studies have reported beneficial biological effects of EVs, such as inhibition of inflammation, enhanced extracellular matrix deposition, and reduced cartilage degradation. Isolation of EVs derived from different source materials such as conditioned cell culture media or biofluids is essential to attribute observed biological effects to EVs as genuine effectors. This chapter presents a density- and a size-based method as well as a combination of both for isolation of EVs from conditioned cell culture media or biofluids. In addition, three methods for characterization of isolated EVs are suggested based on physical properties, protein profiling, and ultrastructural morphology.

Temporomandibular Joint Osteoarthritis: Pathogenic Mechanisms Involving the Cartilage and Subchondral Bone, and Potential Therapeutic Strategies for Joint Regeneration

The temporomandibular joint (TMJ) is a specialized synovial joint that is crucial for the movement and function of the jaw. TMJ osteoarthritis (TMJ OA) is the result of disc dislocation, trauma, functional overburden, and developmental anomalies. TMJ OA affects all joint structures, including the articular cartilage, synovium, subchondral bone, capsule, ligaments, periarticular muscles, and sensory nerves that innervate the tissues. The present review aimed to illustrate the main pathomechanisms involving cartilage and bone changes in TMJ OA and some therapeutic options that have shown potential restorative properties regarding these joint structures in vivo. Chondrocyte loss, extracellular matrix (ECM) degradation, and subchondral bone remodeling are important factors in TMJ OA. The subchondral bone actively participates in TMJ OA through an abnormal bone remodeling initially characterized by a loss of bone mass, followed by reparative mechanisms that lead to stiffness and thickening of the condylar osteochondral interface. In recent years, such therapies as intraarticular platelet-rich plasma (PRP), hyaluronic acid (HA), and mesenchymal stem cell-based treatment (MSCs) have shown promising results with respect to the regeneration of joint structures or the protection against further damage in TMJ OA. Nevertheless, PRP and MSCs are more frequently associated with cartilage and/or bone repair than HA. According to recent findings, the latter could enhance the restorative potential of other therapies (PRP, MSCs) when used in combination, rather than repair TMJ structures by itself. TMJ OA is a complex disease in which degenerative changes in the cartilage and bone develop through intricate mechanisms. The regenerative potential of such therapies as PRP, MSCs, and HA regarding the cartilage and subchondral bone (alone or in various combinations) in TMJ OA remains a matter of further research, with studies sometimes obtaining discrepant results.

The Effect of Different Frequencies of Pulsed Electromagnetic Fields on Cartilage Repair of Adipose Mesenchymal Stem Cell-Derived Exosomes in Osteoarthritis

BACKGROUND

The intra-articular injection of mesenchymal stem cell (MSC)-derived exosomes has already been proved to reverse osteoarthritic cartilage degeneration. Pulsed electromagnetic field (PEMF) has been found to regulate the biogenic function of MSCs. However, the effect of PEMF on MSC-derived exosomes has not yet been characterized. The aim of this study was to elucidate the regulatory role of different frequencies of PEMF in promoting the osteoarthritic cartilage regeneration of MSC-derived exosomes.

METHODS

The adipose tissue-derived MSCs (AMSCs) were extracted from the epididymal fat of healthy rats and further exposed to the PEMF at 1 mT amplitude and a frequency of 15, 45, and 75 Hz, respectively, in an incubator. The chondrocytes were treated with interlukin-1β (IL-1β) and the regenerative effect of co-culturing with PEMF-exposed AMSC-derived exosomes was assessed via Western blot, quantitative polymerase chain reaction, and ELISA assays. A rat model of osteoarthritis was established by anterior cruciate ligament transection (ACLT) surgery and received 4 times intra-articular injection of PEMF-exposed AMSC-derived exosomes once a week. After 8 weeks, the knee joint specimens of rats were collected for micro-computed tomography and histologic analyses.

RESULTS

PEMF-exposed AMSC-derived exosomes could be endocytosed with IL-1β-induced chondrocytes. Compared with the AMSC-derived exosomes alone, the PEMF-exposed AMSC-derived exosomes substantially suppressed the inflammation and extracellular matrix degeneration of IL-1β-induced chondrocytes as shown by higher expression of transcripts and proteins of COL2A1, SOX9, and ACAN and lower expression of MMP13 and caspase-1. Of these, the 75-Hz PEMF presented a more significant inhibitive effect than the 15-Hz and 45-Hz PEMFs. Furthermore, the intra-articular injection of 75-Hz PEMF-exposed exosomes could obviously increase the number of tibial epiphyseal trabeculae, lead to a remarkable decrease in Osteoarthritis Research Society International score, and upregulate the COL2A1 and ACAN protein level of the degenerated cartilage.

CONCLUSION

The present study demonstrated that PEMF stimulation could effectively promote the regeneration effects of AMSC-derived exosomes on osteoarthritic cartilage. Compared with other frequency parameters, the PEMF at a frequency of 75 Hz showed a superior positive effect on AMSC-derived exosomes in suppressing the IL-1β-induced chondrocyte inflammation and extracellular matrix catabolism, as well as the osteoarthritic cartilage degeneration.

p53/p21 Inhibits Osteoarthritis Progression by Regulating Chondrocyte Pyroptosis

This study aimed to explore the role of p53/p21 in osteoarthritis (OA). OA animal model was established by the anterior cruciate ligamentotomy (ACLT). 24 rats were randomly divided into control, OA, OA+p53 inhibitor and OA+pyroptosis inducer groups (n = 6). In the knee joint tissue, microstructural changes were analysed by Micro-CT. Histopathological changes were stained by HE and safranin-fast green. NLRP3 and Caspase-1 were detected by immunohistochemistry. The chondrocytes C-28I2 were divided into control, LPS+ ATP and p53 inhibitor groups. The cell viability, apoptosis, and LDH release were measured by MTT assay, TUNEL staining and LDH kit. The expression of p53/p21 and pyroptosis pathways were examined by western blot. The p53 inhibitor reduced the relative volume of trabecular bone (BV/TV) and trabecular bone thickness (Tb.Th), while increased trabecular separation (Tb.Sp). Moreover, the p53 inhibitor improved histopathological changes in the knee joint, attenuated cartilage damage, and reduced the expression of p53/p21 and pyroptosis pathways-related proteins. In vitro assay showed that the p53 inhibitor increased C-28I2 cell activity, reduced LDH release and apoptosis and reduced p53/p21 and pyroptosis pathways-related proteins. Totally, p53 inhibitors improved the cartilage tissue and chondrocyte damage, inhibited cell pyroptosis and the progression of OA.

Intraarticular Injections of Mesenchymal Stem Cells in Knee Osteoarthritis: A Review of Their Current Molecular Mechanisms of Action and Their Efficacy

More than 10% of the world's population suffers from osteoarthritis (OA) of the knee, with a lifetime risk of 45%. Current treatments for knee OA pain are as follows: weight control; oral pharmacological treatment (non-steroidal anti-inflammatory drugs, paracetamol, opioids); mechanical aids (crutches, walkers, braces, orthotics); therapeutic physical exercise; and intraarticular injections of corticosteroids, hyaluronic acid, and platelet-rich plasma (PRP). The problem is that such treatments usually relieve joint pain for only a short period of time. With respect to intraarticular injections, corticosteroids relieve pain for several weeks, while hyaluronic acid and PRP relieve pain for several months. When the above treatments fail to control knee pain, total knee arthroplasty (TKA) is usually indicated; however, although a very effective surgical technique, it can be associated with medical and postoperative (surgery-related) complications. Therefore, it seems essential to look for safe and effective alternative treatments to TKA. Recently, there has been much research on intraarticular injections of mesenchymal stem cells (MSCs) for the management of OA of the knee joint. This article reviews the latest information on the molecular mechanisms of action of MSCs and their potential therapeutic benefit in clinical practice in patients with painful knee OA. Although most recent publications claim that intraarticular injections of MSCs relieve joint pain in the short term, their efficacy remains controversial given that the existing scientific information on MSCs is indecisive. Before recommending intraarticular MSCs injections routinely in patients with painful knee OA, more studies comparing MSCs with placebo are needed. Furthermore, a standard protocol for intraarticular injections of MSCs in knee OA is needed.

Intra-articular injection choice for osteoarthritis: making sense of cell source-an updated systematic review and dual network meta-analysis

BACKGROUND

Intra-articular injection is indicated for mild or moderate osteoarthritis (OA). However, the superiority of cell-based injection and the role of diverse cell sources are still unclear. This study aimed to compare the therapeutic effect of intra-articular injection with mesenchymal stem cells (MSCs) and cell-free methods for OA treatment.

METHODS

A literature search of published scientific data was carried out from PubMed, MEDLINE, Embase, Cochrane Library, Web of Science, and China National Knowledge Internet (CNKI). Randomized controlled trials (RCTs) compared the efficacy and safety of MSC and cell-free intra-articular injection treatments for OA with at least 6-month follow-up.

RESULTS

Dual network meta-analysis validated the therapeutic advantages of MSC treatments (VAS, Bayesian: 90% versus 10% and SUCRA: 94.9% versus 5.1%; WOMAC total, Bayesian: 83% versus 17% and SUCRA: 90.1% versus 9.9%) but also suggested a potential negative safety induced by cell injection (adverse events, Bayesian: 100% versus 0% and SUCRA: 98.2% versus 1.8%). For the MSC source aspect, adipose mesenchymal stem cells (ADMSCs) and umbilical cord mesenchymal stem cells (UBMSCs) showed a better curative effect on pain relief and function improvement compared with bone marrow mesenchymal stem cells (BMMSCs).

CONCLUSION

Intra-articular injection of MSCs is associated with more effective pain alleviation and function improvement than cell-free OA treatment. However, the potential complications induced by MSCs should be emphasized. A comparative analysis of the MSC sources showed that ADMSCs and UBMSCs exerted a better anti-arthritic efficacy than BMMSCs. Schematic illustration of MSC-based intra-articular injection for treating OA. Three major MSCs (UBMSCs, ADMSCs, and BMMSCs) are extracted and expanded in vitro. Subsequently, the amplified MSCs are concentrated and injected into the knee joint to treat OA.

Molecular Characterization of Secreted Factors and Extracellular Vesicles-Embedded miRNAs from Bone Marrow-Derived Mesenchymal Stromal Cells in Presence of Synovial Fluid from Osteoarthritis Patients

Bone marrow-derived mesenchymal stromal cells (BMSCs)-based therapies show a great potential to manage inflammation and tissue degeneration in osteoarthritis (OA) patients. Clinical trials showed the ability to manage pain and activation of immune cells and allowed restoration of damaged cartilage. To date, a molecular fingerprint of BMSC-secreted molecules in OA joint conditions able to support clinical outcomes is missing; the lack of that molecular bridge between BMSC activity and clinical results hampers clinical awareness and translation into practice. In this study, BMSCs were cultured in synovial fluid (SF) obtained from OA patients and, for the first time, a thorough characterization of soluble factors and extracellular vesicles (EVs)-embedded miRNAs was performed in this condition. Molecular data were sifted through the sieve of molecules and pathways characterizing the OA phenotype in immune cells and joint tissues. One-hundred and twenty-five secreted factors and one-hundred and ninety-two miRNAs were identified. The combined action of both types of molecules was shown to, first, foster BMSCs interaction with the most important OA immune cells, such as macrophages and T cells, driving their switch towards an anti-inflammatory phenotype and, second, promote cartilage homeostasis assisting chondrocyte proliferation and attenuating the imbalance between destructive and protective extracellular matrix-related players. Overall, molecular data give an understanding of the clinical results observed in OA patients and can enable a faster translation of BMSC-based products into everyday clinical practice.

Randomized control trial of mesenchymal stem cells versus hyaluronic acid in patients with knee osteoarthritis - A Hong Kong pilot study

Objective

This pilot study evaluated the efficacy of autologous bone marrow-derived mesenchymal stem cells (BM-MSCs) versus hyaluronic acid (HA) in surgically naïve patients with knee osteoarthritis (OA).

Methods

Single-centre, single-blind randomized study of patients with knee OA. Twenty patients were randomized into groups of 10 each for intra-articular injection of cultured BM-MSCs (6 ​ml of BM-MSCs at 1 ​× ​10⁶ ​cells/mL) or HA (6 ​ml). Clinical assessments of pain, quality of life, radiographic imaging, and magnetic resonance imaging (MRI) compositional change were performed at baseline and 12 months follow-up.

Results

Compared with HA, BM-MSCs injection resulted in significant improvement in qualify of life and reduction in pain as reflected by visual analogue scale (VAS) pain score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and 36-Item Short Form Survey (SF-36) score collectively. T2-relaxation time tended to decrease more in the BM-MSCs group with a 38 ​± ​24.0% reduction in 6 out of 10 BM-MSC participants; while there was only a 12 ​± ​7.9% reduction in 4 out of 10 HA participants at the end of follow-up. The remaining participants showed either no response or had relaxation time increased on MRI assessment.

Conclusions

This pilot study found that autologous BM-MSCs significantly reduced pain, improved functional assessment score, and improved quality of life parameters comparing with HA at one year follow-up. Further clinical trial with larger sample size and longer follow up duration is warranted.

The Translational Potential of this Article

This pilot RCT demonstrated the feasibility and potential effectiveness of BM-MSCs advanced therapy for patients with knee OA compared to HA injection. Further multi-center clinical trial with a larger sample size and longer follow up duration in accordance with latest regulatory guidelines is warranted to ascertain the long term safety and effectiveness of MSCs therapy for cartilage regeneration in OA.

Registration

The study was registered in the Centre for Clinical Research Biostatistics - Clinical Trials Registry (CUHK_CCT00469).

The Analgesic Efficacy of Intradiscal Injection of Bone Marrow Aspirate Concentrate and Culture-Expanded Bone Marrow Mesenchymal Stromal Cells in Discogenic Pain: A Systematic Review

Pain originating from the intervertebral disc (discogenic pain) is a prevalent manifestation of low back pain and is often challenging to treat. Of recent interest, regenerative medicine options with injectable biologics have been trialed in discogenic pain and a wide variety of other painful musculoskeletal conditions. In particular, the role of bone marrow aspirate concentrate (BMAC) and culture-expanded bone marrow derived mesenchymal stromal cells (BM-MSCs) in treating discogenic pain remains unclear. The primary objective of this systematic review was to appraise the evidence of intradiscal injection with BMAC and culture-expanded BM-MSCs in alleviating pain intensity from discogenic pain. Secondary outcomes included changes in physical function after intradiscal injection, correlation between stromal cell count and pain intensity, and anatomical changes of the disc assessed by radiographic imaging after intradiscal injection. Overall, 16 studies consisting of 607 participants were included in qualitative synthesis without pooling. Our synthesis revealed that generally intradiscal autologous or allogeneic BMAC and culture-expanded BM-MSCs improved discogenic pain compared to baseline. Intradiscal injection was also associated with improvements in physical functioning and positive anatomical changes on spine magnetic resonance imaging (improved disc height, disc water content, Pfirrmann grading) although anatomical findings were inconsistent across studies. However, the overall GRADEscore for this study was very low due to heterogeneity and poor generalizability. There were no serious adverse events reported post intradiscal injection except for a case of discitis.

Breakthrough of extracellular vesicles in pathogenesis, diagnosis and treatment of osteoarthritis

Osteoarthritis (OA) is a highly prevalent whole-joint disease that causes disability and pain and affects a patient's quality of life. However, currently, there is a lack of effective early diagnosis and treatment. Although stem cells can promote cartilage repair and treat OA, problems such as immune rejection and tumorigenicity persist. Extracellular vesicles (EVs) can transmit genetic information from donor cells and mediate intercellular communication, which is considered a functional paracrine factor of stem cells. Increasing evidences suggest that EVs may play an essential and complex role in the pathogenesis, diagnosis, and treatment of OA. Here, we introduced the role of EVs in OA progression by influencing inflammation, metabolism, and aging. Next, we discussed EVs from the blood, synovial fluid, and joint-related cells for diagnosis. Moreover, we outlined the potential of modified and unmodified EVs and their combination with biomaterials for OA therapy. Finally, we discuss the deficiencies and put forward the prospects and challenges related to the application of EVs in the field of OA.

The Effectiveness and Safety of Mesenchymal Stem Cells in the Treatment of Osteoarthritis: A Systematic Review and Meta-analysis of 28 Randomized Controlled Trials

Objective

To evaluate the effectiveness and safety of mesenchymal stem cells (MSCs) in the treatment of osteoarthritis (OA).

Methods

Chinese databases (such as CNKI and SinoMed) and English databases (such as PubMed and Embase) were searched to collect randomized controlled trials (RCTs) of MSCs in the treatment of OA. The retrieval time is from inception to October 10, 2021. The literature was strictly selected according to the inclusion and exclusion criteria, data was extracted, and the quality was evaluated. RevMan 5.3 software was used for meta-analysis. STATA was used to evaluate publication bias. The registration number of this systematic review and meta-analysis is CRD42021277145.

Results

A total of 28 RCTs involving 1494 participants were included. The primary outcomes showed that MSCs may reduce WOMAC pain and VAS at the 3rd-month follow-up [WOMAC pain: -3.81 (-6.95, -0.68), P = 0.02. VAS: -1.11 (-1.53, -0.68), P < 0.00001], and the effect lasts for at least 12 months [WOMAC pain: -4.29 (-7.12, -1.47), P = 0.003. VAS: -1.77 (-2.43, -1.12), P < 0.00001]. MSCs may also reduce WOMAC stiffness and physical function at the 6th-month follow-up [WOMAC stiffness: -1.12 (-2.09, -0.14), P = 0.03. WOMAC physical function: -4.40 (-6.84, -1.96), P = 0.0004], and the effect lasts for at least 12 months [WOMAC stiffness: -0.99 (-1.95, -0.03), P = 0.04. WOMAC physical function: -3.26 (-5.91, -0.61), P = 0.02]. The improvement of WOMAC pain, VAS, WOMAC stiffness, and WOMAC physical function may be clinically significant. Meanwhile, after the MSC injection, Lequesne had been reduced compared with the control group [-4.49 (-8.21, -0.77), P = 0.002]. For adverse events, there is no significant difference in the safety of MSC injection and the control group [1.20 (0.97, 1.48), P = 0.09]. The quality of WOMAC physical function and adverse events were moderate.

Conclusion

Based on current evidence, MSCs may be a safety therapy that have a good curative effect in the treatment of OA, the onset time is no later than 3 months, and the time to maintain the curative effect is no less than 12 months. However, these results should be generalized with caution due to the generally low quality of evidence and RCTs.

The potential therapeutic role of extracellular vesicles in osteoarthritis

Osteoarthritis (OA) is a worldwide and disabling disease, which cause severe pain and heavy socioeconomic burden. However, pharmacologic or surgical therapies cannot mitigate OA progression. Mesenchymal stem cells (MSCs) therapy has emerged as potential approach for OA treatment, while the immunogenicity and ethical audit of cell therapy are unavoidable. Compared with stem cell strategy, EVs induce less immunological rejection, and they are more stable for storage and in vivo application. MSC-EVs-based therapy possesses great potential in regulating inflammation and promoting cartilage matrix reconstruction in OA treatment. To enhance the therapeutic effect, delivery efficiency, tissue specificity and safety, EVs can be engineered via different modification strategies. Here, the application of MSC-EVs in OA treatment and the potential underlying mechanism were summarized. Moreover, EV modification strategies including indirect MSC modification and direct EV modification were reviewed.

Exosome-based strategy for degenerative disease in orthopedics: Recent progress and perspectives

BACKGROUND

Degenerative diseases in orthopaedics have become a significant global public health issue with the aging of the population worldwide. The traditional medical interventions, including physical therapy, pharmacological therapy and even surgery, hardly work to modify degenerative progression. Stem cell-based therapy is widely accepted to treat degenerative orthopaedic disease effectively but possesses several limitations, such as the need for strict monitoring of production and storage and the potential risks of tumorigenicity and immune rejection in clinical translation. Furthermore, the ethical issues surrounding the acquisition of embryonic stem cells are also broadly concerned. Exosome-based therapy has rapidly grown in popularity in recent years and is regarded as an ideal alternative to stem cell-based therapy, offering a promise to achieve 'cell-free' tissue regeneration.

METHODS

Traditionally, the native exosomes extracted from stem cells are directly injected into the injured site to promote tissue regeneration. Recently, several modified exosome-based strategies were developed to overcome the limitations of native exosomes, which include mainly exogenous molecule loading and exosome delivery through scaffolds. In this paper, a systematic review of the exosome-based strategy for degenerative disease in orthopaedics is presented.

RESULTS

Treatment strategies based on the native exosomes are effective but with several disadvantages such as rapid diffusion and insufficient and fluctuating functional contents. The modified exosome-based strategies can better match the requirements of the regeneration in some complex healing processes.

CONCLUSION

Exosome-based strategies hold promise to manage degenerative disease in orthopaedics prior to patients reaching the advanced stage of disease in the future. The timely summary and highlights offered herein could provide a research perspective to promote the development of exosome-based therapy, facilitating the clinical translation of exosomes in orthopaedics.

TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Exosome-based therapy is superior in anti-senescence and anti-inflammatory effects and possesses lower risks of tumorigenicity and immune rejection relative to stem cell-based therapy. Exosome-based therapy is regarded as an ideal alternative to stem cell-based therapy, offering a promise to achieve 'cell-free' tissue regeneration.

Micro-fragmented adipose tissue (mFAT) associated with arthroscopic debridement provides functional improvement in knee osteoarthritis: a randomized controlled trial

PURPOSE

Current conservative treatments for knee OA provide limited benefits, with symptoms relief for a short amount of time. Regenerative medicine approaches such as the use of microfragmented adipose tissue (mFAT) showed promising results in terms of durable effects and the possibility to enhance tissue healing and counteract the progression of the pathology. Nevertheless, up to today, the large part of clinical data about mFAT use refers to uncontrolled studies, especially in the surgical setting. The purpose of this study was to evaluate the effectiveness of mFAT applied in association with arthroscopic debridement (AD) for the treatment of knee OA, in terms of symptoms relief and tissue healing.

METHODS

This study is a prospective, randomized controlled clinical trial. 78 patients affected by knee OA grade 3-4 according to KL classification were randomly assigned to AD or AD + mFAT treatment groups. Clinical, radiological and serological assessments were performed at 6 months after treatment. Additional clinical evaluation was performed at the end of the study with an average follow-up of 26.1 ± 9.5 months. VAS, KOOS, WOMAC and SF-12 were also collected at both timepoints, KSS only at 6 months.

RESULTS

Treatment with AD + mFAT improved functional scores at both 6 months (KOOS-PS: + 11.7 ± 20.2 vs + 24.4 ± 22.5, in AD and AD + mFAT, respectively, p = 0.024; KSS: + 14.9 ± 15.9 vs + 24.8 ± 23.5, in AD and AD + mFAT, respectively, p = 0.046) and 24-month follow-ups (KOOS-PS Functional subscale: - 2.0 ± 3.5 vs - 4.7 ± 4.2, in AD and AD + mFAT, respectively, p = 0.012). Lower T2-mapping scores were obtained in AD + mFAT-treated group in medial and lateral condyle compartments (p < 0.001). Slight increase was observed in the levels of a serum biomarker of cartilage deposition (PIIINP) in both groups at 6-month follow-up (p = 0.037).

CONCLUSION

mFAT improves functional outcome and MRI appearance when used in association with AD, therefore supporting its use in the treatment of knee OA in an arthroscopic setting.

Autologous Stem Cells Transplants in the Treatment of Temporomandibular Joints Disorders: A Systematic Review and Meta-Analysis of Clinical Trials

This systematic review aims to analyze the outcomes of the treatment of temporomandibular joint (TMJ) articular pain (AP) and restricted maximum mouth opening (MMO) with intra-articular administration of mesenchymal stem cells (MSCs). The inclusion criteria allowed primary studies involving AP and/or MMO pre-treatment and post-intervention values. Medical databases that were covered by ACM Digital, BASE, EBSCOhost, Google Scholar, PubMed, Scopus, and Web of Science engines were searched. The risk of bias was assessed with RoB 2 and ROBINS-I tools. The results were tabulated, plotted, and analyzed for regression. A total of 5 studies involving 51 patients/69 TMJs were identified, and 4 studies on 50 patients/67 TMJs were synthesized. Interventions were each time effective in decreasing AP and increasing MMO in a 6-month follow-up period by an average of about 85% and over 40%, respectively. Regression analysis showed a good fit of the logarithmic model for AP relief (5.8 − 0.8 ln x; R² = 0.90) and MMO increase (33.5 + 2.4 ln x; R² = 0.89). The results for AP and MMO were based on 3 studies in 39 patients and 4 studies in 50 patients, respectively, all at high risk of bias. The intra-articular administration of MSCs to TMJs, based on weak evidence, may be highly effective in reducing AP and improving MMO. This study received no funding.

An improved diagnostic tool to predict cartilage formation in an osteoarthritic joint environment

Osteoarthritis (OA) is a degenerative joint disease with progressive articular cartilage loss. Due to the chondrogenic potential of human mesenchymal stromal cells (MSCs), MSC-based therapies are promising treatment strategies for cartilage loss. However, the local joint microenvironment has a great impact on the success of cartilage formation by MSCs. This local joint environment is different between patients and therefore the outcome of MSC therapies is uncertain. We previously developed gene promoter-based reporter assays as a novel tool to predict the effect of a patient's OA joint microenvironment on the success of MSC-based cartilage formation. Here we describe an improved version of this molecular tool with increased prediction accuracy. For this, we generated fourteen stable cell lines using transcription factor (TF) binding elements (AP1, ARE, CRE, GRE, ISRE, NFAT5, NFκB, PPRE, SBE, SIE, SOX9, SRE, SRF, TCF/LEF) to drive luciferase reporter gene expression, and evaluated the cell lines for their responsiveness to an osteoarthritic microenvironment by stimulation with OA synovium-conditioned medium (OAs-cm; n=31). To study the effect of this OA microenvironment on MSC-based cartilage formation, MSCs were cultured in a three-dimensional pellet culture model while stimulated with OAs-cm. Cartilage formation was assessed histologically and by quantifying sulfated glycosaminoglycan (sGAG) production. Six TF reporters correlated significantly with the effect of OAs-cm on cartilage formation. We validated the predictive value of these TF reporters with an independent cohort of OAs-cm (n=22) and compared the prediction accuracy between our previous and the current new tool. Furthermore, we investigated which combination of reporters could predict the effect of the OA microenvironment on cartilage repair with the highest accuracy. A combination between the TF (NFκB) and the promoter-based (IL6) reporter proved to reach a more accurate prediction compared to the tools separately. These developments are an important step towards a diagnostic tool that can be used for personalized cartilage repair strategies for OA patients.

In Vitro Characterization of the Human Skeletal Stem Cell-like Properties of Primary Bone-Derived Mesenchymal Stem/Stromal Cells in Patients with Late and Early Hip Osteoarthritis

Human skeletal stem cells (hSSCs) were recently identified as podoplanin (PDPN)/CD73/CD164-positive and CD146-negative cells that decline with age, and play a role in the pathogenesis of osteoarthritis (OA). The aim of this study was to identify the hSSC-like properties of bone-derived mesenchymal stem/stromal cells (MSCs) of patients with late and early OA. Methods: First, we performed gene expression profiling for the hSSC markers in 32 patients with late and early OA, and donors without OA. Having identified the low expression of hSSC markers in late OA patients, we further performed trilineage differentiation and immunophenotyping for hSSC makers in the selected subsets from each donor group. Results: Our results show no differences in osteogenesis, chondrogenesis, and adipogenesis between the MSCs from the three groups. However, the immunophenotyping shows lower CD164 in MSCs from early OA patients in comparison with late and no OA subjects (p = 0.002 and p = 0.017). Conclusions: Our study shows that the in vitro hSSC-like properties of bone-derived MSCs are similar in patients with early and late OA, and in donors without OA. However, the lower percentage of CD164-positive MSCs in early OA patients indicates the potential of CD164 as a marker of the onset of OA.

MicroRNA-378 contributes to osteoarthritis by regulating chondrocyte autophagy and bone marrow mesenchymal stem cell chondrogenesis

Osteoarthritis (OA) is the most common joint disease; thus, understanding the pathological mechanisms of OA initiation and progression is critical for OA treatment. MicroRNAs (miRNAs) have been shown to be involved in the progression of osteoarthritis, one candidate is microRNA-378 (miR-378), which is highly expressed in the synovium of OA patients during late-stage disease, but its function and the underlying mechanisms of how it contributes to disease progression remain poorly understood. In this study, miR-378 transgenic (TG) mice were used to study the role of miR-378 in OA development. miR-378 TG mice developed spontaneous OA and also exaggerated surgery-induced disease progression. Upon in vitro OA induction, miR-378 expression was upregulated and correlated with elevated inflammation and chondrocyte hypertrophy. Chondrocytes isolated from articular cartilage from miR-378 TG mice showed impaired chondrogenic differentiation. The bone marrow mesenchymal stem cells (BMSCs) collected from miR-378 TG mice also showed repressed chondrogenesis compared with the control group. The autophagy-related protein Atg2a, as well as chondrogenesis regulator Sox6, were identified as downstream targets of miR-378. Ectopic expression of Atg2a and Sox6 rescued miR-378-repressed chondrocyte autophagy and BMSC chondrogenesis, respectively. Anti-miR-378 lentivirus intra-articular injection in an established OA mouse model was shown to ameliorate OA progression, promote articular regeneration, and repress hypertrophy. Atg2a and Sox6 were again confirmed to be the target of miR-378 in vivo. In conclusion, miR-378 amplified OA development via repressing chondrocyte autophagy and by inhibiting BMSCs chondrogenesis, thus indicating miR-378 may be a potential therapeutic target for OA treatments.

The Hunt Is On! In Pursuit of the Ideal Stem Cell Population for Cartilage Regeneration

Cartilage injury and degeneration are hallmarks of osteoarthritis (OA), the most common joint disease. OA is a major contributor to pain, loss of function, and reduced quality of life. Over the last decade, considerable research efforts have focused on cell-based therapies, including several stem cell-derived approaches to reverse the cartilage alterations associated with OA. Although several tissue sources for deriving cell-based therapies have been identified, none of the resident stem cell populations have adequately fulfilled the promise of curing OA. Indeed, many cell products do not contain true stem cells. As well, issues with aggressive marketing efforts, combined with a lack of evidence regarding efficacy, lead the several national regulatory bodies to discontinue the use of stem cell therapy for OA until more robust evidence becomes available. A review of the evidence is timely to address the status of cell-based cartilage regeneration. The promise of stem cell therapy is not new and has been used successfully to treat non-arthritic diseases, such as hematopoietic and muscle disorders. These fields of regenerative therapy have the advantage of a considerable foundation of knowledge in the area of stem cell repair mechanisms, the role of the stem cell niche, and niche-supporting cells. This foundation is lacking in the field of cartilage repair. So, where should we look for the ideal stem cell to regenerate cartilage? It has recently been discovered that cartilage itself may contain a population of SC-like progenitors. Other potential tissues include stem cell-rich dental pulp and the adolescent growth plate, the latter of which contains chondrocyte progenitors essential for producing the cartilage scaffold needed for bone growth. In this article, we review the progress on stem cell therapies for arthritic disorders, focusing on the various stem cell populations previously used for cartilage regeneration, successful cases of stem cell therapies in muscle and hemopoietic disorders, some of the reasons why these other fields have been successful (i.e., "lessons learned" to be applied to OA stem cell therapy), and finally, novel potential sources of stem cells for regenerating damaged cartilage in vivo.

Characterisation of Extracellular Vesicles from Equine Mesenchymal Stem Cells

Extracellular vesicles (EVs) are nanosized lipid bilayer-encapsulated particles secreted by virtually all cell types. EVs play an essential role in cellular crosstalk in health and disease. The cellular origin of EVs determines their composition and potential therapeutic effect. Mesenchymal stem/stromal cell (MSC)-derived EVs have shown a comparable therapeutic potential to their donor cells, making them a promising tool for regenerative medicine. The therapeutic application of EVs circumvents some safety concerns associated with the transplantation of viable, replicating cells and facilitates the quality-controlled production as a ready-to-go, off-the-shelf biological therapy. Recently, the International Society for Extracellular Vesicles (ISEV) suggested a set of minimal biochemical, biophysical and functional standards to define extracellular vesicles and their functions to improve standardisation in EV research. However, nonstandardised EV isolation methods and the limited availability of cross-reacting markers for most animal species restrict the application of these standards in the veterinary field and, therefore, the species comparability and standardisation of animal experiments. In this study, EVs were isolated from equine bone-marrow-derived MSCs using two different isolation methods, stepwise ultracentrifugation and size exclusion chromatography, and minimal experimental requirements for equine EVs were established and validated. Equine EVs were characterised using a nanotracking analysis, fluorescence-triggered flow cytometry, Western blot and transelectron microscopy. Based on the ISEV standards, minimal criteria for defining equine EVs are suggested as a baseline to allow the comparison of EV preparations obtained by different laboratories.

Epigenetic Regulation of Chondrocytes and Subchondral Bone in Osteoarthritis

The aim of this review is to provide an updated review of the epigenetic factors involved in the onset and development of osteoarthritis (OA). OA is a prevalent degenerative joint disease characterized by chronic inflammation, ectopic bone formation within the joint, and physical and proteolytic cartilage degradation which result in chronic pain and loss of mobility. At present, no disease-modifying therapeutics exist for the prevention or treatment of the disease. Research has identified several OA risk factors including mechanical stressors, physical activity, obesity, traumatic joint injury, genetic predisposition, and age. Recently, there has been increased interest in identifying epigenetic factors involved in the pathogenesis of OA. In this review, we detail several of these epigenetic modifications with known functions in the onset and progression of the disease. We also review current therapeutics targeting aberrant epigenetic regulation as potential options for preventive or therapeutic treatment.

Methodological quality and risk of bias of systematic reviews and meta-analyses on stem cells for knee osteoarthritis: A cross-sectional survey

Clinical guidelines need high-quality studies to support clinical decision-making, in which the evidence often was collected from systematic reviews (SRs) and/or meta-analyses (MAs). At present, the methodological quality and risk of bias (RoB) of SRs/MAs on stem cell therapy for the treatment of knee osteoarthritis (KOA) has been poorly investigated. This study aims to strictly evaluate the methodological quality and RoB in SRs/MAs of stem cell therapy for KOA. Four electronic databases (PubMed, Embase, Cochrane Library, and Web of Science databases) were searched, from inception to October 5th, 2021. SRs/MAs involving randomized control trials (RCTs) or cohort studies on stem cell therapy for the treatment of KOA were included. The methodological quality and RoB were assessed using AMSTAR 2 and ROBIS tool respectively. In total, 22 SRs/MAs were included. According to the results obtained by AMSTAR 2 tool, all SRs/MAs were rated as "Critically low". Main methodological weaknesses were as follows: up to 81.82% did not meet protocol registration requirements, only 13.64% provided a list of excluded studies and justification, and 13.64% investigated and discussed the publication bias.. ROBIS-based RoB assessment showed that all the SRs/MAs were rated as "High". Besides, the lack of following the implementation of the PRISMA reporting guideline seems to reduce the methodological quality of the studies. The overall methodological quality of the SRs/MAs concerning the application of stem cell therapy in treating KOA is "Critically low", while the RoB is high. It is difficult to provide effective evidence for the formulation of guidelines for KOA treatment. We suggest that the relevant methodological quality assessment should be carried out in the future before the SRs/MAs are used as clinical evidence. In addition, it may be necessary for many journals to include the checklist with a submitted manuscript.

Triamcinolone acetonide-loaded nanoparticles encapsulated by CD90+ MCSs-derived microvesicles drive anti-inflammatory properties and promote cartilage regeneration after osteoarthritis

Background

Osteoarthritis (OA) is a highly prevalent human degenerative joint disorder that has long plagued patients. Glucocorticoid injection into the intra-articular (IA) cavity provides potential short-term analgesia and anti-inflammatory effects, but long-term IA injections cause loss of cartilage. Synovial mesenchymal stem cells (MSCs) reportedly promote cartilage proliferation and increase cartilage content.

Methods

CD90⁺ MCS-derived micro-vesicle (CD90@MV)-coated nanoparticle (CD90@NP) was developed. CD90⁺ MCSs were extracted from human synovial tissue. Cytochalasin B (CB) relaxed the interaction between the cytoskeleton and the cell membranes of the CD90⁺ MCSs, stimulating CD90@MV secretion. Poly (lactic-co-glycolic acid) (PLGA) nanoparticle was coated with CD90@MV, and a model glucocorticoid, triamcinolone acetonide (TA), was encapsulated in the CD90@NP (T-CD90@NP). The chondroprotective effect of T-CD90@NP was validated in rabbit and rat OA models.

Results

The CD90@MV membrane proteins were similar to that of CD90⁺ MCSs, indicating that CD90@MV bio-activity was similar to the cartilage proliferation-inducing CD90⁺ MCSs. CD90@NP binding to injured primary cartilage cells was significantly stronger than to erythrocyte membrane-coated nanoparticles (RNP). In the rabbit OA model, the long-term IA treatment with T-CD90@NP showed significantly enhanced repair of damaged cartilage compared to TA and CD90⁺ MCS treatments. In the rat OA model, the short-term IA treatment with T-CD90@NP showed effective anti-inflammatory ability similar to that of TA treatment. Moreover, the long-term IA treatment with T-CD90@NP induced cartilage to restart the cell cycle and reduced cartilage apoptosis. T-CD90@NP promoted the regeneration of chondrocytes, reduced apoptosis via the FOXO pathway, and influenced type 2 macrophage polarization to regulate inflammation through IL-10.

Conclusion

This study confirmed that T-CD90@NP promoted chondrocyte proliferation and anti-inflammation, improving the effects of a clinical glucocorticoid treatment plan.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01367-z.

Long-term injection of glucocorticoids in the knee joint cavity promotes loss of cartilage content.

CD90-positive stem cell vesicles encapsulated with Triamcinolone acetonide-loaded nanoparticles have good materials.

T-CD90@NPs drive anti-inflammatory properties and promote cartilage regeneration after osteoarthritis.

T-CD90@NPs regulate the polarization of type 2 macrophages to resist inflammation.

T-CD90@NPs promote chondrocyte regeneration through the FOXO signaling pathway.

Human Mesenchymal Stem/Stromal Cells in Immune Regulation and Therapy

Studies of mesenchymal stem (or stromal) cells (MSCs) have moved from bedside to bench and back again. The stromal cells or fibroblasts are found in all tissues and participate in building the extracellular matrix (ECM). Bone marrow (BM)-derived MSCs have been studied for more than 50 years and have multiple roles. They function as stem cells and give rise to bone, cartilage, and fat in the BM (these are stem cells); support hematopoiesis (pericytes); and participate in sensing environmental changes and balancing pro- and anti-inflammatory conditions. In disease states, they migrate to sites of injury and release cytokines, hormones, nucleic acids depending on the microenvironment they find. Clinicians have begun to exploit these properties of BM, adipose tissue, and umbilical cord MSCs because they are easy to harvest and expand in culture. In this review, I describe the uses to which MSCs have been put, list ongoing clinical trials by organ system, and outline how MSCs are thought to regulate the innate and adaptive immune systems. I will discuss some of the reasons why clinical applications are still lacking. Much more work will have to be done to find the sources, doses, and culture conditions needed to exploit MSCs optimally and learn their healing potential. They are worth the effort.

Methodological Flaws in Meta-Analyses of Clinical Studies on the Management of Knee Osteoarthritis with Stem Cells: A Systematic Review

(1) Background: Conclusions of meta-analyses of clinical studies may substantially influence opinions of prospective patients and stakeholders in healthcare. Nineteen meta-analyses of clinical studies on the management of primary knee osteoarthritis (pkOA) with stem cells, published between January 2020 and July 2021, came to inconsistent conclusions regarding the efficacy of this treatment modality. It is possible that a separate meta-analysis based on an independent, systematic assessment of clinical studies on the management of pkOA with stem cells may reach a different conclusion. (2) Methods: PubMed, Web of Science, and the Cochrane Library were systematically searched for clinical studies and meta-analyses of clinical studies on the management of pkOA with stem cells. All clinical studies and meta-analyses identified were evaluated in detail, as were all sub-analyses included in the meta-analyses. (3) Results: The inconsistent conclusions regarding the efficacy of treating pkOA with stem cells in the 19 assessed meta-analyses were most probably based on substantial differences in literature search strategies among different authors, misconceptions about meta-analyses themselves, and misconceptions about the comparability of different types of stem cells with regard to their safety and regenerative potential. An independent, systematic review of the literature yielded a total of 183 studies, of which 33 were randomized clinical trials, including a total of 6860 patients with pkOA. However, it was not possible to perform a scientifically sound meta-analysis. (4) Conclusions: Clinicians should interpret the results of the 19 assessed meta-analyses of clinical studies on the management of pkOA with stem cells with caution and should be cautious of the conclusions drawn therein. Clinicians and researchers should strive to participate in FDA and/or EMA reviewed and approved clinical trials to provide clinically and statistically valid efficacy.

Preclinical studies and clinical trials on mesenchymal stem cell therapy for knee osteoarthritis: A systematic review on models and cell doses

AIM

To provide a systematic analysis of the study design in knee osteoarthritis (OA) preclinical studies, focusing on the characteristics of animal models and cell doses, and to compare these to the characteristics of clinical trials using mesenchymal stem cells (MSCs) for the treatment of knee OA.

METHOD

A systematic and comprehensive search was conducted using the PubMed, Web of Science, Ovid, and Embase electronic databases for research papers published in 2009-2020 on testing MSC treatment in OA animal models. The PubMed database and ClinicalTrials.gov website were used to search for published studies reporting clinical trials of MSC therapy for knee OA.

RESULTS

In total, 9234 articles and two additional records were retrieved, of which 120 studies comprising preclinical and clinical studies were included for analysis. Among the preclinical studies, rats were the most commonly used species for modeling knee OA, and anterior cruciate ligament transection was the most commonly used method for inducing OA. There was a correlation between the cell dose and body weight of the animal. In clinical trials, there was large variation in the dose of MSCs used to treat knee OA, ranging from 1 × 10⁶ to 200 × 10⁶ cells with an average of 37.91 × 10⁶ cells.

CONCLUSION

Mesenchymal stem cells have shown great potential in improving pain relief and tissue protection in both preclinical and clinical studies of knee OA. Further high-quality preclinical and clinical studies are needed to explore the dose effectiveness relationship of MSC therapy and to translate the findings from preclinical studies to humans.

Intrauterine infusion of clinically graded human umbilical cord-derived mesenchymal stem cells for the treatment of poor healing after uterine injury: a phase I clinical trial

Background

Intrauterine adhesion and cesarean scar diverticulum are the main complications of poor healing after uterine injury. Human umbilical cord MSCs transplantation has been regarded as the most potential treatment in the clinic, the safety and efficacy of which in the clinic, however, remains unclear.

Methods

In this study, ten patients were enrolled: six with intrauterine adhesion and four with cesarean scar diverticulum. All the patients were injected with human umbilical cord MSCs twice into the uterus. Beside the chest X-ray, ECG and abdominal ultrasound, many laboratory tests including blood routine, liver and renal function, ovarian function, tumor biomarkers, and immune function were used to estimate the safe after stem cell transplanted. In addition, the efficacy of stem cell transplanted was shown by the endometrial thickness, the volume of the uterus, and cesarean scar diverticulum based on 3D ultrasound imaging.

Results

We found that all results of these laboratory tests were normal in these enrolled patients before and after cell injection. Meanwhile, the results of the chest X-ray and ECG were also normal in the treatment process. The abdominal ultrasound showed that the size of the left and right kidneys was inconsistent in one patient after cell therapy, while those of other patients were normal. In addition, endometrial thickness, the volume of the uterus, and cesarean scar diverticulum showed an improving tendency, but no significant difference was noted.

Conclusion

In summary, intrauterine injection of clinically graded human umbilical cord MSCs was safe for poor healing after uterus injury.

Trial registration NCT03386708. Registered 27 December 2017, https://clinicaltrials.gov/ct2/show/NCT03386708?cond=CSD&cntry=CN&draw=2&rank=2

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02756-9.

Advances in Use of Nanomaterials for Musculoskeletal Regeneration

Since the worldwide incidence of bone disorders and cartilage damage has been increasing and traditional therapy has reached its limits, nanomaterials can provide a new strategy in the regeneration of bones and cartilage. The nanoscale modifies the properties of materials, and many of the recently prepared nanocomposites can be used in tissue engineering as scaffolds for the development of biomimetic materials involved in the repair and healing of damaged tissues and organs. In addition, some nanomaterials represent a noteworthy alternative for treatment and alleviating inflammation or infections caused by microbial pathogens. On the other hand, some nanomaterials induce inflammation processes, especially by the generation of reactive oxygen species. Therefore, it is necessary to know and understand their effects in living systems and use surface modifications to prevent these negative effects. This contribution is focused on nanostructured scaffolds, providing a closer structural support approximation to native tissue architecture for cells and regulating cell proliferation, differentiation, and migration, which results in cartilage and bone healing and regeneration.

American Medical Society for Sports Medicine Position Statement: Principles for the Responsible Use of Regenerative Medicine in Sports Medicine

ABSTRACT

Many sports medicine physicians are currently considering introducing regenerative medicine into their practice. Regenerative medicine and the subclassification of orthobiologics are a complicated topic and have produced widely varying opinions. Although there is concern by government regulators, clinicians, scientists, patient advocacy organizations, and the media regarding the use of regenerative medicine products, there is also excitement about the potential benefits with growing evidence that certain regenerative medicine products are safe and potentially efficacious in treating musculoskeletal conditions. Sports medicine physicians would benefit from decision-making guidance about whether to introduce orthobiologics into their practice and how to do it responsibly. The purpose of this position statement is to provide sports medicine physicians with information regarding regenerative medicine terminology, a brief review of basic science and clinical studies within the subclassification of orthobiologics, regulatory considerations, and best practices for introducing regenerative medicine into clinical practice. This information will help sports medicine physicians make informed and responsible decisions about the role of regenerative medicine and orthobiologics in their practice.

Potential of Exosomes as Cell-Free Therapy in Articular Cartilage Regeneration: A Review

Treatment of cartilage defects such as osteoarthritis (OA) and osteochondral defect (OCD) remains a huge clinical challenge in orthopedics. OA is one of the most common chronic health conditions and is mainly characterized by the degeneration of articular cartilage, shown in the limited capacity for intrinsic repair. OCD refers to the focal defects affecting cartilage and the underlying bone. The current OA and OCD management modalities focus on symptom control and on improving joint functionality and the patient’s quality of life. Cell-based therapy has been evaluated for managing OA and OCD, and its chondroprotective efficacy is recognized mainly through paracrine action. Hence, there is growing interest in exploiting extracellular vesicles to induce cartilage regeneration. In this review, we explore the in vivo evidence of exosomes on cartilage regeneration. A total of 29 in vivo studies from the PubMed and Scopus databases were identified and analyzed. The studies reported promising results in terms of in vivo exosome delivery and uptake; improved cartilage morphological, histological, and biochemical outcomes; enhanced subchondral bone regeneration; and improved pain behavior following exosome treatment. In addition, exosome therapy is safe, as the included studies documented no significant complications. Modifying exosomal cargos further increased the cartilage and subchondral bone regeneration capacity of exosomes. We conclude that exosome administration is a potent cell-free therapy for alleviating OA and OCD. However, additional studies are needed to confirm the therapeutic potential of exosomes and to identify the standard protocol for exosome-based therapy in OA and OCD management.

Pro-regenerative Dialogue Between Macrophages and Mesenchymal Stem/Stromal Cells in Osteoarthritis

Osteoarthritis (OA), the most common degenerative and inflammatory joint disorder, is multifaceted. Indeed, OA characteristics include cartilage degradation, osteophytes formation, subchondral bone changes, and synovium inflammation. The difficulty in discovering new efficient treatments for OA patients up to now comes from the adoption of monotherapy approaches targeting either joint tissue repair/catabolism or inflammation to address the diverse components of OA. When satisfactory, these approaches only provide short-term beneficial effects, since they only result in the repair and not the full structural and functional reconstitution of the damaged tissues. In the present review, we will briefly discuss the current therapeutic approaches used to repair the damaged OA cartilage. We will highlight the results obtained with cell-based products in clinical trials and demonstrate how the current strategies result in articular cartilage repair showing restricted early-stage clinical improvements. In order to identify novel therapeutic targets and provide to OA patients long-term clinical benefits, herein, we will review the basis of the regenerative process. We will focus on macrophages and their ambivalent roles in OA development and tissue regeneration, and review the therapeutic strategies to target the macrophage response and favor regeneration in OA.