Single-stage cell-based cartilage repair in a rabbit model: cell tracking and in vivo chondrogenesis of human umbilical cord blood-derived mesenchymal stem cells and hyaluronic acid hydrogel composite

3D Bioprinting Strategies for Articular Cartilage Tissue Engineering

Articular cartilage is the avascular and aneural tissue which is the primary connective tissue covering the surface of articulating bone. Traumatic damage or degenerative diseases can cause articular cartilage injuries that are common in the population. As a result, the demand for new therapeutic options is continually increasing for older people and traumatic young patients. Many attempts have been made to address these clinical needs to treat articular cartilage injuries, including osteoarthritis (OA); however, regenerating highly qualified cartilage tissue remains a significant obstacle. 3D bioprinting technology combined with tissue engineering principles has been developed to create biological tissue constructs that recapitulate the anatomical, structural, and functional properties of native tissues. In addition, this cutting-edge technology can precisely place multiple cell types in a 3D tissue architecture. Thus, 3D bioprinting has rapidly become the most innovative tool for manufacturing clinically applicable bioengineered tissue constructs. This has led to increased interest in 3D bioprinting in articular cartilage tissue engineering applications. Here, we reviewed current advances in bioprinting for articular cartilage tissue engineering.

Endogenus chondrocytes immobilized by G-CSF in nanoporous gels enable repair of critical-size osteochondral defects

Injured articular cartilage is a leading cause for osteoarthritis. We recently discovered that endogenous stem/progenitor cells not only reside in the superficial zone of mouse articular cartilage, but also regenerated heterotopic bone and cartilage in vivo. However, whether critical-size osteochondral defects can be repaired by pure induced chemotatic cell homing of these endogenous stem/progenitor cells remains elusive. Here, we first found that cells in the superficial zone of articular cartilage surrounding surgically created 3 × 1 mm defects in explant culture of adult goat and rabbit knee joints migrated into defect-filled fibrin/hylaro1nate gel, and this migration was significantly more robust upon delivery of exogenous granulocyte-colony stimulating factor (G-CSF). Remarkably, G-CSF-recruited chondrogenic progenitor cells (CPCs) showed significantly stronger migration ability than donor-matched chondrocytes and osteoblasts. G-CSF-recruited CPCs robustly differentiated into chondrocytes, modestly into osteoblasts, and barely into adipocytes. In vivo, critical-size osteochondral defects were repaired by G-CSF-recruited endogenous cells postoperatively at 6 and 12 weeks in comparison to poor healing by gel-only group or defect-only group. ICRS and O'Driscoll scores of articular cartilage were significantly higher for both 6- and 12-week G-CSF samples than corresponding gel-only and defect-only groups. Thus, endogenous stem/progenitor cells may be activated by G-CSF, a Food and Drug Administration (FDA)-cleared bone-marrow stimulating factor, to repair osteochondral defects.

Protecting the regenerative environment: selecting the optimal delivery vehicle for cartilage repair-a narrative review

Focal cartilage defects are common in youth and older adults, cause significant morbidity and constitute a major risk factor for developing osteoarthritis (OA). OA is the most common musculoskeletal (MSK) disease worldwide, resulting in pain, stiffness, loss of function, and is currently irreversible. Research into the optimal regenerative approach and methods in the setting of either focal cartilage defects and/or OA holds to the ideal of resolving both diseases. The two fundamentals required for cartilage regenerative treatment are 1) the biological element contributing to the regeneration (e.g., direct application of stem cells, or of an exogenous secretome), and 2) the vehicle by which the biological element is suspended and delivered. The vehicle provides support to the regenerative process by providing a protective environment, a structure that allows cell adherence and migration, and a source of growth and regenerative factors that can activate and sustain regeneration. Models of cartilage diseases include osteochondral defect (OCD) (which usually involve one focal lesion), or OA (which involves a more diffuse articular cartilage loss). Given the differing nature of these models, the optimal regenerative strategy to treat different cartilage diseases may not be universal. This could potentially impact the translatability of a successful approach in one condition to that of the other. An analogy would be the repair of a pothole (OCD) versus repaving the entire road (OA). In this narrative review, we explore the existing literature evaluating cartilage regeneration approaches for OCD and OA in animal then in human studies and the vehicles used for each of these two conditions. We then highlight strengths and challenges faced by the different approaches presented and discuss what might constitute the optimal cartilage regenerative delivery vehicle for clinical cartilage regeneration.

Cartilage regeneration using transforming growth factor-beta 3-loaded injectable crosslinked hyaluronic acid hydrogel

Cartilage defects can be difficult to heal, potentially leading to complications such as osteoarthritis. Recently, a tissue engineering approach that uses scaffolds and growth factors has been proposed to regenerate new cartilage tissues. Herein, we investigated the application of hyaluronic acid (HA) gel loaded with transforming growth factor-beta 3 (TGF-β3) for enhanced cartilage regeneration. We assessed the clinical conditions required to efficiently enhance the ability of the modified HA gel to repair defective cartilage. Based on our findings, the prepared HA gel exhibited good physicochemical and mechanical properties and was non-toxic and non-inflammatory. Moreover, HA gel-loaded TGF-β3 (HAT) had improved biocompatibility and promoted the synthesis of cartilage-specific matrix and collagen, further improving its ability to repair defects. The application of HAT resulted in an initial burst release of HA, which degraded slowly in vivo. Finally, HAT combined with microfracture-inducing bone marrow stem cells could significantly improve the cartilage microenvironment and regeneration of cartilage defects. Our results indicate that HA is a suitable material for developing growth factor carriers, whereas HAT is a promising candidate for cartilage regeneration. Furthermore, this differentiated strategy provides a rapid and effective clinical approach for next-generation cartilage regeneration.

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.

Selective Extracellular Matrix Guided Mesenchymal Stem Cell Self-Aggregate Engineering for Replication of Meniscal Zonal Tissue Gradient in a Porcine Meniscectomy Model

Degenerative meniscus tears (DMTs) are prevalent findings in osteoarthritic knees, yet current treatment is mostly limited to arthroscopic partial meniscectomy rather than regeneration, which further exacerbates arthritic changes. Translational research regarding meniscus regeneration is hindered by the complex, composite nature of the meniscus which exhibit a gradient from inner cartilage-like tissue to outer fibrous tissue, as well as engineering hurdles often requiring growth factors and cross-linking agents. Here, a meniscus zonal tissue gradient is proposed using zone-specific decellularized meniscus extracellular matrix (DMECM) and autologous synovial mesenchymal stem cells (SMSC) via self-aggregation without the use of growth factors or cross-linking agents. Combination with zone-specific DMECM during self-aggregation of MSCs forms zone-specific meniscus tissue that reflects the respective DMECM harvest site. The implantation of these constructs leads to the regeneration of meniscus tissue resembling the native meniscus, demonstrating inner cartilaginous and outer fibrous characteristics as well as recovery of native meniscal microarchitecture in a porcine partial meniscectomy model at 6 months. In all, the findings offer a potential regenerative therapy for DMTs that may improve current partial meniscectomy-based patient care.

Higher ratios of chondrocyte to mesenchymal stem cells elevate the therapeutic effects of extracellular vesicles harvested from chondrocyte/mesenchymal stem cell co-culture on osteoarthritis in a rat model

Extracellular vesicles (EVs) may have a key therapeutic role and offer an innovative treatment for osteoarthritis (OA). Studies have shown that ratio of MSC/chondrocyte could affect their therapeutic outcomes. Here, we investigate the chondrogenic potential and therapeutic effect of EVs derived from MSCs and chondrocytes in the naïve, chondrogenically primed, and co-culture states to treat OA. EVs are isolated from naïve MSCs (M-EV), chondrogenically primed MSCs (cpM-EV), chondrocytes (C-EV), and co-cultures of chondrocytes plus MSCs at ratios of 1:1 (C/M-EV), 2:1 (2C/M-EV), and 4:1 (4C/M-EV). We characterized the isolated EVs in terms of surface markers, morphology, size, and zeta potential, and evaluated their chondrogenic potential in vitro by qRT-PCR and histological analyses. Next, these EVs were intra-articularly injected into osteoarthritic cartilage of a rat model and assessed by radiography, gait parameters, and histological and immunohistochemical analyses. EVs obtained from chondrocytes co-cultured with MSCs resulted in improved matrix production and functional differentiation. Our research showed that close proximity between the two cell types was essential for this response, and improved chondrogenesis and matrix formation were the outcomes of this interaction in vitro. Furthermore, in the in vivo rat OA model induced by a monoiodoacetate (MIA), we observed recovery from OA by increasing ratio of the C/M-derived EV group compared to the other groups. Our findings show that the increasing chondrocyte ratio to MSC leads to high chondrogenic induction and the therapeutic effect of harvested EVs for cartilage repair.

Human umbilical cord mesenchymal stem cells promoting knee joint chondrogenesis for the treatment of knee osteoarthritis: a systematic review

PURPOSE

The onset of OA is affected by a variety of factors, which eventually lead to the loss of cartilage in the joints, the formation of osteophytes, the loss of normal knee mobility, and pain and discomfort, which seriously affects the quality of life. HUC-MSCs can promote cartilage production and have been widely used in research in the past decade. This article systematically summarizes that it is well used in basic research and clinical studies to promote inflammatory chondrogenesis in the treatment of OA. Provide a theoretical basis for clinical treatment.

PATIENTS AND METHODS

This study collected CNKI, Wanfang, PubMed, and articles related to the treatment of OA with HUC-MSCs since their publication, excluding non-basic and clinical studies such as reviews and meta-analysis. A total of 31 basic experimental studies and 12 clinical studies were included. Systematically analyze the effects of HUC-MSCs on inhibiting inflammatory factors, promoting chondrocyte production, and current clinical treatment.

RESULTS

HUC-MSCs can reduce inflammatory factors such as MMP-13, ADAMTS-5, IL-1β, IL-1, IL-6, TNF-α, induced conversion from M1 to M2 in OA to protect cartilage damage and reduce OA inflammation. Synthesize ColII, SOX9, and aggrecan at the same time to promote cartilage synthesis.

CONCLUSION

HUC-MSCs not only have typical stem cell biological characteristics, but also have rich sources and convenient material extraction. Compared with stem cells from other sources, HUC-MSCs have stronger proliferation, differentiation, and immune regulation abilities. Furthermore, there are no ethical issues associated with their use.

SAFETY

Primarily attributed to pain, the majority of individuals experience recovery within 24 h following injection. HUC-MSCs possess the ability to alleviate pain, enhance knee joint function, and potentially postpone the need for surgical intervention in both non-surgical and other cases, making them highly deserving of clinical promotion and application.

Mild Synovitis Impairs Chondrogenic Joint Environment

The impact of mild synovitis on the chondrogenic environment in the joint pertaining to cartilage repair is often neglected. In this study, 21 synovial samples were collected from foot surgeries for histology and isolation of fibroblast-like synoviocytes (FLSs). Of the 21 samples, 13 were normal and eight were mild synovitis, according to their synovitis scores. In mild synovitis, CD3+ lymphocytes were increased in the sublining layer. When chondrocytes were cultured and treated with the conditioned medium produced by FLSs, their glycosaminoglycan production was negatively correlated with the synovitis scores of the synovium, from which FLSs were isolated. In conclusion, mild synovitis in common joint conditions compromises the process of chondrogenesis, via inhibiting chondrocyte matrix production by FLSs. The results suggest that the concomitant synovitis, even being mild, could significantly alter the joint environment for chondrogenesis and impair the outcome of cartilage repair.

Regenerative methods in osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis that can affect all joint structures. The primary goals of osteoarthritis treatment are to alleviate pain, reduce functional limitations, and improve quality of life. Despite its high prevalence, treatment options for osteoarthritis are limited, with most therapeutic approaches focusing on symptom management. Tissue engineering and regenerative strategies based on biomaterials, cells, and other bioactive molecules have emerged as viable options for osteoarthritis cartilage repair. Platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) are the most commonly used regenerative therapies today to protect, restore, or increase the function of damaged tissues. Despite promising results, there is conflicting evidence regarding the efficacy of regenerative therapies, and their efficacy remains unknown. The data suggest that more research and standardization are required for the use of these therapies in osteoarthritis. This article provides an overview of the application of MSCs and PRP applications.

Current knowledge and future perspectives on exosomes in the field of regenerative medicine: a bibliometric analysis

Objective: This study aimed to use bibliometric analysis to qualitatively and quantitatively evaluate the research of exosomes in the field of regenerative medicine and to provide research hotspots and trends in this field. Materials & methods: Bibliometric analysis and data presentation were performed by VOSviewer and Microsoft Excel. Results: China was the major contributor to research in this field and enjoys a high reputation in academia. The highest contributing institution is Shanghai Jiao Tong University. Research hotspots included exosome-mediated neurovascular regeneration, exosome mechanism research, exosome-mediated cartilage regeneration and repair and exosome-mediated cardiac regeneration. Research was trending in the treatment of osteoarthritis, knee disease and cartilage regeneration and repair. Conclusion: This study provides a panoramic view of the application of exosomes in regenerative medicine.

Potency Assay Considerations for Cartilage Repair, Osteoarthritis and Use of Extracellular Vesicles

Articular cartilage covers the ends of bones in synovial joints acting as a shock absorber that helps movement of bones. Damage of the articular cartilage needs treatment as it does not repair itself and the damage can progress to osteoarthritis. In osteoarthritis all the joint tissues are involved with characteristic progressive cartilage degradation and inflammation. Autologous chondrocyte implantation is a well-proven cell-based treatment for cartilage defects, but a main downside it that it requires two surgeries. Multipotent, aka mesenchymal stromal cell (MSC)-based cartilage repair has gained attention as it can be used as a one-step treatment. It is proposed that a combination of immunomodulatory and regenerative capacities make MSC attractive for the treatment of osteoarthritis. Furthermore, since part of the paracrine effects of MSCs are attributed to extracellular vesicles (EVs), small membrane enclosed particles secreted by cells, EVs are currently being widely investigated for their potential therapeutic effects. Although MSCs have entered clinical cartilage treatments and EVs are used in in vivo efficacy studies, not much attention has been given to determine their potency and to the development of potency assays. This chapter provides considerations and suggestions for the development of potency assays for the use of MSCs and MSC-EVs for the treatment of cartilage defects and osteoarthritis.

Mast4 determines the cell fate of MSCs for bone and cartilage development

Mesenchymal stromal cells (MSCs) differentiation into different lineages is precisely controlled by signaling pathways. Given that protein kinases play a crucial role in signal transduction, here we show that Microtubule Associated Serine/Threonine Kinase Family Member 4 (Mast4) serves as an important mediator of TGF-β and Wnt signal transduction in regulating chondro-osteogenic differentiation of MSCs. Suppression of Mast4 by TGF-β1 led to increased Sox9 stability by blocking Mast4-induced Sox9 serine 494 phosphorylation and subsequent proteasomal degradation, ultimately enhancing chondrogenesis of MSCs. On the other hand, Mast4 protein, which stability was enhanced by Wnt-mediated inhibition of GSK-3β and subsequent Smurf1 recruitment, promoted β-catenin nuclear localization and Runx2 activity, increasing osteogenesis of MSCs. Consistently, Mast4-/- mice demonstrated excessive cartilage synthesis, while exhibiting osteoporotic phenotype. Interestingly, Mast4 depletion in MSCs facilitated cartilage formation and regeneration in vivo. Altogether, our findings uncover essential roles of Mast4 in determining the fate of MSC development into cartilage or bone.

Material-Assisted Strategies for Osteochondral Defect Repair

The osteochondral (OC) unit plays a pivotal role in joint lubrication and in the transmission of constraints to bones during movement. The OC unit does not spontaneously heal; therefore, OC defects are considered to be one of the major risk factors for developing long-term degenerative joint diseases such as osteoarthritis. Yet, there is currently no curative treatment for OC defects, and OC regeneration remains an unmet medical challenge. In this context, a plethora of tissue engineering strategies have been envisioned over the last two decades, such as combining cells, biological molecules, and/or biomaterials, yet with little evidence of successful clinical transfer to date. This striking observation must be put into perspective with the difficulty in comparing studies to identify overall key elements for success. This systematic review aims to provide a deeper insight into the field of material-assisted strategies for OC regeneration, with particular considerations for the therapeutic potential of the different approaches (with or without cells or biological molecules), and current OC regeneration evaluation methods. After a brief description of the biological complexity of the OC unit, the recent literature is thoroughly analyzed, and the major pitfalls, emerging key elements, and new paths to success are identified and discussed.

Combined Mesenchymal Stem Cells and Cartilage Acellular Matrix Injection Therapy for Osteoarthritis in Goats

BACKGROUND

Human umbilical cord blood-derived MSCs (hUCB-MSCs) have been studied in osteoarthritis (OA) and cartilage regeneration. Our previous study demonstrated that hUCB-MSCs combined with cartilage acellular matrix injection (CAM Inj.) represent potential therapeutic agents for structural improvement and anti-inflammatory effects in a rabbit model of OA.

METHODS

Based on a previous study, this study has evaluated the safety and efficacy of hUCB-MSCs combined with CAM Inj. in an anterior cruciate ligament transection (ACLT) with medial meniscectomy (MMx) in a goat model. In this study, 27 goats were divided into 5 groups: normal (n = 3), OA (n = 6), OA + CAM Inj. (n = 6), OA + hUCB-MSCs (n = 6), and OA + hUCB-MSCs + CAM Inj. (n = 6). Lameness and radiographic parameters were assessed 6 months after administration, and macroscopic and histological evaluations of the goat articular cartilage were performed 6 months after intervention.

RESULTS

The results showed significant improvement in lameness score only in the OA + hUCB-MSCs group at 5 months after treatment (*p < 0.05), whereas the K&L score showed significant improvement only in the OA + hUCB-MSCs + CAM Inj. group 6 months after intervention (*p < 0.05). In addition, the gross findings showed significance in OA + CAM Inj. and OA + hUCB-MSCs + CAM Inj. groups 6 months after treatment (*p < 0.05 and **p < 0.01).

CONCLUSION

In conclusion, treatment with a combination of hUCB-MSCs and CAM Inj. reduced OA symptoms and induced effective cartilage tissue repair in a goat model. We suggest the combination of hUCB-MSCs and CAM Inj. as an alternative therapy for OA.

Infiltration of the Hoffa's fat pad in patients with osteoarthritis of the knee-Results after one year of follow-up

Objectives

Cell therapy using multipotential stromal cells (MSCs) is being used in a variety of clinical settings to induce tissue regeneration. Promising results have also been achieved in the therapy of osteoarthritis. MSCs have been demonstrated to be safe (Borakati et al., 2018). They can be used in a one step procedure as minimally manipulated mesenchymal stem cells or after in vitro expansion. The in vitro step allows for the selection of a more homogeneous cell population, meeting the standard criteria for MSC identification (Lv et al., 2014). In vitro expansion of MSCs is cost intensive, time consuming and furthermore associated with gradual accumulation of senescent cells (Wagner et al., 2008), telomere erosion (Baxter et al., 2004), and changing phenotypes (Jones et al., 2010; Halfon et al., 2011). These disadvantages could be surpassed by the use of “minimally manipulated mesenchymal stem cells” from bone marrow or adipose tissue (Di Matteo et al., 2019) such as the adipogenic stromal-vascular fraction (SVF).

The study investigates whether infiltration of the Hoffa fat pad with autologous SVF is an effective and safe treatment option for patients with gonarthrosis. Furthermore, the number and vitality of the injected cells as well as the clinical efficacy will be evaluated.

Materials and methods

We conduct a prospective study. Patients with osteoarthritis of the knee receive infiltration of SVF into the Hoffa fat pad. The number and vitality of the cells are measured with a cell counter. The clinical outcome is checked using VAS, KOOS and SF12 questionnaires with a follow-up period of 1 year.

Results

A total of 33 patients and 36 knees were included in this Study. An average of 45 million cells were injected with a standard deviation of 2,5 million Cells. After 6 months a significant improvement of the VAS and the respective subscales of the KOOS could be observed compared to the baseline. After one year of follow-up, a significant improvement in all KOOS subscales compared to baseline was still observed. A significant correlation between reduced knee pain on the VAS and the number of injected cells could be observed as well. Thus, patients injected with a higher number of cells seem to have a better outcome. The average viability of the cells was 64,4% with a standard deviation of 15,9%. A correlation between higher cell viability and better outcome on the QOL subscale of the KOOS was observed. There were no major complications or side effects.

Discussion

These initial results indicate that treatment with SVF is a safe therapeutic option that has the potential to relieve joint pain and significantly improved function. The cell number and vitality of the injected cells appear to be important factors influencing the success of the therapy.

Algorithm for Treatment of Focal Cartilage Defects of the Knee: Classic and New Procedures

OBJECTIVE

To create a treatment algorithm for focal grade 3 or 4 cartilage defects of the knee using both classic and novel cartilage restoration techniques.

DESIGN

A comprehensive review of the literature was performed highlighting classic as well as novel cartilage restoration techniques supported by clinical and/or basic science research and currently being employed by orthopedic surgeons.

RESULTS

There is a high level of evidence to support the treatment of small to medium size lesions (<2-4 cm2) without subchondral bone involvement with traditional techniques such as marrow stimulation, osteochondral autograft transplant (OAT), or osteochondral allograft transplant (OCA). Newer techniques such as autologous matrix-induced chondrogenesis and bone marrow aspirate concentrate implantation have also been shown to be effective in select studies. If subchondral bone loss is present OAT or OCA should be performed. For large lesions (>4 cm2), OCA or matrix autologous chondrocyte implantation (MACI) may be performed. OCA is preferred over MACI in the setting of subchondral bone involvement while cell-based modalities such as MACI or particulated juvenile allograft cartilage are preferred in the patellofemoral joint.

CONCLUSIONS

Numerous techniques exist for the orthopedic surgeon treating focal cartilage defects of the knee. Treatment strategies should be based on lesion size, lesion location, subchondral bone involvement, and the level of evidence supporting each technique in the literature.

ADSC-Based Cell Therapies for Musculoskeletal Disorders: A Review of Recent Clinical Trials

Recently published clinical trials involving the use of adipose-derived stem cells (ADSCs) indicated that approximately one-third of the studies were conducted on musculoskeletal disorders (MSD). MSD refers to a wide range of degenerative conditions of joints, bones, and muscles, and these conditions are the most common causes of chronic disability worldwide, being a major burden to the society. Conventional treatment modalities for MSD are not sufficient to correct the underlying structural abnormalities. Hence, ADSC-based cell therapies are being tested as a form of alternative, yet more effective, therapies in the management of MSDs. Therefore, in this review, MSDs subjected to the ADSC-based therapy were further categorized as arthritis, craniomaxillofacial defects, tendon/ligament related disorders, and spine disorders, and their brief characterization as well as the corresponding conventional therapeutic approaches with possible mechanisms with which ADSCs produce regenerative effects in disease-specific microenvironments were discussed to provide an overview of under which circumstances and on what bases the ADSC-based cell therapy was implemented. Providing an overview of the current status of ADSC-based cell therapy on MSDs can help to develop better and optimized strategies of ADSC-based therapeutics for MSDs as well as help to find novel clinical applications of ADSCs in the near future.

Cell Sources for Cartilage Repair-Biological and Clinical Perspective

Cell-based therapy represents a promising treatment strategy for cartilage defects. Alone or in combination with scaffolds/biological signals, these strategies open many new avenues for cartilage tissue engineering. However, the choice of the optimal cell source is not that straightforward. Currently, various types of differentiated cells (articular and nasal chondrocytes) and stem cells (mesenchymal stem cells, induced pluripotent stem cells) are being researched to objectively assess their merits and disadvantages with respect to the ability to repair damaged articular cartilage. In this paper, we focus on the different cell types used in cartilage treatment, first from a biological scientist’s perspective and then from a clinician’s standpoint. We compare and analyze the advantages and disadvantages of these cell types and offer a potential outlook for future research and clinical application.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

Umbilical cord mesenchymal stem/stromal cells potential to treat organ disorders; an emerging strategy

Currently, mesenchymal stem/stromal cells (MSCs) have attracted growing attention in the context of cell-based therapy in regenerative medicine. Following the first successful procurement of human MSCs from bone marrow (BM), these cells isolation has been conducted from various origins, in particular, the umbilical cord (UC). Umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs) can be acquired by a non-invasive plan and simply cultured, and thereby signifies their superiority over MSCs derived from other sources for medical purposes. Due to their unique attributes, including self-renewal, multipotency, and accessibility concomitant with their immunosuppressive competence and lower ethical concerns, UC-MSCs therapy is described as encouraging therapeutic options in cell-based therapies. Regardless of their unique aptitude to adjust inflammatory response during tissue recovery and delivering solid milieu for tissue restoration, UC-MSCs can be differentiated into a diverse spectrum of adult cells (e.g., osteoblast, chondrocyte, type II alveolar, hepatocyte, and cardiomyocyte). Interestingly, they demonstrate a prolonged survival and longer telomeres compared with MSCs derived from other sources, suggesting that UC-MSCs are desired source to use in regenerative medicine. In the present review, we deliver a brief review of UC-MSCs isolation, expansion concomitantly with immunosuppressive activities, and try to collect and discuss recent pre-clinical and clinical researches based on the use of UC-MSCs in regenerative medicine, focusing on with special focus on in vivo researches.

Therapeutic Effects of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Combined with Cartilage Acellular Matrix Mediated Via Bone Morphogenic Protein 6 in a Rabbit Model of Articular Cruciate Ligament Transection

Osteoarthritis (OA) is a general joint disease. Cartilage damage is associated with a decrease in the density of chondrocytes. Mesenchymal stem cells (MSCs) differentiate into adipocytes, osteocytes and chondrocytes, and are an excellent source of cell therapy. Cartilage-derived extracellular matrix (ECM) promotes chondrogenesis of MSCs. However, the role of MSCs stimulated by ECM is not well known in OA. The purpose of this study is to determine the role of specific factors generated by the application of ECM and umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) in managing OA symptoms. Cartilage acellular matrix (CAM), which is a cartilage-derived ECM, was used to promote the chondrogenesis of UCB-MSCs. Induced MSCs were analyzed using chondrogenic markers (aggrecan, collagen type 2, and SOX9) and bone morphogenic protein 6 (BMP6). BMP6 is known to be involved in early chondrogenesis of MSCs. As a result, treatment with CAM significantly increased the expression of chondrogenic markers and BMP6 in UCB-MSCs. Treatment with recombinant human BMP6 also dramatically increased the levels of chondrogenic markers in UCB-MSCs. In addition, UCB-MSCs and CAM were used to evaluate OA symptom improvement in a rabbit articular cruciate ligament transection (ACLT) model. Application of UCB-MSCs and CAM enhanced not only the structure and synthesis of proteoglycan and collagen type 2 but also anti-inflammatory effects in both rabbit joint and synovial fluid. Moreover, the detection of human cells and involvement of BMP6 were confirmed in rabbit cartilage tissues. This study indicates that therapeutic potential of UCB-MSCs with CAM is mediated via BMP6 in OA.

Adipose-Derived Stem Cells Promote Bone Coupling in Bisphosphonate-Related Osteonecrosis of the Jaw by TGF-β1

This study aimed to investigate molecularly targeted therapy to revive bone remodeling and prevent BRONJ by local adipose-derived stem cells (ADSCs) transplantation. Clinical samples of BRONJ and healthy jawbones were used to examine the bone coupling-related cells and TGF-β1 expression. Bone coupling-related cells and TGF-β1 expression were also assessed in BRONJ-like animal model to confirm the results in clinical samples. ADSCs were locally administered in vivo and the therapeutic effects were evaluated by gross observation, radiological imaging, and histological examination. Furthermore, ADSCs-conditioned medium (ADSCs-CM) and neutralizing antibody were applied to assess the effects of ADSCs-derived TGF-β1 on restoring bone coupling in vivo. Osteoclast formation and resorption assays were performed to evaluate the effects of ADSCs-derived TGF-β1 on ZA-treated pre-osteoclasts. Cell migration was performed to assess the effects of ADSCs-derived TGF-β1 on patients’ bone marrow stem cells (BMSCs). The number of osteoclasts, Runx2-positive bone-lining cells (BLCs) and TGF-β1 expression were decreased in BRONJ and animal model jaw bone samples. These reductions were significantly rescued and necrotic jawbone healing was effectively promoted by local ADSCs administration in BRONJ-like animal models. Mechanistically, ADSCs-CM mainly contributed to promoting bone coupling, while TGF-β1 neutralizing antibody in the conditioned medium inhibited these effects. Besides, osteoclastogenesis and patients’ BMSCs migration were also rescued by ADSCs-derived TGF-β1. Furthermore, bone resorption-released bone matrix TGF-β1, together with ADSCs-derived TGF-β1, synergistically contributed to rescuing BMSCs migration. Collectively, ADSCs promoted bone healing of BRONJ by TGF-β1-activated osteoclastogenesis and BMSCs migration capacities.

Secretome of human adipose-derived mesenchymal stem cell relieves pain and neuroinflammation independently of the route of administration in experimental osteoarthritis

OBJECTIVE

Treatment of pain associated with osteoarthritis (OA) is unsatisfactory and innovative approaches are needed. The secretome from human adipose-derived mesenchymal stem cells (hASC-Conditioned Medium, CM) has been successfully used to relieve painful symptoms in models of chronic pain. The aim of this study was to explore the efficacy of the hASC-CM to control pain and neuroinflammation in an animal model of OA.

METHODS

OA was induced in mice by intra-articular monosodium-iodoacetate (MIA) injection. Thermal hyperalgesia and mechanical allodynia were assessed. Once hypersensitivity was established (7 days after MIA), hASC-CM was injected by IA, IPL and IV route and its effect monitored over time. Neuroinflammation in nerve, dorsal root ganglia and spinal cord was evaluated measuring proinflammatory markers and mediators by RT-qPCR. Protein content analysis of secretome by Mass Spectrometry was performed.

RESULTS

A single injection with hASC-CM induced a fast and long lasting antihyperalgesic and antiallodynic effect. The IV route of administration appeared to be the most efficacious although all the treatments were effective. The effect on pain correlated with the ability of hASC-CM to reduce the neuroinflammatory condition in both the peripheral and central nervous system. Furthermore, the secretome analysis revealed 101 factors associated with immune regulation.

CONCLUSION

We suggest that hASC-CM is a valid treatment option for controlling OA-related hypersensitivity, exerting a rapid and long lasting pain relief. The mechanisms underpinning its effects are likely linked to the positive modulation of neuroinflammation in peripheral and central nervous system that sustains peripheral and central sensitization.

In Vivo Cartilage Regeneration with Cell-Seeded Natural Biomaterial Scaffold Implants: 15-Year Study

Articular cartilage can be easily damaged from human's daily activities, leading to inflammation and to osteoarthritis, a situation that can diminish the patients' quality of life. For larger cartilage defects, scaffolds are employed to provide cells the appropriate three-dimensional environment to proliferate and differentiate into healthy cartilage tissue. Natural biomaterials used as scaffolds, attract researchers' interest because of their relative nontoxic nature, their abundance as natural products, their easy combination with other materials, and the relative easiness to establish Marketing Authorization. The last 15 years were chosen to review, document, and elucidate the developments on cell-seeded natural biomaterials for articular cartilage treatment in vivo. The parameters of the experimental designs and their results were all documented and presented. Considerations about the newly formed cartilage and the treatment of cartilage defects were discussed, along with difficulties arising when applying natural materials, research limitations, and tissue engineering approaches for hyaline cartilage regeneration.

Substrate stiffness directs the phenotype and polarization state of cord blood derived macrophages

Cord blood (CB) mononuclear cell populations have demonstrated significant promise in biomaterials-based regenerative therapies; however, the contributions of monocyte and macrophage subpopulations towards proper tissue healing and regeneration are not well understood, and the phenotypic responses of macrophage to microenvironmental cues have not been well-studied. In this work, we evaluated the effects of cytokine stimulation and altered substrate stiffness. Macrophage derived from CB CD14⁺ monocytes adopted distinct inflammatory (M1) and anti-inflammatory (M2a and M2c) phenotypes in response to cytokine stimulation (M1: lipopolysaccharide (LPS) and interferon (IFN-γ); M2a: interleukin (IL)-4 and IL-13; M2c: IL-10) as determined through expression of relevant cell surface markers and growth factors. Cytokine-induced macrophage readily altered their phenotypes upon sequential administration of different cytokine cocktails. The impact of substrate stiffness on macrophage phenotype was evaluated by seeding CB-derived macrophage on 3wt%, 6wt%, and 14wt% poly(ethylene glycol)-based hydrogels, which exhibited swollen shear moduli of 0.1, 3.4, and 10.3 kPa, respectively. Surface marker expression and cytokine production varied depending on modulus, with anti-inflammatory phenotypes increasing with elevated substrate stiffness. Integration of specific hydrogel moduli and cytokine cocktail treatments resulted in the differential regulation of macrophage phenotypic biomarkers. These data suggest that CB-derived macrophages exhibit predictable behaviors that can be directed and finely tuned by combinatorial modulation of substrate physical properties and cytokine profiles.

Transplantation of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Improves Cartilage Repair in a Rabbit Model

The aim of this study was to investigate the therapeutic efficacy and safety of transplanting human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in the treatment of cartilage injury. First, the articular cartilage defect model in rabbits was constructed. Then, the identified hUCB-MSCs and rabbit bone marrow stem cells (rBM-MSCs) were transplanted into the bone defect, respectively, and the cartilage repair effect was observed by hematoxylin-eosin (HE) staining and immunohistochemistry. Besides, the glycosaminoglycan (GAG) content and biomechanics of the restoration area were also evaluated. In our study, hUCB-MSCs and rBM-MSCs exhibited typical MSC characteristics, with positive expressions of CD73, CD105, and CD90 and negative for CD45, CD34, CD14, and HLA-DR. After the transplantation of hUCB-MSCs and rBM-MSCs, the overall quality of cartilage tissue was significantly improved, and the recipients did not show significant side effects in general. However, the expression of matrix metalloproteinase-13 (MMP-13) in the de novo tissues of the hUCB-MSCs and rBM-MSCs groups was both increased, indicating that the novel tissues may have some potential osteoarthritic changes. In conclusion, our results suggest the therapeutic effect of hUCB-MSCs transplantation in cartilage regeneration, providing a promising future in the clinical treatment of cartilage injury.

Current status of regenerative medicine in osteoarthritis

The high prevalence of osteoarthritis (OA), as well as the current lack of disease-modifying drugs for OA, has provided a rationale for regenerative medicine as a possible treatment modality for OA treatment. In this editorial, the current status of regenerative medicine in OA including stem cells, exosomes, and genes is summarized along with the author’s perspectives. Despite a tremendous interest, so far there is very little evidence proving the efficacy of this modality for clinical application. As symptomatic relief is not sufficient to justify the high cost associated with regenerative medicine, definitive structural improvement that would last for years or decades and obviate or delay the need for joint arthroplasty is essential for regenerative medicine to retain a place among OA treatment methods.

Cite this article: Bone Joint Res 2021;10(2):134–136.

Cell-based strategies for IVD repair: clinical progress and translational obstacles

Intervertebral disc (IVD) degeneration is a major cause of low back pain, a prevalent and chronic condition that has a striking effect on quality of life. Currently, no approved pharmacological interventions or therapies are available that prevent the progressive destruction of the IVD; however, regenerative strategies are emerging that aim to modify the disease. Progress has been made in defining promising new treatments for disc disease, but considerable challenges remain along the entire translational spectrum, from understanding disease mechanism to useful interpretation of clinical trials, which make it difficult to achieve a unified understanding. These challenges include: an incomplete appreciation of the mechanisms of disc degeneration; a lack of standardized approaches in preclinical testing; in the context of cell therapy, a distinct lack of cohesion regarding the cell types being tested, the tissue source, expansion conditions and dose; the absence of guidelines regarding disease classification and patient stratification for clinical trial inclusion; and an incomplete understanding of the mechanisms underpinning therapeutic responses to cell delivery. This Review discusses current approaches to disc regeneration, with a particular focus on cell-based therapeutic strategies, including ongoing challenges, and attempts to provide a framework to interpret current data and guide future investigational studies.

Allogeneic Umbilical Cord Blood-Derived Mesenchymal Stem Cell Implantation Versus Microfracture for Large, Full-Thickness Cartilage Defects in Older Patients: A Multicenter Randomized Clinical Trial and Extended 5-Year Clinical Follow-up

Background:

There is currently no optimal method for cartilage restoration in large, full-thickness cartilage defects in older patients.

Purpose:

To determine whether implantation of a composite of allogeneic umbilical cord blood–derived mesenchymal stem cells and 4% hyaluronate (UCB-MSC-HA) will result in reliable cartilage restoration in patients with large, full-thickness cartilage defects and whether any clinical improvements can be maintained up to 5 years postoperatively.

Study Design:

Randomized controlled trial; Level of evidence, 1.

Methods:

A randomized controlled phase 3 clinical trial was conducted for 48 weeks, and the participants then underwent extended 5-year observational follow-up. Enrolled were patients with large, full-thickness cartilage defects (International Cartilage Repair Society [ICRS] grade 4) in a single compartment of the knee joint, as confirmed by arthroscopy. The defect was treated either with UCB-MSC-HA implantation through mini-arthrotomy or with microfracture. The primary outcome was proportion of participants who improved by ≥1 grade on the ICRS Macroscopic Cartilage Repair Assessment (blinded evaluation) at 48-week arthroscopy. Secondary outcomes included histologic assessment; changes in pain visual analog scale (VAS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and International Knee Documentation Committee (IKDC) score from baseline; and adverse events.

Results:

Among 114 randomized participants (mean age, 55.9 years; 67% female; body mass index, 26.2 kg/m²), 89 completed the phase 3 clinical trial and 73 were enrolled in the 5-year follow-up study. The mean defect size was 4.9 cm² in the UCB-MSC-HA group and 4.0 cm² in the microfracture group (P = .051). At 48 weeks, improvement by ≥1 ICRS grade was seen in 97.7% of the UCB-MSC-HA group versus 71.7% of the microfracture group (P = .001); the overall histologic assessment score was also superior in the UCB-MSC-HA group (P = .036). Improvement in VAS pain, WOMAC, and IKDC scores were not significantly different between the groups at 48 weeks, however the clinical results were significantly better in the UCB-MSC-HA group at 3- to 5-year follow-up (P < .05). There were no differences between the groups in adverse events.

Conclusion:

In older patients with symptomatic, large, full-thickness cartilage defects with or without osteoarthritis, UCB-MSC-HA implantation resulted in improved cartilage grade at second-look arthroscopy and provided more improvement in pain and function up to 5 years compared with microfracture.

Registration:

NCT01041001, NCT01626677 (ClinicalTrials.gov identifier).

Prospects for the therapeutic development of umbilical cord blood-derived mesenchymal stem cells

Umbilical cord blood (UCB) is a primitive and abundant source of mesenchymal stem cells (MSCs). UCB-derived MSCs have a broad and efficient therapeutic capacity to treat various diseases and disorders. Despite the high latent self-renewal and differentiation capacity of these cells, the safety, efficacy, and yield of MSCs expanded for ex vivo clinical applications remains a concern. However, immunomodulatory effects have emerged in various disease models, exhibiting specific mechanisms of action, such as cell migration and homing, angiogenesis, anti-apoptosis, proliferation, anti-cancer, anti-fibrosis, anti-inflammation and tissue regeneration. Herein, we review the current literature pertaining to the UCB-derived MSC application as potential treatment strategies, and discuss the concerns regarding the safety and mass production issues in future applications.

Machine learning to predict mesenchymal stem cell efficacy for cartilage repair

Inconsistent therapeutic efficacy of mesenchymal stem cells (MSCs) in regenerative medicine has been documented in many clinical trials. Precise prediction on the therapeutic outcome of a MSC therapy based on the patient's conditions would provide valuable references for clinicians to decide the treatment strategies. In this article, we performed a meta-analysis on MSC therapies for cartilage repair using machine learning. A small database was generated from published in vivo and clinical studies. The unique features of our neural network model in handling missing data and calculating prediction uncertainty enabled precise prediction of post-treatment cartilage repair scores with coefficient of determination of 0.637 ± 0.005. From this model, we identified defect area percentage, defect depth percentage, implantation cell number, body weight, tissue source, and the type of cartilage damage as critical properties that significant impact cartilage repair. A dosage of 17 - 25 million MSCs was found to achieve optimal cartilage repair. Further, critical thresholds at 6% and 64% of cartilage damage in area, and 22% and 56% in depth were predicted to significantly compromise on the efficacy of MSC therapy. This study, for the first time, demonstrated machine learning of patient-specific cartilage repair post MSC therapy. This approach can be applied to identify and investigate more critical properties involved in MSC-induced cartilage repair, and adapted for other clinical indications.

High tibial osteotomy with human umbilical cord blood-derived mesenchymal stem cells implantation for knee cartilage regeneration

BACKGROUND

High tibial osteotomy (HTO) is a well-established method for the treatment of medial compartment osteoarthritis of the knee with varus deformity. However, HTO alone cannot adequately repair the arthritic joint, necessitating cartilage regeneration therapy. Cartilage regeneration procedures with concomitant HTO are used to improve the clinical outcome in patients with varus deformity.

AIM

To evaluate cartilage regeneration after implantation of allogenic human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) with concomitant HTO.

METHODS

Data for patients who underwent implantation of hUCB-MSCs with concomitant HTO were evaluated. The patients included in this study were over 40 years old, had a varus deformity of more than 5°, and a full-thickness International Cartilage Repair Society (ICRS) grade IV articular cartilage lesion of more than 4 cm² in the medial compartment of the knee. All patients underwent second-look arthroscopy during hardware removal. Cartilage regeneration was evaluated macroscopically using the ICRS grading system in second-look arthroscopy. We also assessed the effects of patient characteristics, such as trochlear lesions, age, and lesion size, using patient medical records.

RESULTS

A total of 125 patients were included in the study, with an average age of 58.3 ± 6.8 years (range: 43-74 years old); 95 (76%) were female and 30 (24%) were male. The average hip-knee-ankle (HKA) angle for measuring varus deformity was 7.6° ± 2.4° (range: 5.0-14.2°). In second-look arthroscopy, the status of medial femoral condyle (MFC) cartilage was as follows: 73 (58.4%) patients with ICRS grade I, 37 (29.6%) with ICRS grade II, and 15 (12%) with ICRS grade III. No patients were staged with ICRS grade IV. Additionally, the scores [except International Knee Documentation Committee (IKDC) at 1 year] of the ICRS grade I group improved more significantly than those of the ICRS grade II and III groups.

CONCLUSION

Implantation of hUCB-MSCs with concomitant HTO is an effective treatment for patients with medial compartment osteoarthritis and varus deformity. Regeneration of cartilage improves the clinical outcomes for the patients.

Effects of umbilical cord mesenchymal stem cells loaded with graphene oxide granular lubrication on cytokine levels in animal models of knee osteoarthritis

BACKGROUND

The aim of this study was to use umbilical cord mesenchymal stem cells (UCMSCs) loaded with graphene oxide (GO) granular lubricant to treat knee osteoarthritis (KOA) animal models and to analyze their effect on cytokine levels in the articular cavity.

METHODS

Twenty-four New Zealand rabbit models of KOA were established by the modified Hulth and cartilage injury method, and they were assigned to the blank group, the GO group, the UCMSC group, and the GO + UCMSC group, each group containing six animal models. The GO and UCMSC groups were treated by a single intra-articular injection. The treatment was started one month after surgical modeling, and the observation period was eight weeks. The expression levels of nitric oxide (NO), interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), glycosaminoglycan (GAG), and collagen-II (COL-II) in serum and articular fluid after treatment were compared to analyze the efficacy.

RESULTS

The GO granular lubricant caused no significant improvement in the intra-articular environment of the knee joint, and UCMSCs caused a certain degree of improvement in the inflammatory environment. The improvement results of NO, IL-6, TNF-α, GAG, and COL-II were the best in the GO + UCMSC group, but the improvement results of inflammatory cytokine levels in serum and articular fluid were not consistent, especially the differences in NO, IL-6, and TNF-α were greater.

CONCLUSION

UCMSCs loaded with the GO granular lubricant can reduce the inflammatory level and improve the level of biochemical environment in the articular cavity, and thus promote cartilage repair.

Histological Comparison of Nanocomposite Multilayer Biomimetic Scaffold, A Chondral Scaffold, and Microfracture Technique to Repair Experimental Osteochondral Defects in Rats

Objective

We used biomimetic scaffolds, chondral scaffolds, and microfractures to repair experimentally created osteochondral defects in rat knees and then compared the results of each method.

Materials and Methods

We used a total of 56 female Wistar albino rats. The rats were grouped into 4 groups, with 14 rats each: biomimetic scaffold, chondral scaffold, microfracture, and control groups. Cylindrical full-thickness osteochondral defects 2.5 mm in diameter and 2 mm in depth were drilled into the right knees with the rats under general anesthesia. The knees of all rats were operated again after 4 weeks. Biomimetic and chondral scaffolds were classified into two groups. Microfractures 0.5 mm in diameter and 0.8 mm in depth were created in the rats of the microfracture group. The control group received no treatment. All the rats were observed for 6 weeks and then sacrificed, with samples subjected to macroscopic and histopathological examinations.

Results

The macroscopic and histopathological results in the biomimetic scaffold group differed significantly from those of the other treatment groups (p<0.05). When we compared the 3 treatment groups, the results of the chondral scaffold group were better than those of the microfracture group. The results of the microfracture group were somewhat better than those of the control group, but the result was not statistically significant (p>0.05).

Conclusions

Nanocomposite multilayer biomimetic scaffolds were better than chondral scaffolds and microfractures when used to treat osteochondral defects.

Regulation and function of SOX9 during cartilage development and regeneration

Chondrogenesis is a highly coordinated event in embryo development, adult homeostasis, and repair of the vertebrate cartilage. Fate decisions and differentiation of chondrocytes accompany differential expression of genes critical for each step of chondrogenesis. SOX9 is a master transcription factor that participates in sequential events in chondrogenesis by regulating a series of downstream factors in a stage-specific manner. SOX9 either works alone or in combination with downstream SOX transcription factors, SOX5 and SOX6 as chondrogenic SOX Trio. SOX9 is reduced in the articular cartilage of patients with osteoarthritis while highly maintained during tumorigenesis of cartilage and bone. Gene therapy using viral and non-viral vectors accompanied by tissue engineering (scaffolds) is a promising tool to regenerate impaired cartilage. Delivery of SOX9 or chondrogenic SOX Trio into cells produces efficient therapeutic effects on chondrogenesis and this event is facilitated by scaffolds. Non-viral vector-guided delivery systems encapsulated or loaded in mechanically stable solid scaffolds are useful for the regeneration of articular cartilage. Here we review major milestones and most recent studies focusing on regulation and function of chondrogenic SOX Trio, during chondrogenesis and cartilage regeneration, and on the development of advanced technologies in gene delivery with tissue engineering to improve efficiency of cartilage repair process.

Engineered cartilage utilizing fetal cartilage-derived progenitor cells for cartilage repair

The aim of this study was to develop a fetal cartilage-derived progenitor cell (FCPC) based cartilage gel through self-assembly for cartilage repair surgery, with clinically useful properties including adhesiveness, plasticity, and continued chondrogenic remodeling after transplantation. Characterization of the gels according to in vitro self-assembly period resulted in increased chondrogenic features over time. Adhesion strength of the cartilage gels were significantly higher compared to alginate gel, with the 2-wk group showing a near 20-fold higher strength (1.8 ± 0.15 kPa vs. 0.09 ± 0.01 kPa, p < 0.001). The in vivo remodeling process analysis of the 2 wk cultured gels showed increased cartilage repair characteristics and stiffness over time, with higher integration-failure stress compared to osteochondral autograft controls at 4 weeks (p < 0.01). In the nonhuman primate investigation, cartilage repair scores were significantly better in the gel group compared to defects alone after 24 weeks (p < 0.001). Cell distribution analysis at 24 weeks showed that human cells remained within the transplanted defects only. A self-assembled, FCPC-based cartilage gel showed chondrogenic repair potential as well as adhesive properties, beneficial for cartilage repair.

Single and repeated intra-articular injections in the tarsocrural joint with allogeneic and autologous equine bone marrow-derived mesenchymal stem cells are safe, but did not reduce acute inflammation in an experimental interleukin-1β model of synovitis

BACKGROUND

Allogeneic and autologous bone marrow-derived mesenchymal stem cells (BMDMSCs) have been administered in equine joints for their anti-inflammatory effects. However, allogeneic BMDMSC offer multiple clinical and practical advantages. Therefore, it is important to determine the relative effectiveness of allogeneic vs autologous BMDMSCs.

OBJECTIVES

The objective of the study was to compare the inflamed joint response to autologous vs allogeneic BMDMSCs injections, and to determine if either treatment generated an anti-inflammatory effect.

STUDY DESIGN

Randomised controlled study.

METHOD

Bone marrow was harvested from eight horses. Autologous BMDMSCs and pooled allogeneic BMDMSCs were culture expanded, cryopreserved and thawed immediately prior to administration. Ten million autologous BMDMSCs were administered with 75 ng rIL-1β into one tarsocrural joint and the contralateral tarsocrural joint received allogeneic BMDMSC plus 75 ng rIL-1β. Repeat injections were performed with the same treatment administered into the same joint. Four additional horses received 75 ng rIL-1β alone in a single tarsocrural joint. Clinical parameters (lameness, joint circumference and joint effusion) and synovial fluid parameters, including nucleated cell count (NCC), differential cell count, total protein (TP), prostaglandin E₂ (PGE₂ ) and C-reactive protein (CRP), were measured at baseline, 6, 12, 24, 72, 168 and 336 hours post-injection.

RESULTS

No difference was detected between autologous and allogeneic treatment groups with respect to subjective lameness, joint effusion, joint circumference, NCC, TP, differential cell count, CRP or PGE₂ . Neither autologous nor allogeneic treatments resulted in an improvement in clinical or cytological parameters over that elicited by rIL-1β alone.

MAIN LIMITATIONS

A single dose of rIL-1β was evaluated and resulted in a severe synovitis which may have been too severe to observe a BMDMSC-mediated effect.

CONCLUSIONS

This study revealed that allogeneic and autologous BMDMSCs resulted in an equivalent clinical and cytological response. Allogeneic and autologous BMDMSCs were equally ineffective in reducing the inflammatory response from acute rIL-1β-induced joint inflammation in horses.

Systematic Review of Human Dental Pulp Stem Cells for Cartilage Regeneration

Background: Symptomatic cartilage lesions and early osteoarthritis produce significant clinical and economic burdens. Cartilage repair can improve the symptoms and delay arthroplasty. The complete healing of damaged cartilage with the consistent reproduction of normal hyaline cartilage has not yet been achieved. The choice of harvesting site might influence the cells' abilities to modulate immunologic and inflammatory responses. Recently, dental pulp has been shown to contain a stem cell niche consisting of dental pulp stem cells (DPSCs) that maintain their self-renewal capacity due to the active environment in the dental pulp of deciduous teeth. Objective: The aim of this study was to critically review the current literature on the potential and limitations of the use of dental pulp-derived mesenchymal stem cells in cell-based therapies for cartilage regeneration. Methods: An electronic, customized search of scientific articles was conducted using the PubMed/MEDLINE and EMBASE databases from their inception to December 2018. The inclusion criteria were applied, and the articles that described the use of DPSC in cartilage treatment were selected for complete evaluation. The articles were classified according to the scaffold used, experimental model, chondrogenic differentiation features, defect location, cartilage evaluation, and results. After the application of the eligibility criteria, a total of nine studies were selected and fully analyzed. Results: A variety of animal models were used, including mice, rats, rabbits, and miniature pigs, to evaluate the quality and safety of human DPSCs in the repair of cartilage defects. Among the articles, two studies focused on preclinical models of cartilage tissue engineering. Five studies implanted DPSCs in other animal sites. Conclusion: The use of DPSCs is a potential new stem cell therapy for articular cartilage repair. The preclinical evidence discussed in this article provides a solid foundation for future clinical trials. Impact statement Osteoarthritis presents an ever-increasing clinical and socioeconomic burden. While cartilage repair has the potential to improve symptoms and delay joint replacement, complete regeneration of hyaline cartilage has been an elusive goal. Dental pulp has been shown to contain a niche that protects dental pulp stem cells (DPSCs) from the cumulative effects of genetic and environmental factors and maintains their self-renewal capacity due to the active environment. Transplantation and preclinical trials have demonstrated the strong potential of regenerative tissue-engineering protocols using DPSCs.

The Effect of Blood-Derived Products on the Chondrogenic and Osteogenic Differentiation Potential of Adipose-Derived Mesenchymal Stem Cells Originated from Three Different Locations

Background

Adipose-derived mesenchymal stem cells (AD-MSCs) from fat tissue considered “surgical waste” during joint surgery may provide a potent source for regenerative medicine. Intra-articular, homologous fat tissue (Hoffa's fat pad, pouch fat) might possess a superior chondrogenic and osteogenic differentiation potential in comparison to extra-articular, nonhomologous fat. Blood products might further enhance this potential.

Methods

AD-MSCs were isolated from fat tissue of 3 donors from 3 locations each, during total knee replacement. Isolated cells were analyzed via flow cytometry. Cells were supplemented with blood products: two types of platelet-rich plasma (EPRP—PRP prepared in the presence of EDTA; CPRP—PRP prepared in the presence of citrate), hyperacute serum (hypACT), and standard fetal calf serum (FCS) as a positive control. The viability of the cells was determined by XTT assay, and the progress of differentiation was tested via histological staining and monitoring of specific gene expression.

Results

Blood products enhance ex vivo cell metabolism. Chondrogenesis is enhanced by EDTA-PRP and osteogenesis by citrate PRP, whereas hyperacute serum enhances both differentiations comparably. This finding was consistent in histological analysis as well as in gene expression. Lower blood product concentrations and shorter differentiation periods lead to superior histological results for chondrogenesis. Both PRP types had a different biological effect depending upon concentration, whereas hyperacute serum seemed to have a more consistent effect, independent of the used concentration.

Conclusion

(i) Blood product preparation method, (ii) type of anticoagulant, (iii) differentiation time, and (iv) blood product concentration have a significant influence on stem cell viability and the differentiation potential, favouring no use of anticoagulation, shorter differentiation time, and lower blood product concentrations. Cell-free blood products like hyperacute serum may be considered as an alternative supplementation in regenerative medicine, especially for stem cell therapies.

Therapeutic "Tool" in Reconstruction and Regeneration of Tissue Engineering for Osteochondral Repair

Repairing osteochondral defects to restore joint function is a major challenge in regenerative medicine. However, with recent advances in tissue engineering, the development of potential treatments is promising. In recent years, in addition to single-layer scaffolds, double-layer or multilayer scaffolds have been prepared to mimic the structure of articular cartilage and subchondral bone for osteochondral repair. Although there are a range of different cells such as umbilical cord stem cells, bone marrow mesenchyml stem cell, and others that can be used, the availability, ease of preparation, and the osteogenic and chondrogenic capacity of these cells are important factors that will influence its selection for tissue engineering. Furthermore, appropriate cell proliferation and differentiation of these cells is also key for the optimal repair of osteochondral defects. The development of bioreactors has enhanced methods to stimulate the proliferation and differentiation of cells. In this review, we summarize the recent advances in tissue engineering, including the development of layered scaffolds, cells, and bioreactors that have changed the approach towards the development of novel treatments for osteochondral repair.

Intra-articularly injected mesenchymal stem cells promote cartilage regeneration, but do not permanently engraft in distant organs

Intra-articular (IA) injection of mesenchymal stem cells (MSCs) promotes articular cartilage repair. However, cell fate and action after transplantation remain unclear. This study aimed at evaluating the biodistribution and efficacy of MSCs after IA injection. We used an immunocompetent, dual transgenic rat model, which is based on donor rats ubiquitously expressing heat stable human placental alkaline phosphatase (ALPP), and recipient rats expressing a heat sensitive ALPP form. A focal cartilage defect was created in the patellofemoral groove of recipient rats. Bone marrow-derived MSCs isolated from donor rats were injected into the synovial cavity of recipients, and cell tracking was performed in distant organs and knees over 6 months post-injection. A few donor MSCs were observed in the lung of one of the recipients, 1 day post-injection. We failed to detect donor MSCs in any of the studied tissues at all later time points. IA-injected MSCs remained in the synovial cavity, engrafted within the cartilage lesion, and were detectable up to 1 month post-injection. Although the number of MSCs decreased over time, MSCs injection promoted cartilage regeneration as evidenced by histology and immunofluorescent collagen staining. Our study supports the safety and efficacy of using MSCs for cartilage repair via IA delivery.

Comparison of Undifferentiated Versus Chondrogenic Predifferentiated Mesenchymal Stem Cells Derived From Human Umbilical Cord Blood for Cartilage Repair in a Rat Model

BACKGROUND

Human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) have gained much interest as a promising cell source for regenerative medicine owing to the noninvasive collection, availability, high expansion capacity, and low immunogenicity. However, few in vivo studies have reported the use of hUCB-MSCs on cartilage repair. Moreover, little study has been conducted on the effects of chondrogenic predifferentiation of hUCB-MSCs on cartilage repair.

PURPOSE

To compare the effectiveness of transplanting undifferentiated versus chondrogenic predifferentiated mesenchymal stem cells (MSCs) for treating osteochondral defects.

STUDY DESIGN

Controlled laboratory study.

METHODS

Critical-sized osteochondral defects were created in the trochlear grooves of rat femurs. In 20 rats, a composite of chondrogenic predifferentiated hUCB-MSCs (chondro-MSCs) and 4% hyaluronic acid (HA) hydrogel was transplanted into defects in the right knees, whereas undifferentiated hUCB-MSCs (undiff-MSCs) and 4% HA hydrogel were transplanted into the left knees. In the control groups, 4% HA hydrogel without MSCs was transplanted into defects in the right knees, and the defects in the left knees were left untreated in 20 rats. The cartilage repair was evaluated at 8 and 16 weeks after surgery.

RESULTS

Transplanting undiff-MSCs resulted in overall superior cartilage repair as compared with chondro-MSCs, HA alone, or no treatment. The articular surfaces of the defect sites in the undiff-MSC group were relatively smoother than those of the other treatments. The undiff-MSC group showed cellular morphology and arrangement similar to surrounding normal articular cartilage tissue at 16 weeks, both of which were also better than those of the other groups. In addition, the undiff-MSC group showed coloration similar to surrounding normal articular cartilage tissue at 16 weeks in safranin O and type II collagen immunohistochemical staining. The histological scores also revealed that cartilage repair with undiff-MSCs was better than that with chondro-MSCs, HA alone, or no treatment ( P < .05 in all).

CONCLUSION

This study demonstrated that treatment with undiff-MSCs resulted in more favorable cartilage repair than that with chondro-MSCs in a rat model. These findings indicate that chondrogenic predifferentiation of MSCs before transplantation does not enhance cartilage repair.

CLINICAL RELEVANCE

The results of this study support the use of undifferentiated MSCs, rather than chondrogenic predifferentiated MSCs, as a stem cell therapy strategy for cartilage repair.

Intra-articular Mesenchymal Stem Cells in Osteoarthritis of the Knee: A Systematic Review of Clinical Outcomes and Evidence of Cartilage Repair

PURPOSE

To provide a systematic review of the clinical literature reporting the efficacy of mesenchymal stem cells (MSCs) in terms of clinical outcomes including pain and function and cartilage repair in patients with osteoarthritis.

METHODS

We systematically reviewed any studies investigating clinical outcomes and cartilage repair after the clinical application of cell populations containing MSCs in human subjects with knee osteoarthritis through MEDLINE, EMBASE, the Cochrane Library, CINAHL, Web of Science, and Scopus. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Studies with a level of evidence of IV or V were excluded. Methodological quality was assessed using the Modified Coleman Methodology Score. Clinical outcomes were assessed using clinical scores, and cartilage repair was assessed using magnetic resonance imaging and second-look arthroscopy findings.

RESULTS

A total of 17 studies that met the criteria of 50 full-text studies were included in this review, with 6 randomized controlled trials, 8 prospective observational studies, and 3 retrospective case-control studies. Among 17 studies, 8 studies used bone marrow-derived MSCs, 6 used adipose tissue-derived stromal vascular fraction, 2 used adipose tissue-derived MSCs, and 1 used umbilical cord blood-derived MSCs. All studies except 2 reported significantly better clinical outcomes in the MSC group or improved clinical outcomes at final follow-up. In terms of cartilage repair, 9 of 11 studies reported improvement of the cartilage state on magnetic resonance imaging, and 6 of 7 studies reported repaired tissue on second-look arthroscopy. The mean Modified Coleman Methodology Score was 55.5 ± 15.5 (range, 28-74).

CONCLUSIONS

Intra-articular MSCs provide improvements in pain and function in knee osteoarthritis at short-term follow-up (<28 months) in many cases. Some efficacy has been shown of MSCs for cartilage repair in osteoarthritis; however, the evidence of efficacy of intra-articular MSCs on both clinical outcomes and cartilage repair remains limited.

LEVEL OF EVIDENCE

Level III; systematic review of level I, II, and III studies.

Comparative efficacy of stem cells and secretome in articular cartilage regeneration: a systematic review and meta-analysis

Articular cartilage defect remains the most challenging joint disease due to limited intrinsic healing capacity of the cartilage that most often progresses to osteoarthritis. In recent years, stem cell therapy has evolved as therapeutic strategies for articular cartilage regeneration. However, a number of studies have shown that therapeutic efficacy of stem cell transplantation is attributed to multiple secreted factors that modulate the surrounding milieu to evoke reparative processes. This systematic review and meta-analysis aim to evaluate and compare the therapeutic efficacy of stem cell and secretome in articular cartilage regeneration in animal models. We systematically searched the PubMed, CINAHL, Cochrane Library, Ovid Medline and Scopus databases until August 2017 using search terms related to stem cells, cartilage regeneration and animals. A random effect meta-analysis of the included studies was performed to assess the treatment effects on new cartilage formation on an absolute score of 0-100% scale. Subgroup analyses were also performed by sorting studies independently based on similar characteristics. The pooled analysis of 59 studies that utilized stem cells significantly improved new cartilage formation by 25.99% as compared with control. Similarly, the secretome also significantly increased cartilage regeneration by 26.08% in comparison to the control. Subgroup analyses revealed no significant difference in the effect of stem cells in new cartilage formation. However, there was a significant decline in the effect of stem cells in articular cartilage regeneration during long-term follow-up, suggesting that the duration of follow-up is a predictor of new cartilage formation. Secretome has shown a similar effect to stem cells in new cartilage formation. The risk of bias assessment showed poor reporting for most studies thereby limiting the actual risk of bias assessment. The present study suggests that both stem cells and secretome interventions improve cartilage regeneration in animal trials. Graphical abstract ᅟ.

Stem Cell Therapy for Articular Cartilage Repair: Review of the Entity of Cell Populations Used and the Result of the Clinical Application of Each Entity

BACKGROUND

Following successful preclinical studies, stem cell therapy is emerging as a candidate for the treatment of articular cartilage lesions. Because stem cell therapy for cartilage repair in humans is at an early phase, confusion and errors are found in the literature regarding use of the term stem cell therapy in this field.

PURPOSE

To provide an overview of the outcomes of cartilage repair, elucidating the various cell populations used, and thus reduce confusion with regard to using the term stem cell therapy.

STUDY DESIGN

Systematic review.

METHODS

The authors systematically reviewed any studies on clinical application of mesenchymal stem cells (MSCs) in human subjects. A comprehensive search was performed in MEDLINE, EMBASE, the Cochrane Library, CINAHL, Web of Science, and Scopus for human studies that evaluated articular cartilage repair with cell populations containing MSCs. These studies were classified as using bone marrow-derived MSCs, adipose tissue-derived MSCs, peripheral blood-derived MSCs, synovium-derived MSCs, and umbilical cord blood-derived MSCs according to the entity of cell population used.

RESULTS

Forty-six clinical studies were identified to focus on cartilage repair with MSCs: 20 studies with bone marrow-derived MSCs, 21 studies with adipose tissue-derived MSCs, 3 studies with peripheral blood-derived MSCs, 1 study with synovium-derived MSCs, and 1 study with umbilical cord blood-derived MSCs. All clinical studies reported that cartilage treated with MSCs showed favorable clinical outcomes in terms of clinical scores or cartilage repair evaluated by MRI. However, most studies were limited to case reports and case series. Among these 46 clinical studies, 18 studies erroneously referred to adipose tissue-derived stromal vascular fractions as "adipose-derived MSCs," 2 studies referred to peripheral blood-derived progenitor cells as "peripheral blood-derived MSCs," and 1 study referred to bone marrow aspirate concentrate as "bone marrow-derived MSCs."

CONCLUSION

Limited evidence is available regarding clinical benefit of stem cell therapy for articular cartilage repair. Because the literature contains substantial errors in describing the therapeutic cells used, researchers need to be alert and observant of proper terms, especially regarding whether the cells used were stem cells or cell populations containing a small portion of stem cells, to prevent confusion in understanding the results of a given stem cell-based therapy.

Advances in stem cell therapy for cartilage regeneration in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a progressive joint disease that compromises the structural integrity of cartilage tissue. Conventional treatments based on medication or surgery are nowadays inefficient and cell-based therapy has emerged as one of the most promising methods for cartilage regeneration. The first therapy developed for cartilage defects was autologous chondrocyte implantation, but in the last few decades stem cells (SCs) from different sources have been proposed as a possible alternative for OA.

AREAS COVERED

SC sources and available delivery procedures (scaffolds/hydrogels) are presented, along with the main issues arisen in this regard. Thereafter, preclinical and clinical trials performed in recent years are reviewed in order to take a glance toward the potential benefits that such therapies could deliver to the patients.

EXPERT OPINION

SCs have proven their potential and safety for OA treatment. Nevertheless, there are still many questions to be resolved before their widespread used in clinical practice, such as the treatment mechanism, the best cell source, the most appropriate processing method, the most effective dose and delivery procedure, and their efficacy. In this sense, long-term follow-up and larger randomized controlled trials utilizing standardized and established outcome scores are mandatory to make objective conclusions.