Mesenchymal stem cells for cartilage regeneration

Electrophoretically deposited Asphaltum punjabianum (Shilajit) coatings on polyvinylalcohol/carboxymethylcellulose hydrogels

The present study aims to develop Asphaltum punjabianum (namely Shilajit) coated Polyvinyl alcohol (PVA)/Carboxymethyl cellulose (CMC) hydrogels and examine their structural, morphological, degradation, and biological properties. Hydrogels were produced at two different concentrations: 70:30 PVA/CMC and 90:10 PVA/CMC. Following that, Shilajit was applied to the synthesized hydrogels using electrophoretic deposition for a duration of 3 min at 30 V. The scanning electron microscopy images showed that the hydrogel's surface had a regular distribution of irregular Shilajit particles. Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the presence of hydrogen bonding between PVA and CMC hydrogels and Shilajit, indicating the successful deposition of Shilajit on the hydrogel. The hydrogels coated with Shilajit exhibited strong antimicrobial activity, resulting in an inhibition zone measuring 34 mm against Escherichia coli (E. coli) and 41 mm against Staphylococcus aureus (S. aureus). The hydrogels exhibited a cell viability of 80 % with mesenchymal stem cells (MSCs), and the release of collagen II also increased. Furthermore, the PVA/CMC/Shilajit hydrogel exhibited a lower degradation rate compared to the PVA/CMC hydrogel. The results of the swelling, degradation, and drug release studies indicate that the shilajit coating is appropriate for the long-term process of tissue and cartilage regeneration.

Effects of Germanium embedded fabric on the chondrogenic differentiation of adipose derived stem cells

Osteoarthritis (OA) is a clinical state which is identified by the degeneration of articular cartilage. OA is a common condition (>500 millions of people affected worldwide), whose frequency is anticipated to continue to rise (> 110 % increase worldwide since 2019). The treatment for early-stage OA is based on a combination of therapeutic approaches, which can include regenerative medicine based on Adipose Derived Stem Cells (ADSCs). Germanium embedded Incrediwear® functional Cred40 fabric has been shown to have positive effects on OA clinically and is envisaged to give encouraging effects also on tissue regeneration. Still, the biological mechanisms underlying this therapeutic modality have not yet been fully defined. We tested the hypothesis that Germanium-embedded Incrediwear® functional Cred40 fabric could enhance chondrogenic differentiation. To this purpose, we applied Incrediwear® to human adipose-derived stem cells (hADSCs) induced to chondrogenic differentiation in vitro. Chondrogenic markers (ACAN, SOX9, RUNX2, COL2A1, COL10A1) were quantified following 21 days of treatment. We also assessed extracellular matrix (ECM) deposition (specifically Collagen and glycosaminoglycans (GAGs)) using Alcian Blue and Sirius Red staining. Here, we provide pilot data to demonstrate that Germanium-embedded Incrediwear® functional Cred40 fabric can enhance hADSCs chondrogenic differentiation and maturity and potentially induce events of cartilage regeneration.

Macroporous PEG-Alginate Hybrid Double-Network Cryogels with Tunable Degradation Rates Prepared via Radical-Free Cross-Linking for Cartilage Tissue Engineering

Trauma or repeated damage to joints can result in focal cartilage defects, significantly elevating the risk of osteoarthritis. Damaged cartilage has an inherently limited self-healing capacity and remains an urgent unmet clinical need. Consequently, there is growing interest in biodegradable hydrogels as potential scaffolds for the repair or reconstruction of cartilage defects. Here, we developed a biodegradable and macroporous hybrid double-network (DN) cryogel by combining two independently cross-linked networks of multiarm polyethylene glycol (PEG) acrylate and alginate.Hybrid DN cryogels are formed using highly biocompatible click reactions for the PEG network and ionic bonding for the alginate network. By judicious selection of various structurally similar cross-linkers to form the PEG network, we can generate hybrid DN cryogels with customizable degradation kinetics. The resulting PEG-alginate hybrid DN cryogels have an interconnected macroporous structure, high mechanical strength, and rapid swelling kinetics. The interconnected macropores in the cryogels support efficient mesenchymal stem cell infiltration at a high density. Finally, we demonstrate that PEG-alginate hybrid DN cryogels allow sustained release of chondrogenic growth factors and support chondrogenic differentiation of mouse mesenchymal stem cells. This study provides a novel method to generate macroporous hybrid DN cryogels with customizable degradation rates and a potential scaffold for cartilage tissue engineering.

Current Non-Surgical Curative Regenerative Therapies for Knee Osteoarthritis

Osteoarthritis (OA) is a prevalent musculoskeletal disease affecting middle-aged and elderly individuals, with knee pain as a common complaint. Standard therapy approaches generally attempt to alleviate pain and inflammation, using various pharmacological and non-pharmacological options. However, the efficacy of these therapies in long-term tissue repair remains debated. As an alternative, regenerative medicine offers a promising strategy, with decreased adverse event rates and increasing evidence of safety and efficacy. This review will outline current advances in regenerative medicine for knee OA, emphasizing outpatient clinic-based therapies that use orthobiological and non-biological products. Different strategies based on orthobiologics are discussed as potential regenerative options for the management of knee OA. Cell-free therapies including platelet-rich plasma, autologous anti-inflammatories, exosomes, human placenta extract, and mitochondrial transplantation are discussed, focusing on their potential for cartilage regeneration. Additionally, cell-based therapies with regenerative properties including bone marrow aspirate concentrate, adipose stromal vascular fraction, microfat, nanofat, stem cell therapy, and genetically modified cells as part of orthobiologics, are being investigated. Also, this study is looking into non-biological approaches such as using gold-induced cytokines, extracorporeal shockwave therapy, and ozone therapy. The mechanisms of action, effectiveness, and clinical applications of each therapy are being explored, providing insights into their role in the management of knee OA.

Dental pulp stem cells-derived cannabidiol-treated organoid-like microspheroids show robust osteogenic potential via upregulation of WNT6

Dental pulp stem cells (DPSC) have shown osteogenic and bone regenerative potential. Improving the in situ bone regeneration potential of DPSC is crucial for their application as seed cells during bone defect reconstruction in clinics. This study aimed to develop DPSC-derived organoid-like microspheroids as effective seeds for bone tissue engineering applications. DPSC osteogenic microspheroids (70 μm diameter) were cultured in a polydimethylsiloxane-mold-based agarose-gel microwell-culture-system with or without cannabidiol (CBD)-treatment. Results of in vitro studies showed higher osteogenic differentiation potential of microspheroids compared with 2D-cultured-DPSC. CBD treatment further improved the osteogenic differentiation potential of microspheroids. The effect of CBD treatment in the osteogenic differentiation of microspheroids was more pronounced compared with that of CBD-treated 2D-cultured-DPSC. Microspheroids showed a higher degree of bone regeneration in nude mice calvarial bone defect compared to 2D-cultured-DPSC. CBD-treated microspheroids showed the most robust in situ bone regenerative potential compared with microspheroids or CBD-treated 2D-cultured-DPSC. According to mRNA sequencing, bioinformatic analysis, and confirmation study, the higher osteogenic potential of CBD-treated microspheroids was mainly attributed to WNT6 upregulation. Taken together, DPSC microspheroids have robust osteogenic potential and can effectively translate the effect of in vitro osteoinductive stimulation during in situ bone regeneration, indicating their application potential during bone defect reconstruction in clinics.

Tissue-Engineered Implant for Hemilaryngectomy Reconstruction with Recurrent Laryngeal Nerve Injury

OBJECTIVE

Laryngeal cancer resections often require excision of portions of the larynx along with sacrifice of the ipsilateral recurrent laryngeal nerve (RLN). In such cases, there are no reconstructive options that reliably restore laryngeal function, rendering patients with severe functional impairment. To address this unmet clinical need, we extend our evaluation of a 3-implant mucosal, muscle, cartilage reconstruction approach aimed at promoting functional laryngeal restoration in a porcine hemilaryngectomy model with ipsilateral RLN transection.

METHODS

Six Yucatan mini-pigs underwent full-thickness hemilaryngectomies with RLN transection followed by transmural reconstruction using fabricated collagen polymeric mucosal, muscle, and cartilage replacements. To determine the effect of adding therapeutic cell populations, subsets of animals received collagen muscle implants containing motor-endplate-expressing muscle progenitor cells (MEEs) and/or collagen cartilage implants containing adipose stem cell (ASC)-derived chondrocyte-like cells. Acoustic vocalization and laryngeal electromyography (L-EMG) provided functional assessments and histopathological analysis with immunostaining was used to characterize the tissue response.

RESULTS

Five of six animals survived the 4-week postoperative period with weight gain, airway maintenance, and audible phonation. No tracheostomy or feeding tube was required. Gross and histological assessments of all animals revealed implant integration and regenerative remodeling of airway mucosa epithelium, muscle, and cartilage in the absence of a material-mediated foreign body reaction or biodegradation. Early voice and L-EMG data were suggestive of positive functional outcomes.

CONCLUSION

Laryngeal reconstruction with collagen polymeric mucosa, muscle, and cartilage replacements may provide effective restoration of function after hemilaryngectomy with RLN transection. Future preclinical studies should focus on long-term functional outcomes.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Progress on Electro-Enhancement of Cell Manufacturing

With the long persistence of complex, chronic diseases in society, there is increasing motivation to develop cells as living medicine to treat diseases ranging from cancer to wounds. While cell therapies can significantly impact healthcare, the shortage of starter cells meant that considerable raw materials must be channeled solely for cell expansion, leading to expensive products with long manufacturing time which can prevent accessibility by patients who either cannot afford the treatment or have highly aggressive diseases and cannot wait that long. Over the last three decades, there has been increasing knowledge on the effects of electrical modulation on proliferation, but to the best of the knowledge, none of these studies went beyond how electro-control of cell proliferation may be extended to enhance industrial scale cell manufacturing. Here, this review is started by discussing the importance of maximizing cell yield during manufacturing before comparing strategies spanning biomolecular/chemical/physical to modulate cell proliferation. Next, the authors describe how factors governing invasive and non-invasive electrical stimulation (ES) including capacitive coupling electric field may be modified to boost cell manufacturing. This review concludes by describing what needs to be urgently performed to bridge the gap between academic investigation of ES to industrial applications.

Recent advancements in cartilage tissue engineering innovation and translation

Articular cartilage was expected to be one of the first successfully engineered tissues, but today, cartilage repair products are few and they exhibit considerable limitations. For example, of the cell-based products that are available globally, only one is marketed for non-knee indications, none are indicated for severe osteoarthritis or rheumatoid arthritis, and only one is approved for marketing in the USA. However, advances in cartilage tissue engineering might now finally lead to the development of new cartilage repair products. To understand the potential in this field, it helps to consider the current landscape of tissue-engineered products for articular cartilage repair and particularly cell-based therapies. Advances relating to cell sources, bioactive stimuli and scaffold or scaffold-free approaches should now contribute to progress in therapeutic development. Engineering for an inflammatory environment is required because of the need for implants to withstand immune challenge within joints affected by osteoarthritis or rheumatoid arthritis. Bringing additional cartilage repair products to the market will require an understanding of the translational vector for their commercialization. Advances thus far can facilitate the future translation of engineered cartilage products to benefit the millions of patients who suffer from cartilage injuries and arthritides.

Translating mesenchymal stem cell and their exosome research into GMP compliant advanced therapy products: Promises, problems and prospects

Mesenchymal stem cells (MSCs) are one of the few stem cell types used in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair, due to their unique paracrine capacity, multiple differentiation potential, active components in exosomes, and effective mitochondria donation. At present, MSCs derived from tissues such as bone marrow and umbilical cord are widely applied in preclinical and clinical studies. Nevertheless, there remain challenges to the maintenance of consistently good quality MSCs derived from different donors or tissues, directly impacting their application as advanced therapy products. In this review, we discuss the promises, problems, and prospects associated with translation of MSC research into a pharmaceutical product. We review the hurdles encountered in translation of MSCs and MSC-exosomes from the research bench to an advanced therapy product compliant with good manufacturing practice (GMP). These difficulties include how to set up GMP-compliant protocols, what factors affect raw material selection, cell expansion to product formulation, establishment of quality control (QC) parameters, and quality assurance to comply with GMP standards. To avoid human error and reduce the risk of contamination, an automatic, closed system that allows real-time monitoring of QC should be considered. We also highlight potential advantages of pluripotent stem cells as an alternative source for MSC and exosomes generation and manufacture.

Adipose-derived regenerative therapies for the treatment of knee osteoarthritis

Knee osteoarthritis is a degenerative condition with a significant disease burden and no disease-modifying therapy. Definitive treatment ultimately requires joint replacement. Therapies capable of regenerating cartilage could significantly reduce financial and clinical costs. The regenerative potential of mesenchymal stromal cells (MSCs) has been extensively studied in the context of knee osteoarthritis. This has yielded promising results in human studies, and is likely a product of immunomodulatory and chondroprotective biomolecules produced by MSCs in response to inflammation. Adipose-derived MSCs (ASCs) are becoming increasingly popular owing to their relative ease of isolation and high proliferative capacity. Stromal vascular fraction (SVF) and micro-fragmented adipose tissue (MFAT) are produced by the enzymatic and mechanical disruption of adipose tissue, respectively. This avoids expansion of isolated ASCs ex vivo and their composition of heterogeneous cell populations, including immune cells, may potentiate the reparative function of ASCs. In this editorial, we comment on a multicenter randomized trial regarding the efficacy of MFAT in treating knee osteoarthritis. We discuss the study's findings in the context of emerging evidence regarding adipose-derived regenerative therapies. An underlying mechanism of action of ASCs is proposed while drawing important distinctions between the properties of isolated ASCs, SVF, and MFAT.

Continuous Low-Intensity Ultrasound Improves Cartilage Repair in Rabbit Model of Subchondral Injury

Subchondral drilling (SD), a bone marrow stimulation technique, is used to repair cartilage lesions that lack regenerative potential. Cartilage repair outcomes upon SD are typically fibrocartilaginous in nature with inferior functionality. The lack of cues to foster the chondrogenic differentiation of egressed mesenchymal stromal cells upon SD can be attributed for the poor outcomes. Continuous low-intensity ultrasound (cLIUS) at 3.8 MHz is proposed as a treatment modality for improving cartilage repair outcomes upon marrow stimulation. Bilateral defects were created by SD on the femoral medial condyle of female New Zealand white rabbits (n = 12), and the left joint received cLIUS treatment (3.8 MHz, 3.5 Vpp, 8 min/application/day) and the contralateral right joint served as the control. On day 7 postsurgery, synovial fluid was aspirated, and the cytokine levels were assessed by Quantibody™ assay. Rabbits were euthanized at 8 weeks and outcomes were assessed macroscopically and histologically. Defect areas in the right joints exhibited boundaries, incomplete fill, irregular cartilage surfaces, loss of glycosaminoglycan (GAG), and absence of chondrocytes. In contrast, the repaired defect area in the joints that received cLIUS showed complete fill, positive staining for GAG with rounded chondrocyte morphology, COL2A1 staining, and columnar organization. Synovial fluid collected from cLIUS-treated left knee joints had lower levels of IL1, TNFα, and IFNγ when compared to untreated right knee joints, alluding to the potential of cLIUS to mitigate early inflammation. Further at 8 weeks, left knee joints (n = 12) consistently scored higher on the O'Driscoll scale, with a higher percent hyaline cartilage score. No adverse impact on bone or change in the joint space was noted. Upon a single exposure of cLIUS to TNFα-treated cells, nuclear localization of pNFκB and SOX9 was visualized by double immunofluorescence and the expression of markers associated with the NFκB pathway was assayed by quantitative real-time polymerase chain reaction. cLIUS extends its chondroprotective effects by titrating pNFκB levels, preventing its nuclear translocation, while maintaining the expression of SOX9, the collagen II transcription factor. Our combined results demonstrate that healing of chondral defects treated with marrow stimulation by SD can be accelerated by employing cLIUS regimen that possesses chondroinductive and chondroprotective properties. Impact statement Repair of cartilage represents an unsolved biomedical burden. In vitro, continuous low-intensity ultrasound (cLIUS) has been demonstrated to possess chondroinductive and chondroprotective potential. To our best knowledge, the use of cLIUS to improve cartilage repair outcomes upon marrow stimulation, in vivo, has not been reported and our work reported here fills that gap. Our results demonstrated enhanced cartilage repair outcomes under cLIUS (3.8 MHz) in a rabbit model of subchondral injury by subchondral drilling. Enhanced repair stemmed from mesenchymal stem cell differentiation in vivo and the subsequent synthesis of articular cartilage-specific matrix.

Mind the Viscous Modulus: The Mechanotransductive Response to the Viscous Nature of Isoelastic Matrices Regulates Stem Cell Chondrogenesis

The design of hydrogels as mimetics of tissues' matrices typically disregards the viscous nature of native tissues and focuses only on their elastic properties. In the case of stem cell chondrogenesis, this has led to contradictory results, likely due to unreported changes in the matrices' viscous modulus. Here, by employing isoelastic matrices with Young's modulus of ≈12 kPa, variations in viscous properties alone (i.e., loss tangent between 0.1 and 0.25) are demonstrated to be sufficient to drive efficient growth factor-free chondrogenesis of human mesenchymal stem cells, both in 2D and 3D cultures. The increase of the viscous component of RGD-functionalized polyacrylamide or polyethylene glycol maleimide hydrogels promotes a phenotype with reduced adhesion, alters mechanosensitive signaling, and boosts cell-cell contacts. In turn, this upregulates the chondrogenic transcription factor SOX9 and supports neocartilage formation, demonstrating that the mechanotransductive response to the viscous nature of the matrix can be harnessed to direct cell fate.

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.

Exosomes derived from MSC as drug system in osteoarthritis therapy

Osteoarthritis (OA) is the most common degenerative disease of the joint with irreversible cartilage damage as the main pathological feature. With the development of regenerative medicine, mesenchymal stem cells (MSCs) have been found to have strong therapeutic potential. However, intraarticular MSCs injection therapy is limited by economic costs and ethics. Exosomes derived from MSC (MSC-Exos), as the important intercellular communication mode of MSCs, contain nucleic acid, proteins, lipids, microRNAs, and other biologically active substances. With excellent editability and specificity, MSC-Exos function as a targeted delivery system for OA treatment, modulating immunity, inhibiting apoptosis, and promoting regeneration. This article reviews the mechanism of action of MSC-Exos in the treatment of osteoarthritis, the current research status of the preparation of MSC-Exos and its application of drug delivery in OA therapy.

Basement membrane extract potentiates the endochondral ossification phenotype of bone marrow-derived mesenchymal stem cell-based cartilage organoids

Endochondral ossification is a developmental process in the skeletal system and bone marrow of vertebrates. During endochondral ossification, primitive cartilaginous anlages derived from mesenchymal stem cells (MSCs) undergo vascular invasion and ossification. In vitro regeneration of endochondral ossification is beneficial for research on the skeletal system and bone marrow development as well as their clinical aspects. However, to achieve the regeneration of endochondral ossification, a stem cell-based artificial cartilage (cartilage organoid, Cart-Org) that possesses an endochondral ossification phenotype is required. Here, we modified a conventional 3D culture method to create stem cell-based Cart-Org by mixing it with a basement membrane extract (BME) and further characterized its chondrogenic and ossification properties. BME enlarged and matured the bone marrow MSC-based Cart-Orgs without any shape abnormalities. Histological analysis using Alcian blue staining showed that the production of cartilaginous extracellular matrices was enhanced in Cart-Org treated with BME. Transcriptome analysis using RNA sequencing revealed that BME altered the gene expression pattern of Cart-Org to a dominant chondrogenic state. BME triggered the activation of the SMAD pathway and inhibition of the NK-κB pathway, which resulted in the upregulation of SOX9, COL2A1, and ACAN in Cart-Org. BME also facilitated the upregulation of genes associated with hypertrophic chondrocytes (IHH, PTH1R, and COL10A1) and ossification (SP7, ALPL, and MMP13). Our findings indicate that BME promotes cartilaginous maturation and further ossification of bone marrow MSC-based Cart-Org, suggesting that Cart-Org treated with BME possesses the phenotype of endochondral ossification.

Research progress of procyanidins in repairing cartilage injury after anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tear is a common sports-related injury, and cartilage injury always emerges as a serious complication following ACL tear, significantly impacting the physical and psychological well-being of affected individuals. Over the years, efforts have been directed toward finding strategies to repair cartilage injury after ACL tear. In recent times, procyanidins, known for their anti-inflammatory and antioxidant properties, have emerged as potential key players in addressing this concern. This article focuses on summarizing the research progress of procyanidins in repairing cartilage injury after ACL tear. It covers the roles, mechanisms, and clinical significance of procyanidins in repairing cartilage injury following ACL tear and explores the future prospects of procyanidins in this domain. This review provides novel insights and hope for the repair of cartilage injury following ACL tear.

Regulation of Oxygen Tension as a Strategy to Control Chondrocytic Phenotype for Cartilage Tissue Engineering and Regeneration

Cartilage defects and osteoarthritis are health problems which are major burdens on health care systems globally, especially in aging populations. Cartilage is a vulnerable tissue, which generally faces a progressive degenerative process when injured. This makes it the 11th most common cause of global disability. Conservative methods are used to treat the initial phases of the illness, while orthopedic management is the method used for more progressed phases. These include, for instance, arthroscopic shaving, microfracturing and mosaicplasty, and joint replacement as the final treatment. Cell-based implantation methods have also been developed. Despite reports of successful treatments, they often suffer from the non-optimal nature of chondrocyte phenotype in the repair tissue. Thus, improved strategies to control the phenotype of the regenerating cells are needed. Avascular tissue cartilage relies on diffusion for nutrients acquisition and the removal of metabolic waste products. A low oxygen content is also present in cartilage, and the chondrocytes are, in fact, well adapted to it. Therefore, this raises an idea that the regulation of oxygen tension could be a strategy to control the chondrocyte phenotype expression, important in cartilage tissue for regenerative purposes. This narrative review discusses the aspects related to oxygen tension in the metabolism and regulation of articular and growth plate chondrocytes and progenitor cell phenotypes, and the role of some microenvironmental factors as regulators of chondrocytes.

Cartilage tissue healing and regeneration based on biocompatible materials: a systematic review and bibliometric analysis from 1993 to 2022

Cartilage, a type of connective tissue, plays a crucial role in supporting and cushioning the body, and damages or diseases affecting cartilage may result in pain and impaired joint function. In this regard, biocompatible materials are used in cartilage tissue healing and regeneration as scaffolds for new tissue growth, barriers to prevent infection and reduce inflammation, and deliver drugs or growth factors to the injury site. In this article, we perform a comprehensive bibliometric analysis of literature on cartilage tissue healing and regeneration based on biocompatible materials, including an overview of current research, identifying the most influential articles and authors, discussing prevailing topics and trends in this field, and summarizing future research directions.

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.

Recent advances in double network hydrogels based on naturally-derived polymers: synthesis, properties, and biological applications

Hydrogels composed of naturally-derived biopolymers have garnered significant research interest due to the bioavailability and biocompatibility of starting materials. However, translating these advantages to practical use is challenged by limitations of mechanical properties and stability of the resulting materials. The development of double network (DN) hydrogels has led to greatly enhanced mechanical properties and shows promise toward broadening the applications of conventional synthetic or natural hydrogels. This review highlights recently developed protein-based and polysaccharide-based DN hydrogels. For each biopolymer, we focus on a subset of DN hydrogels centered around a theme related to synthetic design or applications. Network structures and crosslinking mechanisms that endow enhanced mechanical properties and performance to the materials are discussed. Important applications, including tissue engineering, drug delivery, bioadhesives, wound healing, and wearable sensors, that arise from the inherent properties of the natural polymer or its combination with other materials are also emphasized. Finally, we discuss ongoing challenges to stimulate the discovery of new design principles for the future of DN hydrogels based on naturally-derived polymers for biological applications.

Double-edged role of mechanical stimuli and underlying mechanisms in cartilage tissue engineering

Mechanical stimuli regulate the chondrogenic differentiation of mesenchymal stem cells and the homeostasis of chondrocytes, thus affecting implant success in cartilage tissue engineering. The mechanical microenvironment plays fundamental roles in the maturation and maintenance of natural articular cartilage, and the progression of osteoarthritis Hence, cartilage tissue engineering attempts to mimic this environment in vivo to obtain implants that enable a superior regeneration process. However, the specific type of mechanical loading, its optimal regime, and the underlying molecular mechanisms are still under investigation. First, this review delineates the composition and structure of articular cartilage, indicating that the morphology of chondrocytes and components of the extracellular matrix differ from each other to resist forces in three top-to-bottom overlapping zones. Moreover, results from research experiments and clinical trials focusing on the effect of compression, fluid shear stress, hydrostatic pressure, and osmotic pressure are presented and critically evaluated. As a key direction, the latest advances in mechanisms involved in the transduction of external mechanical signals into biological signals are discussed. These mechanical signals are sensed by receptors in the cell membrane, such as primary cilia, integrins, and ion channels, which next activate downstream pathways. Finally, biomaterials with various modifications to mimic the mechanical properties of natural cartilage and the self-designed bioreactors for experiment in vitro are outlined. An improved understanding of biomechanically driven cartilage tissue engineering and the underlying mechanisms is expected to lead to efficient articular cartilage repair for cartilage degeneration and disease.

Construction of ultrasonically treated collagen/silk fibroin composite scaffolds to induce cartilage regeneration

A novel tissue-specific functional tissue engineering scaffold for cartilage repair should have a three-dimensional structure, good biosafety and biological activity, and should be able to promote cartilage tissue regeneration. This study aimed to determine the effect of ultrasound-treated collagen/silk fibroin (Col/SF) composite scaffolds with good mechanical properties and high biological activity on cartilage repair. The characteristics of the scaffolds with different Col/SF ratios (7:3, 8:2, and 9:1) were determined by scanning electron microscopy, Fourier-transform infrared spectroscopy, and porosity, water absorption, and compression tests. In vitro evaluations revealed the biocompatibility of the Col/SF scaffolds. Results suggested that the optimal ratio of Col/SF composite scaffolds was 7:3. The Col/SF scaffolds induced adipose-derived stem cells to undergo chondrogenic differentiation under chondrogenic culture conditions. The efficiency of Col/SF scaffolds for cartilage regeneration applications was further evaluated using an in vivo model of full-thickness articular cartilage defects in New Zealand rabbits. The Col/SF scaffolds effectively promoted osteochondral regeneration as evidenced by macroscopic, histological, and immunohistochemical evaluation. The study demonstrates that ultrasound-treated Col/SF scaffolds show great potential for repairing cartilage defects.

Vascularization ability of glioma stem cells in different three-dimensional microenvironments

Glioblastoma (GBM) is among the most common and aggressive adult central nervous system tumors. One prominent characteristic of GBM is the presence of abnormal microvessels. A significant correlation between angiogenesis and prognosis has been observed. Accurately reconstructing this neovascularization and tumor microenvironment through personalized in vitro disease models presents a significant challenge. However, it is crucial to develop new anti-angiogenic therapies for GBM. In this study, 3D bioprinted glioma stem cell (GSC)-laden hydrogel scaffolds, hybrid GSC hydrogels and cell-free hydrogel scaffolds were manufactured to investigate the vascularization ability of GSCs in varying 3D microenvironments. Our results demonstrated that the bioactivity of GSCs in the 3D bioprinted GSC-laden hydrogel scaffold was preferable and stable, and the amounts of vascular endothelial growth factor A and basic fibroblast growth factor were the highest in the microenvironment. When the three different models were co-cultured with human umbilical vein endothelial cells, the expression of angiogenesis-related markers was the most abundant in the bioprinted GSC-laden hydrogel scaffold. Additionally, xenograft tumors formed by bioprinted GSC-laden hydrogel scaffolds more closely resembled human gliomas regarding color, texture and vascularization. Notably, in xenograft tumors derived from 3D bioprinted GSC-laden hydrogel scaffolds, the number of human CD105+ cells was significantly higher, and human endothelial vascular lumen-like structures were observed. This indicates that the 3D bioprinted GSC-laden hydrogel scaffold is a suitable model for mimicking the glioma microenvironment and studying tumor angiogenesis.

Bioadhesive and Injectable Hydrogels and Their Correlation with Mesenchymal Stem Cells Differentiation for Cartilage Repair: A Mini-Review

Injectable bioadhesive hydrogels, known for their capacity to carry substances and adaptability in processing, offer great potential across various biomedical applications. They are especially promising in minimally invasive stem cell-based therapies for treating cartilage damage. This approach harnesses readily available mesenchymal stem cells (MSCs) to differentiate into chondrocytes for cartilage regeneration. In this review, we investigate the relationship between bioadhesion and MSC differentiation. We summarize the fundamental principles of bioadhesion and discuss recent trends in bioadhesive hydrogels. Furthermore, we highlight their specific applications in conjunction with stem cells, particularly in the context of cartilage repair. The review also encompasses a discussion on testing methods for bioadhesive hydrogels and direct techniques for differentiating MSCs into hyaline cartilage chondrocytes. These approaches are explored within both clinical and laboratory settings, including the use of genetic tools. While this review offers valuable insights into the interconnected aspects of these topics, it underscores the need for further research to fully grasp the complexities of their relationship.

Regeneration of injured articular cartilage using the recombinant human amelogenin protein

Aims

Cartilage injuries rarely heal spontaneously and often require surgical intervention, leading to the formation of biomechanically inferior fibrous tissue. This study aimed to evaluate the possible effect of amelogenin on the healing process of a large osteochondral injury (OCI) in a rat model.

Methods

A reproducible large OCI was created in the right leg femoral trochlea of 93 rats. The OCIs were treated with 0.1, 0.5, 1.0, 2.5, or 5.0 μg/μl recombinant human amelogenin protein (rHAM+) dissolved in propylene glycol alginate (PGA) carrier, or with PGA carrier alone. The degree of healing was evaluated 12 weeks after treatment by morphometric analysis and histological evaluation. Cell recruitment to the site of injury as well as the origin of the migrating cells were assessed four days after treatment with 0.5 μg/μl rHAM+ using immunohistochemistry and immunofluorescence.

Results

A total of 12 weeks after treatment, 0.5 μg/μl rHAM+ brought about significant repair of the subchondral bone and cartilage. Increased expression of proteoglycan and type II collagen and decreased expression of type I collagen were revealed at the surface of the defect, and an elevated level of type X collagen at the newly developed tide mark region. Conversely, the control group showed osteoarthritic alterations. Recruitment of cells expressing the mesenchymal stem cell (MSC) markers CD105 and STRO-1, from adjacent bone marrow toward the OCI, was noted four days after treatment.

Conclusion

We found that 0.5 μg/μl rHAM+ induced in vivo healing of injured articular cartilage and subchondral bone in a rat model, preventing the destructive post-traumatic osteoarthritic changes seen in control OCIs, through paracrine recruitment of cells a few days after treatment.

An MMP-2 Responsive Nanotheranostic Probe Enabled Synergistic Therapy of Rheumatoid Arthritis and MR/CT Assessment of Therapeutic Response In Situ

This study reports a facile and green synthesis of a new multifunctional nanotheranostic probe for the synergistic therapy of rheumatoid arthritis (RA) and in situ assessment of therapeutic response. The probe is synthesized through a one-step self-assembly of two exquisitely designed peptide-amphiphilic block copolymers (PEG-DTIPA-KGPLGVRK-MTX and Pal-GGGGHHHHD-TCZ) under mild conditions, requiring minimal energy input. The resultant probe demonstrates excellent biocompatibility, water solubility, and colloidal stability. It exhibits a strong IL-6R targeting ability toward inflamed joints, and releases drugs in an MMP-2-responsive manner. The co-loading of methotrexate(MTX) and tocilizumab (TCZ) into the probe enables synergistic RA therapy with improved efficacy by simultaneously decreasing the activity of adenosine synthetase and interfering with the binding of IL-6 to its receptor. In addition, the resultant probe exhibits a high r1 relaxation rate (7.00 mm-1  s-1 ) and X-ray absorption capability (69.04 Hu mm-1 ), enabling sensitive MR and CT dual-modal imaging for simultaneous evaluation of synovial thickness and bone erosion. Both in vitro experiments using lipopolysaccharide-treated RAW264.7 cells and in vivo experiments using collagen-induced arthritis mice demonstrate the probe's high effectiveness in synergistically inhibiting inflammation. This study provides new insights into RA theranostics, therapeutic monitoring, the design of multifunctional theranostic probes, and beyond.

Hyaluronic scaffold transplantation with bone marrow concentrate for the treatment of osteochondral lesions of the talus: durable results up to a minimum of 10 years

PURPOSE

The aim of this study was to evaluate the long-term clinical results of the transplantation of a hyaluronic acid membrane augmented with bone marrow aspirate concentrate (BMAC) in an one-step technique for the treatment of patients affected by osteochondral lesions of the talus (OLT).

METHODS

A total of 101 patients (64 men, 37 women, age 32.9 ± 10.9) were evaluated for a minimum of 10 years of follow-up (151.5 ± 18.4 months) The mean lesion size was 2.2 ± 1.4 cm2, the lesion had a post-traumatic origin in 73 patients, 15 patients previously had an ankle fracture, 22 patients had ankle osteoarthritis. All patients were clinically evaluated at baseline and at 2, 5, and a minimum of 10 years after treatment using the AOFAS score, the NRS for pain, and the Tegner score. A survival analysis was performed to check the survival to failure up to the last follow-up.

RESULTS

The AOFAS score significantly improved from baseline (59.6 ± 13.9) to the final follow-up (82.3 ± 14.2) (p < 0.0005). A significant reduction in the AOFAS score was found from 2 to 10 years (p < 0.0005). The NRS for pain changed from 7.0 ± 1.3 at baseline to 3.9 ± 2.7 at the final follow-up (p < 0.0005). A significant worsening was documented between 5 years and the final follow-up (p < 0.0005). The Tegner score improved from the preoperative value of 2.0 (range 1-7) to 3.0 (range 1-7) at the final follow-up (p < 0.0005), although it remained lower as compared to the preinjury level of 4.0 (range 1-9) (p < 0.0005). Better results were documented in male and younger patients with smaller lesions, without the previous surgery, and without the previous ankle fractures or osteoarthritis. At the final follow-up, 85 patients considered their general health status "satisfactory" and 84 patients reported feeling "better" than the preoperative condition. Five patients were considered failures and underwent prosthetic ankle replacement or repeated the same surgery.

CONCLUSION

This one-step technique showed to be an effective procedure for the treatment of OLT, providing a low failure rate and offering durable clinical improvements up to a minimum of 10 years of follow-up. However, this technique demonstrated a small yet significant decrease over the years in terms of pain and function and poor results in terms of sports activity level.

LEVEL OF EVIDENCE

Level IV.

The potential role of synovial cells in the progression and treatment of osteoarthritis

Osteoarthritis (OA), the commonest arthritis, is characterized by the progressive destruction of cartilage, leading to disability. The Current early clinical treatment strategy for OA often centers on anti-inflammatory or analgesia medication, weight loss, improved muscular function and articular cartilage repair. Although these treatments can relieve symptoms, OA tends to be progressive, and most patients require arthroplasty at the terminal stages of OA. Recent studies have shown a close correlation between joint pain, inflammation, cartilage destruction and synovial cells. Consequently, understanding the potential mechanisms associated with the action of synovial cells in OA could be beneficial for the clinical management of OA. Therefore, this review comprehensively describes the biological functions of synovial cells, the synovium, together with the pathological changes of synovial cells in OA, and the interaction between the cartilage and synovium, which is lacking in the present literature. Additionally, therapeutic approaches based on synovial cells for OA treatment are further discussed from a clinical perspective, highlighting a new direction in the treatment of OA.

Clinical Potential of Cellular Material Sources in the Generation of iPSC-Based Products for the Regeneration of Articular Cartilage

Inflammatory joint diseases, among which osteoarthritis and rheumatoid arthritis are the most common, are characterized by progressive degeneration of the cartilage tissue, resulting in the threat of limited or lost joint functionality in the absence of treatment. Currently, treating these diseases is difficult, and a number of existing treatment and prevention measures are not entirely effective and are complicated by the patients' conditions, the multifactorial nature of the pathology, and an incomplete understanding of the etiology. Cellular technologies based on induced pluripotent stem cells (iPSCs) can provide a vast cellular resource for the production of artificial cartilage tissue for replacement therapy and allow the possibility of a personalized approach. However, the question remains whether a number of etiological abnormalities associated with joint disease are transmitted from the source cell to iPSCs and their chondrocyte derivatives. Some data state that there is no difference between the iPSCs and their derivatives from healthy and sick donors; however, there are other data indicating a dissimilarity. Therefore, this topic requires a thorough study of the differentiation potential of iPSCs and the factors influencing it, the risk factors associated with joint diseases, and a comparative analysis of the characteristics of cells obtained from patients. Together with cultivation optimization methods, these measures can increase the efficiency of obtaining cell technology products and make their wide practical application possible.

Autologous Mesenchymal Stromal Cells Immobilized in Plasma-Based Hydrogel for the Repair of Articular Cartilage Defects in a Large Animal Model

The treatment of cartilage defects in trauma injuries and degenerative diseases represents a challenge for orthopedists. Advanced mesenchymal stromal cell (MSC)-based therapies are currently of interest for the repair of damaged cartilage. However, an approved system for MSC delivery and maintenance in the defect is still missing. This study aimed to evaluate the effect of autologous porcine bone marrow MSCs anchored in a commercially available polyglycolic acid-hyaluronan scaffold (Chondrotissue®) using autologous blood plasma-based hydrogel in the repair of osteochondral defects in a large animal model. The osteochondral defects were induced in twenty-four minipigs with terminated skeletal growth. Eight animals were left untreated, eight were treated with Chondrotissue® and eight received Chondrotissue® loaded with MSCs. The animals were terminated 90 days after surgery. Macroscopically, the untreated defects were filled with newly formed tissue to a greater extent than in the other groups. The histological evaluations showed that the defects treated with Chondrotissue® and Chondrotissue® loaded with pBMSCs contained a higher amount of hyaline cartilage and a lower amount of connective tissue, while untreated defects contained a higher amount of connective tissue and a lower amount of hyaline cartilage. In addition, undifferentiated connective tissue was observed at the edges of defects receiving Chondrotissue® loaded with MSCs, which may indicate the extracellular matrix production by transplanted MSCs. The immunological analysis of the blood samples revealed no immune response activation by MSCs application. This study demonstrated the successful and safe immobilization of MSCs in commercially available scaffolds and defect sites for cartilage defect repair.

Menstrual Blood-Derived Stem Cell Paracrine Factors Possess Stimulatory Effects on Chondrogenesis In Vitro and Diminish the Degradation of Articular Cartilage during Osteoarthritis

Articular cartilage is an avascular tissue with a limited capacity for self-regeneration, leading the tissue to osteoarthritis (OA). Mesenchymal stem cells (MSCs) are promising for cartilage tissue engineering, as they are capable of differentiating into chondrocyte-like cells and secreting a number of active molecules that are important for cartilage extracellular matrix (ECM) synthesis. The aim of this study was to evaluate the potential of easily accessible menstrual blood-derived MSC (MenSC) paracrine factors in stimulating bone marrow MSC (BMMSCs) chondrogenic differentiation and to investigate their role in protecting cartilage from degradation in vitro. MenSCs and BMMSCs chondrogenic differentiation was induced using four different growth factors: TGF-β3, activin A, BMP-2, and IGF-1. The chondrogenic differentiation of BMMSCs was stimulated in co-cultures with MenSCs and cartilage explants co-cultured with MenSCs for 21 days. The chondrogenic capacity of BMMSCs was analyzed by the secretion of four growth factors and cartilage oligomeric matrix protein, as well as the release and synthesis of cartilage ECM proteins, and chondrogenic gene expression in cartilage explants. Our results suggest that MenSCs stimulate chondrogenic response in BMMSCs by secreting activin A and TGF-β3 and may have protective effects on cartilage tissue ECM by decreasing the release of GAGs, most likely through the modulation of activin A related molecular pathway. In conclusion, paracrine factors secreted by MenSCs may turn out to be a promising therapeutical approach for cartilage tissue protection and repair.

Drug-Embedded Nanovesicles Assembled from Peptide-Decorated Hyaluronic Acid for Rheumatoid Arthritis Synergistic Therapy

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes endless pain and poor quality of life in patients. Usage of a lubricant combined with anti-inflammatory therapy is considered a reasonable and effective approach for the treatment of RA. Herein, inspired by glycopeptides, a peptide-decorated hyaluronic acid was synthesized, and the grafted Fmoc-phenylalanine-phenylalanine-COOH (FmocFF) peptide self-assembled with β-sheet conformations could induce the folding of polymer molecular chains to form a vesicle structure in aqueous solution. The hydrophobic anti-inflammatory drug curcumin (Cur) could be embedded in the vesicle walls through π-π interactions with the FmocFF peptide. Furthermore, the inflammation suppression function of the Cur-loaded vesicles both in vitro and in vivo was demonstrated to be an effective treatment for RA therapy. This work proposes new insights into the folding and hierarchical assembly of glycopeptide mimics, providing an efficient approach for constructing intelligent platforms for drug delivery, disease therapy, and diagnostic applications.

Recent development in multizonal scaffolds for osteochondral regeneration

Osteochondral (OC) repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue. In contrast to the current surgical approaches which yield only short-term relief of symptoms, tissue engineering strategy has been shown more promising outcomes in treating OC defects since its emergence in the 1990s. In particular, the use of multizonal scaffolds (MZSs) that mimic the gradient transitions, from cartilage surface to the subchondral bone with either continuous or discontinuous compositions, structures, and properties of natural OC tissue, has been gaining momentum in recent years. Scrutinizing the latest developments in the field, this review offers a comprehensive summary of recent advances, current hurdles, and future perspectives of OC repair, particularly the use of MZSs including bilayered, trilayered, multilayered, and gradient scaffolds, by bringing together onerous demands of architecture designs, material selections, manufacturing techniques as well as the choices of growth factors and cells, each of which possesses its unique challenges and opportunities.

Regenerative Effect of Mesenchymal Stem Cell on Cartilage Damage in a Porcine Model

Osteoarthritis (OA) is a major public and animal health challenge with significant economic consequences. Cartilage degradation plays a critical role in the initiation and progression of degenerative joint diseases, such as OA. Mesenchymal stem cells (MSCs) have become increasingly popular in the field of cartilage regeneration due to their promising results. The objective of this preclinical study was to evaluate the regenerative effects of mesenchymal stem cells (MSCs) in the repair of knee cartilage defects using a porcine model. Seven healthy LYD breed white pigs, aged 9-10 weeks and weighing approximately 20 ± 3 kg, were used in the experimental protocol. Full-thickness defects measuring 8 mm in diameter and 5 mm in depth were induced in the lateral femoral condyle of the posterior limbs in both knee joints using a sterile puncture technique while the knee was maximally flexed. Following a 1-week induction phase, the pig treatment groups received a 0.3 million/kg MSC transplant into the damaged knee region, while the placebo group received a control solution as a treatment. Magnetic resonance imaging (MRI), computerized tomography (CT), visual macroscopic examination, histological analysis, and cytokine concentration analysis were used to assess cartilage regeneration. The findings revealed that human adipose-derived mesenchymal stem cells (hADSCs) were more effective in repairing cartilage than pig umbilical cord-derived mesenchymal stem cells (pUCMSCs). These results suggest that MSC-based treatments hold promise as a treatment option for cartilage repair, which aid in the treatment of OA. However, further studies with larger sample sizes and longer follow-up periods are required to fully demonstrate the safety and efficacy of these therapies in both animals and humans.

YY1/miR-140-5p/Jagged1/Notch axis mediates cartilage progenitor/stem cells fate reprogramming in knee osteoarthritis

Osteoarthritis is a multifactorial disease characterized by cartilage degeneration, while cartilage progenitor/stem cells (CPCs) are responsible for endogenous cartilage repair. However, the relevant regulatory mechanisms of CPCs fate reprogramming in OA are rarely reported. Recently, we observed fate disorders in OA CPCs and found that microRNA-140-5p (miR-140-5p) protects CPCs from fate changes in OA. This study further mechanistically investigated the upstream regulator and downstream effectors of miR-140-5p in OA CPCs fate reprogramming. As a result, luciferase reporter assay and validation assays revealed that miR-140-5p targets Jagged1 and inhibits Notch signaling in human CPCs, and the loss-/gain-of-function experiments and rescue assays discovered that miR-140-5p improves OA CPCs fate, but this effect can be counteracted by Jagged1. Moreover, increased transcription factor Ying Yang 1 (YY1) was associated with OA progression, and YY1 could disturb CPCs fate via transcriptionally repressing miR-140-5p and enhancing the Jagged1/Notch signaling. Finally, the relevant changes and mechanisms of YY1, miR-140-5p, and Jagged1/Notch signaling in OA CPCs fate reprogramming were validated in rats. Conclusively, this study identified a novel YY1/miR-140-5p/Jagged1/Notch signaling axis that mediates OA CPCs fate reprogramming, wherein YY1 and Jagged1/Notch signaling exhibits an OA-stimulative role, and miR-140-5p plays an OA-protective effect, providing attractive targets for OA therapeutics.

Mesenchymal Stem Cells: Generalities and Clinical Significance in Feline and Canine Medicine

Mesenchymal stem cells (MSCs) are multipotent cells: they can proliferate like undifferentiated cells and have the ability to differentiate into different types of cells. A considerable amount of research focuses on the potential therapeutic benefits of MSCs, such as cell therapy or tissue regeneration, and MSCs are considered powerful tools in veterinary regenerative medicine. They are the leading type of adult stem cells in clinical trials owing to their immunosuppressive, immunomodulatory, and anti-inflammatory properties, as well as their low teratogenic risk compared with pluripotent stem cells. The present review details the current understanding of the fundamental biology of MSCs. We focus on MSCs' properties and their characteristics with the goal of providing an overview of therapeutic innovations based on MSCs in canines and felines.

Enhancement of mesenchymal stem cells' chondrogenic potential by type II collagen-based bioscaffolds

BACKGROUND

Osteoarthritis (OA) is a common degenerative chronic disease accounting for physical pain, tissue stiffness and mobility restriction. Current therapeutic approaches fail to prevent the progression of the disease considering the limited knowledge on OA pathobiology. During OA progression, the extracellular matrix (ECM) of the cartilage is aberrantly remodeled by chondrocytes. Chondrocytes, being the main cell population of the cartilage, participate in cartilage regeneration process. To this end, modern tissue engineering strategies involve the recruitment of mesenchymal stem cells (MSCs) due to their regenerative capacity as to promote chondrocyte self-regeneration.

METHODS AND RESULTS

In the present study, we evaluated the role of type II collagen, as the main matrix macromolecule in the cartilage matrix, to promote chondrogenic differentiation in two MSC in vitro culture systems. The chondrogenic differentiation of human Wharton's jelly- and dental pulp-derived MSCs was investigated over a 24-day culture period on type II collagen coating to improve the binding affinity of MSCs. Functional assays, demonstrated that type II collagen promoted chondrogenic differentiation in both MSCs tested, which was confirmed through gene and protein analysis of major chondrogenic markers.

CONCLUSIONS

Our data support that type II collagen contributes as a natural bioscaffold enhancing chondrogenesis in both MSC models, thus enhancing the commitment of MSC-based therapeutic approaches in regenerative medicine to target OA and bring therapy closer to the clinical use.

Mechano-responsive hydrogel for direct stem cell manufacturing to therapy

Bone marrow-derived mesenchymal stem cell (MSC) is one of the most actively studied cell types due to its regenerative potential and immunomodulatory properties. Conventional cell expansion methods using 2D tissue culture plates and 2.5D microcarriers in bioreactors can generate large cell numbers, but they compromise stem cell potency and lack mechanical preconditioning to prepare MSC for physiological loading expected in vivo. To overcome these challenges, in this work, we describe a 3D dynamic hydrogel using magneto-stimulation for direct MSC manufacturing to therapy. With our technology, we found that dynamic mechanical stimulation (DMS) enhanced matrix-integrin β1 interactions which induced MSCs spreading and proliferation. In addition, DMS could modulate MSC biofunctions including directing MSC differentiation into specific lineages and boosting paracrine activities (e.g., growth factor secretion) through YAP nuclear localization and FAK-ERK pathway. With our magnetic hydrogel, complex procedures from MSC manufacturing to final clinical use, can be integrated into one single platform, and we believe this 'all-in-one' technology could offer a paradigm shift to existing standards in MSC therapy.

Macromolecule-based hydrogels nanoarchitectonics with mesenchymal stem cells for regenerative medicine: A review

The role of regenerative medicine in clinical therapies is becoming increasingly vital. Under specific conditions, mesenchymal stem cells (MSCs) are capable of differentiating into mesoblastema (i.e., adipocytes, chondrocytes, and osteocytes) and other embryonic lineages. Their application in regenerative medicine has attracted a great deal of interest among researchers. To maximize the potential applications of MSCs, materials science could provide natural extracellular matrices and provide an effective means to understand the various mechanisms of differentiation for the growth of MSCs. Pharmaceutical fields are represented among the research on biomaterials by macromolecule-based hydrogel nanoarchitectonics. Various biomaterials have been used to prepare hydrogels with their unique chemical and physical properties to provide a controlled microenvironment for the culture of MSCs, laying the groundwork for future practical applications in regenerative medicine. This article currently describes and summarizes the sources, characteristics, and clinical trials of MSCs. In addition, it describes the differentiation of MSCs in various macromolecule-based hydrogel nanoarchitectonics and highlights the preclinical studies of MSCs-loaded hydrogel materials in regenerative medicine conducted over the past few years. Finally, the challenges and prospects of MSC-loaded hydrogels are discussed, and the future development of macromolecule-based hydrogel nanoarchitectonics is outlined by comparing the current literature.

The Current State of Osteoarthritis Treatment Options Using Stem Cells for Regenerative Therapy: A Review

Articular cartilage has very low metabolic activity. While minor injuries may be spontaneously repaired within the joint by chondrocytes, there is very little chance of a severely impaired joint regenerating itself when damaged. Therefore, any significant joint injury has little chance of spontaneously healing without some type of therapy. This article is a review that will examine the causes of osteoarthritis, both acute and chronic, and how it may be treated using traditional methods as well as with the latest stem cell technology. The latest regenerative therapy is discussed, including the use and potential risks of mesenchymal stem cells for tissue regeneration and implantation. Applications are then discussed for the treatment of OA in humans after using canine animal models. Since the most successful research models of OA were dogs, the first applications for treatment were veterinary. However, the treatment options have now advanced to the point where patients suffering from osteoarthritis may be treated with this technology. A survey of the literature was performed in order to determine the current state of stem cell technology being used in the treatment of osteoarthritis. Then, the stem cell technology was compared with traditional treatment options.

Polyvinyl Alcohol-Chitosan Scaffold for Tissue Engineering and Regenerative Medicine Application: A Review

Tissue engineering and regenerative medicine (TERM) holds great promise for addressing the growing need for innovative therapies to treat disease conditions. To achieve this, TERM relies on various strategies and techniques. The most prominent strategy is the development of a scaffold. Polyvinyl alcohol-chitosan (PVA-CS) scaffold emerged as a promising material in this field due to its biocompatibility, versatility, and ability to support cell growth and tissue regeneration. Preclinical studies showed that the PVA-CS scaffold can be fabricated and tailored to fit the specific needs of different tissues and organs. Additionally, PVA-CS can be combined with other materials and technologies to enhance its regenerative capabilities. Furthermore, PVA-CS represents a promising therapeutic solution for developing new and innovative TERM therapies. Therefore, in this review, we summarized the potential role and functions of PVA-CS in TERM applications.

Low-intensity pulsed ultrasound promotes mesenchymal stem cell transplantation-based articular cartilage regeneration via inhibiting the TNF signaling pathway

BACKGROUND

Mesenchymal stem cell (MSC) transplantation therapy is highly investigated for the regenerative repair of cartilage defects. Low-intensity pulsed ultrasound (LIPUS) has the potential to promote chondrogenic differentiation of MSCs. However, its underlying mechanism remains unclear. Here, we investigated the promoting effects and mechanisms underlying LIPUS stimulation on the chondrogenic differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs) and further evaluated its regenerative application value in articular cartilage defects in rats.

METHODS

LIPUS was applied to stimulate cultured hUC-MSCs and C28/I2 cells in vitro. Immunofluorescence staining, qPCR analysis, and transcriptome sequencing were used to detect mature cartilage-related markers of gene and protein expression for a comprehensive evaluation of differentiation. Injured articular cartilage rat models were established for further hUC-MSC transplantation and LIPUS stimulation in vivo. Histopathology and H&E staining were used to evaluate the repair effects of the injured articular cartilage with LIPUS stimulation.

RESULTS

The results showed that LIPUS stimulation with specific parameters effectively promoted the expression of mature cartilage-related genes and proteins, inhibited TNF-α gene expression in hUC-MSCs, and exhibited anti-inflammation in C28/I2 cells. In addition, the articular cartilage defects of rats were significantly repaired after hUC-MSC transplantation and LIPUS stimulation.

CONCLUSIONS

Taken together, LIPUS stimulation could realize articular cartilage regeneration based on hUC-MSC transplantation due to the inhibition of the TNF signaling pathway, which is of clinical value for the relief of osteoarthritis.

Encapsulation of Human Umbilical Cord Mesenchymal Stem Cells in LunaGel Photocrosslinkable Extracellular Matrix and Subcutaneous Transplantation in Mice

Stem cells have significant potential in regenerative medicines. However, a major issue with implanting stem cells in the regeneration of new tissue is the methods to implant them and cell viability and functions before and after implantation. Here we developed a simple yet effective method that used photo-crosslinkable gelatin-based hydrogel (LunaGel^TM) as a scaffold for the encapsulation, expansion, and eventually, transplantation of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) into mice subcutaneously. We demonstrated the proliferation and maintenance of the original expression of mesenchymal stem cell markers as well as the ability to differentiate into mesoderm-derived cells. The hydrogel was highly stable with no signs of degradation after 20 days in PBS. The hUC-MSCs remained viable after transplantation into mice's subcutaneous pockets and migrated to integrate with the surrounding tissues. We showed a collagen-rich layer surrounding the transplanted cell-laden scaffold indicating the effects of growth factors secreted by the hUC-MSCs. A connective tissue layer was found between the implanted cell-laden scaffold and the collagen layer, and immunohistochemical staining results suggested that this tissue was derived from the MSCs which migrated from within the scaffold. The results, thus, also suggested a protective effect the scaffold has on the encapsulated cells from the antibodies and cytotoxic cells of the host immune system.

Cartilage regeneration in zebrafish depends on Nrg1/ErbB signaling pathway

Objective: Cartilage, as the majority of adult mammalian tissues, has limited regeneration capacity. Cartilage degradation consecutive to joint injury or aging then leads to irreversible joint damage and diseases. In contrast, several vertebrate species such as the zebrafish have the remarkable capacity to spontaneously regenerate skeletal structures after severe injuries. The objective of our study was to test the regenerative capacity of Meckel's cartilage (MC) upon mechanical injury in zebrafish and to identify the mechanisms underlying this process. Methods and Results: Cartilage regenerative capacity in zebrafish larvae was investigated after mechanical injuries of the lower jaw MC in TgBAC(col2a1a:mCherry), to visualize the loss and recovery of cartilage. Confocal analysis revealed the formation of new chondrocytes and complete regeneration of MC at 14 days post-injury (dpi) via chondrocyte cell cycle re-entry and proliferation of pre-existing MC chondrocytes near the wound. Through expression analyses, we showed an increase of nrg1 expression in the regenerating lower jaw, which also expresses Nrg1 receptors, ErbB3 and ErbB2. Pharmacological inhibition of the ErbB pathway and specific knockdown of Nrg1 affected MC regeneration indicating the pivotal role of this pathway for cartilage regeneration. Finally, addition of exogenous NRG1 in an in vitro model of osteoarthritic (OA)-like chondrocytes induced by IL1β suggests that Nrg1/ErbB pathway is functional in mammalian chondrocytes and alleviates the increased expression of catabolic markers characteristic of OA-like chondrocytes. Conclusion: Our results show that the Nrg1/ErbB pathway is required for spontaneous cartilage regeneration in zebrafish and is of interest to design new therapeutic approaches to promote cartilage regeneration in mammals.

Alginate sulfate/ECM composite hydrogel containing electrospun nanofiber with encapsulated human adipose-derived stem cells for cartilage tissue engineering

Stem cell therapy is a promising strategy for cartilage tissue engineering, and cell transplantation using polymeric scaffolds has recently gained attention. Herein, we encapsulated human adipose-derived stem cells (hASCs) within the alginate sulfate hydrogel and then added them to polycaprolactone/gelatin electrospun nanofibers and extracellular matrix (ECM) powders to mimic the cartilage structure and characteristic. The composite hydrogel scaffolds were developed to evaluate the relevant factors and conditions in mechanical properties, cell proliferation, and differentiation to enhance cartilage regeneration. For this purpose, different concentrations (1-5 % w/v) of ECM powder were initially loaded within an alginate sulfate solution to optimize the best composition for encapsulated hASCs viability. Adding 4 % w/v of ECM resulted in optimal mechanical and rheological properties and better cell viability. In the next step, electrospun nanofibrous layers were added to the alginate sulfate/ECM composite to prepare different layered hydrogel-nanofiber (2, 3, and 5-layer) structures with the ability to mimic the cartilage structure and function. The 3-layer structure was selected as the optimum layered composite scaffold, considering cell viability, mechanical properties, swelling, and biodegradation behavior; moreover, the chondrogenesis potential was assessed, and the results showed promising features for cartilage tissue engineering application.

Function and mechanism of mesenchymal stem cells in the healing of diabetic foot wounds

Diabetes has become a global public health problem. Diabetic foot is one of the most severe complications of diabetes, which often places a heavy economic burden on patients and seriously affects their quality of life. The current conventional treatment for the diabetic foot can only relieve the symptoms or delay the progression of the disease but cannot repair damaged blood vessels and nerves. An increasing number of studies have shown that mesenchymal stem cells (MSCs) can promote angiogenesis and re-epithelialization, participate in immune regulation, reduce inflammation, and finally repair diabetic foot ulcer (DFU), rendering it an effective means of treating diabetic foot disease. Currently, stem cells used in the treatment of diabetic foot are divided into two categories: autologous and allogeneic. They are mainly derived from the bone marrow, umbilical cord, adipose tissue, and placenta. MSCs from different sources have similar characteristics and subtle differences. Mastering their features to better select and use MSCs is the premise of improving the therapeutic effect of DFU. This article reviews the types and characteristics of MSCs and their molecular mechanisms and functions in treating DFU to provide innovative ideas for using MSCs to treat diabetic foot and promote wound healing.

Bibliometric and visualization analysis of stem cell therapy for meniscal regeneration from 2012 to 2022

Background: Meniscus injuries, a common joint disease caused by long-term wear, trauma and inflammation, usually cause chronic dysfunction and pain in the joint. Current clinical surgeries mainly aim to remove the diseased tissue to alleviate patient suffering instead of helping with meniscus regeneration. As an emerging treatment, stem cell therapy has been verified to facilitate meniscus regeneration effectively. The purpose of this study is to investigate the publication conditions of stem cell therapy for meniscal regeneration and to visualize the research trends and frontiers. Methods: Relevant publications relevant to stem cells for meniscal regeneration was retrieved SCI-Expanded of the Web of Science database from 2012 to 2022. Research trends in the field were analysed and visualized by CiteSpace and VOSviewer. Results: A total of 354 publications were collected and analysed. The United States contributed the largest number of publications (118, 34.104%). Tokyo Medical Dental University has contributed the largest number of publications (34) among all full-time institutions. Stem cell research therapy has published the largest number of researches on stem cells for meniscal regeneration (17). SEKIYA. I contributed the majority of publications in this field (31), while Horie, M was the most frequently cited authors (166). #1 tissue engineering, #2 articular cartilage, #3 anterior cruciate ligament, #4 regenerative medicine, #5 scaffold are the chief keywords. This indicates that the current research hotspot has been transformed from basic surgical research to tissue engineering. Conclusion: Stem cell therapy is a promising therapeutic method for meniscus regeneration. This is the first visualized and bibliometric study to thoroughly construct the development trends and knowledge structure in the research field of stem cell therapy for meniscal regeneration in the past 10 years. The results thoroughly summarize and visualize the research frontiers, which will shed light on the research direction of stem cell therapy for meniscal regeneration.

3D Bioprinting Using Synovium-Derived MSC-Laden Photo-Cross-Linked ECM Bioink for Cartilage Regeneration

In this study, inspired by the components of cartilage matrix, a photo-cross-linked extracellular matrix (ECM) bioink composed of modified proteins and polysaccharides was presented, including gelatin methacrylate, hyaluronic acid methacrylate, and chondroitin sulfate methacrylate. The systematic experiments were performed, including morphology, swelling, degradation, mechanical and rheological tests, printability analysis, biocompatibility and chondrogenic differentiation characterization, and RNA sequencing (RNA-seq). The results indicated that the photo-cross-linked ECM hydrogels possessed suitable degradation rate and excellent mechanical properties, and the three-dimensional (3D) bioprinted ECM scaffolds obtained favorable shape fidelity and improved the basic properties, biological properties, and chondrogenesis of synovium-derived MSCs (SMSCs). The strong stimulation of transforming growth factor-beta 1 (TGF-β1) enhanced the aggregation, proliferation, and differentiation of SMSCs, thereby enhancing chondrogenic ECM deposition. In vivo animal experiments and gait analysis further confirmed that the ECM scaffold combined with TGF-β1 could effectively promote cartilage regeneration and functional recovery of injured joints. To sum up, the photo-cross-linked ECM bioink for 3D printing of functional cartilage tissue may become an attractive strategy for cartilage regeneration.

Bone Marrow-Derived Mesenchymal Stem Cell Implants for the Treatment of Focal Chondral Defects of the Knee in Animal Models: A Systematic Review and Meta-Analysis

Osteoarthritis remains an unfortunate long-term consequence of focal cartilage defects of the knee. Associated with functional loss and pain, it has necessitated the exploration of new therapies to regenerate cartilage before significant deterioration and subsequent joint replacement take place. Recent studies have investigated a multitude of mesenchymal stem cell (MSC) sources and polymer scaffold compositions. It is uncertain how different combinations affect the extent of integration of native and implant cartilage and the quality of new cartilage formed. Implants seeded with bone marrow-derived MSCs (BMSCs) have demonstrated promising results in restoring these defects, largely through in vitro and animal studies. A PRISMA systematic review and meta-analysis was conducted using five databases (PubMed, MEDLINE, EMBASE, Web of Science, and CINAHL) to identify studies using BMSC-seeded implants in animal models of focal cartilage defects of the knee. Quantitative results from the histological assessment of integration quality were extracted. Repair cartilage morphology and staining characteristics were also recorded. Meta-analysis demonstrated that high-quality integration was achieved, exceeding that of cell-free comparators and control groups. This was associated with repair tissue morphology and staining properties which resembled those of native cartilage. Subgroup analysis showed better integration outcomes for studies using poly-glycolic acid-based scaffolds. In conclusion, BMSC-seeded implants represent promising strategies for the advancement of focal cartilage defect repair. While a greater number of studies treating human patients is necessary to realize the full clinical potential of BMSC therapy, high-quality integration scores suggest that these implants could generate repair cartilage of substantial longevity.

Thermosensitive and biodegradable PCL-based hydrogels: potential scaffolds for cartilage tissue engineering

Due to a lack of sufficient blood supply and unique physicochemical properties, the treatment of injured cartilage is laborious and needs an efficient strategy. Unfortunately, most of the current therapeutic approaches are, but not completely, unable to restore the function of injured cartilage. Tissue engineering-based modalities are an alternative option to reconstruct the injured tissue. Considering the unique structure and consistency of cartilage tissue (osteochondral junction), it is mandatory to apply distinct biomaterials with unique properties slightly different from scaffolds used for soft tissues. PCL is extensively used for the fabrication of fine therapeutic scaffolds to accelerate the restorative process. Thermosensitive PCL hydrogels with distinct chemical compositions have paved the way for sophisticated cartilage regeneration. This review aimed to collect recent findings regarding the application of PCL in hydrogels blended with natural, synthetic materials in the context of cartilage healing.