Osteoarthritis prevention through meniscal regeneration induced by intra-articular injection of meniscus stem cells

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Preclinical Studies and Clinical Trials on Cell-Based Treatments for Meniscus Regeneration

This study aims at performing a thorough review of cell-based treatment strategies for meniscus regeneration in preclinical and clinical studies. The PubMed, Embase, and Web of Science databases were searched for relevant studies (both preclinical and clinical) published from the time of database construction to December 2022. Data related to cell-based therapies for in situ regeneration of the meniscus were extracted independently by two researchers. Assessment of risk of bias was performed according to the Cochrane Handbook for Systematic Reviews of Interventions. Statistical analyses based on the classification of different treatment strategies were performed. A total of 5730 articles were retrieved, of which 72 preclinical studies and 6 clinical studies were included in this review. Mesenchymal stem cells (MSCs), especially bone marrow MSCs (BMSCs), were the most commonly used cell type. Among preclinical studies, rabbit was the most commonly used animal species, partial meniscectomy was the most commonly adopted injury pattern, and 12 weeks was the most frequently chosen final time point for assessing repair outcomes. A range of natural and synthetic materials were used to aid cell delivery as scaffolds, hydrogels, or other morphologies. In clinical trials, there was large variation in the dose of cells, ranging from 16 × 106 to 150 × 106 cells with an average of 41.52 × 106 cells. The selection of treatment strategy for meniscus repair should be based on the nature of the injury. Cell-based therapies incorporating various "combination" strategies such as co-culture, composite materials, and extra stimulation may offer greater promise than single strategies for effective meniscal tissue regeneration, restoring natural meniscal anisotropy, and eventually achieving clinical translation. Impact Statement This review provides an up-to-date and comprehensive overview of preclinical and clinical studies that tested cell-based treatments for meniscus regeneration. It presents novel perspectives on studies published in the past 30 years, giving consideration to the cell sources and dose selection, delivery methods, extra stimulation, animal models and injury patterns, timing of outcome assessment, and histological and biomechanical outcomes, as well as a summary of findings for individual studies. These unique insights will help to shape future research on the repair of meniscus lesions and inform the clinical translation of new cell-based tissue engineering strategies.

Reconstruction of Fibrocartilage with Fibrous Alignment of Type I Collagen in Scaffold-Free Manner

For functional reconstruction of fibrocartilage, it is necessary to reproduce the essential mechanical property exhibited by natural fibrocartilage. The distinctive mechanical property of fibrocartilage is originated from the specific histological features of fibrocartilage composed of highly aligned type I collagen (Col I) and an abundant cartilaginous matrix. While the application of tensile stimulation induces highly aligned Col I, our study reveals that it also exerts an antichondrogenic effect on scaffold-free tissues constructed with meniscal chondrocytes (MCs) and induces downregulation of Sox-9 expression and attenuated glycosaminoglycan production. Modulation of mechanotransduction by blocking nuclear translocation of Yes-associated protein (YAP) ameliorated the antichondrogenic effect in the presence of tensile stimulation. Since MCs subjected to mechanical doses either by surface stiffness or tensile stimulation showed reversibility of YAP status even after a long-term exposure to mechanotransduction, fibrocartilage tissue was constructed by sequentially inducing tissue alignment by tensile stimulation followed by inducing cartilaginous matrix production in a tension-released state. The minimal tensile dose to constitute durable tissue alignment was screened by investigating the alignment of cytoskeleton and Col I after culturing the scaffold-free tissue constructs with various tensile doses (10% static tension for 1, 3, 7, and 10 days) followed by maintaining in a released state for 5 days. Fluorescence-conjugated phalloidin binding and immunofluorescence of Col I indicated that the duration of static tension for more than 7 days resulted in durable tissue alignment for at least 5 days in the tension-released state. The tissues subjected to tensile stimulation for 7 days followed by 14 days in a released state in chondrogenic media resulted in abundant cartilaginous matrix as well as uniaxial anisotropic alignment. Our results show that the optimized tensile dose can facilitate the successful reconstruction of fibrocartilage by modulating the characteristics of matrix production by MCs.

Kartogenin-loaded hydrogel promotes intervertebral disc repair via protecting MSCs against reactive oxygen species microenvironment by Nrf2/TXNIP/NLRP3 axis

Intervertebral disc (IVD) degeneration (IDD) and the consequent low back pain present a major medical challenge. Stem cell-based tissue engineering is promising for the treatment of IDD. However, stem cell-based treatment is severely impaired by the increased generation of reactive oxygen species (ROS) in degenerative disc, which can lead to a high level of cell dysfunction and even death. In this study, a kartogenin (KGN)@PLGA-GelMA/PRP composite hydrogel was designed and used as a carrier of ADSCs-based therapies in disc repair. Injectable composite hydrogel act as a carrier for controlled release of KGN and deliver ADSCs to the degenerative disc. The released KGN can stimulate the differentiation of ADSCs into a nucleus pulposus (NP) -like phenotype and boost antioxidant capacity of ADSCs via activating Nrf2/TXNIP/NLRP3 axis. Furthermore, the composite hydrogel combined with ADSCs attenuated the in vivo degeneration of rat IVDs, maintained IVD tissue integrity and accelerated the synthesis of NP-like extracellular matrix. Therefore, the KGN@PLGA-GelMA/PRP composite hydrogel is a promising strategy for stem cell-based therapies of IDD.

"Slow walk" mimetic tensile loading maintains human meniscus tissue resident progenitor cells homeostasis in photocrosslinked gelatin hydrogel

Meniscus, the cushion in knee joint, is a load-bearing tissue that transfers mechanical forces to extracellular matrix (ECM) and tissue resident cells. The mechanoresponse of human tissue resident stem/progenitor cells in meniscus (hMeSPCs) is significant to tissue homeostasis and regeneration but is not well understood. This study reports that a mild cyclic tensile loading regimen of ∼1800 loads/day on hMeSPCs seeded in 3-dimensional (3D) photocrosslinked gelatin methacryloyl (GelMA) hydrogel is critical in maintaining cellular homeostasis. Experimentally, a "slow walk" biomimetic cyclic loading regimen (10% tensile strain, 0.5 Hz, 1 h/day, up to 15 days) is applied to hMeSPCs encapsulated in GelMA hydrogel with a magnetic force-controlled loading actuator. The loading significantly increases cell differentiation and fibrocartilage-like ECM deposition without affecting cell viability. Transcriptomic analysis reveals 332 mechanoresponsive genes, clustered into cell senescence, mechanical sensitivity, and ECM dynamics, associated with interleukins, integrins, and collagens/matrix metalloproteinase pathways. The cell-GelMA constructs show active ECM remodeling, traced using a green fluorescence tagged (GFT)-GelMA hydrogel. Loading enhances nascent pericellular matrix production by the encapsulated hMeSPCs, which gradually compensates for the hydrogel loss in the cultures. These findings demonstrate the strong tissue-forming ability of hMeSPCs, and the importance of mechanical factors in maintaining meniscus homeostasis.

Carnosine Alleviates Knee Osteoarthritis and Promotes Synoviocyte Protection via Activating the Nrf2/HO-1 Signaling Pathway: An In-Vivo and In-Vitro Study

The most common joint disease in the elderly is knee osteoarthritis (OA). It is distinguished by cartilage degradation, subchondral bone loss, and a decrease in joint space. We studied the effects of carnosine (CA) on knee OA in male Wistar rats. OA is induced by anterior cruciate ligament transection combined with medial meniscectomy (ACLT+MMx) method and in vitro studies are conducted in fibroblast-like synoviocyte cells (FLS). The pain was assessed using weight-bearing and paw-withdrawal tests. CA supplementation significantly reduced pain. The enzyme-linked immunosorbent assay (ELISA) method was used to detect inflammatory proteins in the blood and intra-articular synovial fluid (IASF), and CA reduced the levels of inflammatory proteins. Histopathological studies were performed on knee-tissue samples using toluidine blue and hematoxylin and eosin (H and E) assays. CA treatment improved synovial protection and decreased cartilage degradation while decreasing zonal depth lesions. Furthermore, Western blotting studies revealed that the CA-treated group activated nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase (HO-1) and reduced the expression of cyclooxygenase-2 (COX-2). FLS cells were isolated from the knee joints and treated with IL-1β to stimulate the inflammatory response and increase reactive oxygen species (ROS). The matrix metalloproteinase protein (MMP's) levels (MMP-3, and MMP-13) were determined using the reverse transcription-polymerase chain reaction (RT-PCR), and CA treatment reduced the MMP's expression levels. When tested using the 2',7'-dicholorodihydrofluroscene diacetate (DCFDA) assay and the 5,5',6,6'-tetracholoro-1,1',3,3'-tertraethylbenzimidazolcarboc janine iodide (JC-1) assay in augmented ROS FLS cells, CA reduced the ROS levels and improved the mitochondrial membrane permeability. This study's investigation suggests that CA significantly alleviates knee OA both in vitro and in vivo.

Demineralized Cortical Bone Matrix Augmented With Peripheral Blood-Derived Mesenchymal Stem Cells for Rabbit Medial Meniscal Reconstruction

Tissue engineering is a promising treatment strategy for meniscal regeneration after meniscal injury. However, existing scaffold materials and seed cells still have many disadvantages. The objective of the present study is to explore the feasibility of peripheral blood-derived mesenchymal stem cells (PBMSCs) augmented with demineralized cortical bone matrix (DCBM) pretreated with TGF-β3 as a tissue-engineered meniscus graft and the repair effect. PBMSCs were collected from rabbit peripheral blood and subjected to three-lineage differentiation and flow cytometry identification. DCBM was prepared by decalcification, decellularization, and cross-linking rabbit cortical bone. Various characteristics such as biomechanical properties, histological characteristics, microstructure and DNA content were characterized. The cytotoxicity and the effects of DCBM on the adhesion and migration of PBMSCs were evaluated separately. The meniscus-forming ability of PBMSCs/DCBM complex in vitro induced by TGF-β3 was also evaluated at the molecular and genetic levels, respectively. Eventually, the present study evaluated the repair effect and cartilage protection effect of PBMSCs/DCBM as a meniscal graft in a rabbit model of medial meniscal reconstruction in 3 and 6 months. The results showed PBMSCs positively express CD29 and CD44, negatively express CD34 and CD45, and have three-lineage differentiation ability, thus can be used as tissue engineering meniscus seed cells. After the sample procedure, the cell and DNA contents of DCBM decreased, the tensile modulus did not decrease significantly, and the DCBM had a pore structure and no obvious cytotoxicity. PBMSCs could adhere and grow on the scaffold. Under induction of TGF-β3, PBMSCs/DCBM composites expressed glycosaminoglycan (GAG), and the related gene expression also increased. The results of the in vivo experiments that the PBMSCs/DCBM group had a better repair effect than the DCBM group and the control group at both 12 and 24 weeks, and the protective effect on cartilage was also better. Therefore, the application of DCBM augmented with PBMSCs for meniscus injury treatment is a preferred option for tissue-engineered meniscus.

Mesenchymal Stem Cells From Different Sources in Meniscus Repair and Regeneration

Meniscus damage is a common trauma that often arises from sports injuries or menisci tissue degeneration. Current treatment methods focus on the repair, replacement, and regeneration of the meniscus to restore its original function. The advance of tissue engineering provides a novel approach to restore the unique structure of the meniscus. Recently, mesenchymal stem cells found in tissues including bone marrow, peripheral blood, fat, and articular cavity synovium have shown specific advantages in meniscus repair. Although various studies explore the use of stem cells in repairing meniscal injuries from different sources and demonstrate their potential for chondrogenic differentiation, their meniscal cartilage-forming properties are yet to be systematically compared. Therefore, this review aims to summarize and compare different sources of mesenchymal stem cells for meniscal repair and regeneration.

Effect of acellular nerve scaffold containing human umbilical cord-derived mesenchymal stem cells on nerve repair and regeneration in rats with sciatic nerve defect

Background

The aim of the present study was to investigate the effect of acellular nerve scaffold (ANS) containing human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) on nerve repair and regeneration in rats with sciatic nerve defect.

Methods

Sciatic nerve trunks were removed from 6 female Sprague-Dawley (SD) rats, and ANS was prepared by lyophilization + enzymatic method and divided into A, B, C, D and E groups according to different treatment times. hUC-MSCs were isolated from the collected umbilical cords and cultured, and then ANS-hUC-MSCs complexes were made. The other 24 adult female SD rats were randomly divided into the control, autograft, ANS, and ANS-hUC-MSCs groups, and a rat model of sciatic nerve defect was established. Hematoxylin-eosin (HE) staining, Luxol fast blue (LFB) staining, Masson staining, and scanning electron microscopy were used to observe the morphology and tissue structure of ANS. The performance of ANS was evaluated by mechanical detection, and hydroxyproline (HYP) content was evaluated using a biochemical kit. Flow cytometry was adopted to detect the levels of hUC-MSCs surface antigens CD29, CD44, and CD34, as well as electrophysiological detection and muscle wet weight recovery rate for measuring rat muscle performance.

Results

ANS was prepared according to group A method and had good mechanical properties, with less residues of cells and myelin, and higher HYP content, indicating that this scaffold had the best performance. ANS-hUC-MSCs significantly reduced myelin injury in the sciatic nerve, and increased axonal regeneration, effectively improving sciatic nerve injury in rats. In addition, ANS-hUC-MSCs significantly increased compound muscle action potential (CMAP), nerve conduction velocity (NCV), and muscle wet weight, and reduced muscle atrophy.

Conclusions

ANS containing hUC-MSCs can promote nerve repair and regeneration in rats with sciatic nerve defects.

Meniscus Regeneration With Multipotent Stromal Cell Therapies

Meniscus is a semilunar wedge-shaped structure with fibrocartilaginous tissue, which plays an essential role in preventing the deterioration and degeneration of articular cartilage. Lesions or degenerations of it can lead to the change of biomechanical properties in the joints, which ultimately accelerate the degeneration of articular cartilage. Even with the manual intervention, lesions in the avascular region are difficult to be healed. Recent development in regenerative medicine of multipotent stromal cells (MSCs) has been investigated for the significant therapeutic potential in the repair of meniscal injuries. In this review, we provide a summary of the sources of MSCs involved in repairing and regenerative techniques, as well as the discussion of the avenues to utilizing these cells in MSC therapies. Finally, current progress on biomaterial implants was reviewed.

Post-Traumatic Osteoarthritis Assessment in Emerging and Advanced Pre-Clinical Meniscus Repair Strategies: A Review

Surgical repair of meniscus injury is intended to help alleviate pain, prevent further exacerbation of the injury, restore normal knee function, and inhibit the accelerated development of post-traumatic osteoarthritis (PTOA). Meniscus injuries that are treated poorly or left untreated are reported to significantly increase the risk of PTOA in patients. Current surgical approaches for the treatment of meniscus injuries do not eliminate the risk of accelerated PTOA development. Through recent efforts by scientists to develop innovative and more effective meniscus repair strategies, the use of biologics, allografts, and scaffolds have come into the forefront in pre-clinical investigations. However, gauging the extent to which these (and other) approaches inhibit the development of PTOA in the knee joint is often overlooked, yet an important consideration for determining the overall efficacy of potential treatments. In this review, we catalog recent advancements in pre-clinical therapies for meniscus injuries and discuss the assessment methodologies that are used for gauging the success of these treatments based on their effect on PTOA severity. Methodologies include histopathological evaluation of cartilage, radiographic evaluation of the knee, analysis of knee function, and quantification of OA predictive biomarkers. Lastly, we analyze the prevalence of these methodologies using a systemic PubMed® search for original scientific journal articles published in the last 3-years. We indexed 37 meniscus repair/replacement studies conducted in live animal models. Overall, our findings show that approximately 75% of these studies have performed at least one assessment for PTOA following meniscus injury repair. Out of this, 84% studies have reported an improvement in PTOA resulting from treatment.

Effects of Video Task With a High-Level Exercise Illustration on Knee Movements in Male Volleyball Spike Jump

Hazardous knee biomechanics, such as excessive knee affordance link with injuries in volleyball spike jumps (SPJs) and can be reconfigured by the enhancement of internal focus. The study aimed to explore the effects of video tasks illustrating a high-level SPJ on knee movement in the volleyball SPJ with 15 elite male volleyball athletes. This study investigated the knee movements in sagittal, coronal, and transverse planes before and after the video task in SPJ using one-dimensional statistical parametric mapping (SPM 1D) and discrete statistics. The SPM 1D indicated a larger knee flexion angle (31.17–73.19%, t = 2.611, and p = 0.012), increased knee flexion moment (19.72–21.38%, t = 0.029, and p = 0.029), and increased knee adduction angular velocity (49.07–62.64%, t = 3.148, and p = 0.004) after video task; alternatively, smaller knee external rotation angular velocity (45.85–49.96%, t = 5.199, and p = 0.017) and vertical ground reaction (vGRF) (3.13–5.94%, t = 4.096, and p = 0.014; 19.83–21.97%, t = 4.096, and p = 0.024) were found after the task. With discrete value statistics, the video task increased the peak of knee flexion angle while decreased the peak of extension moment, flexion moment, abduction moment, external moment, the first peak vGRF, and related loading rate.

Conclusions: The results indicate that knee biomechanics in volleyball SPJ positively influenced by the video task. The task has the athletes control the knee movements more actively and improves the original hazardous movement strategies. Therefore, the video task presumably can abate the occurrence of knee injuries in volleyball SPJ. Further validation especially in the exercise effect is needed in the future.

Injectable Fibrin/Polyethylene Oxide Semi-IPN Hydrogel for a Segmental Meniscal Defect Regeneration

BACKGROUND

Meniscal deficiency from meniscectomy is a common situation in clinical practices. Regeneration of the deficient meniscal portion, however, is still not feasible.

PURPOSE

To develop an injectable hydrogel system consisting of fibrin (Fb) and polyethylene oxide (PEO) and to estimate its clinical potential for treating a segmental defect of the meniscus in a rabbit meniscal defect model.

STUDY DESIGN

Controlled laboratory study.

METHODS

The Fb/PEO hydrogel was fabricated by extruding 100 mg·mL^-1 of fibrinogen solution and 2,500 U·mL^-1 of thrombin solution containing 100 mg·mL^-1 of PEO through a dual-syringe system. The hydrogels were characterized by rheological analysis and biodegradation tests. The meniscal defects of New Zealand White male rabbits were generated by removing 60% of the medial meniscus from the anterior side. The removed portion included the central portion. The Fb/PEO hydrogel was injected into the meniscal defect of the experimental knee through the joint space between the femoral condyle and tibial plateau at the anterior knee without a skin incision. The entire medial menisci from both knees of each rabbit were collected and photographed before placement in formalin for histological processing. Hematoxylin and eosin, safranin O, and immunohistochemical staining for type II collagen was performed. The biomechanical property of the regenerated meniscus was evaluated using a universal tensile machine.

RESULTS

The Fb/PEO hydrogel was fabricated by an in situ gelation process, and the hydrogel displayed a semi-interpenetrating polymer network structure. We demonstrated that the mechanical properties of Fb-based hydrogels increased in a PEO-dependent manner. Furthermore, the addition of PEO delayed the biodegradation of the hydrogel. Our in vivo data demonstrated that, as compared with Fb hydrogel, Fb/PEO hydrogel injection into the meniscectomy model showed improved tissue regeneration. The regenerated meniscal tissue by Fb/PEO hydrogel showed enhanced tissue quality, which was supported by the histological and biomechanical properties.

CONCLUSION

The Fb/PEO hydrogel had an effective tissue-regenerative ability through injection into the in vivo rabbit meniscal defect model.

CLINICAL RELEVANCE

This injectable hydrogel system can promote meniscal repair and be readily utilized in clinical application.

Assessing the Resident Progenitor Cell Population and the Vascularity of the Adult Human Meniscus

PURPOSE

To identify, characterize, and compare the resident progenitor cell populations within the red-red, red-white, and white-white (WW) zones of freshly harvested human cadaver menisci and to characterize the vascularity of human menisci using immunofluorescence and 3-dimensional (3D) imaging.

METHODS

Fresh adult human menisci were harvested from healthy donors. Menisci were enzymatically digested, mononuclear cells isolated, and characterized using flow cytometry with antibodies against mesenchymal stem cell surface markers (CD105, CD90, CD44, and CD29). Cells were expanded in culture, characterized, and compared with bone marrow-derived mesenchymal stem cells. Trilineage differentiation potential of cultured cells was determined. Vasculature of menisci was mapped in 3D using a modified uDisco clearing and immunofluorescence against vascular markers CD31, lectin, and alpha smooth muscle actin.

RESULTS

There were no significant differences in the clonogenicity of isolated cells between the 3 zones. Flow cytometry showed presence of CD44⁺CD105⁺CD29⁺CD90⁺ cells in all 3 zones with high prevalence in the WW zone. Progenitors from all zones were found to be potent to differentiate to mesenchymal lineages. Larger vessels in the red-red zone of meniscus were observed spanning toward red-white, sprouting to smaller arterioles and venules. CD31⁺ cells were identified in all zones using the 3D imaging and co-localization of additional markers of vasculature (lectin and alpha smooth muscle actin) was observed.

CONCLUSIONS

The presence of resident mesenchymal progenitors was evident in all 3 meniscal zones of healthy adult donors without injury. In addition, our results demonstrate the presence of vascularization in the WW zone.

CLINICAL RELEVANCE

The existence of progenitors and presence of microvasculature in the WW zone of the meniscus suggests the potential for repair and biologic augmentation strategies in that zone of the meniscus in young healthy adults. Further research is necessary to fully define the functionality of the meniscal blood supply and its implications for repair.

Meniscus regeneration with injectable Pluronic/PMMA-reinforced fibrin hydrogels in a rabbit segmental meniscectomy model

Injectable hydrogel systems are a facile approach to apply to the damaged meniscus in a minimally invasive way. We herein developed a clinically applicable and injectable semi-interpenetrated network (semi-IPN) hydrogel system based on fibrin (Fb), reinforced with Pluronic F127 (F127) and polymethyl methacrylate (PMMA), to improve the intrinsic weak mechanical properties. Through the dual-syringe device system, the hydrogel could form a gel state within about 50 s, and the increment of compressive modulus of Fb hydrogels was achieved by adding F127 from 3.0% (72.0 ± 4.3 kPa) to 10.0% (156.0 ± 9.8 kPa). The shear modulus was enhanced by adding PMMA microbeads (26.0 ± 1.1 kPa), which was higher than Fb (13.5 ± 0.5 kPa) and Fb/F127 (21.7 ± 0.8 kPa). Moreover, the addition of F127 and PMMA also delayed the rate of enzymatic biodegradation of Fb hydrogel. Finally, we confirmed that both Fb/F127 and Fb/F127/PMMA hydrogels showed accelerated tissue repair in the in vivo segmental defect of the rabbit meniscus model. In addition, the histological analysis showed that the quality of the regenerated tissues healed by Fb/F127 was particularly comparable to that of healthy tissue. The biomechanical strength of the regenerated tissues of Fb/F127 (3.50 ± 0.35 MPa) and Fb/F127/PMMA (3.59 ± 0.89 MPa) was much higher than that of Fb (0.82 ± 0.05 MPa) but inferior to that of healthy tissue (6.63 ± 1.12 MPa). These results suggest that the reinforcement of Fb hydrogel using FDA-approved synthetic biomaterials has great potential to be used clinically.

Endogenous cell recruitment strategy for articular cartilage regeneration

In the absence of timely and proper treatments, injuries to articular cartilage (AC) can lead to cartilage degeneration and ultimately result in osteoarthritis. Regenerative medicine and tissue engineering techniques are emerging as promising approaches for AC regeneration and repair. Although the use of cell-seeded scaffolds prior to implantation can regenerate and repair cartilage lesions to some extent, these approaches are still restricted by limited cell sources, excessive costs, risks of disease transmission and complex manufacturing practices. Recently developed acellular scaffold approaches that rely on the recruitment of endogenous cells to the injured sites avoid these drawbacks and offer great promise for in situ AC regeneration. Multiple endogenous stem/progenitor cells (ESPCs) are found in joint-resident niches and have the capability to migrate to sites of injury to participate in AC regeneration. However, the natural recruitment of ESPCs is insufficient, and the local microenvironment is hostile after injury. Hence, an endogenous cell recruitment strategy based on the combination of chemoattractants and acellular scaffolds to effectively and specifically recruit ESPCs and improve local microenvironment may provide new insights into in situ AC regeneration. This review provides a brief overview of: (1) the status of endogenous cell recruitment strategy; (2) the subpopulations, potential migration routes (PMRs) of joint-resident ESPCs and their immunomodulatory and reparative effects; (3) chemoattractants and their potential adverse effects; (4) scaffold-based drug delivery systems (SDDSs) that are utilized for in situ AC regeneration; and (5) the challenges and future perspectives of endogenous cell recruitment strategy for AC regeneration. STATEMENT OF SIGNIFICANCE: Although the endogenous cell recruitment strategy for articular cartilage (AC) regeneration has been investigated for several decades, much work remains to be performed in this field. Future studies should have the following aims: (1) reporting the up-to-date progress in the endogenous cell recruitment strategies; (2) determining the subpopulations of ESPCs, the cellular and molecular mechanisms underlying the migration of these cells and their anti-inflammatory, immunomodulatory and reparative effects; (3) elucidating the chemoattractants that enhance ESPC recruitment and their potential adverse effects; and (4) developing advanced SDDSs for chemoattractant dispatch. Herein, we present a systematic overview of the aforementioned issues to provide a better understanding of endogenous cell recruitment strategies for AC regeneration and repair.

Intra-articular injection of hUC-MSCs expressing miR-140-5p induces cartilage self-repairing in the rat osteoarthritis

INTRODUCTION

Currently, osteoarthritis (OA) receives global increasing attention because it associates severe joint pain and serious disability. Stem cells intra-articular injection therapy showed a potential therapeutic superiority to reduce OA development and to improve treating outputs. However, the long-term effect of stem cells intra-articular injection on the cartilage regeneration remains unclear. Recently, miR-140-5p was confirmed as a critical positive regulator in chondrogenesis. We hypothesized that hUC-MSCs overexpressing miR-140-5p have better therapeutic effect on osteoarthritis.

MATERIALS AND METHODS

To enhance stem cell chondrogenic differentiation, we have transfected human umbilical cord mesenchymal stem cells (hUC-MSCs) with miR-140-5p mimics and miR-140-5p lentivirus to overexpress miR-140-5p in a short term or a long term accordingly. Thereafter, MSCs proliferation, chondrogenic genes expression and extracellular matrix were assessed. Destabilization of the medial meniscus (DMM) surgery was performed on the knee joints of SD rats as an OA model, and then intra-articular injection of hUC-MSCs or hUC-MSCs transfected with miR-140-5p lentivirus was carried to evaluate the cartilage healing effect with histological staining and OARSI scores. The localization of hUC-MSCs after intra-articular injection was further confirmed by immunohistochemical staining.

RESULTS

Significant induction of chondrogenic differentiation in the miR-140-5p-hUC-MSCs (140-MSCs), while its proliferation was not influenced. Interestingly, intra-articular injection of 140-MSCs significantly enhanced articular cartilage self-repairing in comparison to normal hUC-MSCs. Moreover, we noticed that intra-articular injection of high 140-MSCs numbers reinforces cells assembling on the impaired cartilage surface and subsequently differentiated into chondrocytes.

CONCLUSIONS

In conclusion, these results indicate therapeutic superiority of hUC-MSCs overexpressing miR-140-5p to treat OA using intra-articular injection.

Expression and function of cartilage-derived pluripotent cells in joint development and repair

Cartilage-derived pluripotent cells reside in hyaline cartilage and fibrocartilage. These cells have the potential for multidirectional differentiation; can undergo adipogenesis, osteogenesis, and chondrogenesis; and have been classified as mesenchymal stem cells (MSCs) conforming to the minimal criteria of the International Society for Cellular Therapy. Cartilage tissue is prone to injury and is difficult to repair. As cartilage-derived pluripotent cells are the closest cell source to cartilage tissue, they are expected to have the strongest ability to differentiate into cartilage compared to other MSCs. This review focuses on the organizational distribution, expression, and function of cartilage-derived pluripotent cells in joint development and repair to help explore the therapeutic potential of in situ cartilage-derived pluripotent cells for joint cartilage repair.

Characterization and Comparison of Postnatal Rat Meniscus Stem Cells at Different Developmental Stages

Meniscus‐derived stem cells (MeSCs) are a potential cell source for meniscus tissue engineering. The stark morphological and structural changes of meniscus tissue during development indicate the complexity of MeSCs at different tissue regions and stages of development. In this study, we characterized and compared postnatal rat meniscus tissue and MeSCs at different tissue regions and stages of development. We observed that the rat meniscus tissue exhibited marked changes in tissue morphology during development, with day 7 being the most representative time point of different developmental stages. All rat MeSCs displayed typical stem cell characteristics. Rat MeSCs derived from day 7 inner meniscus tissue exhibited the highest self‐renewal capacity, cell proliferation, differentiation potential toward various mesenchymal lineage and the highest expression levels of chondrogenic genes and proteins. Transplantation of rat MeSCs derived from day 7 inner meniscus tissue promoted neo‐tissue formation and effectively protected joint surface cartilage in vivo. Our results demonstrated for the first time that rat MeSCs are not necessarily better at earlier developmental stages, and that rat MeSCs derived from day 7 inner meniscus tissue may be a superior cell source for effective meniscus regeneration and articular cartilage protection. This information could make a significant contribution to human meniscus tissue engineering in the future. stem cells translational medicine2019;8:1318&1329

(A): Meniscus tissue at different tissue regions and stages of development. (B): MeSCs at different tissue regions and stages of development. (C): Intra‐articular injection of MeSCs for meniscus regeneration and OA suppression. *Significant difference between two groups at p < .05. **Significant difference between two groups at p < .01. ***Significant difference between two groups at p < .001. ****Significant difference between two groups at p < .0001. N.S., No significant difference between two groups at p ≥ .05.

A collagen-coated sponge silk scaffold for functional meniscus regeneration

Tissue engineering is a promising solution for meniscal regeneration after meniscectomy. However, in situ reconstruction still poses a formidable challenge due to multifunctional roles of the meniscus in the knee. In this study, we fabricate a silk sponge from 9% (w/v) silk fibroin solution through freeze drying and then coat its internal space and external surface with collagen sponge. Subsequently, various characteristics of the silk-collagen scaffold are evaluated, and cytocompatibility of the construct is assessed in vitro and subcutaneously. The efficacy of this composite scaffold for meniscal regeneration is evaluated through meniscus reconstruction in a rabbit meniscectomy model. It is found that the internally coated collagen sponge enhances the cytocompatibility of the silk sponge, and the external layer of collagen sponge significantly improves the initial frictional property. Additionally, the silk-collagen composite group shows more tissue ingrowth and less cartilage wear than the pure silk sponge group at 3 months postimplantation in situ. These findings thus demonstrate that the composite scaffold had less damage to the joint surface than the silk alone through promoting functional meniscal regeneration after meniscectomy, which indicates its clinical potential in meniscus reconstruction.

Current Concepts in Meniscus Tissue Engineering and Repair

The meniscus is the most commonly injured structure in the human knee. Meniscus deficiency has been shown to lead to advanced osteoarthritis (OA) due to abnormal mechanical forces, and replacement strategies for this structure have lagged behind other tissue engineering endeavors. The challenges include the complex 3D structure with individualized size parameters, the significant compressive, tensile and shear loads encountered, and the poor blood supply. In this progress report, a review of the current clinical treatments for different types of meniscal injury is provided. The state-of-the-art research in cellular therapies and novel cell sources for these therapies is discussed. The clinically available cell-free biomaterial implants and the current progress on cell-free biomaterial implants are reviewed. Cell-based tissue engineering strategies for the repair and replacement of meniscus are presented, and the current challenges are identified. Tissue-engineered meniscal biocomposite implants may provide an alternative solution for the treatment of meniscal injury to prevent OA in the long run, because of the limitations of the existing therapies.

Tissue Engineering of Large Full-Size Meniscus Defects by a Polyurethane Scaffold: Accelerated Regeneration by Mesenchymal Stromal Cells

The endogenous healing potential of avascular meniscal lesions is poor. Up to now, partial meniscectomy is still the treatment of choice for meniscal lesions within the avascular area. However, the large loss of meniscus substance predisposes the knee for osteoarthritic changes. Tissue engineering techniques for the replacement of such lesions could be a promising alternative treatment option. Thus, a polyurethane scaffold, which is already in clinical use, loaded with mesenchymal stromal cells, was analyzed for the repair of critical meniscus defects in the avascular zone. Large, approximately 7 mm broad meniscus lesions affecting both the avascular and vascular area of the lateral rabbit meniscus were treated with polyurethane scaffolds either loaded or unloaded with mesenchymal stromal cells. Menisci were harvested at 6 and 12 weeks after initial surgery. Both cell-free and cell-loaded approaches led to well-integrated and stable meniscus-like repair tissue. However, an accelerated healing was achieved by the application of mesenchymal stromal cells. Dense vascularization was detected throughout the repair tissue of both treatment groups. Overall, the polyurethane scaffold seems to promote the vessel ingrowth. The application of mesenchymal stromal cells has the potential to speed up the healing process.

Intra-articular injection of mesenchymal stem cells in treating knee osteoarthritis: a systematic review of animal studies

PURPOSE

Mesenchymal stem cells (MSCs) injection has emerged as a novel treatment for knee osteoarthritis (KOA) but with inconsistent results in the experimental studies. Thus, the purpose of the present study is to evaluate the preclinical animal studies of MSCs injection for KOA and to determine the evidence for a role for MSCs in further clinical trials.

METHODS

A systematic search of KOA animal studies published through Aug 2017 was conducted using the PubMed, Embase and Web of science. Criteria for eligibility were animal studies assessing the therapeutic effects of MSCs intra-articular injection to animals with KOA. The methodological quality of included studies was assessed by the SYRCLE tool for assessing risk of bias in animal intervention studies. Descriptive synthesis was performed. Evidence quality was evaluated based on the Confidence in the Evidence from Reviews of Qualitative research (CERQual) tool.

RESULTS

Twenty-three KOA animal studies were eligible for inclusion. According to the SYRCLE's tool, all included studies had high risk of bias. Between-study heterogeneity was substantial. The included studies varied in terms of species, modeling methods, MSCs origin, treatment timing, injections frequency, transplantation type and dose of MSCs. The following outcomes, gross morphology, histological analysis, immunohistochemical analysis, radiological evaluation or behavior analysis, were reported in the primary studies. For all outcomes, the evidence quality was low or very low.

CONCLUSIONS

We do not have absolute confidence to recommend use MSCs injection for KOA clinical trials. Based on the internal and external validity of current animal studies, high quality experimental studies and efforts for effective translation from preclinical studies to clinical trials are still required.

Age-related changes in the knee meniscus

BACKGROUND

Aging is the most prominent risk factor for the development of osteoarthritis (OA), which affects knees and causes major health burdens. Meniscal dysfunction mostly based on degeneration contributes to the development and progression of knee OA. Meniscal degeneration is caused by various extrinsic factors, such as repetitive trauma or leg malalignment, while meniscal aging is considered as internal changes, such as molecular or cellular changes. Little is known about age-related changes in the meniscus. Therefore, this review aimed to summarize and clarify the understanding of the aged meniscus.

METHODS

There are few articles about natural aging in the meniscus, because most reports only demonstrate the effects of OA on the meniscus. We searched PubMed (1948 to November 2016) to identify and summarize all English-language articles evaluating natural aging in the meniscus.

RESULTS

There is evidence of compositional change in the meniscus with aging, involving cells, collagens, and proteoglycans. In addition, as recent reports on the natural aging of cartilage have indicated, senescence of the meniscal cells may also lead to disruption of meniscal cells and tissue homeostasis. Due to the low turnover rate of collagen, accumulation of advanced glycation end-products largely contributes to tissue stiffness and vulnerability, and finally results in degenerative changes or tears. Furthermore, environmental factors such as joint fluid secreted by inflamed synovium could also contribute to meniscal tissue deterioration.

CONCLUSIONS

Age-related changes induce meniscal tissue vulnerability and finally lead to meniscal dysfunction.

Plasticity of Human Meniscus Fibrochondrocytes: A Study on Effects of Mitotic Divisions and Oxygen Tension

Meniscus fibrochondrocytes (MFCs) may be the optimal cell source to repair non-healing meniscus injuries using tissue engineering strategies. In this study, we investigated the effects of mitotic divisions and oxygen tension on the plasticity of adult human MFCs. Our assessment techniques included gene expression, biochemical, histological, and immunofluorescence assays. MFCs were expanded in monolayer culture with combined growth factors TGFβ1 and FGF-2 (T1F2) under normoxia (21% O₂). Trilineage (adipogenesis, chondrogenesis and osteogenesis) differentiation was performed under both normoxic (21% O₂) and hypoxic (3% O₂) conditions. The data demonstrated that MFCs with a mean total population doubling of 10 can undergo adipogenesis and chondrogenesis. This capability was enhanced under hypoxic conditions. The MFCs did not undergo osteogenesis. In conclusion, our findings suggest that extensively expanded human MFCs have the capacity to generate tissues with the functional matrix characteristics of avascular meniscus. To this end, expanded MFCs may be an ideal cell source for engineering functional constructs for the replacement or repair of avascular meniscus.

Stem cell delivery in tissue-specific hydrogel enabled meniscal repair in an orthotopic rat model

Interest in non-invasive injectable therapies has rapidly risen due to their excellent safety profile and ease of use in clinical settings. Injectable hydrogels can be derived from the extracellular matrix (ECM) of specific tissues to provide a biomimetic environment for cell delivery and enable seamless regeneration of tissue defects. We investigated the in situ delivery of human mesenchymal stem cells (hMSCs) in decellularized meniscus ECM hydrogel to a meniscal defect in a nude rat model. First, decellularized meniscus ECM hydrogel retained tissue-specific proteoglycans and collagens, and significantly upregulated expression of fibrochondrogenic markers by hMSCs versus collagen hydrogel alone in vitro. The meniscus ECM hydrogel in turn supported delivery of hMSCs for integrative repair of a full-thickness defect model in meniscal explants after in vitro culture and in vivo subcutaneous implantation. When applied to an orthotopic model of meniscal injury in nude rat, hMSCs in meniscus ECM hydrogel were retained out to eight weeks post-injection, contributing to tissue regeneration and protection from joint space narrowing, pathologic mineralization, and osteoarthritis development, as evidenced by macroscopic and microscopic image analysis. Based on these findings, we propose the use of tissue-specific meniscus ECM-derived hydrogel for the delivery of therapeutic hMSCs to treat meniscal injury.

Cell-Based Meniscus Repair and Regeneration: At the Brink of Clinical Translation?: A Systematic Review of Preclinical Studies

Background:

Meniscus damage can be caused by trauma or degeneration and is therefore common among patients of all ages. Repair or regeneration of the menisci could be of great importance not only for pain relief or regaining function but also to prevent degenerative disease and osteoarthritis. Current treatment does not offer consistent long-term improvement. Although preclinical research focusing on augmentation of meniscal tear repair and regeneration after meniscectomy is encouraging, clinical translation remains difficult.

Purpose:

To systematically evaluate the literature on in vivo meniscus regeneration and explore the optimal cell sources and conditions for clinical translation. We aimed at thorough evaluation of current evidence as well as clarifying the challenges for future preclinical and clinical studies.

Study Design:

Systematic review.

Methods:

A search was conducted using the electronic databases of MEDLINE, Embase, and the Cochrane Collaboration. Search terms included meniscus, regeneration, and cell-based.

Results:

After screening 81 articles based on title and abstract, 51 articles on in vivo meniscus regeneration could be included; 2 additional articles were identified from the references. Repair and regeneration of the meniscus has been described by intra-articular injection of multipotent mesenchymal stromal (stem) cells from adipose tissue, bone marrow, synovium, or meniscus or the use of these cell types in combination with implantable or injectable scaffolds. The use of fibrochondrocytes, chondrocytes, and transfected myoblasts for meniscus repair and regeneration is limited to the combination with different scaffolds. The comparative in vitro and in vivo studies mentioned in this review indicate that the use of allogeneic cells is as successful as the use of autologous cells. In addition, the implantation or injection of cell-seeded scaffolds increased tissue regeneration and led to better structural organization compared with scaffold implantation or injection of a scaffold alone. None of the studies mentioned in this review compare the effectiveness of different (cell-seeded) scaffolds.

Conclusion:

There is heterogeneity in animal models, cell types, and scaffolds used, and limited comparative studies are available. The comparative in vivo research that is currently available is insufficient to draw strong conclusions as to which cell type is the most promising. However, there is a vast amount of in vivo research on the use of different types of multipotent mesenchymal stromal (stem) cells in different experimental settings, and good results are reported in terms of tissue formation. None of these studies compare the effectiveness of different cell-scaffold combinations, making it hard to conclude which scaffold has the greatest potential.

Scaffold-Free Tissue-Engineered Allogenic Adipose-Derived Stem Cells Promote Meniscus Healing

PURPOSE

To determine whether meniscal tissue could be healed histologically by the implantation of allogenic three-dimensional formed adipose-derived stem cells (ADSCs) in a rabbit model of partial meniscectomy.

METHODS

Forty Japanese white rabbits (aged 15-17 weeks) were assigned to 2 groups. Defects 1.5 mm in diameter were created in the anterior horn of the medial menisci. The defects were left empty in the control group and were filled with cylindrical plugs of allogenic ADSCs extracted from adipose tissue in the experimental group. Macroscopic scoring (range, 0-3), histological scoring (range, 0-12), and immunohistological stainability of type I collagen were evaluated at 2, 4, 8, and 12 weeks postoperatively (n = 5 rabbits for each week).

RESULTS

Macroscopically, the height of the healing tissue in the experimental group was significantly greater than that of the control group at 2 weeks (3 vs 0, P = .01), 4 weeks (3 vs 1, P = .01), and 8 weeks (3 vs 2, P = .02). Histologically, safranin-O staining was noted at 2 weeks and increased gradually over time in the experimental group. In contrast, the intensity of staining was lower in controls at all weeks. Tissue quality scores were significantly higher in the experimental group than in the controls at all weeks (3 vs 0 at 2 weeks [P = .00009], 4.5 vs 2 at 4 weeks [P = .00023], 9 vs 5 at 8 weeks [P = .0047], 10.5 vs 6 at 12 weeks [P = .00026]). The implanted tissue was positive for type I collagen, and stainability was increased gradually over time.

CONCLUSIONS

Three-dimensional scaffold-free allogenic ADSCs implanted into a 1.5-mm avascular meniscal defect survived, adhered to the defect, and promoted histological meniscus healing in a rabbit model.

CLINICAL RELEVANCE

ADSC implantation designed to promote meniscal healing may play an important role as a tool for meniscus healing.

Advances and Prospects in Stem Cells for Cartilage Regeneration

The histological features of cartilage call attention to the fact that cartilage has a little capacity to repair itself owing to the lack of a blood supply, nerves, or lymphangion. Stem cells have emerged as a promising option in the field of cartilage tissue engineering and regenerative medicine and could lead to cartilage repair. Much research has examined cartilage regeneration utilizing stem cells. However, both the potential and the limitations of this procedure remain controversial. This review presents a summary of emerging trends with regard to using stem cells in cartilage tissue engineering and regenerative medicine. In particular, it focuses on the characterization of cartilage stem cells, the chondrogenic differentiation of stem cells, and the various strategies and approaches involving stem cells that have been used in cartilage repair and clinical studies. Based on the research into chondrocyte and stem cell technologies, this review discusses the damage and repair of cartilage and the clinical application of stem cells, with a view to increasing our systematic understanding of the application of stem cells in cartilage regeneration; additionally, several advanced strategies for cartilage repair are discussed.

Intra-articular Implantation of Mesenchymal Stem Cells, Part 2: A Review of the Literature for Meniscal Regeneration

Knee osteoarthritis (OA) after partial or total meniscectomy is a prevalent issue that patients must face. Various methods of replacing meniscal tissue have been studied to avoid this progression, including meniscal allograft transplantation, meniscal scaffolds, and synthetic meniscus replacement. Studies have shown that meniscal scaffolds may improve symptoms but have not been shown to prevent progression of OA. Recently, mesenchymal stem cells (MSCs) have been proposed as a possible biological therapy for meniscal regeneration. Several animal studies and 1 human study have evaluated the effect of transplanting MSCs into the knee joint after partial meniscectomy. The purpose of this review was to assess the outcomes of intra-articular transplantation of MSCs on meniscal regeneration in animals and humans after partial meniscectomy. Limited results from animal studies suggest that there is some potential for intra-articular injection of MSCs for the regeneration of meniscal tissue. However, further studies are necessary to determine the quality of regenerated meniscal tissue through histological and biomechanical testing.

Intra-articular Implantation of Mesenchymal Stem Cells, Part 1: A Review of the Literature for Prevention of Postmeniscectomy Osteoarthritis

Osteoarthritis (OA) after a partial or total meniscectomy procedure is a common pathology. Because of the high incidence of meniscectomy in the general population, as well as the significant burden of knee OA, there is increasing interest in determining methods for delaying postmeniscectomy OA. Biological therapies, including mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and platelet-rich plasma (PRP), have been proposed as possible therapies that could delay OA in this and other settings. Several studies in various animal models have evaluated the effect of injecting MSCs into the knee joints of animals with OA induced either by meniscal excision with or without anterior cruciate ligament transection. When compared with control groups receiving injections without progenitor cells, short-term benefits in the experimental groups have been reported. In human subjects, there are limited data to determine the effect of biological therapies for use in delaying or preventing the onset of OA after a meniscectomy procedure. The purpose of this review is to highlight the findings in the presently available literature on the use of intra-articular implantation of MSCs postmeniscectomy and to offer suggestions for future research with the goal of delaying or treating early OA postmeniscectomy with MSCs.

Isolation, Characterization, and Multipotent Differentiation of Mesenchymal Stem Cells Derived from Meniscal Debris

This study aimed to culture and characterize mesenchymal stem cells derived from meniscal debris. Cells in meniscal debris from patients with meniscal injury were isolated by enzymatic digestion, cultured in vitro to the third passage, and analyzed by light microscopy to observe morphology and growth. Third-passage cultures were also analyzed for immunophenotype and ability to differentiate into osteogenic, adipogenic, and chondrogenic lineages. After 4-5 days in culture, cells showed a long fusiform shape and adhered to the plastic walls. After 10-12 days, cell clusters and colonies were observed. Third-passage cells showed uniform morphology and good proliferation. They expressed CD44, CD90, and CD105 but were negative for CD34 and CD45. Cultures induced to differentiate via osteogenesis became positive for Alizarin Red staining as well as alkaline phosphatase activity. Cultures induced to undergo adipogenesis were positive for Oil Red O staining. Cultures induced to undergo chondrogenesis were positive for staining with Toluidine Blue, Alcian Blue, and type II collagen immunohistochemistry, indicating cartilage-specific matrix. These results indicate that the cells we cultured from meniscal debris are mesenchymal stem cells capable of differentiating along three lineages. These stem cells may be valuable source for meniscal regeneration.

Safety Studies for Use of Adipose Tissue-Derived Mesenchymal Stromal/Stem Cells in a Rabbit Model for Osteoarthritis to Support a Phase I Clinical Trial

Adipose‐derived mesenchymal stem cells (AMSCs) offer potential as a therapeutic option for clinical applications in musculoskeletal regenerative medicine because of their immunomodulatory functions and capacity for trilineage differentiation. In preparation for a phase I clinical trial using AMSCs to treat patients with osteoarthritis, we carried out preclinical studies to assess the safety of human AMSCs within the intra‐articular joint space. Culture‐expanded human AMSCs grown in human platelet‐lysate were delivered via intra‐articular injections into normal healthy rabbit knees and knees at risk for the development of osteoarthritis after bilateral medial anterior hemimeniscectomy. Treatment outcomes and safety were evaluated by assessing the general health, function, and behavior of the animals. Joint tissues were analyzed by x‐ray, magnetic resonance imaging, and histopathology. Intra‐articular AMSC therapy was well tolerated in this study. We did not observe adverse systemic reactions, nor did we find evidence of damage to intra‐articular joint tissues. Thus, the data generated in this study show a favorable safety profile for AMSCs within the joint space in support of a phase I clinical trial evaluating the clinical utility of AMSCs to treat osteoarthritis. Stem Cells Translational Medicine2017;6:910–922

Mesenchymal stromal cells for cartilage repair in osteoarthritis

Treatment for articular cartilage damage is quite challenging as it shows limited repair and regeneration following injury. Non-operative and classical surgical techniques are inefficient in restoring normal anatomy and function of cartilage in osteoarthritis (OA). Thus, investigating new and effective strategies for OA are necessary to establish feasible therapeutic solutions. The emergence of the new discipline of regenerative medicine, having cell-based therapy as its primary focus, may enable us to achieve repair and restore the damaged articular cartilage. This review describes progress and development of employing mesenchymal stromal cell (MSC)-based therapy as a promising alternative for OA treatment. The objective of this review is to first, discuss how in vitro MSC chondrogenic differentiation mimics in vivo embryonic cartilage development, secondly, to describe various chondrogenic differentiation strategies followed by pre-clinical and clinical studies demonstrating their feasibility and efficacy. However, several challenges need to be tackled before this research can be translated to the clinics. In particular, better understanding of the post-transplanted cell behaviour and learning to enhance their potency in the disease microenvironment is essential. Final objective is to underscore the importance of isolation, storage, cell shipment, route of administration, optimum dosage and control batch to batch variations to realise the full potential of MSCs in OA clinical trials.

A study to identify and characterize the stem/progenitor cell in rabbit meniscus

The repair of meniscus in the avascular zone remains a great challenge, largely owing to their limited healing capacity. Stem cells based tissue engineering provides a promising treatment option for damaged meniscus because of their multiple differentiation potential. We hypothesized that meniscus-derived stromal cells (MMSCs) may be present in meniscal tissue, and if their pluripotency and character can be established, they may play a role in meniscal healing. To test our hypothesis, we isolated MMSCs, bone marrow-derived stromal cells (BMSCs) and fibrochondrocytes from rabbits. In order to avoid bone marrow mesenchymal stromal cell contamination, the parameniscal tissues and vascular zone of meniscus were removed. The characters of these three types of cells were identified by evaluating morphology, colony formation, proliferation, immunocytochemistry and multi-differentiation. Moreover, a wound in the center of rabbit meniscus was created and used to analyze the effect of BMSCs and MMSCs on wounded meniscus healing. BMSCs & MMSCs expressed the stem cell markers SSEA-4, Nanog, nucleostemin and STRO-1, while fibrochondrocytes expressed none of these markers. Morphologically, MMSCs displayed smaller cell bodies and larger nuclei than ordinary fibrochondrocytes. Moreover, it was certified that MMSCs and BMSCs were all able to differentiate into adipocytes, osteocytes, and chondrocytes in vitro. However, more cartilage formation was found in wounded meniscus filled with MMSCs than that filled with BMSCs. We showed that rabbit menisci harbor the unique cell population MMSCs that has universal stem cell characteristics and posses a tendency to differentiate into chondrocytes. Future research should investigate the mechanobiology of MMSCs and explore the possibility of using MMSCs to more effectively repair or regenerate injured meniscus.

Mesenchymal stem cells for the management of inflammation in osteoarthritis: state of the art and perspectives

Osteoarthritis (OA) is the most common form of degenerative arthritis, mainly characterized by the degradation of articular cartilage and associated with subchondral bone lesions. Novel therapeutic approaches for OA include cell-based therapies that have become thriving areas of research and development. In this context, mesenchymal stem or stromal cells (MSCs) have gained much interest based on their trophic and immunomodulatory properties that can help tissue repair/regeneration. The present review article discusses the interest of using MSCs in cell-therapy approaches with a focus on the mechanisms by which MSCs might exhibit a therapeutic potential in OA. Special attention is given to the anti-inflammatory function of MSCs and on miRNA modulation in OA for possible future innovative strategies. The paper also presents the current data on the undergoing MSCs-based clinical trials in OA.

Meniscus repair using mesenchymal stem cells - a comprehensive review

The menisci are a pair of semilunar fibrocartilage structures that play an essential role in maintaining normal knee function. Injury to the menisci can disrupt joint stability and lead to debilitating results. Because natural meniscal healing is limited, an efficient method of repair is necessary. Tissue engineering (TE) combines the principles of life sciences and engineering to restore the unique architecture of the native meniscus. Mesenchymal stem cells (MSCs) have been investigated for their therapeutic potential both in vitro and in vivo. This comprehensive review examines the English literature identified through a database search using Medline, Embase, Engineering Village, and SPORTDiscus. The search results were classified based on MSC type, animal model, and method of MSC delivery/culture. A variety of MSC types, including bone marrow-derived, synovium-derived, adipose-derived, and meniscus-derived MSCs, has been examined. Research results were categorized into and discussed by the different animal models used; namely murine, leporine, porcine, caprine, bovine, ovine, canine, equine, and human models of meniscus defect/repair. Within each animal model, studies were categorized further according to MSC delivery/culture techniques. These techniques included direct application, fibrin glue/gel/clot, intra-articular injection, scaffold, tissue-engineered construct, meniscus tissue, pellets/aggregates, and hydrogel. The purpose of this review is to inform the reader about the current state and advances in meniscus TE using MSCs. Future directions of MSC-based meniscus TE are also suggested to help guide prospective research.

Mesenchymal stem cells in rabbit meniscus and bone marrow exhibit a similar feature but a heterogeneous multi-differentiation potential: superiority of meniscus as a cell source for meniscus repair

Background

The restoration of damaged meniscus has always been a challenge due to its limited healing capacity. Recently, bone marrow-derived mesenchymal stem cells (BMSCs) provide a promising alternative to repair meniscal defects. However, BMSCs are not ideal chondroprogenitor cells for meniscus repair because they have a high propensity for cartilage hypertrophy and bone formation. Our hypothesis is that mesenchymal stem cells (MSCs) reside in meniscus maintain specific traits distinct from others which may be more conducive to meniscus regeneration.

Methods

MSCs were isolated from bone marrow and menisci of the rabbits. The similarities and differences between BMSCs and MMSCs were investigated in vitro by a cell culture model, ex vivo by a rabbit meniscus defect model and in vivo by a nude rat implantation model using histochemistry, immunocytochemistry, qRT-PCR and western blotting.

Results

Our data showed that two types of MSCs have universal stem cell characteristics including clonogenicity, multi-potency and self-renewal capacity. They both express stem cell markers including SSEA-4, Nanog, nucleostemin, strol-1, CD44 and CD90.

However, MMSCs differed from BMSCs. MMSC colonies were much smaller and grew more slowly than BMSC colonies. Moreover, fewer MMSCs expressed CD34 than BMSCs. Finally, MMSCs always appeared a pronounced tendency to chondrogenic differentiation while BMSCs exhibited significantly greater osteogenic potential, whatever in vitro and in vivo.

Conclusions

This study shows the similarities and differences between MMSCs and BMSCs for the first time. MMSCs are a promising source of mesenchymal stem cells in repairing meniscus defect.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0511-8) contains supplementary material, which is available to authorized users.

Management of Osteoarthritis with Avocado/Soybean Unsaponifiables

Osteoarthritis (OA) is a painful and life-altering disease that severely limits the daily activity of millions of Americans, and is one of the most common causes of disability in the world. With obesity on the rise and the world's population living longer, the prevalence of OA is expected to increase dramatically in the coming decades, generating burdensome socioeconomic costs. This review summarizes current pharmaceutical, non-pharmaceutical, and prospective new treatments for OA, with primary focus on the dietary supplement Avocado/Soybean Unsaponifiables (ASU). ASU modulates OA pathogenesis by inhibiting a number of molecules and pathways implicated in OA. Anticatabolic properties prevent cartilage degradation by inhibiting the release and activity of matrix metalloproteinases (MMP-2,3,13) and increasing tissue inhibitors of these catabolic enzymes (TIMP-1). ASU also inhibits fibrinolysis by stimulating the expression of plasminogen activator inhibitor (PAI-1). Anabolic properties promote cartilage repair by stimulating collagen and aggrecan synthesis via inhibition of inflammatory cytokines such as IL1, IL6, IL8, TNF, ERK, and PGE2. Chondroprotective effects are mediated by correcting growth factor abnormalities, increasing TGFβ while decreasing vascular endothelial growth factor (VEGF) in synovial fluid. ASU also inhibits cholesterol absorption and endogenous cholesterol biosynthesis, which mediate reactive oxygen species pathology in chondrocytes. At the clinical level, ASU reduces pain and stiffness while improving joint function, resulting in decreased dependence on analgesics.

Intra-articular injection of human meniscus stem/progenitor cells promotes meniscus regeneration and ameliorates osteoarthritis through stromal cell-derived factor-1/CXCR4-mediated homing

Meniscus injury is frequently encountered in clinical practice. Current surgical therapy involving partial or complete meniscectomy relieves pain in the short-term but often leads to osteoarthritis (OA) in the long-term. In this study, we report a new strategy of articular cartilage protection by intra-articular injection of novel human meniscus stem/progenitor cells (hMeSPCs). We found that hMeSPCs displayed both mesenchymal stem cell characteristics and high expression levels of collagen II. In the rat meniscus injury model, hMeSPC transplantation not only led to more neo-tissue formation and better-defined shape but also resulted in more rounded cells and matured extracellular matrix. Stromal cell-derived factor-1 (SDF-1) enhanced the migration of hMeSPCs, whereas AMD3100 abolished the chemotactic effects of SDF-1 on hMeSPCs, both in vitro and in vivo. In an experimental OA model, transplantation of hMeSPCs effectively protected articular cartilage, as evidenced by reduced expression of OA markers such as collagen I, collagen X, and hypoxia-inducible factor 2α but increased expression of collagen II. Our study demonstrated for the first time that intra-articular injection of hMeSPCs enhanced meniscus regeneration through the SDF-1/CXCR4 axis. Our study highlights a new strategy of intra-articular injection of hMeSPCs for meniscus regeneration.