In vitro cartilage formation of composites of synovium-derived mesenchymal stem cells with collagen gel

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.

Anatomy, molecular structures, and hyaluronic acid - Gelatin injectable hydrogels as a therapeutic alternative for hyaline cartilage recovery: A review

Cartilage damage caused by trauma or osteoarthritis is a common joint disease that can increase the social and economic burden in society. Due to its avascular characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Hydrogels have been developed into one of the most suitable biomaterials for the regeneration of cartilage because of its characteristics such as high-water absorption, biodegradation, porosity, and biocompatibility similar to natural extracellular matrix. Therefore, the present review article presents a conceptual framework that summarizes the anatomical, molecular structure and biochemical properties of hyaline cartilage located in long bones: articular cartilage and growth plate. Moreover, the importance of preparation and application of hyaluronic acid - gelatin hydrogels for cartilage tissue engineering are included. Hydrogels possess benefits of stimulating the production of Agc1, Col2α1-IIa, and SOX9, molecules important for the synthesis and composition of the extracellular matrix of cartilage. Accordingly, they are believed to be promising biomaterials of therapeutic alternatives to treat cartilage damage.

Chondrogenesis of Adipose-Derived Stem Cells Using an Arrayed Spheroid Format

Objective

The chondrogenic response of adipose-derived stem cells (ASCs) is often assessed using 3D micromass protocols that use upwards of hundreds of thousands of cells. Scaling these systems up for high-throughput testing is technically challenging and wasteful given the necessary cell numbers and reagent volumes. However, adopting microscale spheroid cultures for this purpose shows promise. Spheroid systems work with only thousands of cells and microliters of medium.

Methods

Molded agarose microwells were fabricated using 2% w/v molten agarose and then equilibrated in medium prior to introducing cells. ASCs were seeded at 50, 500, 5k cells/microwell; 5k, 50k, cells/well plate; and 50k and 250k cells/15 mL centrifuge tube to compare chondrogenic responses across spheroid and micromass sizes. Cells were cultured in control or chondrogenic induction media. ASCs coalesced into spheroids/pellets and were cultured at 37 °C and 5% CO2 for 21 days with media changes every other day.

Results

All culture conditions supported growth of ASCs and formation of viable cell spheroids/micromasses. More robust growth was observed in chondrogenic conditions. Sulfated glycosaminoglycans and collagen II, molecules characteristics of chondrogenesis, were prevalent in both 5000-cell spheroids and 250,000-cell micromasses. Deposition of collagen I, characteristic of fibrocartilage, was more prevalent in the large micromasses than small spheroids.

Conclusions

Chondrogenic differentiation was consistently induced using high-throughput spheroid formats, particularly when seeding at cell densities of 5000 cells/spheroid. This opens possibilities for highly arrayed experiments investigating tissue repair and remodeling during or after exposure to drugs, toxins, or other chemicals.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00746-8.

A three-dimensional (3D), serum-free, Collagen Type I system for chondrogenesis of canine bone marrow-derived multipotent stromal cells (cMSCs)

The dog is an underrepresented large animal translational model for orthopedic cell-based tissue engineering. While chondrogenic differentiation of canine multipotent stromal cells (cMSCs) has been reported using the classic micromass technique, cMSCs respond inconsistently to this method. The objectives of this study were to develop a three-dimensional (3D), serum-free, Collagen Type I system to facilitate cMSC chondrogenesis and, once established, to determine the effect of chondrogenic growth factors on cMSC chondrogenesis. Canine MSCs were polymerized in 100 μL Collagen Type I gels (5 mg/mL) at 1 x 10⁶ cells/construct. Constructs were assessed using morphometry, live/dead staining, and histology in 10 various chondrogenic media. Four media were selected for additional in-depth analyses via lactate dehydrogenase release, total glycosaminoglycan content, qPCR (COL1A1, COL2A, SOX9, ACAN, BGLAP and SP7), immunofluorescence, and TUNEL staining. In the presence of dexamethasone and transforming growth factor-β3 (TGF-β3), both bone morphogenic protein-2 (BMP-2) and basic fibroblast growth factor (bFGF) generated larger chondrogenic constructs, although BMP-2 was required to achieve histologic characteristics of chondrocytes. Chondrogenic medium containing dexamethasone, TGF-β3, BMP-2 and bFGF led to a significant decrease in lactate dehydrogenase release at day 3 and glycosaminoglycan content was significantly increased in these constructs at day 3, 10, and 21. Both osteogenic and chondrogenic transcripts were induced in response to dexamethasone, TGF-β3, BMP-2 and bFGF. Collagen Type II and X were detected in all groups via immunofluorescence. Finally, TUNEL staining was positive in constructs lacking BMP-2 or bFGF. In conclusion, the 3D, serum-free, Collagen Type-I assay described herein proved useful in assessing cMSC differentiation and will serve as a productive system to characterize cMSCs or to fabricate tissue engineering constructs for clinical use.

Short cytoplasmic isoform of IL1R1/CD121a mediates IL1β induced proliferation of synovium-derived mesenchymal stem/stromal cells through ERK1/2 pathway

Objectives

IL1β enhances proliferation of synovial mesenchymal stem/stromal cells (synMSCs) although they don't express its receptor, IL1R1/CD121a, on the cell surface. This study was aimed to elucidate the underlying mechanisms of IL1β-mediated growth promotion.

Methods

Human synMSCs were isolated from the suprapatellar synovial membrane. Cell proliferation was measured by MTT. Flowcytometric analyses were performed for surface antigen expression. Intracellular signaling pathway was analyzed by western blotting, immunocytochemistry and Q-PCR.

Results

IL1β enhanced proliferation through IL1R1/CD121a because IL1 receptor antagonist (IL1Ra) completely inhibited it. Expression analyses indicated that a short isoform of IL1R1/CD121a is expressed in synMSCs. Immunocytochemistry indicated that IL1R1/CD121a was majorly localized to the cytoplasm. Western blotting indicated that IL1β induced delayed timing of the ERK1/2 phosphorylation and IκBα degradation in synMSCs. Q-PCR analyses for IL1β-target genes indicated that cyclin D was specifically downregulated by a MAPK/ERK inhibitor, U0126, but not by a NFκB inhibitor, TPCA-1. In contrast, the expression of inflammatory cytokines such as IL1α and IL6 are significantly decreased by TPCA-1 but less effectively decreased by U0126.

Conclusion

Our data indicated that the cytoplasmic IL1R1/CD121a transduced IL1β signal in synMSCs. And the growth-promoting effect of IL1β can be separated from its inflammatory cytokine-inducing function in synMSCs.

Current State and Issues of Regenerative Medicine for Rheumatic Diseases

The prognosis of rheumatic diseases is generally better than that of malignant diseases. However, some cases with poor prognoses resist conventional therapies and cause irreversible functional and organ damage. In recent years, there has been much research on regenerative medicine, which uses stem cells to restore the function of missing or dysfunctional tissues and organs. The development of regenerative medicine is also being attempted in rheumatic diseases. In diseases such as systemic sclerosis (SSc), systemic lupus erythematosus (SLE), and rheumatoid arthritis, hematopoietic stem cell transplantation has been attempted to correct and reconstruct abnormalities in the immune system. Mesenchymal stem cells (MSCs) have also been tried for the treatment of refractory skin ulcers in SSc using the ability of MSCs to differentiate into vascular endothelial cells and for the treatment of systemic lupus erythematosus SLE using the immunosuppressive effect of MSCs. CD34-positive endothelial progenitor cells (EPCs), which are found in the mononuclear cell fraction of bone marrow and peripheral blood, can differentiate into vascular endothelial cells at the site of ischemia. Therefore, EPCs have been used in research on vascular regeneration therapy for patients with severe lower limb ischemia caused by rheumatic diseases such as SSc. Since the first report of induced pluripotent stem cells (iPSCs) in 2007, research on regenerative medicine using iPSCs has been actively conducted, and their application to rheumatic diseases is expected. However, there are many safety issues and bioethical issues involved in regenerative medicine research, and it is essential to resolve these issues for practical application and spread of regenerative medicine in the future. The environment surrounding regenerative medicine research is changing drastically, and the required expertise is becoming higher. This paper outlines the current status and challenges of regenerative medicine in rheumatic diseases.

Mesenchymal Stem Cell Therapy in Chondral Defects of Knee: Current Concept Review

PURPOSE

Full-thickness cartilage defects if left alone would increase the risk of osteoarthritis (OA) with severe associated pain and functional disability. Articular cartilage defect may result from direct trauma or chronic degeneration. The capability of the mesenchymal stem cells (MSCs) to repair and regenerate cartilage has been widely investigated. This review describes current trends in MSC biology, the sourcing, expansion, application and role of MSCs in chondral defects of human knees.

METHODS

The studies referencing MSCs and knee osteoarthritis were searched (from1998 to 2020) using PubMed, EMBASE, Cochrane Library, Web of Science and the ClinicalTrials.gov with keywords (MSCs, chondral defects or cartilage degeneration of knee, cartilage regeneration, chondrogenesis, tissue engineering, efficacy and safety). The inclusion criteria were based on use of MSCs for treatment of chondral defects and osteoarthritis of the knee, English language and human studies.

RESULTS

The history of MSC research from the initial discovery of their multipotency to the more recent recognition of their role in cartilage defects of knee is elucidated. Several studies have demonstrated promising results in the clinical application for repair of chondral defects as an adjuvant or independent procedure. Intra-articular MSCs provide improvements in pain and function in knee osteoarthritis at short-term follow-up in many studies. The tendency of MSCs to differentiate into fibrocartilage affecting the outcome is a common issue faced by researchers.

CONCLUSION

Some efficacy has been shown of MSCs for cartilage repair in osteoarthritis; however, the evidence of efficacy of intra-articular MSCs on both clinical outcomes and cartilage repair remains limited. Despite the high quality of evidence to support, MSC therapy has emerged but further refinement of methodology will be necessary to support its routine clinical use.

Safety of Technique and Procedure of Stromal Vascular Fraction Therapy: From Liposuction to Cell Administration

BACKGROUND

Stromal vascular fraction (SVF) therapy has been performed over the past six years to treat 421 patients by our group in five clinical centers. Autologous SVF, which is a substance containing stem cells, was isolated from lipoaspirate, mixed with platelet-rich plasma (PRP), and administered to patients with degenerative diseases, autoimmune diseases, trauma, aging, and other diseases with unknown etiology. This study aimed to determine the safety of SVF and PRP that were given through infusion, spinal, and intra-articular injection.

METHODS

The lipoaspirate was treated with a tissue-dissociating enzyme, and then, through centrifugation, SVF was isolated. In addition, blood was drawn from each patient, and PRP was isolated. Autologous PRP and SVF were administered to all subjects by intravenous (IV) injection. A minority group within the population received an additional spinal or intra-articular injection. The type of intervention was determined by each disease evaluation. The cell doses and adverse events for each patient were documented and analyzed.

RESULTS

Cell dose that was considered to be safe was less than 10 billion SVF cells in 250 cc of normal saline, for IV injection, and less than 1 billion SVF, for intra-articular and spinal injection. Adverse events were not severe and were treated successfully. Any observed adverse events were identified as a result of spinal or intra-articular injections and were not related to SVF or PRP.

CONCLUSIONS

Our results showed that administration of high dose of SVF until 10 billion cells in a majority of 421 patients through infusion, spinal, and intra-articular injection was feasible without causing major adverse events and should be further investigated in well-designed phase I-II clinical trial to address the safety and efficacy of therapy.

Enhanced chondrogenic differentiation of equine bone marrow-derived mesenchymal stem cells in zirconia microwell substrata

In human cartilage tissue engineering, three-dimensional zirconia substrata have the potential advantage of producing many uniform cell clusters of controlled size without xenobiotic material, allowing easy clinical application. The objective of this study was to evaluate the possibility of using zirconia porous three-dimensional microwell substrata for chondrogenic differentiation of equine bone marrow-derived mesenchymal stem cells (BMMSCs) in vitro. In regular medium, 8 × 10⁵, 2 × 10⁶, and 5 × 10⁶ equine BMMSCs from five thoroughbred horses were cultured on zirconia microwell substrata for 4 days to allow formation of clusters. The medium was replaced by chondrogenic culture medium. After chondrogenic culture for 7, 14 and 21 days, analysis of collagen type II alpha 1 gene (COL2A1) gene expression and observation of chondrogenic aggregates by scanning electron microscopy (SEM) were performed. SEM showed size-controlled cell clusters and increasing extracellular matrix over time when using 5 × 10⁶ cells. The expression of COL2A1 on day 7 and 14 with 5 × 10⁶ cells was significantly higher than that of conventional pellet culture with 2 × 10⁶ cells. Histological evaluation by immunohistochemical staining for type II collagen (ColII) was performed after chondrogenic culture for 7 days. The clusters showed wide distribution of ColII. The results suggest that the zirconia substrata have the potential to enhance the chondrogenic differentiation of equine BMMSCs, allowing effective equine cartilage tissue engineering without xenobiotic materials.

Tailoring the Interface of Biomaterials to Design Effective Scaffolds

Tissue engineering (TE) is a multidisciplinary science, which including principles from material science, biology and medicine aims to develop biological substitutes to restore damaged tissues and organs. A major challenge in TE is the choice of suitable biomaterial to fabricate a scaffold that mimics native extracellular matrix guiding resident stem cells to regenerate the functional tissue. Ideally, the biomaterial should be tailored in order that the final scaffold would be (i) biodegradable to be gradually replaced by regenerating new tissue, (ii) mechanically similar to the tissue to regenerate, (iii) porous to allow cell growth as nutrient, oxygen and waste transport and (iv) bioactive to promote cell adhesion and differentiation. With this perspective, this review discusses the options and challenges facing biomaterial selection when a scaffold has to be designed. We highlight the possibilities in the final mold the materials should assume and the most effective techniques for its fabrication depending on the target tissue, including the alternatives to ameliorate its bioactivity. Furthermore, particular attention has been given to the influence that all these aspects have on resident cells considering the frontiers of materiobiology. In addition, a focus on chitosan as a versatile biomaterial for TE scaffold fabrication has been done, highlighting its latest advances in the literature on bone, skin, cartilage and cornea TE.

Influence of Kartogenin on Chondrogenic Differentiation of Human Bone Marrow-Derived MSCs in 2D Culture and in Co-Cultivation with OA Osteochondral Explant

Articular cartilage has limited capacity for natural regeneration and repair. In the present study, we evaluated kartogenin (KGN), a bioactive small heterocyclic molecule, for its effect on in vitro proliferation and chondrogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBMSCs) in monolayer culture and in co-culture models in vitro. OA osteochondral cylinders and hBMSCs were collected during total knee replacement. The effect of KGN on hBMSCs during 21 days of culture was monitored by real-time proliferation assay, immunofluorescence staining, histological assay, scanning electron microscopy (SEM) (imaging and multiplex enzyme-linked immunosorbent assay) ELISA assay. The rate of proliferation of hBMSCs was significantly increased by treatment with 10 µM KGN during nine days of culture. Histological and SEM analyses showed the ability of hBMSCs in the presence of KGN to colonize the surface of OA cartilage and to produce glycosaminoglycans and proteoglycans after 21 days of co-culture. KGN treated hBMSCs secreted higher concentrations of TIMPs and the secretion of pro-inflammatory molecules (MMP 13, TNF-α) were significantly suppressed in comparison with control without hBMSCs. Our preliminary results support the concept that 10 µM KGN enhances proliferation and chondrogenic differentiation of hBMSCs and suggest that KGN is a potential promoter for cell-based therapeutic application for cartilage regeneration.

In-vitro characterization of canine multipotent stromal cells isolated from synovium, bone marrow, and adipose tissue: a donor-matched comparative study

Background

The dog represents an excellent large animal model for translational cell-based studies. Importantly, the properties of canine multipotent stromal cells (cMSCs) and the ideal tissue source for specific translational studies have yet to be established. The aim of this study was to characterize cMSCs derived from synovium, bone marrow, and adipose tissue using a donor-matched study design and a comprehensive series of in-vitro characterization, differentiation, and immunomodulation assays.

Methods

Canine MSCs were isolated from five dogs with cranial cruciate ligament rupture. All 15 cMSC preparations were evaluated using colony forming unit (CFU) assays, flow cytometry analysis, RT-PCR for pluripotency-associated genes, proliferation assays, trilineage differentiation assays, and immunomodulation assays. Data were reported as mean ± standard deviation and compared using repeated-measures analysis of variance and Tukey post-hoc test. Significance was established at p < 0.05.

Results

All tissue samples produced plastic adherent, spindle-shaped preparations of cMSCs. Cells were negative for CD34, CD45, and STRO-1 and positive for CD9, CD44, and CD90, whereas the degree to which cells were positive for CD105 was variable depending on tissue of origin. Cells were positive for the pluripotency-associated genes NANOG, OCT4, and SOX2. Accounting for donor and tissue sources, there were significant differences in CFU potential, rate of proliferation, trilineage differentiation, and immunomodulatory response. Synovium and marrow cMSCs exhibited superior early osteogenic activity, but when assessing late-stage osteogenesis no significant differences were detected. Interestingly, bone morphogenic protein-2 (BMP-2) supplementation was necessary for early-stage and late-stage osteogenic differentiation, a finding consistent with other canine studies. Additionally, synovium and adipose cMSCs proliferated more rapidly, displayed higher CFU potential, and formed larger aggregates in chondrogenic assays, although proteoglycan and collagen type II staining were subjectively decreased in adipose pellets as compared to synovial and marrow pellets. Lastly, cMSCs derived from all three tissue sources modulated murine macrophage TNF-α and IL-6 levels in a lipopolysaccharide-stimulated coculture assay.

Conclusions

While cMSCs from synovium, marrow, and adipose tissue share a number of similarities, important differences in proliferation and trilineage differentiation exist and should be considered when selecting cMSCs for translational studies. These results and associated methods will prove useful for future translational studies involving the canine model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0639-6) contains supplementary material, which is available to authorized users.

The use of mesenchymal stem cells for cartilage repair and regeneration: a systematic review

BACKGROUND

The management of articular cartilage defects presents many clinical challenges due to its avascular, aneural and alymphatic nature. Bone marrow stimulation techniques, such as microfracture, are the most frequently used method in clinical practice however the resulting mixed fibrocartilage tissue which is inferior to native hyaline cartilage. Other methods have shown promise but are far from perfect. There is an unmet need and growing interest in regenerative medicine and tissue engineering to improve the outcome for patients requiring cartilage repair. Many published reviews on cartilage repair only list human clinical trials, underestimating the wealth of basic sciences and animal studies that are precursors to future research. We therefore set out to perform a systematic review of the literature to assess the translation of stem cell therapy to explore what research had been carried out at each of the stages of translation from bench-top (in vitro), animal (pre-clinical) and human studies (clinical) and assemble an evidence-based cascade for the responsible introduction of stem cell therapy for cartilage defects. This review was conducted in accordance to PRISMA guidelines using CINHAL, MEDLINE, EMBASE, Scopus and Web of Knowledge databases from 1st January 1900 to 30th June 2015. In total, there were 2880 studies identified of which 252 studies were included for analysis (100 articles for in vitro studies, 111 studies for animal studies; and 31 studies for human studies). There was a huge variance in cell source in pre-clinical studies both of terms of animal used, location of harvest (fat, marrow, blood or synovium) and allogeneicity. The use of scaffolds, growth factors, number of cell passages and number of cells used was hugely heterogeneous.

SHORT CONCLUSIONS

This review offers a comprehensive assessment of the evidence behind the translation of basic science to the clinical practice of cartilage repair. It has revealed a lack of connectivity between the in vitro, pre-clinical and human data and a patchwork quilt of synergistic evidence. Drivers for progress in this space are largely driven by patient demand, surgeon inquisition and a regulatory framework that is learning at the same pace as new developments take place.

Can chondral healing be improved following microfracture? The effect of adipocyte tissue derived stem cell therapy

BACKGROUND

We aimed to investigate the effect of adipose tissue-derived mesenchymal stem cells (ADSCs) on chondral healing using the microfracture (MF) technique.

METHODS

Thirty male rabbits were randomly divided into three groups. Standard cylindrical osteochondral defects (OCDs) were created in the weight-bearing areas of the medial condyles of all the right knees; the defects were four millimeters in diameter and two millimeters in depth. The control group (group A) was restricted to spontaneous healing. For group B, we performed MF with a 1.5-mm drill. For group C, we applied MF using the same method and then applied 3×10(6) ADSCs to the defect area. At eight weeks post-operation, the subjects were sacrificed, and the distal femoral joint surfaces were evaluated histopathologically for chondral healing. The samples were scored according to the International Cartilage Repair Society (ICRS) scale.

RESULTS

The results for group C were significantly better than those for group A in terms of the surface properties (p=0.003). The matrix evaluation was better for group A than for group C (p=0.01). The cell distribution, cell viability and subchondral bone parameters were similar between the groups (p=0.198, p=0.387 and p=0.699). The cartilage mineralization parameter was better for group C than for group A (p=0.001). The signs of healing were better for group C than for group B, but the differences were not significant (p=0.185).

CONCLUSIONS

Improvements with additional ADSC treatments were not statistically significant in cases in which ADSC treatment was compared with isolated MF treatment.

CLINICAL RELEVANCE

Additional ADSCs treatment may have positive effect on chondral healing but it doesn't seem significant.

In Vitro Engineering of High Modulus Cartilage-Like Constructs

To date, the outcomes of cartilage repair have been inconsistent and have frequently yielded mechanically inferior fibrocartilage, thereby increasing the chances of damage recurrence. Implantation of constructs with biochemical composition and mechanical properties comparable to natural cartilage could be advantageous for long-term repair. This study attempted to create such constructs, in vitro, using tissue engineering principles. Bovine synoviocytes were seeded on nonwoven polyethylene terephthalate fiber scaffolds and cultured in chondrogenic medium for 4 weeks, after which uniaxial compressive loading was applied using an in-house bioreactor for 1 h per day, at a frequency of 1 Hz, for a further 84 days. The initial loading conditions, determined from the mechanical properties of the immature constructs after 4 weeks in chondrogenic culture, were strains ranging between 13% and 23%. After 56 days (sustained at 84 days) of loading, the constructs were stained homogenously with Alcian blue and for type-II collagen. Dynamic compressive moduli were comparable to the high end values for native cartilage and proportional to Alcian blue staining intensity. We suggest that these high moduli values were attributable to the bioreactor setup, which caused the loading regime to change as the constructs developed, that is, the applied stress and strain increased with construct thickness and stiffness, providing continued sufficient cell stimulation as further matrix was deposited. Constructs containing cartilage-like matrix with response to load similar to that of native cartilage could produce long-term effective cartilage repair when implanted.

Tissue-engineered cartilage: the crossroads of biomaterials, cells and stimulating factors

Damage to cartilage represents one of the most challenging tasks of musculoskeletal therapeutics due to its limited propensity for healing and regenerative capabilities. Lack of current treatments to restore cartilage tissue function has prompted research in this rapidly emerging field of tissue regeneration of functional cartilage tissue substitutes. The development of cartilaginous tissue largely depends on the combination of appropriate biomaterials, cell source, and stimulating factors. Over the years, various biomaterials have been utilized for cartilage repair, but outcomes are far from achieving native cartilage architecture and function. This highlights the need for exploration of suitable biomaterials and stimulating factors for cartilage regeneration. With these perspectives, we aim to present an overview of cartilage tissue engineering with recent progress, development, and major steps taken toward the generation of functional cartilage tissue. In this review, we have discussed the advances and problems in tissue engineering of cartilage with strong emphasis on the utilization of natural polymeric biomaterials, various cell sources, and stimulating factors such as biophysical stimuli, mechanical stimuli, dynamic culture, and growth factors used so far in cartilage regeneration. Finally, we have focused on clinical trials, recent innovations, and future prospects related to cartilage engineering.

Controlled release of transforming growth factor-β3 from cartilage-extra-cellular-matrix-derived scaffolds to promote chondrogenesis of human-joint-tissue-derived stem cells

The objective of this study was to develop a scaffold derived from cartilaginous extracellular matrix (ECM) that could be used as a growth factor delivery system to promote chondrogenesis of stem cells. Dehydrothermal crosslinked scaffolds were fabricated using a slurry of homogenized porcine articular cartilage, which was then seeded with human infrapatellar-fat-pad-derived stem cells (FPSCs). It was found that these ECM-derived scaffolds promoted superior chondrogenesis of FPSCs when the constructs were additionally stimulated with transforming growth factor (TGF)-β3. Cell-mediated contraction of the scaffold was observed, which could be limited by the additional use of 1-ethyl-3-3dimethyl aminopropyl carbodiimide (EDAC) crosslinking without suppressing cartilage-specific matrix accumulation within the construct. To further validate the utility of the ECM-derived scaffold, we next compared its chondro-permissive properties to a biomimetic collagen-hyaluronic acid (HA) scaffold optimized for cartilage tissue engineering (TE) applications. The cartilage-ECM-derived scaffold supported at least comparable chondrogenesis to the collagen-HA scaffold, underwent less contraction and retained a greater proportion of synthesized sulfated glycosaminoglycans. Having developed a promising scaffold for TE, with superior chondrogenesis observed in the presence of exogenously supplied TGF-β3, the final phase of the study explored whether this scaffold could be used as a TGF-β3 delivery system to promote chondrogenesis of FPSCs. It was found that the majority of TGF-β3 that was loaded onto the scaffold was released in a controlled manner over the first 10days of culture, with comparable long-term chondrogenesis observed in these TGF-β3-loaded constructs compared to scaffolds where the TGF-β3 was continuously added to the media. The results of this study support the use of cartilage-ECM-derived scaffolds as a growth factor delivery system for use in articular cartilage regeneration.

Articular cartilage repair: procedures versus products

This review discusses the current perspectives and practices regarding the treatment of articular cartilage injury. Specifically, the authors have delineated and examined articular cartilage repair techniques as either surgical procedures or manufactured products. Although both methodologies are used to treat articular cartilage injury, there are obvious advantages and disadvantages to the application of both, with the literature providing few recommendations on the most suitable regimen for the patient and surgeon. In recent times, cell-based tissue engineering products, predominantly autologous chondrocyte implantation, have been the subject of much research and have become clinically popular. Herein, we review the most used procedures and products in cartilage repair, compare and contrast their outcomes, and evaluate the issues that must be overcome in order to improve patient efficacy in the future.

Chondrogenic differentiation of immortalized human mesenchymal stem cells on zirconia microwell substrata

Human mesenchymal stem cells (hMSCs) that can differentiate into chondrocytes are a potential autologous cell source for repair of damaged tissue. Current methods usually induce the formation of all three chondrocyte phenotypes, hyaline, fibrous, and elastic, without the ability to selectively induce only one of them. By controlling the size of hMSC cell clusters, it may be possible to direct differentiation more uniformly toward hyaline chondrocytes. We designed new cell culture platforms containing microwells of different diameters. The platforms and wells were composed of a zirconia ceramics substratum. hMSCs briefly adhered to the substratum before releasing and entering the microwells. The physical restraints imposed by the microwells enabled hMSC clusters to homogenously differentiate into hyaline chondrocyte-like cells. Chondrogenic aggregates in microwells expressed the hyaline chondrocyte-specific genes Col II, aggrecan (ACAN), and cartilage oligomeric protein (COMP). The cultures also produced hyaline chondrocyte-specific matrix proteins Col II and ACAN homogenously throughout the aggregates. In contrast, chondrogenesis in pellet cultures was heterogeneous with the expression of nonhyaline chondrocyte genes CD105, Col X, and Col I. In these pellet cultures, hyaline and nonhyaline chondrocyte-specific matrix proteins were distributed heterogeneously. Thus, this novel ceramic microwell substratum technology efficiently directed the differentiation of hyaline chondrocyte-like cells from hMSCs. These results indicate that there is a close relationship between hMSC cluster size regulation in the microwells and differentiation tendency. This microwell culture differentiation method will provide a valuable experimental system for both experimental and potential clinical studies.

Controlling self-renewal and differentiation of stem cells via mechanical cues

The control of stem cell response in vitro, including self-renewal and lineage commitment, has been proved to be directed by mechanical cues, even in the absence of biochemical stimuli. Through integrin-mediated focal adhesions, cells are able to anchor onto the underlying substrate, sense the surrounding microenvironment, and react to its properties. Substrate-cell and cell-cell interactions activate specific mechanotransduction pathways that regulate stem cell fate. Mechanical factors, including substrate stiffness, surface nanotopography, microgeometry, and extracellular forces can all have significant influence on regulating stem cell activities. In this paper, we review all the most recent literature on the effect of purely mechanical cues on stem cell response, and we introduce the concept of "force isotropy" relevant to cytoskeletal forces and relevant to extracellular loads acting on cells, to provide an interpretation of how the effects of insoluble biophysical signals can be used to direct stem cells fate in vitro.

Tissue engineering and cartilage

Human articular cartilage is an avascular structure, which, when injured, poses significant hurdles to repair strategies. Not only does the defect need to be repopulated with cells, but preferentially with hyaline-like cartilage.SUCCESSFUL TISSUE ENGINEERING RELIES ON FOUR SPECIFIC CRITERIA: cells, growth factors, scaffolds, and the mechanical environment. The cell population utilized may originate from cartilage itself (chondrocytes) or from growth factors that direct the development of mesenchymal stem cells toward a chondrogenic phenotype. These stem cells may originate from various mesenchymal tissues including bone marrow, synovium, adipose tissue, skeletal muscle, and periosteum. Another unique population of multipotent cells arises from Wharton's jelly in human umbilical cords. A number of growth factors have been associated with chondrogenic differentiation of stem cells and the maintenance of the chondrogenic phenotype by chondrocytes in vitro, including TGFbeta; BMP-2, 4 and 7; IGF-1; and GDF-5.Scaffolds chosen for effective tissue engineering with respect to cartilage repair can be protein based (collagen, fibrin, and gelatin), carbohydrate based (hyaluronan, agarose, alginate, PLLA/PGA, and chitosan), or formed by hydrogels. Mechanical compression, fluid-induced shear stress, and hydrostatic pressure are aspects of mechanical loading found in within the human knee joint, both during gait and at rest. Utilizing these factors may assist in stimulating the development of more robust cells for implantation.Effective tissue engineering has the potential to improve the quality of life of millions of patients and delay future medical costs related to joint arthroplasty and associated procedures.

Mesenchymal stem cell therapy in the sports knee: where are we in 2011?

Background:

The relationship between biological tissue healing following knee injury or surgery and long-term clinical outcome has come to the forefront of sports medicine practice. This has led many knee surgeons to incorporate biologically mediated healing factors into the management of knee injuries. In particular, the clinical use of mesenchymal stem cells has opened new horizons.

Evidence Acquisition:

Relevant studies were identified through a search of PubMed from January 2000 to April 2011, combining the term mesenchymal stem cells with articular cartilage, anterior cruciate ligament, and meniscus. Relevant citations from the reference lists of selected studies were also reviewed.

Results:

Knee injury treatment with mesenchymal stem cells shows potential. Most reports represent animal model studies; few advances have been translated to human clinical applications.

Conclusion:

Mesenchymal stem cell use to promote healing following knee injury is likely to increase. There are scientific methodological concerns and ethical and legal issues regarding mesenchymal stem cell use for treating knee injuries.

The role of environmental factors in regulating the development of cartilaginous grafts engineered using osteoarthritic human infrapatellar fat pad-derived stem cells

Engineering functional cartilaginous grafts using stem cells isolated from osteoarthritic human tissue is of fundamental importance if autologous tissue engineering strategies are to be used in the treatment of diseased articular cartilage. It has previously been demonstrated that human infrapatellar fat pad (IFP)-derived stem cells undergo chondrogenesis in pellet culture; however, the ability of such cells to generate functional cartilaginous grafts has not been adequately addressed. The objective of this study was to explore how environmental conditions regulate the functional development of cartilaginous constructs engineered using diseased human IFP-derived stem cells (FPSCs). FPSCs were observed to display a diminished chondrogenic potential upon encapsulation in a three-dimensional hydrogel compared with pellet culture, synthesizing significantly lower levels of glycosaminoglycan and collagen on a per cell basis. To engineer more functional cartilaginous grafts, we next explored whether additional biochemical and biophysical stimulations would enhance chondrogenesis within the hydrogels. Serum stimulation was observed to partially recover the diminished chondrogenic potential within hydrogel culture. Over 42 days, stem cells that had first been expanded in a low-oxygen environment proliferated extensively on the outer surface of the hydrogel in response to serum stimulation, assembling a dense type II collagen-positive cartilaginous tissue resembling that formed in pellet culture. The application of hydrostatic pressure did not further enhance extracellular matrix synthesis within the hydrogels, but did appear to alter the spatial accumulation of extracellular matrix leading to the formation of a more compact tissue with superior mechanically functionality. Further work is required in order to recapitulate the environmental conditions present during pellet culture within scaffolds or hydrogels in order to engineer more functional cartilaginous grafts using human osteoarthritic FPSCs.

Cell-based meniscal tissue engineering: a case for synoviocytes

BACKGROUND

Avascular meniscal injuries are largely incapable of healing; the most common treatment remains partial meniscectomy despite the risk of subsequent osteoarthritis. Meniscal responses to injury are partially mediated through synovial activity and strategies have been investigated to encourage healing through stimulating or transplanting adjacent synovial lining. However, with their potential for chondrogenesis, synovial fibroblast-like stem cells hold promise for meniscal cartilage tissue engineering.

QUESTIONS/PURPOSES

Thus, specific purposes of this review were to (1) examine how the synovial intima and synoviomeniscal junction affect current meniscal treatment modalities; and (2) examine the components of tissue engineering (cells, scaffolds, bioactive agents, and bioreactors) in the specific context of how cells of synovial origin may be used for meniscal healing or regeneration.

METHODS

An online bibliographic search through PubMed was performed in March 2010. Studies were subjectively evaluated and reviewed if they addressed the question posed. Fifty-four resources were initially retrieved, which offered information on the chondrogenic potential of synovial-based cells that could prove valuable for meniscal fibrocartilage engineering.

RESULTS

Based on the positive effects of adjoining synovium on meniscal healing as used in some current treatment modalities, the chondrogenic potential of fibroblast-like stem cells of synovial origin make this cell source a promising candidate for cell-based tissue engineering strategies.

CONCLUSIONS

The abundance of autologous synovial lining, its ability to regenerate, and the potential of synovial-derived stem cells to produce a wide spectrum of chondral matrix components make it an ideal candidate for future meniscal engineering investigations.

Expansion in the presence of FGF-2 enhances the functional development of cartilaginous tissues engineered using infrapatellar fat pad derived MSCs

MSCs from non-cartilaginous knee joint tissues such as the infrapatellar fat pad (IFP) and synovium possess significant chondrogenic potential and provide a readily available and clinically feasible source of chondroprogenitor cells. Fibroblast growth factor-2 (FGF-2) has been shown to be a potent mitotic stimulator during ex vivo expansion of MSCs, as well as regulating their subsequent differentiation potential. The objective of this study was to investigate the longer term effects of FGF-2 expansion on the functional development of cartilaginous tissues engineered using MSCs derived from the IFP. IFP MSCs were isolated and expanded to passage 2 in a standard media formulation with or without FGF-2 (5 ng/ml) supplementation. Expanded cells were encapsulated in agarose hydrogels, maintained in chondrogenic media for 42 days and analysed to determine their mechanical properties and biochemical composition. Culture media, collected at each feed, was also analysed for biochemical constituents. MSCs expanded in the presence of FGF-2 proliferated more rapidly, with higher cell yields and lower population doubling times. FGF-2 expanded MSCs generated the most mechanically functional tissue. Matrix accumulation was dramatically higher after 21 days for FGF-2 expanded MSCs, but decreased between day 21 and 42. By day 42, FGF-2 expanded MSCs had still accumulated ∼1.4 fold higher sGAG and ∼1.7 fold higher collagen compared to control groups. The total amount of sGAG synthesised (retained in hydrogels and released into the media) was ∼2.4 fold higher for FGF-2 expanded MSCs, with only ∼25% of the total amount generated being retained within the constructs. Further studies are required to investigate whether IFP derived MSCs have a diminished capacity to synthesise other matrix components important in the aggregation, assembly and retention of proteoglycans. In conclusion, expanding MSCs in the presence of FGF-2 rapidly accelerates chondrogenesis in 3D agarose cultures resulting in superior mechanical functionality.

In vitro targeted magnetic delivery and tracking of superparamagnetic iron oxide particles labeled stem cells for articular cartilage defect repair

To assess a novel cell manipulation technique of tissue engineering with respect to its ability to augment superparamagnetic iron oxide particles (SPIO) labeled mesenchymal stem cells (MSCs) density at a localized cartilage defect site in an in vitro phantom by applying magnetic force. Meanwhile, non-invasive imaging techniques were use to track SPIO-labeled MSCs by magnetic resonance imaging (MRI). Human bone marrow MSCs were cultured and labeled with SPIO. Fresh degenerated human osteochondral fragments were obtained during total knee arthroplasty and a cartilage defect was created at the center. Then, the osteochondral fragments were attached to the sidewalls of culture flasks filled with phosphate-buffered saline (PBS) to mimic the human joint cavity. The SPIO-labeled MSCs were injected into the culture flasks in the presence of a 0.57 Tesla (T) magnetic force. Before and 90 min after cell targeting, the specimens underwent T2-weighted turbo spin-echo (SET2WI) sequence of 3.0 T MRI. MRI results were compared with histological findings. Macroscopic observation showed that SPIO-labeled MSCs were steered to the target region of cartilage defect. MRI revealed significant changes in signal intensity (P<0.01). HE staining exibited that a great number of MSCs formed a three-dimensional (3D) cell "sheet" structure at the chondral defect site. It was concluded that 0.57 T magnetic force permits spatial delivery of magnetically labeled MSCs to the target region in vitro. High-field MRI can serve as an very sensitive non-invasive technique for the visualization of SPIO-labeled MSCs.

Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes

BACKGROUND

For current tissue engineering or regenerative medicine strategies, chondrocyte (CC)- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists.

OBJECTIVE

The objective of this study was to investigate how CCs and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources.

EXPERIMENTAL DESIGN

Cell-encapsulated agarose hydrogel constructs (seeded with CCs or infrapatellar fat pad (IFP) derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (CCs and MSCs) or absence (CCs only) of transforming growth factor-beta3 (TGF-β3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically.

RESULTS

Low oxygen tension (5%) was observed to promote extracellular matrix (ECM) production by CCs cultured in the absence of TGF-β3, but was inhibitory in the presence of TGF-β3. In contrast, a low oxygen tension enhanced chondrogenesis of IFP constructs in the presence of TGF-β3, leading to superior mechanical functionality compared to CCs cultured in identical conditions.

CONCLUSIONS

Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, CCs maintained in normoxic conditions in the presence of TGF-β3 generate the most mechanically functional tissue.

Use of synovium-derived stromal cells and chitosan/collagen type I scaffolds for cartilage tissue engineering

The objective was to investigate synovium-derived stromal cells (SDSCs) coupled with chitosan/collagen type I (CS/COL-I) scaffolds for cartilage engineering. CS/COL-I scaffolds were fabricated through freeze-drying and cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. SDSCs were isolated from synovium and cultured onto CS/COL-I scaffolds, constructs of which were incubated in serum-free chondrogenic medium with sequential application of TGF-β1 and bFGF for up to 21 days and then implanted into nude mice. The physical characteristics of the scaffolds were examined. The quality of the in vitro constructs was assessed in terms of DNA content by PicoGreen assay and cartilaginous matrix by histological examination. The implants of the constructs were evaluated by histological and immunohistochemical examinations and reverse transcription PCR. Results indicated that the CS/COL-I scaffold showed porous structures, and the DNA content of SDSCs in CS/COL-I scaffolds increased at 1 week culture time. Both of the constructs in vitro and the implants were examined with positive stained GAGs histologically and the implants with positive collagen type II immunohistochemically. RT-PCR of the implants indicated that aggrecan and collagen type II expressed. It suggested that SDSCs coupled with CS/COL-I scaffolds treated sequentially with TGF-β1 and bFGF in vitro were highly competent for engineered cartilage formation in vitro and in vivo.

In vitro osteogenesis of synovium mesenchymal cells induced by controlled release of alendronate and dexamethasone from a sintered microspherical scaffold

In vitro osteogenesis was successfully achieved with synovium-derived mesenchymal stem cells (SMSCs), which intrinsically have a strong chondrogenic tendency, by in situ release of alendronate (AL) and dexamethasone (Dex) from poly(lactic-co-glycolic acid) (PLGA)/hydroxyapatite (HA) sintered microspherical scaffold (PLGA/HA-SMS). Cumulative release profiles of AL and Dex from PLGA/HA-SMS and the influence on SMSCs osteogenic commitment were investigated. SMSCs seeded in Al-/Dex-loaded PLGA/HA-SMS (PLGA/HA-Com-SMS) exhibited significant osteogenic differentiation, as indicated by high yields of alkaline phosphatase (ALP) and bone calcification. In addition, mechanical properties (compressional) of PLGA/HA-Com-SMSs were also evaluated and approved. In conclusion, by promoting osteogenic commitment of SMSCs in vitro, this newly designed controlled-release system opens a new door to bone reparation and regeneration.

Fat grafting to the breast and adipose-derived stem cells: recent scientific consensus and controversy

Recent technical advances in fat grafting and the development of surgical devices such as liposuction cannulae have made fat grafting a relatively safe and effective procedure. However, new guidelines issued by the American Society of Plastic Surgeons in 2009 announced that fat grafting to the breast is not a strongly recommended procedure, as there are limited scientific data on the safety and efficacy of this particular type of fat transfer. Recent progress by several groups has revealed that multipotent adult stem cells are present in human adipose tissue. This cell population, termed adipose-derived stem cells (ADSC), represents a promising approach to future cell-based therapies, such as tissue engineering and regeneration. In fact, several reports have shown that ADSC play a pivotal role in graft survival through both adipogenesis and angiogenesis. Although tissue augmentation by fat grafting does have several advantages in that it is a noninvasive procedure and results in minimal scarring, it is essential that such a procedure be supported by evidence-based medicine and that further basic scientific and clinical research is conducted to ensure that fat grafting is a safe and effective procedure.

In vitro engineered cartilage using synovium-derived mesenchymal stem cells with injectable gellan hydrogels

Synovium-derived mesenchymal stem cells (SMSC), a novel line of stem cells, are regarded as a promising cell source for cartilage tissue engineering. The goal of this study was to investigate rabbit SMSC coupled with injectable gellan hydrogels for in vitro engineered cartilage. SMSC were isolated from rabbit synovial tissue, amplified to passage 4 in monolayer, and encapsulated in injectable gellan hydrogels, constructs of which were cultured in chondrogenic medium supplemented with TGF-beta1, TGF-beta3 or BMP-2 for up to 42 days. The quality of the constructs was assessed in terms of cell proliferation and chondrocytic gene/protein expression using WST-1 assay, real-time RT-PCR, biochemical analysis, histology and immunohistochemical analysis. Results indicate that the viability of SMSC in hydrogels treated with TGF-beta1, TGF-beta3 and BMP-2 remained high at culture time. The constructs formed cartilaginous tissue with the expression of chondrocytic genes (collagen type II, aggrecan, biglycan, SOX 9) and cartilaginous matrix (sulphated glycosaminoglycan and collagen) as early as 21 days in culture. Both TGF-beta1 and TGF-beta3 treated SMSC-laden hydrogels showed more chondrogenesis compared with BMP-2 treated SMSC-laden hydrogels. It demonstrates that injectable SMSC-laden gels, when treated with TGF-beta1, TGF-beta3 or BMP-2, are highly competent for in vitro engineered cartilage formation, which lays a foundation for their potential application in clinical cartilage repair.

Functional properties of cartilaginous tissues engineered from infrapatellar fat pad-derived mesenchymal stem cells

Articular cartilage has a poor intrinsic capacity for self-repair. The advent of autologous chondrocyte implantation has provided a feasible method to treat cartilage defects. However, the associated drawbacks with the isolation and expansion of chondrocytes from autologous tissue has prompted research into alternative cell sources such as mesenchymal stem cells (MSCs) which have been found to exist in the bone marrow as well as other joint tissues such as the infrapatellar fat pad (IFP), synovium and within the synovial fluid itself. In this work we assessed the chondrogenic potential of IFP-derived porcine cells over a 6 week period in agarose hydrogel culture in terms of mechanical properties, biochemical content and histology. It was found that IFP cells underwent robust chondrogenesis as assessed by glycosaminoglycan (1.47+/-0.22% w/w) and collagen (1.44+/-0.22% w/w) accumulation after 42 days of culture. The 1Hz dynamic modulus of the engineered tissue at this time point was 272.8 kPa (+/-46.8). The removal of TGF-beta3 from culture after 21 days was shown to have a significant effect on both the mechanical properties and biochemical content of IFP constructs after 42 days, with minimal increases occurring from day 21 to day 42 without continued supplementation of TGF-beta3. These findings further strengthen the case that the IFP may be a promising cell source for putative cartilage repair strategies.

Novel mesoporous silica-based antibiotic releasing scaffold for bone repair

Tissue engineering scaffolds with a micro- or nanoporous structure and able to deliver special drugs have already been confirmed to be effective in bone repair. In this paper, we first evaluated the biomineralization properties and drug release properties of a novel mesoporous silica-hydroxyapatite composite material (HMS-HA) which was used as drug vehicle and filler for polymer matrices. Biomineralization can offer a credible prediction of bioactivity for the synthetic bone regeneration materials. We found HMS-HA exhibited good apatite deposition properties after being soaked in simulated body fluid (SBF) for 7 days. Drug delivery from HMS-HA particle was in line with Fick's law, and the release process lasted 12 h after an initial burst release with 60% drug release. A novel tissue engineering scaffold with the function of controlled drug delivery was developed, which was based on HMS-HA particles, poly(lactide-co-glycolide) (PLGA) and microspheres sintering techniques. Mechanical testing on compression, degradation behavior, pH-compensation effect and drug delivery behavior of PLGA/HMS-HA microspheres sintered scaffolds were analyzed. Cell toxicity and cell proliferation on the scaffolds was also evaluated. The results indicated that the PLGA/HMS-HA scaffolds could effectively compensate the increased pH values caused by the acidic degradation product of PLGA. The compressive strength and modulus of PLGA/HMS-HA scaffolds were remarkably high compared to pure PLGA scaffold. Drug delivery testing of the PLGA/HMS-HA scaffolds indicated that PLGA slowed gentamycin sulfate (GS) release from HMS-HA particles, and the release lasted for nearly one month. Adding HMS-HA to PLGA scaffolds improved cytocompatibility. The scaffolds demonstrated low cytotoxicity, and supported mesenchymal stem cells growth more effectively than pure PLGA scaffolds. To summarize, the data supports the development of PLGA/HMS-HA scaffolds as potential degradable and drug delivery materials for bone replacement.

Synovium-derived mesenchymal stem cells: a new cell source for musculoskeletal regeneration

Ever since synovium-derived mesenchymal stem cells (SMSCs) were first identified and successfully isolated in 2001, as a brand new member in MSC families, they have been increasingly regarded as a promising therapeutic cell species for musculoskeletal regeneration, particularly for reconstructions of cartilage, bones, tendons, and muscles. Besides the general multipotency in common among the MSC community, SMSCs excel other sourced MSCs in higher ability of proliferation and superiority in chondrogenesis. This review summarizes the latest advances in SMSC-related studies covering their specific isolation methodologies, biological insights, and practical applications in musculoskeletal therapeutics of which an emphasis is cast on engineered chondrogenesis.