Major biological obstacles for persistent cell-based regeneration of articular cartilage

Extracellular vesicles: Potential role in osteoarthritis regenerative medicine

Osteoarthritis (OA) is a prevalent whole joint disease characterised by cartilage degradation, subchondral bone sclerosis and bone remodelling, and synovium inflammation, leading to pain, deformity, and cartilage dysfunction. Currently, there is no appropriate therapy for OA, and available treatments simply aim to reduce pain and swelling. Exosomes are membrane-bound extracellular vesicles secreted by almost all cells, receiving increasing interest because of their effect in cell-to-cell communication. Increasing evidence suggests that exosomes play an important role in cartilage physiological and pathological effects. This article reviews the potential role of exosomes in OA regenerative medicine. Special attention is given to mesenchymal stem cells-derived exosomes due to the extensive research on their cartilage repair property and their function as miRNA cargo. More investigations are needed for the effects of exosomes from synovial fluid and chondrocytes in joints. A better understanding of the mechanisms will contribute to a novel and promising therapy for OA patients.

The translational potential of this article

A better understanding of the role of extracellular vesicles in regenerative medicine will contribute to a novel and promising therapy for OA patients.

Gene expression markers in horse articular chondrocytes: Chondrogenic differentiaton IN VITRO depends on the proliferative potential and ageing. Implication for tissue engineering of cartilage

Chondrocyte dedifferentiation is a key limitation in therapies based on autologous chondrocyte implantation for cartilage repair. Articular chondrocytes, obtained from (metacarpophalangeal and metatarsophalangeal) joints of different aged horses, were cultured in monolayer for several passages (P0 to P8). Cumulative Populations Doublings Levels (PDL) and gene expression of relevant chondrocyte phenotypic markers were analysed during culturing. Overall data confirmed that, during proliferation in vitro, horse chondrocytes undergo marked morphological and phenotypic alterations of their differentiation status. Particularly, the dedifferentiation started early in culture (P0-P1) and was very marked at P3 subculture (PDL 4-6): proliferative phase after P3 could be critical for maintenance/loss of differentiation potential. In elderly animals, chondrocytes showed aspects of dedifferentiation shortly after their isolation, associated with reduced proliferative capacity. Regarding the gene expression of major cartilage markers (Col2, Aggrecan, SOX9) there was a very early reduction (P1) in proliferating chondrocytes independent of age. The chondrocytes from adult donors showed a more stable expression (up to P3) of some (Col6, Fibromodulin, SOX6, TGβ1) markers of mature cartilage; these markers could be tested as parameter to determine the dedifferentiation level. This study can provide parameters to identify up to which "culture step" chondrocytes for implantation with a conserved phenotypic potential can be obtained, and to test the efficiency of biomaterial scaffold or chondroinductive media/signals to maintain/recover the chondrocyte phenotype. Moreover, the determination of levels and time related expression of these markers can be useful during the chondroinduction of mesenchymal stem cells.

lncRNA ADAMTS9-AS2 Controls Human Mesenchymal Stem Cell Chondrogenic Differentiation and Functions as a ceRNA

Long noncoding RNAs (lncRNAs) have emerged as key regulators of cell differentiation and development. However, potential roles for lncRNAs in chondrogenic differentiation have remained poorly understood. Here we identify lncRNA ADAMTS9 antisense RNA 2, ADAMTS9-AS2, which controls the chondrogenic differentiation by acting as a competing endogenous RNA (ceRNA) in human mesenchymal stem cells (hMSCs). We screen out ADAMTS9-AS2 of undifferentiated and differentiated cells during chondrogenic differentiation by microarrays. Suppression or overexpression of lncRNA ADAMTS9-AS2 correlates with inhibition and promotion of hMSC chondrogenic differentiation, respectively. We find that ADAMTS9-AS2 can sponge miR-942-5p to regulate the expression of Scrg1, a transcription factor promoting chondrogenic gene expression. Finally, we confirm the function of ADAMTS9-AS2 to cartilage repair in the absence of transforming growth factor β (TGF-β) in vivo. In conclusion, ADAMTS9-AS2 plays an important role in chondrogenic differentiation as a ceRNA, so that it can be regarded as a therapy target for cartilage repair.

Enrichment of CD146+ Adipose-Derived Stem Cells in Combination with Articular Cartilage Extracellular Matrix Scaffold Promotes Cartilage Regeneration

Heterogeneity of mesenchymal stem cells (MSCs) influences the cell therapy outcome and the application in tissue engineering. Also, the application of subpopulations of MSCs in cartilage regeneration remains poorly characterized. CD146+ MSCs are identified as the natural ancestors of MSCs and the expression of CD146 are indicative of greater pluripotency and self-renewal potential. Here, we sorted a CD146⁺ subpopulation from adipose-derived mesenchymal stem cells (ADSCs) for cartilage regeneration.

Methods: CD146⁺ ADSCs were sorted using magnetic activated cell sorting (MACS). Cell surface markers, viability, apoptosis and proliferation were evaluated in vitro. The molecular signatures were analyzed by mRNA and protein expression profiling. By intra-articular injections of cells in a rat osteochondral defect model, we assessed the role of the specific subpopulation in cartilage microenvironment. Finally, CD146⁺ ADSCs were combined with articular cartilage extracellular matrix (ACECM) scaffold for long term (3, 6 months) cartilage repair.

Results: The enriched CD146⁺ ADSCs showed a high expression of stem cell and pericyte markers, good viability, and immune characteristics to avoid allogeneic rejection. Gene and protein expression profiles revealed that the CD146⁺ ADSCs had different cellular functions especially in regulation inflammation. In a rat model, CD146⁺ ADSCs showed a better inflammation-modulating property in the early stage of intra-articular injections. Importantly, CD146⁺ ADSCs exhibited good biocompatibility with the ACECM scaffold and the CD146⁺ cell-scaffold composites produced less subcutaneous inflammation. The combination of CD146⁺ ADSCs with ACECM scaffold can promote better cartilage regeneration in the long term.

Conclusion: Our data elucidated the function of the CD146⁺ ADSC subpopulation, established their role in promoting cartilage repair, and highlighted the significance of cell subpopulations as a novel therapeutic for cartilage regeneration.

Functional Biomolecule Delivery Systems and Bioengineering in Cartilage Regeneration

Osteoarthritis (OA) is a common degenerative disease which involves articular cartilage, and leads to total joint disability in the advanced stages. Due to its avascular and aneural nature, damaged cartilage cannot regenerate itself. Stem cell therapy and tissue engineering represent a promising route in OA therapy, in which cooperation of mesenchymal stem cells (MSCs) and three-dimensional (3D) scaffolds contribute to cartilage regeneration. However, this approach still presents some limits such as poor mechanical properties of the engineered cartilage. The natural dynamic environment of the tissue repair process involves a collaboration of several signals expressed in the biological system in response to injury. For this reason, tissue engineering involving exogenous "influencers" such as mechanostimulation and functional biomolecule delivery systems (BDS), represent a promising innovative approach to improve the regeneration process. BDS provide a controlled release of biomolecules able to interact between them and with the injured tissue. Nano-dimensional BDS is the future hope for the design of personalized scaffolds, able to overcome the delivery problems. MSC-derived extracellular vesicles (EVs) represent an attractive alternative to BDS, due to their innate targeting abilities, immunomodulatory potential and biocompatibility. Future advances in cartilage regeneration should focus on multidisciplinary strategies such as modular assembly strategies, EVs, nanotechnology, 3D biomaterials, BDS, mechanobiology aimed at constructing the functional scaffolds for actively targeted biomolecule delivery. The aim of this review is to run through the different approaches adopted for cartilage regeneration, with a special focus on biomaterials, BDS and EVs explored in terms of their delivery potential, healing capabilities and mechanical features.

Application of mesenchymal stem cell therapy for the treatment of osteoarthritis of the knee: A concise review

Osteoarthritis (OA) refers to a chronic joint disease characterized by degenerative changes of articular cartilage and secondary bone hyperplasia. Since articular cartilage has a special structure, namely the absence of blood vessels as well as the low conversion rate of chondrocytes in the cartilage matrix, the treatment faces numerous clinical challenges. Traditional OA treatment (e.g., arthroscopic debridement, microfracture, autologous or allogeneic cartilage transplantation, chondrocyte transplantation) is primarily symptomatic treatment and pain management, which cannot contribute to regenerating degenerated cartilage or reducing joint inflammation. Also, the generated mixed fibrous cartilage tissue is not the same as natural hyaline cartilage. Mesenchymal stem cells (MSCs) have turned into the most extensively explored new therapeutic drugs in cell-based OA treatment as a result of their ability to differentiate into chondrocytes and their immunomodulatory properties. In this study, the preliminary results of preclinical (OA animal model)/clinical trials regarding the effects of MSCs on cartilage repair of knee joints are briefly summarized, which lay a solid application basis for more and deeper clinical studies on cell-based OA treatment.

Association between Extracellular Matrix Accumulation and Oxidative Stress-Induced Apoptosis in Chondrocytes Cultured on 3D-Porous Scaffolds in Static versus Dynamic Cultures

The aim of this study was to investigate the relation between the amount of glycosaminoglycans (GAGs) secreted and the level of apoptosis induced by hydrogen peroxide (H2O2) in porcine chondrocytes cultured on two different biodegradable PCL/PHBV scaffolds: one had primary pores solely, while the other possessed both primary and secondary pores, namely PCL/PHBV/0%NaCl and PCL/PHBV/50%NaCl scaffolds, respectively. The scaffolds with an average primary pore size of 200 μm were primarily fabricated by a fused deposition modeling (FDM) machine, and secondary pores on the material surface were then generated after NaCl leaching in a sodium hydroxide solution. The investigation was performed comparatively under static and dynamic environments. In static culture study, more pronounced GAG accumulation was found on the PCL/PHBV/50%NaCl scaffold, suggesting that the secondary pores could promote the chondrogenic function of chondrocytes, and the primary pores could further accommodate the cells to grow and function more productively. Meanwhile, the significant reductions in the levels of apoptosis of chondrocytes, studied in a H2O2-dose dependent manner (0-2 mM), were observed with a use of a flow cytometer when the chondrocytes were cultured on the PCL/PHBV/50%NaCl scaffold in which more GAG content was found. In dynamic culture study, although the total GAG content detected on the PCL/PHBV/50%NaCl scaffold was still significantly higher than that measured on the PCL/PHBV/0%NaCl scaffold, these GAG accumulations were tremendously greater than those found in the static culture. As a consequence, far less oxidative stress-induced apoptotic death was observed in the cells cultured under the dynamic culture. Moreover, cells seemed to be well protected from apoptosis, in the presence of considerable amounts of GAGs; similar degrees of apoptosis (~25%) were observed on the cells cultured on each scaffold at all H2O2 concentrations studied. The obtained results had demonstrated that the degree of chondrocyte apoptosis was somehow related to the level of GAG accumulation.

Intra-articular implantation of autologous bone marrow-derived mesenchymal stromal cells to treat knee osteoarthritis: a randomized, triple-blind, placebo-controlled phase 1/2 clinical trial

BACKGROUND

The intra-articular implantation of mesenchymal stromal cells (MSCs) as a treatment for knee osteoarthritis (OA) is an emerging new therapy. In this study, patients with knee OA received intra-articular implantations of autologous bone marrow-derived MSCs. We sought to assess the safety and efficacy of this implantation.

MATERIALS AND METHODS

This was a phase 1/2 single-center, triple-blind, randomized controlled trial (RCT) with a placebo control. The subjects consisted of patients with knee OA randomly assigned to either an intra-articular implantation of MSCs (40 × 10⁶ cells) or 5 mL normal saline (placebo). Patients were followed up for 6 months after the implantations. The pain level and function improvements for patient-reported outcomes were assessed based on a visual analog scale (VAS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and its subscales, walking distance, painless walking distance, standing time and knee flexion compared with the placebo group at 3 and 6 months following the implantations.

RESULTS

Overall, 43 patients (Kellgren-Lawrence grades 2, 3 and 4) were assigned to either the MSCs (n = 19) or placebo (n = 24) group. Patients who received MSCs experienced significantly greater improvements in WOMAC total score, WOMAC pain and physical function subscales and painless walking distance compared with patients who received placebo. There were no major adverse events attributed to the MSC therapy.

CONCLUSION

This randomized, triple-blind, placebo-controlled RCT demonstrated the safety and efficacy of a single intra-articular implantation of 40 × 10⁶ autologous MSCs in patients with knee OA. Intra-articular implantation of MSCs provided significant and clinically relevant pain relief over 6 months versus placebo and could be considered a promising novel treatment for knee OA. We propose that further investigations should be conducted over an extended assessment period and with a larger cohort.

Pre-transplantational Control of the Post-transplantational Fate of Human Pluripotent Stem Cell-Derived Cartilage

Cartilage pellets generated from ectomesenchymal progeny of human pluripotent stem cells (hPSCs) in vitro eventually show signs of commitment of chondrocytes to hypertrophic differentiation. When transplanted subcutaneously, most of the surviving pellets were fully mineralized by 8 weeks. In contrast, treatment with the adenylyl cyclase activator, forskolin, in vitro resulted in slightly enlarged cartilage pellets containing an increased proportion of proliferating immature chondrocytes that expressed very low levels of hypertrophic/terminally matured chondrocyte-specific genes. Forskolin treatment also enhanced hyaline cartilage formation by reducing type I collagen gene expression and increasing sulfated glycosaminoglycan accumulation in the developed cartilage. Chondrogenic mesoderm from hPSCs and dedifferentiated nasal chondrocytes responded similarly to forskolin. Furthermore, forskolin treatment in vitro increased the frequency at which the cartilage pellets maintained unmineralized chondrocytes after subcutaneous transplantation. Thus, the post-transplantational fate of chondrocytes originating from hPSC-derived chondroprogenitors can be controlled during their genesis in vitro.

•

Forskolin/cAMP suppresses/delays BMP-induced chondrocyte maturation in vitro

•

Forskolin supports chondrocyte proliferation and hyaline chondrogenesis in vitro

•

Forskolin suppresses osteogenesis and BMP signaling gene expression in cartilage

•

In vitro forskolin treatment improves in vivo maintenance of uncalcified cartilage

Effect of electric stimulation on human chondrocytes and mesenchymal stem cells under normoxia and hypoxia

During joint movement and mechanical loading, electric potentials occur within cartilage tissue guiding cell development and regeneration. Exposure of cartilage exogenous electric stimulation (ES) may imitate these endogenous electric fields and promote healing processes. Therefore, the present study investigated the influence of electric fields on human chondrocytes, mesenchymal stem cells and the co-culture of the two. Human chondrocytes isolated from articular cartilage obtained post-mortally and human mesenchymal stem cells derived from bone marrow (BM-MSCs) were seeded onto a collagen-based scaffold separately or as co-culture. Following incubation with the growth factors over 3 days, ES was performed using titanium electrodes applying an alternating electric field (700 mV, 1 kHz). Cells were exposed to an electric field over 7 days under either hypoxic or normoxic culture conditions. Following this, metabolic activity was investigated and synthesis rates of extracellular matrix proteins were analyzed. ES did not influence metabolic activity of chondrocytes or BM-MSCs. Gene expression analyses demonstrated that ES increased the expression of collagen type II mRNA and aggrecan mRNA in human chondrocytes under hypoxic culture conditions. Likewise, collagen type II synthesis was significantly increased following exposure to electric fields under hypoxia. BM-MSCs and the co-culture of chondrocytes and BM-MSCs revealed a similar though weaker response regarding the expression of cartilage matrix proteins. The electrode setup may be a valuable tool to investigate the influence of ES on human chondrocytes and BM-MSCs contributing to fundamental knowledge including future applications of ES in cartilage repair.

In vitro study of matrix metalloproteinases 1, 2, 9, 13 and serum amyloid A mRNAs expression in equine fibroblast-like synoviocytes treated with doxycycline

Application of synthetic matrix metalloproteinases (MMPs) inhibitors, such as doxycycline is one of the possible therapeutic options for osteoarthritis. However, little is known about the protective mechanism of doxycycline in equine models on MMPs inhibitors as well as on serum amyloid A (SAA) gene expression. This study investigated the effects of doxycycline on mRNA expression of MMP-1, MMP-2, MMP-9, MMP-13, and SAA of equine fibroblast-like synoviocytes (FLSs). The FLSs were established from synovial fluids of clinically normal metacarpophalangeal joints of 6 skeletally mature horses. The cells were treated with either 10 or 100 μg/mL of doxycycline for 48 h. The mRNA expression of MMP-1, MMP-2, MMP-9, MMP-13, and SAA were assessed using real-time polymerase chain reaction (PCR). Treatment with doxycycline resulted in significantly decreased mRNA expression of MMP-1 in FLSs at both concentrations (P = 0.001). No significant differences were detected among groups for MMP-2, MMP-9, and MMP-13 (P > 0.05). Only a tendency towards a decrease in mRNA expression level of SAA in the presence of doxycycline could be detected. Doxycycline inhibits MMP-1 gene expression at the transcript level. These findings indicate that doxycycline can protect the articular environment through inhibition of MMP-1 at transcript level.

Interplay between stiffness and degradation of architectured gelatin hydrogels leads to differential modulation of chondrogenesis in vitro and in vivo

The limited capacity of cartilage to heal large lesions through endogenous mechanisms has led to extensive effort to develop materials to facilitate chondrogenesis. Although physical-chemical properties of biomaterials have been shown to impact in vitro chondrogenesis, whether these findings are translatable in vivo is subject of debate. Herein, architectured 3D hydrogel scaffolds (ArcGel) (produced by crosslinking gelatin with ethyl lysine diisocyanate (LDI)) were used as a model system to investigate the interplay between scaffold mechanical properties and degradation on matrix deposition by human articular chondrocytes (HAC) from healthy donors in vitro and in vivo. Using ArcGel scaffolds of different tensile and shear modulus, and degradation behavior; in this study, we compared the fate of ex vivo engineered ArcGels-chondrocytes constructs, i.e. the traditional tissue engineering approach, with thede novoformation of cartilaginous tissue in HAC laden ArcGels in an ectopic nude mouse model. While the softer and fast degrading ArcGel (LNCO3) was more efficient at promoting chondrogenic differentiation in vitro, upon ectopic implantation, the stiffer and slow degrading ArcGel (LNCO8) was superior in maintaining chondrogenic phenotype in HAC and retention of cartilaginous matrix. Furthermore, surprisingly the de novo formation of cartilage tissue was promoted only in LNCO8. Since HAC cultured for only three days in the LNCO8 environment showed upregulation of hypoxia-associated genes, this suggests a potential role for hypoxia in the observed in vivo outcomes. In summary, this study sheds light on how immediate environment (in vivo versus in vitro) can significantly impact the outcomes of cell-laden biomaterials.

STATEMENT OF SIGNIFICANCE

In this study, 3D architectured hydrogels (ArcGels) with different mechanical and biodegradation properties were investigated for their potential to promote formation of cartilaginous matrix by human articular chondrocytes in vitro and in vivo. Two paradigms were explored (i) ex vivo engineering followed by in vivo implantation in ectopic site of nude mice and (ii) short in vitro culture (3 days) followed by implantation to induce de novo cartilage formation. Softer and fast degrading ArcGel were better at promoting chondrogenesis in vitro, while stiffer and slow degrading ArcGel were strikingly superior in both maintaining chondrogenesis in vivo and inducing de novo formation of cartilage. Our findings highlight the importance of the interplay between scaffold mechanics and degradation in chondrogenesis.

Repair of articular cartilage defects with acellular cartilage sheets in a swine model

Acellular cartilage sheets (ACSs) have been demonstrated as a good biomaterial for cartilage regeneration as a result of their natural cartilage matrix components, cartilage-specific structures, and good biocompatibility. However, it remains unknown whether allogeneic ACSs could promote cartilage regeneration and repair cartilage defects in a large animal model. The current study explored the feasibility of repairing articular cartilage defects using ACS scaffold with or without autologous bone marrow stromal cells (BMSCs) in a swine model. According to the current results, ACSs retained natural cartilage structure, primary cartilage matrices, and cartilage-specific growth factors. After cell seeding, ACSs presented good biocompatibility with BMSCs, which produced abundant extracellular matrix (ECM) proteins to cover the lacuna structures. In vivo results indicated that ACSs alone could induce endogenous host cells to regenerate cartilage and achieve generally satisfactory repair of cartilage defects at 6 months post-operation, including good interface integration and cartilage-specific ECM deposition. After combination with autologous BMSCs, BMSC-ACS constructs achieved more satisfactory repair of cartilage defects even without in vitro pre-induction of chondrogenesis. More importantly, all defects in both BMSC-ACS and ACS-only groups showed enhanced cartilage regeneration compared with BMSC-polyglycolic acid and blank groups, which mainly exhibited fibrogenesis in defect areas. Collectively, the current results indicate that ACSs can efficiently repair articular cartilage defects by promoting chondrogenic differentiation of BMSCs or inducing endogenous chondrogenesis in situ, thus serving as a good cartilage regeneration scaffold for recovery of articular function.

Gene Delivery of TGF-β3 and BMP2 in an MSC-Laden Alginate Hydrogel for Articular Cartilage and Endochondral Bone Tissue Engineering

Incorporating therapeutic genes into three-dimensional biomaterials is a promising strategy for enhancing tissue regeneration. Alginate hydrogels have been extensively investigated for cartilage and bone tissue engineering, including as carriers of transfected cells to sites of injury, making them an ideal gene delivery platform for cartilage and osteochondral tissue engineering. The objective of this study was to develop gene-activated alginate hydrogels capable of supporting nanohydroxyapatite (nHA)-mediated nonviral gene transfer to control the phenotype of mesenchymal stem cells (MSCs) for either cartilage or endochondral bone tissue engineering. To produce these gene-activated constructs, MSCs and nHA complexed with plasmid DNA (pDNA) encoding for transforming growth factor-beta 3 (pTGF-β3), bone morphogenetic protein 2 (pBMP2), or a combination of both (pTGF-β3-pBMP2) were encapsulated into alginate hydrogels. Initial analysis using reporter genes showed effective gene delivery and sustained overexpression of the transgenes were achieved. Confocal microscopy demonstrated that complexing the plasmid with nHA before hydrogel encapsulation led to transport of the plasmid into the nucleus of MSCs, which did not happen with naked pDNA. Gene delivery of TGF-β3 and BMP2 and subsequent cell-mediated expression of these therapeutic genes resulted in a significant increase in sulfated glycosaminoglycan and collagen production, particularly in the pTGF-β3-pBMP2 codelivery group in comparison to the delivery of either pTGF-β3 or pBMP2 in isolation. In addition, stronger staining for collagen type II deposition was observed in the pTGF-β3-pBMP2 codelivery group. In contrast, greater levels of calcium deposition were observed in the pTGF-β3- and pBMP2-only groups compared to codelivery, with a strong staining for collagen type X deposition, suggesting these constructs were supporting MSC hypertrophy and progression along an endochondral pathway. Together, these results suggest that the developed gene-activated alginate hydrogels were able to support transfection of encapsulated MSCs and directed their phenotype toward either a chondrogenic or an osteogenic phenotype depending on whether TGF-β3 and BMP2 were delivered in combination or isolation.

The Challenge in Using Mesenchymal Stromal Cells for Recellularization of Decellularized Cartilage

Some decellularized musculoskeletal extracellular matrices (ECM)s derived from tissues such as bone, tendon and fibrocartilaginous meniscus have already been clinical use for tissue reconstruction. Repair of articular cartilage with its unique zonal ECM architecture and composition is still an unsolved problem, and the question is whether allogenic or xenogeneic decellularized cartilage ECM could serve as a biomimetic scaffold for this purpose.Hence, this survey outlines the present state of preparing decellularized cartilage ECM-derived scaffolds or composites for reconstruction of different cartilage types and of reseeding it particularly with mesenchymal stromal cells (MSCs).The preparation of natural decellularized cartilage ECM scaffolds hampers from the high density of the cartilage ECM and lacking interconnectivity of the rather small natural pores within it: the chondrocytes lacunae. Nevertheless, the reseeding of decellularized ECM scaffolds before implantation provided superior results compared with simply implanting cell-free constructs in several other tissues, but cartilage recellularization remains still challenging. Induced by cartilage ECM-derived scaffolds MSCs underwent chondrogenesis.Major problems to be addressed for the application of cell-free cartilage were discussed such as to maintain ECM structure, natural chemistry, biomechanics and to achieve a homogenous and stable cell recolonization, promote chondrogenic and prevent terminal differentiation (hypertrophy) and induce the deposition of a novel functional ECM. Some promising approaches were proposed including further processing of the decellularized ECM before recellularization of the ECM with MSCs, co-culturing of MSCs with chondrocytes and establishing bioreactor culture e.g. with mechanostimulation, flow perfusion pressure and lowered oxygen tension. Graphical Abstract Synopsis of tissue engineering approaches based on cartilage-derived ECM.

Fixation of Hydrogel Constructs for Cartilage Repair in the Equine Model: A Challenging Issue

OBJECTIVE

To report on the experiences with the use of commercial and autologous fibrin glue (AFG) and of an alternative method based on a 3D-printed polycaprolactone (PCL) anchor for the fixation of hydrogel-based scaffolds in an equine model for cartilage repair.

METHODS

In a first study, three different hydrogel-based materials were orthotopically implanted in nine horses for 1-4 weeks in 6 mm diameter full-thickness cartilage defects in the medial femoral trochlear ridge and fixated with commercially available fibrin glue (CFG). One defect was filled with CFG only as a control. In a second study, CFG and AFG were compared in an ectopic equine model. The third study compared the efficacy of AFG and a 3D-printed PCL-based osteal anchor for fixation of PCL-reinforced hydrogels in three horses for 2 weeks, with a 4-week follow-up to evaluate integration of bone with the PCL anchor. Short-term scaffold integration and cell infiltration were evaluated by microcomputed tomography and histology as outcome parameters.

RESULTS

The first study showed signs of subchondral bone resorption in all defects, including the controls filled with CFG only, with significant infiltration of neutrophils. Ectopically, CFG induced clear inflammation with strong neutrophil accumulation; AFG was less reactive, showing fibroblast infiltration only. In the third study the fixation potential for PCL-reinforced hydrogels of AFG was inferior to the PCL anchor. PCL reinforcement had disappeared from two defects and showed signs of dislodging in the remaining four. All six constructs fixated with the PCL anchor were still in place after 2 weeks. At 4 weeks, the PCL anchor showed good integration and signs of new bone formation.

CONCLUSIONS

The use of AFG should be preferred to xenogeneic products in the horse, but AFG is subject to individual variations and laborious to make. The PCL anchor provides the best fixation; however, this technique involves the whole osteochondral unit, which entails a different conceptual approach to cartilage repair.

Adipose-derived stem cell sheet encapsulated construct of micro-porous decellularized cartilage debris and hydrogel for cartilage defect repair

Challenges of repairing injuries and damage to the cartilage still remain in orthopedics. The characteristics of cartilage structure, especially avascular, make it a limited capacity of self-renewal. Articular cartilage defect or damage result from various causes will lead to degenerative osteoarthritis (OA). Surgical treatment and non-surgical treatment can temporarily alleviate symptoms to some extent but can't fundamentally restore the normal structure and function of cartilage, and therefore give rise to progressive degeneration. Autologous or allogeneic cartilage transplantation has been employed to the treatment of osteoarthritis for years. Nevertheless, the major deficiency of cartilage grafting is the inability and insufficiency to repair large cartilage defect. Implants are also unable to integrate with native tissue well. Adipose-derived stem cells (ASCs) can be easily isolated from subcutaneous fat tissues and harvest as intact cell sheets containing extracellular matrix (ECM), intercellular connect, ion channel, growth factor receptors, nexin and other important cell surface proteins by means of temperature-responsive culture dish (TCD). A cell sheet can provide a large amount of extracellular matrix, fibronectin, and cells contributing to the integration of cartilage. Decellularized extracellular matrix (DECM) of cartilage debris with excellent cell affinity and signal transduction is capable of driving cartilage homeostasis and regeneration. Appropriate decellularization process would remove cellular remnants of cartilage debris, keep the mechanical properties, and avoid the adverse immune response of allografts effectively. Micro-porous cartilage debris conduces to cell migration and angiogenesis. The cell-round shape of adipose-derived stem cells cultured in the three-dimensional (3D) system provided by hydrogel is more susceptible to chondrogenic stimulation and prevents it from fibroblast-like phenotypic conversion. We hypothesize that adipose-derived stem cell sheet encapsulated construct of micro-porous decellularized cartilage debris and hydrogel can effectively promote regeneration of cartilage defect. The construct of decellularized cartilage debris and hydrogel provide a favorable microenvironment for stem cells. Adipose-derived stem cells sheet supply fibronectin, collagen, and cells contributing to integration and regeneration of cartilage restore. Moreover, the constructs can be shaped and fabricated according to the configuration of target defect, especially in osteoarthritis, which is promising for clinical application.

Synergistic effects on mesenchymal stem cell-based cartilage regeneration by chondrogenic preconditioning and mechanical stimulation

Background

Mesenchymal stem cells (MSCs) hold promising translational potential in cartilage regeneration. However, the efficacy of MSC-based tissue engineering is not satisfactory in the treatment of cartilage defect because of the inevitable cellular functional changes during ex vivo cell expansion. How to maintain the chondrogenic capacity of MSCs to improve their therapeutic outcomes remains an outstanding question.

Methods

Bone marrow-derived MSCs were firstly primed in chondrogenic induction medium which was then replaced with normal growth medium to attain the manipulated cells (M-MSCs). Methacrylated hyaluronic acid (MeHA) was synthesized as a scaffold to encapsulate the cells. The MSC- or M-MSC-laden constructs were treated with dynamic compressive loading (DL) in a bioreactor or with free loading (FL) for 14 days. Afterwards, the constructs were implanted in nude mice or rat models of osteochondral defects to test their efficiency in cartilage regeneration or repair.

Results

Data showed that the resulting M-MSCs exhibited superior chondrogenic differentiation potential and survivability compared with untreated MSCs. More importantly, we found that DL significantly promoted neocartilage formation in the MeHA hydrogel encapsulated with M-MSCs after 30 days of implantation in nude mice. Furthermore, the constructs laden with M-MSCs after DL for 14 days significantly enhanced cartilage healing in a rat model of osteochondral defect.

Conclusions

Findings from this study highlight the importance of maintaining chondrogenic potential of MSCs by in-vitro chondrogenic preconditioning and a synergistic effect of mechanical stimulation in cartilage engineering, which may shed light on the stem cell-based tissue engineering for cartilage repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0672-5) contains supplementary material, which is available to authorized users.

REAC regenerative treatment efficacy in experimental chondral lesions: a pilot study on ovine animal model

Radioelectric asymmetric conveyor (REAC) technology is a platform designed to optimize cell polarity. Cell polarity is a universal biological phenomenon that is implicated in cell differentiation, proliferation, morphogenesis, aging, and rejuvenation. In this work, we investigate a timing and administration protocol for tissue optimization regenerative treatment type C, in order to treat aging-related chondral damage or injuries and gain insights into regenerative processes of articular cartilage in humans. The chondral lesion produced in this study in an animal model (6 knee joints of 4 adult sheep) was 6 mm in diameter and about 2 mm deep. These lesions, which did not involve subchondral bone, tend to increase in size and depth and are not completely repaired with normal hyaline articular cartilage since adult articular cartilage is avascular and has a very slow turnover at the cellular and molecular level. Moreover, the hydration of articular cartilage is reduced with aging and with decreased mitotic activity, synthesis, and population size of chondrocytes. Six months posttreatment, lesions appeared filled, though not completely, with newly generated tissue of the light opalescent color of healthy articular cartilage, which otherwise covered the underlying subchondral bone. The newly formed tissue surface appeared to be quite regular. Nearly complete regeneration of subchondral bone occurred, with little vascularization and ossification nuclei almost absent. The results of this study confirm previous data obtained in vitro on the regenerative effects of REAC technology on human normal and osteoarthritic chondrocytes exposed to IL-1β. The present findings indicate that REAC tissue optimization-regenerative treatment type C is a promising therapeutic tool among the other REAC regenerative treatment protocols for the treatment of cartilage lesions.

Tissue engineering-relevant characteristics of ex vivo and monolayer-expanded chondrocytes from the notch versus trochlea of human knee joints

PURPOSE

The aim was to analyse the biological characteristics of chondrocytes from the two biopsy sites notch vs. trochlea of human knee joints. The question was whether tissue engineering-relevant characteristics such as viability and mRNA expression profile would be comparable ex vivo and after monolayer expansion, as these are parts of routine autologous chondrocyte implantation (ACI).

METHODS

Biopsies from the intercondylar notch and the lateral aspect of the trochlea from 20 patients with ICRS grades 3 and 4 cartilage defects were harvested during arthroscopy. Collagen types 1, 2, and 10 mRNA were quantified by polymerase chain reaction.

RESULTS

Compared with notch chondrocytes, ex vivo trochlea chondrocytes had comparable cell numbers, vitality and aggrecan, collagen types 1, -2 and -10 mRNA expression. After monolayer expansion both notch and trochlea chondrocyte characteristics were comparably altered, regardless of their biopsy origin, and no significant differences in viability and mRNA expression were noted.

CONCLUSIONS

Collectively, these findings suggest that tissue engineering-relevant characteristics of notch and trochlea chondrocytes are comparable ex vivo and after monolayer expansion. Thus, trochlea chondrocytes promise clinical potential and chondrocytes for ACI could potentially be generated from both notch and trochlea biopsy sites.

Exosomes from embryonic mesenchymal stem cells alleviate osteoarthritis through balancing synthesis and degradation of cartilage extracellular matrix

Background

Mesenchymal stem cell therapy for osteoarthritis (OA) has been widely investigated, but the mechanisms are still unclear. Exosomes that serve as carriers of genetic information have been implicated in many diseases and are known to participate in many physiological processes. Here, we investigate the therapeutic potential of exosomes from human embryonic stem cell-induced mesenchymal stem cells (ESC-MSCs) in alleviating osteoarthritis (OA).

Methods

Exosomes were harvested from conditioned culture media of ESC-MSCs by a sequential centrifugation process. Primary mouse chondrocytes treated with interleukin 1 beta (IL-1β) were used as an in vitro model to evaluate the effects of the conditioned medium with or without exosomes and titrated doses of isolated exosomes for 48 hours, prior to immunocytochemistry or western blot analysis. Destabilization of the medial meniscus (DMM) surgery was performed on the knee joints of C57BL/6 J mice as an OA model. This was followed by intra-articular injection of either ESC-MSCs or their exosomes. Cartilage destruction and matrix degradation were evaluated with histological staining and OARSI scores at the post-surgery 8 weeks.

Results

We found that intra-articular injection of ESC-MSCs alleviated cartilage destruction and matrix degradation in the DMM model. Further in vitro studies illustrated that this effect was exerted through ESC-MSC-derived exosomes. These exosomes maintained the chondrocyte phenotype by increasing collagen type II synthesis and decreasing ADAMTS5 expression in the presence of IL-1β. Immunocytochemistry revealed colocalization of the exosomes and collagen type II-positive chondrocytes. Subsequent intra-articular injection of exosomes derived from ESC-MSCs successfully impeded cartilage destruction in the DMM model.

Conclusions

The exosomes from ESC-MSCs exert a beneficial therapeutic effect on OA by balancing the synthesis and degradation of chondrocyte extracellular matrix (ECM), which in turn provides a new target for OA drug and drug-delivery system development.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0632-0) contains supplementary material, which is available to authorized users.

Induced Redifferentiation of Human Chondrocytes from Articular Cartilage Lesion in Alginate Bead Culture After Monolayer Dedifferentiation: An Alternative Cell Source for Cell-Based Therapies?

Human chondrocytes isolated from articular cartilage (AC) lesions as an alternative cell source to the standard nonweight-bearing notch biopsy site may hold clinical potential for cell-based therapies. The aim was to characterize human AC lesion site chondrocytes, compare them to notch chondrocytes, and evaluate their redifferentiation potential after monolayer expansion and subsequent three-dimensional (3D) alginate bead culture. Lesion chondrocytes from knee joints of 20 patients with International Cartilage Repair Society (ICRS) grade 3 and 4 cartilage defects were analyzed ex vivo or cultured in primary alginate bead culture, monolayer expansion, or redifferentiated in alginate culture following monolayer expansion. The mRNA expression of the types I, II, and X collagen, and the proteoglycan aggrecan was compared between the four groups. In addition, notch chondrocytes of nine patients were compared to lesion chondrocytes ex vivo. AC lesion chondrocytes displayed ex vivo a nondegenerative phenotype, characterized by a relatively high mRNA expression of aggrecan and type II and X collagen, but a low type I collagen expression and a low ratio of type I to II collagen mRNA expression. Compared to notch chondrocytes, the mRNA expression of aggrecan and type II collagen was comparable and the ratio of type I to II collagen mRNA expression was below 1 in both groups, indicating a functional chondrocyte phenotype. Dedifferentiation led to a significantly altered degenerative mRNA expression profile. Induced redifferentiation in alginate beads after monolayer expansion significantly improved the mRNA expression of aggrecan, the type I and II collagen, and the type I to II collagen ratio, compared to monolayer expansion only. These data suggested that redifferentiating lesion chondrocytes after monolayer expansion in alginate beads resulted in a pool of cells with greater chondrogenic potential, compared to expanded dedifferentiated chondrocytes. Collectively, these data suggest that ex vivo and redifferentiated lesion chondrocytes may hold nonutilized clinical potential for the tissue engineering of AC.

Effects of insulin-like growth factor 1 and basic fibroblast growth factor on the morphology and proliferation of chondrocytes embedded in Matrigel in a microfluidic platform

An integrated microfluidic device was utilized in the present study to investigate the morphology and proliferation of rabbit articular chondrocytes embedded in Matrigel in the presence of insulin-like growth factor 1 (IGF-1) and/or basic fibroblast growth factor (bFGF). The microfluidic device was composed of two parallel channels and a central perfusion-based three-dimensional cell culture module. The rabbit chondrocytes were cultured for 2 weeks at series of concentration gradients of IGF-1 and/or bFGF, which were generated through a diffusion process. At the end of the experiment, the morphology and quantity of cells were measured. Since high expression of collagen II is essential to the function of hyaline cartilage, immunofluorescent images of collagen II expression prior to and after the experiments were gathered for each group. The mean fluorescence intensity ratio (MIR) of collagen II in each group was calculated. The MIRs of collagen II in chondrocytes treated with IGF-1 ranged from 0.6-0.81, those in the cells treated with bFGF ranged from 0.47-0.52, and those in cells treated with a combination of IGF-1 and bFGF ranged from 0.63-0.83. Chondrocyte aggregations were observed in the group treated with 75-100 ng/ml IGF-1 (3.46-fold proliferation ratio). Similarly, a 3.83-fold proliferation ratio was identified in chondrocytes treated with 2.5-5.0 ng/ml bFGF. The group treated with 50-75 ng/ml IGF-1 and 2.5-5.0 ng/ml bFGF exhibited the optimum increase in proliferation (4.83-fold proliferation ratio). The microfluidic device used in the present study can be easily adapted to investigate other growth factors at any concentration gradient. In addition, parallel experiments can be performed simultaneously with a small quantity of cells, making it an attractive platform for the high-throughput screening of cell culture parameters. This platform will aid in the optimization of culture conditions for the in vitro expansion of chondrocytes while maintaining their in vivo morphology, which will improve autologous chondrocyte implantation capabilities for the treatment of cartilage injury.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

PPARD is an Inhibitor of Cartilage Growth in External Ears

Peroxisome proliferator-activated receptor beta/delta (PPARD) is an important determinant of multiple biological processes. Our previous studies identified a missense mutation in the PPARD gene that significantly reduces its transcription activity, and consequently causes enlarged external ears in pigs. However, the mechanisms underlying the causality has remained largely unknown. Here, we show that PPARD retards the development of auricular cartilage by accelerating the apoptosis of cartilage stem/progenitor cells (CSPCs), the terminal differentiation of cartilage cells and the degradation of cartilage extracellular matrix in the auricle. At the transcription level, PPARD upregulates a set of genes that are associated with CSPCs apoptosis and chondrogenic differentiation, chondroblast differentiation and extracellular matrix degradation. ChIP-seq identified direct target genes of PPARD, including a well-documented gene for cartilage development: PPARG. We further show that compared to wild-type PPARD, the G32E mutant up-regulates the expression of PPARG and subsequently leads to the downregulation of critical genes that inhibit cartilage growth. These findings allow us to conclude that PPARD is an inhibitor of auricular cartilage growth in pigs. The causative mutation (G32E) in the PPARD gene attenuates the PPARD-mediated retardation of cartilage growth in the auricle, contributing to enlarged ears in pigs. The findings advance our understanding of the mechanisms underlying auricular development in mammals, and shed insight into the studies of innate pinna disorders and cartilage regeneration medicine in humans.

Rescued Chondrogenesis of Mesenchymal Stem Cells under Interleukin 1 Challenge by Foamyviral Interleukin 1 Receptor Antagonist Gene Transfer

Background: Mesenchymal stem cells (MSCs) and their chondrogenic differentiation have been extensively investigated in vitro as MSCs provide an attractive source besides chondrocytes for cartilage repair therapies. Here we established prototype foamyviral vectors (FVV) that are derived from apathogenic parent viruses and are characterized by a broad host range and a favorable integration pattern into the cellular genome. As the inflammatory cytokine interleukin 1 beta (IL1β) is frequently present in diseased joints, the protective effects of FVV expressing the human interleukin 1 receptor antagonist protein (IL1RA) were studied in an established in vitro model (aggregate culture system) of chondrogenesis in the presence of IL1β.

Materials and Methods: We generated different recombinant FVVs encoding enhanced green fluorescent protein (EGFP) or IL1RA and examined their transduction efficiencies and transgene expression profiles using different cell lines and human primary MSCs derived from bone marrow-aspirates. Transgene expression was evaluated by fluorescence microscopy (EGFP), flow cytometry (EGFP), and ELISA (IL1RA). For evaluation of the functionality of the IL1RA transgene to block the inhibitory effects of IL1β on chondrogenesis of primary MSCs and an immortalized MSC cell line (TERT4 cells), the cells were maintained following transduction as aggregate cultures in standard chondrogenic media in the presence or absence of IL1β. After 3 weeks of culture, pellets were harvested and analyzed by histology and immunohistochemistry for chondrogenic phenotypes.

Results: The different FVV efficiently transduced cell lines as well as primary MSCs, thereby reaching high transgene expression levels in 6-well plates with levels of around 100 ng/ml IL1RA. MSC aggregate cultures which were maintained in chondrogenic media without IL1β supplementation revealed a chondrogenic phenotype by means of strong positive staining for collagen type II and matrix proteoglycan (Alcian blue). Addition of IL1β was inhibitory to chondrogenesis in untreated control pellets. In contrast, foamyviral mediated IL1RA expression rescued the chondrogenesis in pellets cultured in the presence of IL1β. Transduced MSC pellets reached thereby very high IL1RA transgene expression levels with a peak of 1087 ng/ml after day 7, followed by a decrease to 194 ng/ml after day 21, while IL1RA concentrations of controls were permanently below 200 pg/ml.

Conclusion: Our results indicate that FVV are capable of efficient gene transfer to MSCs, while reaching IL1RA transgene expression levels, that were able to efficiently block the impacts of IL1β in vitro. FVV merit further investigation as a means to study the potential as a gene transfer tool for MSC based therapies for cartilage repair.

Anti-IL-20 monoclonal antibody inhibited inflammation and protected against cartilage destruction in murine models of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive destruction of articular cartilage. Interleukin (IL)-20 is a proinflammatory cytokine involved in the pathogenesis of rheumatoid arthritis. We investigated the role of IL-20 in OA and evaluated whether anti-IL-20 antibody (7E) treatment attenuates disease severity in murine models of surgery-induced OA. Immunohistochemical staining was used to detect IL-20 and its receptors expression in synovial tissue and cartilage from OA patients, and in OA synovial fibroblasts (OASFs) and chondrocytes (OACCs) from rodents with surgery-induced OA. RTQ-PCR and western blotting were used to determine IL-20-regulated OA-associated gene expression in OASFs and OACCs. OA rats and OA mice were treated with 7E. Arthritis severity was determined based on the degree of cartilage damage and the arthritis severity score. We found that IL-20 and its receptors were expressed in OASFs and OACCs. IL-20 induced TNF-α, IL-1β, MMP-1, and MMP-13 expression by activating ERK-1/2 and JNK signals in OASFs. IL-20 not only upregulated MCP-1, IL-6, MMP-1, and MMP-13 expression, but also downregulated aggrecan, type 2 collagen, TGF-β, and BMP-2 expression in OACCs. Arthritis severity was significantly lower in 7E-treated OA rats, and 7E- or MSC-treated OA mice. Therefore, we concluded that IL-20 was involved in the progression and development of OA through inducing proinflammatory cytokines and OA-associated gene expression in OASFs and OACCs. 7E reduced the severity of arthritis in murine models of surgery-induced OA. Our findings provide evidence that IL-20 is a novel target and that 7E is a potential therapeutic agent for OA.

Nanoparticle design considerations for molecular imaging of apoptosis: Diagnostic, prognostic, and therapeutic value

The present review analyzes various approaches for the design and synthesis of different nanoparticles for imaging and therapy. Nanoparticles for computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and optical imaging are discussed. The influence of nanoparticle size, shape, surface charge, composition, surface functionalization, active targeting and other factors on imaging and therapeutic efficacy is analyzed. Cyto- and genotoxicity of nanoparticles are also discussed. Special attention in the review is paid to the imaging of apoptotic tissues and cells in different diseases.

Cartilage repair by mesenchymal stem cells: Clinical trial update and perspectives

Osteoarthritis is a degenerative disease of joints with destruction of articular cartilage associated with subchondral bone hypertrophy and inflammation. OA is the leading cause of joint pain resulting in significant worsening of the quality-of-life in the elderly. Numerous efforts have been spent to overcome the inherently poor healing ability of articular cartilage. Mesenchymal stem cells (MSCs) have been in the limelight of cell-based therapies to promote cartilage repair. Despite progressive advancements in MSC manipulation and the introduction of various bioactive scaffolds and growth factors in preclinical studies, current clinical trials are still at early stages with preliminary aims to evaluate safety, feasibility and efficacy. This review summarises recently reported MSC-based clinical trials and discusses new research directions with particular focus on the potential application of MSC-derived extracellular vehicles, miRNAs and advanced gene editing techniques which may shed light on the development of novel treatment strategies. The translational potential of this article: This review summarises recent MSC-related clinical research that focuses on cartilage repair. We also propose a novel possible translational direction for hyaline cartilage formation and a new paradigm making use of extra-cellular signalling and epigenetic regulation in the application of MSCs for cartilage repair.

Comparison of exosomes secreted by induced pluripotent stem cell-derived mesenchymal stem cells and synovial membrane-derived mesenchymal stem cells for the treatment of osteoarthritis

Background

Osteoarthritis (OA) is the most common joint disease worldwide. In the past decade, mesenchymal stem cells (MSCs) have been used widely for the treatment of OA. A potential mechanism of MSC-based therapies has been attributed to the paracrine secretion of trophic factors, in which exosomes may play a major role. In this study, we aimed to compare the effectiveness of exosomes secreted by synovial membrane MSCs (SMMSC-Exos) and exosomes secreted by induced pluripotent stem cell-derived MSCs (iMSC-Exos) on the treatment of OA.

Methods

Induced pluripotent stem cell-derived MSCs and synovial membrane MSCs were characterized by flow cytometry. iMSC-Exos and SMMSC-Exos were isolated using an ultrafiltration method. Tunable resistive pulse-sensing analysis, transmission electron microscopy, and western blots were used to identify exosomes. iMSC-Exos and SMMSC-Exos were injected intra-articularly in a mouse model of collagenase-induced OA and the efficacy of exosome injections was assessed by macroscopic, histological, and immunohistochemistry analysis. We also evaluated the effects of iMSC-Exos and SMMSC-Exos on proliferation and migration of human chondrocytes by cell-counting and scratch assays, respectively.

Results

The majority of iMSC-Exos and SMMSC-Exos were approximately 50–150 nm in diameter and expressed CD9, CD63, and TSG101. The injection of iMSC-Exos and SMMSC-Exos both attenuated OA in the mouse OA model, but iMSC-Exos had a superior therapeutic effect compared with SMMSC-Exos. Similarly, chondrocyte migration and proliferation were stimulated by both iMSC-Exos and SMMSC-Exos, with iMSC-Exos exerting a stronger effect.

Conclusions

The present study demonstrated that iMSC-Exos have a greater therapeutic effect on OA than SMMSC-Exos. Because autologous iMSCs are theoretically inexhaustible, iMSC-Exos may represent a novel therapeutic approach for the treatment of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0510-9) contains supplementary material, which is available to authorized users.

Repair of osteochondral defects with in vitro engineered cartilage based on autologous bone marrow stromal cells in a swine model

Functional reconstruction of large osteochondral defects is always a major challenge in articular surgery. Some studies have reported the feasibility of repairing articular osteochondral defects using bone marrow stromal cells (BMSCs) and biodegradable scaffolds. However, no significant breakthroughs have been achieved in clinical translation due to the instability of in vivo cartilage regeneration based on direct cell-scaffold construct implantation. To overcome the disadvantages of direct cell-scaffold construct implantation, the current study proposed an in vitro cartilage regeneration strategy, providing relatively mature cartilage-like tissue with superior mechanical properties. Our strategy involved in vitro cartilage engineering, repair of osteochondral defects, and evaluation of in vivo repair efficacy. The results demonstrated that BMSC engineered cartilage in vitro (BEC-vitro) presented a time-depended maturation process. The implantation of BEC-vitro alone could successfully realize tissue-specific repair of osteochondral defects with both cartilage and subchondral bone. Furthermore, the maturity level of BEC-vitro had significant influence on the repaired results. These results indicated that in vitro cartilage regeneration using BMSCs is a promising strategy for functional reconstruction of osteochondral defect, thus promoting the clinical translation of cartilage regeneration techniques incorporating BMSCs.

The superior regenerative potential of muscle-derived stem cells for articular cartilage repair is attributed to high cell survival and chondrogenic potential

Three populations of muscle-derived cells (PP1, PP3, and PP6) were isolated from mouse skeletal muscle using modified preplate technique and retrovirally transduced with BMP4/GFP.  In vitro, the PP1 cells (fibroblasts) proliferated significantly slower than the PP3 (myoblasts) and PP6 cells (muscle-derived stem cells); the PP1 and PP6 cells showed a superior rate of survival compared with PP3 cells under oxidative stress; and the PP6 cells showed significantly superior chondrogenic capabilities than PP1 and PP3 cells. In vivo, the PP6 cells promoted superior cartilage regeneration compared with the other muscle-derived cell populations. The cartilage defects in the PP6 group had significantly higher histological scores than those of the other muscle-derived cell groups, and GFP detection revealed that the transplanted PP6 cells showed superior in vivo cell survival and chondrogenic capabilities compared with the PP1 and PP3 cells. PP6 cells (muscle-derived stem cells) are superior to other primary muscle-derived cells for use as a cellular vehicle for BMP4-based ex vivo gene therapy to heal full-thickness osteo-chondral defects. The superiority of the PP6/muscle-derived stem cells appears to be attributable to a combination of increased rate of in vivo survival and superior chondrogenic differentiation capacity.

Chemically defined serum-free conditions for cartilage regeneration from human embryonic stem cells

AIMS

The aim of this study was to improve a method that induce cartilage differentiation of human embryoid stem cells (hESCs) in vitro, and test the effect of in vivo environments on the further maturation of hESCs derived cells.

MAIN METHODS

Embryoid bodies (EBs) formed from hESCs, with serum-free KSR-based medium and mesodermal specification related factors, CHIR, and Noggin for first 8days. Then cells were digested and cultured as micropellets in serum-free KSR-based chondrogenic medium that was supplemented with PDGF-BB, TGF β3, BMP4 in sequence for 24days. The morphology, FACS, histological staining as well as the expression of chondrogenic specific genes were detected in each stage, and further in vivo experiments, cell injections and tissue transplantations, further verified the formation of chondrocytes.

KEY FINDINGS

We were able to obtain chondrocyte/cartilage from hESCs using serum-free KSR-based conditioned medium. qPCR analysis showed that expression of the chondroprogenitor genes and the chondrocyte/cartilage matrix genes. Morphology analysis demonstrated we got PG+COL2+COL1-particles. It indicated we obtained hyaline cartilage-like particles. 32-Day differential cells were injected subcutaneous. Staining results showed grafts developed further mature in vivo. But when transplanted in subrenal capsule, their effect was not good as in subcutaneous. Microenvironment might affect the cartilage formation.

SIGNIFICANCE

The results of this study provide an absolute serum-free and efficient approach for generation of hESC-derived chondrocytes, and cells will become further maturation in vivo. It provides evidence and technology for the hypothesis that hESCs may be a promising therapy for the treatment of cartilage disease.

Investigation of Migration and Differentiation of Human Mesenchymal Stem Cells on Five-Layered Collagenous Electrospun Scaffold Mimicking Native Cartilage Structure

Cartilage degeneration is the major cause of chronic pain, lost mobility, and reduced quality of life for over estimated 150 million osteoarthritis sufferers worldwide. Despite intensive research, none of the available therapies can restore the hyaline cartilage surface beyond just fibrous repair. To overcome these limitations, numerous cell-based approaches for cartilage repair are being explored that aim to provide an appropriate microenvironment for chondrocyte maintenance and differentiation of multipotent mesenchymal stem cells (MSCs) toward the chondrogenic lineage. Articular cartilage is composed of highly organized collagen network that entails the tissue into four distinct zones and each zone into three different regions based on differences in matrix morphology and biochemistry. Current cartilage implants cannot establish the hierarchical tissue organization that seems critical for normal cartilage function. Therefore, in this study, a structured, multilayered collagen scaffold designed for the replacement of damaged cartilage is presented that allows repopulation by host cells and synthesis of a new natural matrix. By using the electrospinning method, the potential to engineer a scaffold consisting of two different collagen types is obtained. With the developed collagen scaffold, a five-layered biomaterial is created that has the potency to induce the differentiation of human bone marrow derived MSCs toward the chondrogenic lineage.

Intra-articular injection of two different doses of autologous bone marrow mesenchymal stem cells versus hyaluronic acid in the treatment of knee osteoarthritis: multicenter randomized controlled clinical trial (phase I/II)

BACKGROUND

Mesenchymal stromal cells are a promising option to treat knee osteoarthritis. Their safety and usefulness must be confirmed and the optimal dose established. We tested increasing doses of bone marrow mesenchymal stromal cells (BM-MSCs) in combination with hyaluronic acid in a randomized clinical trial.

MATERIALS

A phase I/II multicenter randomized clinical trial with active control was conducted. Thirty patients diagnosed with knee OA were randomly assigned to intraarticularly administered hyaluronic acid alone (control), or together with 10 × 10(6) or 100 × 10(6) cultured autologous BM-MSCs, and followed up for 12 months. Pain and function were assessed using VAS and WOMAC and by measuring the knee motion range. X-ray and magnetic resonance imaging analyses were performed to analyze joint damage.

RESULTS

No adverse effects were reported after BM-MSC administration or during follow-up. BM-MSC-administered patients improved according to VAS during all follow-up evaluations and median value (IQR) for control, low-dose and high-dose groups change from 5 (3, 7), 7 (5, 8) and 6 (4, 8) to 4 (3, 5), 2 (1, 3) and 2 (0,4) respectively at 12 months (low-dose vs control group p = 0.005 and high-dose vs control group p < 0.009). BM-MSC-administered patients were also superior according to WOMAC, although improvement in control and low-dose patients could not be significantly sustained beyond 6 months. On the other hand, the BM-MSC high-dose group exhibited an improvement of 16.5 (12, 19) points at 12 months (p < 0.01). Consistent with WOMAC and VAS values, motion ranges remained unaltered in the control group but improved at 12 months with BM-MSCs. X-ray revealed a reduction of the knee joint space width in the control group that was not seen in BM-MSCs high-dose group. MRI (WORMS protocol) showed that joint damage decreased only in the BM-MSC high-dose group, albeit slightly.

CONCLUSIONS

The single intraarticular injection of in vitro expanded autologous BM-MSCs together with HA is a safe and feasible procedure that results in a clinical and functional improvement of knee OA, especially when 100 × 10(6) cells are administered. These results pave the way for a future phase III clinical trial.

CLINICAL TRIALS

gov identifier NCT02123368. Nº EudraCT: 2009-017624-72.

Intra-articular injection of two different doses of autologous bone marrow mesenchymal stem cells versus hyaluronic acid in the treatment of knee osteoarthritis: multicenter randomized controlled clinical trial (phase I/II)

Background

Mesenchymal stromal cells are a promising option to treat knee osteoarthritis. Their safety and usefulness must be confirmed and the optimal dose established. We tested increasing doses of bone marrow mesenchymal stromal cells (BM-MSCs) in combination with hyaluronic acid in a randomized clinical trial.

Materials

A phase I/II multicenter randomized clinical trial with active control was conducted. Thirty patients diagnosed with knee OA were randomly assigned to intraarticularly administered hyaluronic acid alone (control), or together with 10 × 10⁶ or 100 × 10⁶ cultured autologous BM-MSCs, and followed up for 12 months. Pain and function were assessed using VAS and WOMAC and by measuring the knee motion range. X-ray and magnetic resonance imaging analyses were performed to analyze joint damage.

Results

No adverse effects were reported after BM-MSC administration or during follow-up. BM-MSC-administered patients improved according to VAS during all follow-up evaluations and median value (IQR) for control, low-dose and high-dose groups change from 5 (3, 7), 7 (5, 8) and 6 (4, 8) to 4 (3, 5), 2 (1, 3) and 2 (0,4) respectively at 12 months (low-dose vs control group p = 0.005 and high-dose vs control group p < 0.009). BM-MSC-administered patients were also superior according to WOMAC, although improvement in control and low-dose patients could not be significantly sustained beyond 6 months. On the other hand, the BM-MSC high-dose group exhibited an improvement of 16.5 (12, 19) points at 12 months (p < 0.01). Consistent with WOMAC and VAS values, motion ranges remained unaltered in the control group but improved at 12 months with BM-MSCs. X-ray revealed a reduction of the knee joint space width in the control group that was not seen in BM-MSCs high-dose group. MRI (WORMS protocol) showed that joint damage decreased only in the BM-MSC high-dose group, albeit slightly.

Conclusions

The single intraarticular injection of in vitro expanded autologous BM-MSCs together with HA is a safe and feasible procedure that results in a clinical and functional improvement of knee OA, especially when 100 × 10⁶ cells are administered. These results pave the way for a future phase III clinical trial.

Clinical Trials.gov identifier NCT02123368. Nº EudraCT: 2009-017624-72

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0998-2) contains supplementary material, which is available to authorized users.

The use of embryonic cells in the treatment of osteochondral defects of the knee: an ovine in vivo study

PURPOSE

the aim of this study was to determine whether local delivery of embryonic stem-like (ESL) cells into osteochondral defects in the femoral condyles of sheep would enhance regeneration of hyaline articular cartilage.

METHODS

male ESL cells embedded in fibrin glue were engrafted into osteochondral defects in the medial condyles (ESL-M) of the left femur in 22 ewes. An identical defect was created in the medial condyle of the contralateral stifle joint and left untreated as a control (empty defect, ED). The ewes were divided into 5 groups. Four sheep each were euthanized at 1, 2, 6, and 12 months from surgery, and 6 ewes were euthanized 24 months post-implantation. To study the effect of varying loads on the long-term regeneration process, an identical defect was also created and ESL cell engraftment performed in the lateral condyle (ESL-L) of the left stifle joint of the animals in the 12- and 24-month groups. The evaluation of regenerated tissue was performed by biomechanical, macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.

RESULTS

no significant differences were found between treated and control sites in the biomechanical assays at any time point. ESL cell grafts showed significantly greater macroscopic evidence of regeneration as compared to controls at 24 months after surgery; significantly better histological evidence of repair in ESL-M samples versus controls was found throughout the considered period. At 24 months from surgery there was significantly improved integration of graft edges with the host tissue in the ESL-M as compared to the ESL-L samples, demonstrating that load bearing positively affects the long-term regeneration process.

CONCLUSIONS

ESL cells enhanced the regeneration of hyaline cartilage. FISH confirmed that the regenerative tissue originated from ESL cells.

CLINICAL RELEVANCE

ESL cells are able to self-renew for prolonged periods without differentiation and, most importantly, to differentiate into a large variety of tissues.

Regeneration of Articular Cartilage by Human ESC-Derived Mesenchymal Progenitors Treated Sequentially with BMP-2 and Wnt5a

The success of cell‐based therapies to restore joint cartilage requires an optimal source of reparative progenitor cells and tight control of their differentiation into a permanent cartilage phenotype. Bone morphogenetic protein 2 (BMP‐2) has been extensively shown to promote mesenchymal cell differentiation into chondrocytes in vitro and in vivo. Conversely, developmental studies have demonstrated decreased chondrocyte maturation by Wingless‐Type MMTV Integration Site Family, Member 5A (Wnt5a). Thus, we hypothesized that treatment of human embryonic stem cell (hESC)‐derived chondroprogenitors with BMP‐2 followed by Wnt5a may control the maturational progression of these cells into a hyaline‐like chondrocyte phenotype. We examined the effects of sustained exposure of hESC‐derived mesenchymal‐like progenitors to recombinant Wnt5a or BMP‐2 in vitro. Our data indicate that BMP‐2 promoted a strong chondrogenic response leading to terminal maturation, whereas recombinant Wnt5a induced a mild chondrogenic response without promoting hypertrophy. Moreover, Wnt5a suppressed BMP‐2‐mediated chondrocyte maturation, preventing the formation of fibrocartilaginous tissue in high‐density cultures treated sequentially with BMP‐2 and Wnt5a. Implantation of scaffoldless pellets of hESC‐derived chondroprogenitors pretreated with BMP‐2 followed by Wnt5a into rat chondral defects induced an articular‐like phenotype in vivo. Together, the data establish a novel role for Wnt5a in controlling the progression from multipotency into an articular‐like cartilage phenotype in vitro and in vivo. Stem Cells Translational Medicine2017;6:40–50

Engineering zonal cartilage through bioprinting collagen type II hydrogel constructs with biomimetic chondrocyte density gradient

Background

Cartilage tissue engineering is a promising approach for repairing and regenerating cartilage tissue. To date, attempts have been made to construct zonal cartilage that mimics the cartilaginous matrix in different zones. However, little attention has been paid to the chondrocyte density gradient within the articular cartilage. We hypothesized that the chondrocyte density gradient plays an important role in forming the zonal distribution of extracellular matrix (ECM).

Methods

In this study, collagen type II hydrogel/chondrocyte constructs were fabricated using a bioprinter. Three groups were created according to the total cell seeding density in collagen type II pre-gel: Group A, 2 × 10⁷ cells/mL; Group B, 1 × 10⁷ cells/mL; and Group C, 0.5 × 10⁷ cells/mL. Each group included two types of construct: one with a biomimetic chondrocyte density gradient and the other with a single cell density. The constructs were cultured in vitro and harvested at 0, 1, 2, and 3 weeks for cell viability testing, reverse-transcription quantitative PCR (RT-qPCR), biochemical assays, and histological analysis.

Results

We found that total ECM production was positively correlated with the total cell density in the early culture stage, that the cell density gradient distribution resulted in a gradient distribution of ECM, and that the chondrocytes’ biosynthetic ability was affected by both the total cell density and the cell distribution pattern.

Conclusions

Our results suggested that zonal engineered cartilage could be fabricated by bioprinting collagen type II hydrogel constructs with a biomimetic cell density gradient. Both the total cell density and the cell distribution pattern should be optimized to achieve synergistic biological effects.

Delivering Nucleic-Acid Based Nanomedicines on Biomaterial Scaffolds for Orthopedic Tissue Repair: Challenges, Progress and Future Perspectives

As well as acting to fill defects and allow for cell infiltration and proliferation in regenerative medicine, biomaterial scaffolds can also act as carriers for therapeutics, further enhancing their efficacy. Drug and protein delivery on scaffolds have shown potential, however, supraphysiological quantities of therapeutic are often released at the defect site, causing off-target side effects and cytotoxicity. Gene therapy involves the introduction of foreign genes into a cell in order to exert an effect; either replacing a missing gene or modulating expression of a protein. State of the art gene therapy also encompasses manipulation of the transcriptome by harnessing RNA interference (RNAi) therapy. The delivery of nucleic acid nanomedicines on biomaterial scaffolds - gene-activated scaffolds -has shown potential for use in a variety of tissue engineering applications, but as of yet, have not reached clinical use. The current state of the art in terms of biomaterial scaffolds and delivery vector materials for gene therapy is reviewed, and the limitations of current procedures discussed. Future directions in the clinical translation of gene-activated scaffolds are also considered, with a particular focus on bone and cartilage tissue regeneration.

Macrophage phagocytosis alters the MRI signal of ferumoxytol-labeled mesenchymal stromal cells in cartilage defects

Human mesenchymal stem cells (hMSCs) are a promising tool for cartilage regeneration in arthritic joints. hMSC labeling with iron oxide nanoparticles enables non-invasive in vivo monitoring of transplanted cells in cartilage defects with MR imaging. Since graft failure leads to macrophage phagocytosis of apoptotic cells, we evaluated in vitro and in vivo whether nanoparticle-labeled hMSCs show distinct MR signal characteristics before and after phagocytosis by macrophages. We found that apoptotic nanoparticle-labeled hMSCs were phagocytosed by macrophages while viable nanoparticle-labeled hMSCs were not. Serial MRI scans of hMSC transplants in arthritic joints of recipient rats showed that the iron signal of apoptotic, nanoparticle-labeled hMSCs engulfed by macrophages disappeared faster compared to viable hMSCs. This corresponded to poor cartilage repair outcomes of the apoptotic hMSC transplants. Therefore, rapid decline of iron MRI signal at the transplant site can indicate cell death and predict incomplete defect repair weeks later. Currently, hMSC graft failure can be only diagnosed by lack of cartilage defect repair several months after cell transplantation. The described imaging signs can diagnose hMSC transplant failure more readily, which could enable timely re-interventions and avoid unnecessary follow up studies of lost transplants.

Should we use cells, biomaterials, or tissue engineering for cartilage regeneration?

For a long time, cartilage has been a major focus of the whole field of tissue engineering, both because of the constantly growing need for more effective options for joint repair and the expectation that this apparently simple tissue will be easy to engineer. After several decades, cartilage regeneration has proven to be anything but easy. With gratifying progress in our understanding of the factors governing cartilage development and function, and cell therapy being successfully used for several decades, there is still a lot to do. We lack reliable methods to generate durable articular cartilage that would resemble the original tissue lost to injury or disease. The question posed here is whether the answer would come from the methods using cells, biomaterials, or tissue engineering. We present a concise review of some of the most meritorious efforts in each area, and propose that the solution will most likely emerge from the ongoing attempts to recapitulate certain aspects of native cartilage development. While an ideal recipe for cartilage regeneration is yet to be formulated, we believe that it will contain cell, biomaterial, and tissue engineering approaches, blended into an effective method for seamless repair of articular cartilage.

Induced pluripotent stem cells in cartilage repair

Articular cartilage repair techniques are challenging. Human embryonic stem cells and induced pluripotent stem cells (iPSCs) theoretically provide an unlimited number of specialized cells which could be used in articular cartilage repair. However thus far chondrocytes from iPSCs have been created primarily by viral transfection and with the use of cocultured feeder cells. In addition chondrocytes derived from iPSCs have usually been formed in condensed cell bodies (resembling embryoid bodies) that then require dissolution with consequent substantial loss of cell viability and phenotype. All of these current techniques used to derive chondrocytes from iPSCs are problematic but solutions to these problems are on the horizon. These solutions will make iPSCs a viable alternative for articular cartilage repair in the near future.