Chondrocytes expressing intracellular collagen type II enter the cell cycle and co-express collagen type I in monolayer culture

The phenotypic characterization of mouse floxed Fam20b chondrocytes, a novel articular cartilage-derived cell line with differentiation potential

FAM20B is a newly identified kinase involved in proteoglycan biosynthesis. Inactivation of Fam20b in joint cartilage leads to chondrosarcoma. Generation of chondrocytes cell line carrying floxed Fam20b allele can offer a valuable tool for the study of the role of Fam20b as well as the molecular events in chondrocyte biology and cartilage diseases. The limitations in the primary culture of chondrocytes necessitate the development of chondrocyte cell line. In this study, we established and characterized the immortalized mouse floxed Fam20b chondrocyte cell line. The primary mouse floxed Fam20b chondrocytes were isolated from the articular cartilage of knee joints and immortalized using lentivirus containing Simian Virus 40 T-antigen (SV40 T-Ag). The immortalized cell line was verified by genomic integration of SV40 T-Ag and proliferated at a high rate relative to their primary counterparts. The immortalized chondrocyte cell line not only retained the typical ultrastructural morphology and important phenotypic characteristics of articular cartilage, but also possessed strong differentiation potential upon three-dimensional pellet culture. Thus, we, for the first time, describe the development of immortalized mouse floxed Fam20b chondrocytes and present an alternative for the limited number of articular chondrocyte cell lines for the study of cartilage biology.

Hyaluronan composite bioink preserves nucleus pulposus cell phenotype in a stiffness-dependent manner

Intervertebral disc degeneration is a major cause of neck and back pain, representing a significant global socioeconomic burden. The polysaccharide hyaluronan is key to maintaining disc physiology and mediating disc disease through its structural and biological roles in the nucleus pulposus, a component of the intervertebral disc highly susceptible to degeneration. In this study, we introduce a novel composite bioink designed for extrusion bioprinting of structures resembling the nucleus pulposus. Our bioink combines levels of hyaluronic acid and collagen that approach physiological concentrations and effectively mimics the disc's hydrated and mechanically resilient environment. We modulated the composite's mechanical properties through the tyramination of hyaluronic acid and subsequent photocrosslinking, influencing morphology and gene expression of embedded bovine nucleus pulposus cells. This allows us to replicate a range of properties from healthy to degenerated human nucleus pulposus, which would be challenging to achieve with traditional cell culture and in vivo models. Our results show that modulating hyaluronan physico-chemical properties influenced embedded cell phenotype. The outcomes of this study inform the future design of biomaterials for the modelling of disc disease and regeneration, and present a versatile platform that can be readily integrated with other biofabricated components to form engineered intervertebral disc-like structures.

Ferroptosis in Osteoarthritis: Towards Novel Therapeutic Strategy

Osteoarthritis (OA) is a chronic, degenerative joint disease primarily characterised by damage to the articular cartilage, synovitis and persistent pain, and has become one of the most common diseases worldwide. In OA cartilage, various forms of cell death have been identified, including apoptosis, necroptosis and autophagic cell death. Ever-growing observations indicate that ferroptosis, a newly-discovered iron-dependent form of regulated cell death, is detrimental to OA occurrence and progression. In this review, we first analyse the pathogenetic mechanisms of OA by which iron overload, inflammatory response and mechanical stress contribute to ferroptosis. We then discuss how ferroptosis exacerbates OA progression, focusing on its impact on chondrocyte viability, synoviocyte populations and extracellular matrix integrity. Finally, we highlight several potential therapeutic strategies targeting ferroptosis that could be explored for the treatment of OA.

Identification of a Regenerative Protocol for Recellularizing Human Auricular Cartilage Scaffolds

OBJECTIVE

Utilizing biological scaffolds for cartilage tissue engineering is a promising tool for improving auricular reconstruction. Decellularized auricular scaffolds provide a means of regenerating cartilage for in vivo implantation, but identifying the ideal regenerative mix remains challenging.

METHODS

Human cadaver auricular cartilage was decellularized and recellularized with either auricular chondrocytes alone, auricular chondrocytes with adipose-derived stem cells, or both cells with platelet-rich plasma. Confirmation of decellularization and recellularization was done by hematoxylin and eosin staining. Extracellular matrix preservation and production were determined by Masson's trichrome, Alcian blue, and Verhoeff-van Gieson staining. Collagen II assessments were made using immunohistochemistry.

RESULTS

Decellularization of cadaver auricular cartilage was confirmed by the absence of cells, reduction in glycosaminoglycans, and the preservation of collagen and elastin. Recellularization was more efficient when chondrocytes were seeded with adipose-derived stem cells, which was enhanced by adding platelet-rich plasma. Coculture with platelet-rich plasma yielded better total collagen (56% increase) and glycosaminoglycan (47% increase) induction. Moreover, when platelet-rich plasma was added, collagen II induction was significantly increased (42%; P < 0.05).

CONCLUSION

We identified a regenerative protocol that included auricular chondrocytes, adipose-derived stem cells, and platelet-rich plasma, which stimulated chondrogenesis on decellularized auricular cartilage. This finding provides a model to explore cartilage formation and the potential for improving auricular and cartilage-based reconstruction.

Protective Effects of an Oligo-Fucoidan-Based Formula against Osteoarthritis Development via iNOS and COX-2 Suppression following Monosodium Iodoacetate Injection

Osteoarthritis (OA) is a debilitating joint disorder characterized by cartilage degradation and chronic inflammation, accompanied by high oxidative stress. In this study, we utilized the monosodium iodoacetate (MIA)-induced OA model to investigate the efficacy of oligo-fucoidan-based formula (FF) intervention in mitigating OA progression. Through its capacity to alleviate joint bearing function and inflammation, improvements in cartilage integrity following oligo-fucoidan-based formula intervention were observed, highlighting its protective effects against cartilage degeneration and structural damage. Furthermore, the oligo-fucoidan-based formula modulated the p38 signaling pathway, along with downregulating cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, contributing to its beneficial effects. Our study provides valuable insights into targeted interventions for OA management and calls for further clinical investigations to validate these preclinical findings and to explore the translational potential of an oligo-fucoidan-based formula in human OA patients.

Strong and Elastic Chitosan/Silk Fibroin Hydrogels Incorporated with Growth-Factor-Loaded Microspheres for Cartilage Tissue Engineering

An emulsification method was developed for fabricating core-shell microspheres with a thick shell layer. Kartogenin (KGN) and platelet-derived growth factor BB (PDGF-BB) were respectively loaded into the core portion and the shell layer of the microspheres with high loading efficiency. The optimally built microspheres were combined with chitosan (CH) and silk fibroin (SF) to construct a new type of composite hydrogel with enhanced strength and elasticity, using genipin or/and tyrosinase as crosslinkers for the intended use in cartilage tissue engineering. The composite hydrogels were found to be thermo-responsive at physiological temperature and pH with well-defined injectability. Rheological measurements revealed that they had an elastic modulus higher than 6 kPa with a high ratio of elastic modulus to viscous modulus, indicative of their mechanically strong features. Compressive measurements demonstrated that they possessed well-defined elasticity. In addition, some gels had the ability to administer the temporal separation release of PDGF-BB and KGN in an approximately linear manner for several weeks. The released PDGF-BB was found to be bioactive based on its effects on Balb/c 3T3 cells. The composite gels supported the growth of seeded chondrocytes while preserving their phenotype. The results suggest that these composite gels have the potential for endogenous cartilage repair.

Cartilage Repair Using Clematis Triterpenoid Saponin Delivery Microcarrier, Cultured in a Microgravity Bioreactor Prior to Application in Rabbit Model

Cartilage tissue engineering provides a promising method for the repair of articular cartilage defects, requiring appropriate biological scaffolds and necessary growth factors to enhance the efficiency of cartilage regeneration. Here, a silk fibroin (SF) microcarrier and a clematis triterpenoid saponin delivery SF (CTS-SF) microcarrier were prepared by the high-voltage electrostatic differentiation and lyophilization method, and chondrocytes were carried under the simulated microgravity condition by a rotating cell culture system. SF and CTS-SF microspheres were relatively uniform in size and had a porous structure with good swelling and cytocompatibility. Further, CTS-SF microcarriers could sustainably release CTSs in the monitored 10 days. Compared with the monolayer culture, chondrocytes under the microgravity condition maintained a better chondrogenic phenotype and showed better proliferation ability after culture on microcarriers. Moreover, the sustained release of CTS from CTS-SF microcarriers upregulated transforming growth factor-β, Smad2, and Smad3 signals, contributing to promote chondrogenesis. Hence, the biophysical effects of microgravity and bioactivities of CTS-ST were used for chondrocyte expansion and phenotype maintenance in vitro. With prolonged expansion, SF- and CTS-SF-based microcarrier-cell composites were directly implanted in vivo to repair rabbit articular defects. Gross evaluations, histopathological examinations, and biochemical analysis indicated that SF- and CTS-SF-based composites exhibited cartilage-like tissue repair compared with the nontreated group. Further, CTS-SF-based composites displayed superior hyaline cartilage-like repair that integrated with the surrounding cartilage better and higher cartilage extracellular matrix content. In conclusion, these results provide an alternative preparation method for drug-delivered SF microcarrier and a culture method for maintaining the chondrogenic phenotype of seed cells based on the microgravity environment. CTS showed its bioactive function, and the application of CTS-SF microcarriers can help repair and regenerate cartilage defects.

Sex-Specific Reduction in Inflammation of Osteoarthritic Human Chondrocytes and Nutraceutical-Dependent Extracellular Matrix Formation

Introduction

The aim of this study was to investigate the ability of osteoarthritic human chondrocytes to produce articular cartilage (AC) tissues with a reduced inflammatory environment in response to 4 anti-inflammatory nutraceuticals: alpha-tocopherol (Alpha), gallic acid (G), ascorbic acid (AA), and catechin hydrate (C).

Methods

Chondrocytes isolated from patients who underwent total knee arthroplasty surgeries were divided into groups (9 male; mean age, 66.2 ± 3.5 years and 11 female; mean age, 64.2 ± 3.1 years). Cells were cultured based on sex and supplemented with either a negative control (NC) medium or NC plus one of the nutraceuticals at a concentration of 50 μM. At day 21, cultures were characterized histologically, biochemically, and for gene expression of vital markers.

Results

At day 21, 62.3% and 66.2% reduction in nitric oxide (NO) content was evident for female and male cells, respectively. G-treatment of female cells resulted in the lowest expression of nitric oxide synthase-2 (NOS2), matrix metalloproteinase-13 (MMP13), and collagen type-10 (COL10). Alpha-treatment of male cells resulted in the lowest expression of NOS2, bone morphogenic protein-2, MMP13, COL10 and tumor necrosis factor alpha induced protein-6 (TNFAIP6) relative to NC. AA and Alpha treatment resulted in the highest glycosaminoglycan (GAG) content for female and male cultures, respectively.

Conclusion

A sex-dependent response of osteoarthritic chondrocytes to nutraceutical treatment was evident. Our results suggest the use of G for female cells and Alpha for male cells in OA applications seems to be favorable in reducing inflammation and enhancing chondrocytes' ability to form AC tissues.

Novel method to repair articular cartilage by direct reprograming of prechondrogenic mesenchymal stem cells

Age-related cartilage loss is worsened by the limited regenerative capacity of chondrocytes. The role of cell-based therapies using mesenchymal stem cells is gaining interest. Adipose tissue-derived mesenchymal stem cells (ADSCs) are an attractive source to generate the optimal number of chondrocytes required to repair a cartilage defect and regenerate hyaline articular cartilage. Here, we report an outstanding technique to prepare chondrocytes for cartilage repair using canine ADSCs. We hypothesized that external electrical fields promote prechondrogenic condensation without requiring genetic modifications or exogenous factors. We analyzed the effect of electrical stimulation (ES) on the differentiation of ADSC micromass into chondrocytes. Highly compact structures were formed within 3 days of ES of canine ADSC micromass. The expression of type I collagen gene was abolished in these cells compared with that in control micromass cultures and monolayer cultures. We further found that ES enhanced the production of proteoglycan, a highly produced extracellular matrix component in chondrocytes. Additionally, single-cell RNA sequencing analysis showed that canine ADSC micromass undergoing ES developed a prechondrogenic cell aggregation, suggesting their metabolic conversion, biogenesis, and calcium ion change. Collectively, our findings demonstrate the capacity of ES to drive the chondrogenesis of ADSCs in the absence of exogenous factors and confirm its commercial potential as a budget-friendly therapy for the repair of cartilage defects.

Zone-Dependent Architecture and Biochemical Composition of Decellularized Porcine Nasal Cartilage Modulate the Activity of Adipose Tissue-Derived Stem Cells in Cartilage Regeneration

Previous anatomical studies have shown different functional zones in human nasal septal cartilage (NC). These zones differ in respect to histological architecture and biochemical composition. The aim of this study was to investigate the influence of these zones on the fate of stem cells from a regenerative perspective. Therefore, decellularized porcine septal cartilage was prepared and subjected to histological assessment to demonstrate its equivalence to human cartilage. Decellularized porcine NC (DPNC) exposed distinct surfaces depending on two different histological zones: the outer surface (OS), which is equivalent to the superficial zone, and the inner surface (IS), which is equivalent to the central zone. Human adipose tissue-derived stem cells (ASCs) were isolated from the abdominal fat tissue of five female patients and were seeded on the IS and OS of DPNC, respectively. Cell seeding efficiency (CSE), vitality, proliferation, migration, the production of sulfated glycosaminoglycans (sGAG) and chondrogenic differentiation capacity were evaluated by histological staining (DAPI, Phalloidin, Live-Dead), biochemical assays (alamarBlue^®, PicoGreen^®, DMMB) and the quantification of gene expression (qPCR). Results show that cell vitality and CSE were not influenced by DPNC zones. ASCs, however, showed a significantly higher proliferation and elevated expression of early chondrogenic differentiation, as well as fibrocartilage markers, on the OS. On the contrary, there was a significantly higher upregulation of hypertrophy marker MMP13 (p < 0.0001) and GAG production (p = 0.0105) on the IS, whereas cell invasion into the three-dimensional DPNC was higher in comparison to the OS. We conclude that the zonal-dependent distinct architecture and composition of NC modulates activities of ASCs seeded on DPNC. These findings might be used for engineering of cartilage substitutes needed in facial reconstructive surgery that yield an equivalent histological and functional structure, such as native NC.

eNAMPT Is Localised to Areas of Cartilage Damage in Patients with Hip Osteoarthritis and Promotes Cartilage Catabolism and Inflammation

Obesity increases the risk of hip osteoarthritis (OA). Recent studies have shown that adipokine extracellular nicotinamide phosphoribosyltransferase (eNAMPT or visfatin) induces the production of IL-6 and matrix metalloproteases (MMPs) in chondrocytes, suggesting it may promote articular cartilage degradation. However, neither the functional effects of extracellular visfatin on human articular cartilage tissue, nor its expression in the joint of hip OA patients of varying BMI, have been reported. Hip OA joint tissues were collected from patients undergoing joint replacement surgery. Cartilage explants were stimulated with recombinant human visfatin. Pro-inflammatory cytokines and MMPs were measured by ELISA and Luminex. Localisation of visfatin expression in cartilage tissue was determined by immunohistochemistry. Cartilage matrix degradation was determined by quantifying proteoglycan release. Expression of visfatin was elevated in the synovial tissue of hip OA patients who were obese, and was co-localised with MMP-13 in areas of cartilage damage. Visfatin promoted the degradation of hip OA cartilage proteoglycan and induced the production of pro-inflammatory cytokines (IL-6, MCP-1, CCL20, and CCL4) and MMPs. The elevated expression of visfatin in the obese hip OA joint, and its functional effects on hip cartilage tissue, suggests it plays a central role in the loss of cartilage integrity in obese patients with hip OA.

Complete mid-portion rupture of the rat achilles tendon leads to remote and time-mismatched changes in uninjured regions

PURPOSE

To examine healing adaptations over 17 weeks post Achilles tendon (AT) rupture in the injured region (IR) compared to an uninjured region (UIR) of the AT.

METHODS

Twenty-four rats were subjected to a complete right-sided AT rupture, while the left side served as a control. ATs were harvested at 1, 2, 8 and 17 weeks post-rupture and stained with antibodies specific to Collagen type I (Col I) and II (Col II) as well as Alcian Blue and Picrosirius Red staining techniques. Histopathological changes, proteoglycan content, collagen alignment and immunoexpression were assessed.

RESULTS

Both regions examined, IR and UIR, exhibited over weeks 1-17 similar healing adaptations of increasing collagen alignment, decreasing Col I immunoexpression, as well as increasing proteoglycan content and Col II occurrence. Increased proteoglycan content was found already at week 2 in the UIR, while it first increased at week 8 in the IR. The area positive to Col II was increased compared to controls at week 8 in the UIR, whereas it first raised at week 17 in the IR. Collagen disorganization successively declined to reach control levels at week 17 in the UIR, but was still higher in the IR.

CONCLUSION

This study demonstrated that uninjured areas of the AT remote from the rupture site also undergo pronounced remodeling, although with time-span differences relative to injured AT portions. These changes including the pathologic heterotopic mineralization and chondrogenic differentiation observed in both regions may have implications in the choice of rehabilitation regimes in order to prevent secondary rupture.

Alginate-poloxamer/silk fibroin hydrogels with covalently and physically cross-linked networks for cartilage tissue engineering

Poloxamer was grafted onto alginate and the optimally synthesized alginate-poloxamer (ALG-POL) copolymer was combined with silk fibroin (SF) to produce thermosensitive ALG-POL/SF hydrogels with covalently and physically crosslinked networks. The formulated ALG-POL/SF gels were found to be injectable with sol-gel transitions near physiological temperature and pH. Rheological measurements showed that some ALG-POL/SF gels had their elastic modulus of around 5 kPa or higher with large ratio of elastic modulus to viscous modulus, indicative of their mechanically strong feature. The achieved ALG-POL/SF gels exhibited concurrent enhancement in strength and elasticity when compared to the gels built with either ALG-POL or SF alone. The microscopic insight into dry ALG-POL/SF gels validated that they were highly porous with well-interconnected pore characteristics. These ALG-POL/SF gels showed abilities to support the in-growth of seeded chondrocytes while effectively maintaining their chondrogenic phenotype. Results suggest promising attributes of ALG-POL/SF gels as alternative biomaterial for cartilage tissue engineering.

Biomarker Signatures of Quality for Engineering Nasal Chondrocyte-Derived Cartilage

The definition of quality controls for cell therapy and engineered product manufacturing processes is critical for safe, effective, and standardized clinical implementation. Using the example context of cartilage grafts engineered from autologous nasal chondrocytes, currently used for articular cartilage repair in a phase II clinical trial, we outlined how gene expression patterns and generalized linear models can be introduced to define molecular signatures of identity, purity, and potency. We first verified that cells from the biopsied nasal cartilage can be contaminated by cells from a neighboring tissue, namely perichondrial cells, and discovered that they cannot deposit cartilaginous matrix. Differential analysis of gene expression enabled the definition of identity markers for the two cell populations, which were predictive of purity in mixed cultures. Specific patterns of expression of the same genes were significantly correlated with cell potency, defined as the capacity to generate tissues with histological and biochemical features of hyaline cartilage. The outlined approach can now be considered for implementation in a good manufacturing practice setting, and offers a paradigm for other regenerative cellular therapies.

Biochemical similarity between cultured chondrocytes and in situ chondrocytes by chemometric analysis from FTIR microspectroscopy

Background aims

Fourier Transform Infrared Micro-spectroscopy (FTIRM) is an emerging tool that obtains images with biochemical information of samples that are too small to be chemically analyzed by conventional Fourier transform infrared (FTIR) spectroscopy techniques. So, the central objective of this project was to study the biochemical similarity between articular and cultured chondrocytes by chemometric analysis from FTIRM.

Methods

Nine samples of knee articular cartilage were obtained; each sample was divided into two fragments, one portion was used for FTIRM characterization in situ, and from another part, chondrocytes were obtained to be cultured (in vitro), which were subjected to an FTIRM to characterize their biomolecular components. The FTIRM spectra were normalized, and the second derivative was calculated. From these data, principal component analysis (PCA) and a chemometric comparison between in situ and cultured chondrocytes were carried out. Finally, the biochemical mapping was conducted obtaining micro-FTIR imaging.

Results

FTIRM spectra of in situ and in vitro chondrocytes were obtained, and different biomolecules were detected, highlighting lipids, proteins, glycosaminoglycans, collagen, and aggrecan. Despite slight differences in the FTIR spectra, the PCA proved the organic similarity between in situ chondrocytes and cultured chondrocytes, which was also observed in the analysis of the ratios related to the degradation of the articular cartilage and collagen. In the same way, the ability of the FTIRM to characterize the molecular biodistribution was demonstrated.

Conclusion

The biochemical composition and biodistribution analysis using FTIRM have been useful for comparing cultured chondrocytes and in situ chondrocytes.

Enhanced dual network hydrogels consisting of thiolated chitosan and silk fibroin for cartilage tissue engineering

Thiolated chitosan (CS-NAC) was synthesized and the selected CS-NAC was used together with silk fibroin (SF) to produce dual network CS-NAC/SF hydrogels. The CS-NAC/SF solutions with formulated compositions were able to form hydrogels at physiological temperature and pH. Rheological measurements showed that elastic modulus of some CS-NAC/SF gels could reach around 3 kPa or higher and was much higher than their respective viscous modulus, indicating that they behaved like strong gels. Deformation measurements verified that CS-NAC/SF gels had well-defined elasticity. The optimized CS-NAC/SF gels exhibited jointly enhanced properties in terms of strength, stiffness and elasticity when compared to the gels resulted from either CS-NAC or SF. Examinations of dry CS-NAC/SF gels revealed that they were highly porous with well-interconnected pore features. Cell culture demonstrated that CS-NAC/SF gels supported the growth of chondrocytes while effectively maintaining their phenotype. Results suggest that these dual network gels have promising potential in cartilage repair.

Non-pathological Chondrogenic Features of Valve Interstitial Cells in Normal Adult Zebrafish

In the heart, unidirectional blood flow depends on proper heart valve function. As, in mammals, regulatory mechanisms of early heart valve and bone development are shown to contribute to adult heart valve pathologies, we used the animal model zebrafish (ZF, Danio rerio) to investigate the microarchitecture and differentiation of cardiac valve interstitial cells in the transition from juvenile (35 days) to end of adult breeding (2.5 years) stages. Of note, light microscopy and immunohistochemistry revealed major differences in ZF heart valve microarchitecture when compared with adult mice. We demonstrate evidence for rather chondrogenic features of valvular interstitial cells by histological staining and immunodetection of SOX-9, aggrecan, and type 2a1 collagen. Collagen depositions are enriched in a thin layer at the atrial aspect of atrioventricular valves and the ventricular aspect of bulboventricular valves, respectively. At the ultrastructural level, the collagen fibrils are lacking obvious periodicity and orientation throughout the entire valve.

PLXNA2 identified as a candidate gene by genome-wide association analysis for mandibular prognathism in human chondrocytes

In a previous genome-wide association study, plexin A2 (PLXNA2) was suggested as one of the candidate genes for mandibular prognathism. PLXNA2 encodes plexin A2, a member of the plexin-A family of semaphorin co-receptors. Semaphorin 3A (sema3A) exerts an osteoprotective effect. However, to the best of our knowledge, there have been no previous studies examining the role of sema3A or plexin A2 on human chondrocytes. The objectives of the present study were to examine the function of sema3A and its receptor, plexin A2, in human chondrocytes. Normal human chondrocytes were cultured in media with either a high (100 ng/ml) or a low (1 ng/ml) concentration of sema3A, or without sema3A as a control. Cells and extracellular matrices were assayed for concentrations of protein and parathyroid hormone-related peptide receptor 1 (PTH-R1) using a bicinchoninic acid assay and an enzyme immunoassay, respectively. At culture day 7, the high and low concentrations of exogenous sema3A significantly increased the protein content compared with the control (P=0.0008 and 0.00002, respectively). At culture day 14, a high concentration of exogenous sema3A significantly increased the protein content and decreased the concentration of PTH-R1 compared with the control (P=0.002). The present study revealed novel results that exogenous sema3A suppresses the expression of PTH-R1 in human proliferative chondrocytes and suggested that sema3A may affect human chondrocytes via its receptor, plexin A2.

Influence of Mechanical Unloading on Articular Chondrocyte Dedifferentiation

Due to the limited self-repair capacity of articular cartilage, the surgical restoration of defective cartilage remains a major clinical challenge. The cell-based approach, which is known as autologous chondrocyte transplantation (ACT), has limited success, presumably because the chondrocytes acquire a fibroblast-like phenotype in monolayer culture. This unwanted dedifferentiation process is typically addressed by using three-dimensional scaffolds, pellet culture, and/or the application of exogenous factors. Alternative mechanical unloading approaches are suggested to be beneficial in preserving the chondrocyte phenotype. In this study, we examined if the random positioning machine (RPM) could be used to expand chondrocytes in vitro such that they maintain their phenotype. Bovine chondrocytes were exposed to (a) eight days in static monolayer culture; (b) two days in static monolayer culture, followed by six days of RPM exposure; and, (c) eight days of RPM exposure. Furthermore, the experiment was also conducted with the application of 20 mM gadolinium, which is a nonspecific ion-channel blocker. The results revealed that the chondrocyte phenotype is preserved when chondrocytes go into suspension and aggregate to cell clusters. Exposure to RPM rotation alone does not preserve the chondrocyte phenotype. Interestingly, the gene expression (mRNA) of the mechanosensitive ion channel TRPV4 decreased with progressing dedifferentiation. In contrast, the gene expression (mRNA) of the mechanosensitive ion channel TRPC1 was reduced around fivefold to 10-fold in all of the conditions. The application of gadolinium had only a minor influence on the results. This and previous studies suggest that the chondrocyte phenotype is preserved if cells maintain a round morphology and that the ion channel TRPV4 could play a key role in the dedifferentiation process.

Long-term evaluation of osteoarthritis sheep knee, treated with TGF-β3 and BMP-6 induced multipotent stem cells

BACKGROUND

Hyaline articular cartilage, which protects the bones of diarthrodial joints from forces associated with load bearing, frictions, and impacts has very limited capacities for self-repair. Over the years, the trend of treatments has shifted to regenerations and researchers have been on the quest for a lasting regeneration. We evaluated the treatment of osteoarthritis by chondrogenically induced ADSCs and BMSCs for a long time functional recovery.

METHODS

Osteoarthritis was induced at the right knee of sheep by complete resection of ACL and medial meniscus. Stem cells from sheep were induced to chondrogenic lineage. Test sheep received 5 mls single doses of 2 × 10⁷ autologous PKH26-labelled ADSCs or BMSCs, while controls received basal medium. Functional recovery of the knees was evaluated via electromyography.

RESULTS

Induced ADSCs had 625, 255, 393, 908, 409, 157 and 1062 folds increases of collagen I, collagen II, aggrecan, SOX9, cartilage oligomeric protein, chondroadherin and fibromodullin compare to uninduced cells, while BMSCs had 702, 657, 321, 276, 337, 233 and 1163 respectively; p = .001. Immunocytochemistry was positive for these chondrogenic markers. 12 months post-treatment, controls scored 4 in most regions using ICRS, while the treated had 8; P = .001. Regenerated cartilages were positive to PKH26 and demonstrated the presence of condensing cartilages on haematoxylin and eosin; and Safranin O. OA degenerations caused significant amplitude shift from right to left hind limb. After treatments, controls persisted with significant decreases; while treated samples regained balance.

CONCLUSIONS

Both ADSCs and BMSCs had increased chondrogenic gene expressions using TGF-β3 and BMP-6. The treated knees had improved cartilage scores; PKH26 can provide elongated tracking, while EMG results revealed improved joint recoveries. These could be suitable therapies for osteoarthritis.

Nano-hydroxyapatite/collagen film as a favorable substrate to maintain the phenotype and promote the growth of chondrocytes cultured in vitro

Autologous chondrocyte implantation (ACI) has emerged as a novel approach to cartilage repair through the use of harvested chondrocytes. However, the expansion of the chondrocytes from the donor tissue in vitro is restricted by the limited cell numbers and the dedifferentiation of the chondrocytes. The present study investigated the effect of collagen-based films, including collagen, hydroxyapatite (HA)/collagen (HC) and in situ synthesis of nano‑HC (nHC), on monolayer cultures of chondrocytes. As a substrate for the chondrocytes monolayer culture in vitro, nHC was able to restrain the dedifferentiation of chondrocytes and facilitate cell expansion, which was detected by methyl thiazolyl tetrazolium assay, scanning electron microscopy, calcein‑acetoxymethyl/propidium iodide staining, hematoxylin and eosin staining, Safranin O staining, immunohistochemical staining and reverse transcription‑quantitative polymerase chain reaction. Furthermore, the nHC films significantly facilitated cell growth and enhanced the expression of cartilage‑specific extracellular matrix (ECM) components, including aggrecan and type II collagen. In addition, nHC films markedly downregulated the expression of collagen type I, an indicator of dedifferentiation. The results indicated that nHC, a collagen‑based substrate optimized by nanoparticles, was able to better support cell growth and preserve cell phenotype compared with collagen alone or HC. The nHC film, which favors cell growth and prevents the dedifferentiation of chondrocytes, may therefore serve as a useful cartilage‑like ECM for chondrocytes. In conclusion, nHC film is a promising substrate for the culture of chondrocytes in cell-based therapy.

Synthetic Poly(Vinylalcohol)-Based Membranes for Cartilage Surgery and Repair

Cell-based therapies for cartilage repair are continually being developed to treat osteoarthritis. The cells are either introduced directly by intra-articular injection or via a cell-seeded matrix scaffold. Here, poly(vinylalcohol)-based membranes are developed to be used for mesenchymal stem cell implantation in cartilage repair procedures, having controllable physicochemical properties such as porosity, mechanical strength, and permeability, and a unique self-sealing property. The membranes possess a bilayer structure with a less porous layer providing mechanical strength and selective permeability, exhibit an elastic modulus of between 0.3 and 0.9 MPa, and are permeable to molecules <40 kDa, which is in the range of cartilage permeability. Three different peptide ligands with the sequences Ac-GCGYGRGDSPG, Ac-GCG(OPG)4REGOFG(OPG)4, and Ac-GCG(OPG)7, respectively, are conjugated to the membranes and subject to in vitro cell adhesion and differentiation assays. Col I/Col II gene expression ratios indicated that the collagen-mimetic peptide, Ac-GCG(OPG)7, best supported mesenchymal stem cell differentiation into the chondrogenic lineage. Although low retention of the membrane is observed in vivo in a rabbit knee model, results suggest that the membrane was able to facilitate mesenchymal stem cell implantation and differentiation to chondrocytes. These PVA-based membranes provide a feasible, synthetic, off-the-shelf material for the delivery of stem cells, and can be modified for other surgical applications.

Silencing of Wnt5a prevents interleukin-1β-induced collagen type II degradation in rat chondrocytes

Osteoarthritis (OA) is a joint disease, and few treatments to date have been able to delay OA progression. The degradation of collagen type II (COL2) in the cartilage matrix is an important initiating factor for OA progression; the upregulation of Wnt5a protein activates COL2 degradation. In the present study, small interfering RNA of Wnt-5a was delivered by a lentiviral vector (LV-Wnt5a-RNAi) to silence Wnt-5a mRNA and prevent COL2 degradation. To determine the function of LV-Wnt5a-RNAi, the OA chondrocyte model (OA-like chondrocytes) were constructed using interleukin (IL)-1β. Detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Wnt-5a mRNA in the OA-like chondrocytes were upregulated in a time-dependent manner, indicating that OA-like chondrocytes were successfully constructed. The bioactivity of OA-like chondrocytes was determined using Live-Dead staining, and the result illustrated that the OA-like chondrocytes stimulated with IL-1β for 6 h remained viable, and these were used in Wnt5a silencing. The OA-like chondrocytes were divided into three groups: Group I, cultivated with common medium; group II, cultivated with common medium supplemented with empty lentiviral vector; group III, cultivated with common medium supplemented with LV-Wnt5a-RNAi. The efficiency of LV-Wnt5a-RNAi transfection was determined using fluorescence microscopy, the result of which indicated that LV-Wnt5a-RNAi could efficiently be transfected into the OA-like chondrocytes. The LV-Wnt5a-RNAi efficiency for the Wnt5a mRNA silencing was determined using RT-qPCR. The result illustrated that the mRNA of Wnt5a in group III was significantly lower in group I compared with that in group II (P<0.05), indicating that the LV-Wnt5a-RNAi could successfully silence Wnt5a mRNA. To further verify whether the silencing of Wnt5a mRNA could prevent COL2 degradation, western blotting and immunohistochemical analyses were performed. The results demonstrated that COL2 in group III was significantly higher compared with that in groups I and II (P<0.05), which illustrated that the silencing of Wnt5a mRNA could prevent COL2 degradation. In conclusion, LV-Wnt5a-RNAi was formed successfully and could efficiently silence Wnt5a mRNA expressed by OA-like chondrocytes. In addition, the silencing of Wnt5a mRNA could prevent the degradation of COL2 in OA-like chondrocytes, confirming that LV-Wnt5a-RNAi may be used as a novel tool for OA treatment.

Culture temperature affects redifferentiation and cartilaginous extracellular matrix formation in dedifferentiated human chondrocytes

To date, there have been few studies on how temperature affects the phenotype and metabolism of human chondrocytes. Thus, the purpose of this study was to elucidate the effects of culture temperature on chondrocyte redifferentiation and extracellular matrix (ECM) formation using dedifferentiated mature human chondrocytes in vitro. Dedifferentiated chondrocytes were cultured in a pellet culture system for up to 21 days. The pellets were randomly divided into three groups with different culture temperature (32, 37, and 41°C). Chondrocyte redifferentiation and ECM formation were evaluated by wet weight, messenger ribonucleic acid (mRNA), histological, and biochemical analyses. The results showed that the wet weight and the mRNA expressions of collagen type II A1 and cartilage oligomeric matrix protein at 37°C were higher than the corresponding values at 32°C. The histological and biochemical analyses revealed that the syntheses of type II collagen and proteoglycan were promoted at 37°C compared to those at 32°C, whereas they were considerably inhibited at 41°C. In conclusion, the results obtained herein indicated that temperature affects chondrocyte redifferentiation and ECM formation, and modulation of temperature might thus represent an advantageous means to regulate the phenotype and biosynthetic activity of chondrocytes.

Transforming growth factor beta signaling is essential for the autonomous formation of cartilage-like tissue by expanded chondrocytes

Cartilage is a tissue with limited self-healing potential. Hence, cartilage defects require surgical attention to prevent or postpone the development of osteoarthritis. For cell-based cartilage repair strategies, in particular autologous chondrocyte implantation, articular chondrocytes are isolated from cartilage and expanded in vitro to increase the number of cells required for therapy. During expansion, the cells lose the competence to autonomously form a cartilage-like tissue, that is in the absence of exogenously added chondrogenic growth factors, such as TGF-βs. We hypothesized that signaling elicited by autocrine and/or paracrine TGF-β is essential for the formation of cartilage-like tissue and that alterations within the TGF-β signaling pathway during expansion interfere with this process. Primary bovine articular chondrocytes were harvested and expanded in monolayer culture up to passage six and the formation of cartilage tissue was investigated in high density pellet cultures grown for three weeks. Chondrocytes expanded for up to three passages maintained the potential for autonomous cartilage-like tissue formation. After three passages, however, exogenous TGF-β1 was required to induce the formation of cartilage-like tissue. When TGF-β signaling was blocked by inhibiting the TGF-β receptor 1 kinase, the autonomous formation of cartilage-like tissue was abrogated. At the initiation of pellet culture, chondrocytes from passage three and later showed levels of transcripts coding for TGF-β receptors 1 and 2 and TGF-β2 to be three-, five- and five-fold decreased, respectively, as compared to primary chondrocytes. In conclusion, the autonomous formation of cartilage-like tissue by expanded chondrocytes is dependent on signaling induced by autocrine and/or paracrine TGF-β. We propose that a decrease in the expression of the chondrogenic growth factor TGF-β2 and of the TGF-β receptors in expanded chondrocytes accounts for a decrease in the activity of the TGF-β signaling pathway and hence for the loss of the potential for autonomous cartilage-like tissue formation.