The effects of protein-coated surfaces on passaged porcine TMJ disc cells

Tissue engineering toward temporomandibular joint disc regeneration

Treatments for temporomandibular joint (TMJ) disc thinning and perforation, conditions prevalent in TMJ pathologies, are palliative but not reparative. To address this, scaffold-free tissue-engineered implants were created using allogeneic, passaged costal chondrocytes. A combination of compressive and bioactive stimulation regimens produced implants with mechanical properties akin to those of the native disc. Efficacy in repairing disc thinning was examined in minipigs. Compared to empty controls, treatment with tissue-engineered implants restored disc integrity by inducing 4.4 times more complete defect closure, formed 3.4-fold stiffer repair tissue, and promoted 3.2-fold stiffer intralaminar fusion. The osteoarthritis score (indicative of degenerative changes) of the untreated group was 3.0-fold of the implant-treated group. This tissue engineering strategy paves the way for developing tissue-engineered implants as clinical treatments for TMJ disc thinning.

Tissue engineering of the temporomandibular joint disc: current status and future trends

INTRODUCTION

Temporomandibular joint disorders are extremely prevalent and there is no ideal treatment clinically for the moment. For severe cases, a discectomy often need to be performed, which will further result in the development of osteoarthritis. In the past thirty years, tissue engineering has provided a promising approach for the effective remedy of severe TMJ disease through the creation of viable, effective, and biological functional implants.

METHODS

Although TMJ disc tissue engineering is still in early stage, unremitting efforts and some achievements have been made over the past decades. In this review, a comprehensive summary of the available literature on the progress and status in tissue engineering of the TMJ disc regarding cell sources, scaffolds, biochemical and biomechanical stimuli, and other prospects relative to this field is provided.

RESULTS AND CONCLUSIONS

Even though research studies in this field are too few compared to other fibrocartilage (e.g., knee meniscus) and numerous, difficult tasks still exist, we believe that our ultimate goal of regenerating a biological implant whose histological, biochemical, and biomechanical properties parallel native TMJ discs for clinical therapy will be achieved in the near future.

The role of nanofibrous structure in osteogenic differentiation of human mesenchymal stem cells with serial passage

Using scaffolds with autologous stem cells is a golden strategy for the treatment of bone defects. In this strategy, human mesenchymal stem cells (hMSCs) have often been isolated and expanded in vitro on a plastic surface to obtain a sufficient cell number before seeding on a suitable scaffold. Materials & Methods: Investigating the influence of serial passages (from passage two to passage eight) on the abilities of proliferation and osteogenic differentiation of hMSCs on 24-well tissue culture polystyrene plates and poly L-lactic acid electrospun nanofibrous scaffolds was performed to determine how prolonged culture affected these cellular abilities and how the nanofibrous scaffolds supported the osteogenic differentiation potential of hMSCs. Results & Conclusion: Serial passage caused adverse changes in hMSCs characteristics, which were indicated by the decline in both proliferation and osteogenic differentiation abilities. Interestingly, the poly L-lactic acid nanofibrous scaffolds showed a significant support in recovering the osteogenic abilities of hMSCs, which had been severely affected by prolonged culture.

Effects of biomimetic surfaces and oxygen tension on redifferentiation of passaged human fibrochondrocytes in 2D and 3D cultures

Due to its limited healing potential within the inner avascular region, functional repair of the meniscus remains a significant challenge in orthopaedic surgery. Tissue engineering of a meniscus implant using meniscal cells offers the promise of enhancing the reparative process and achieving functional meniscal repair. In this work, using quantitative real-time reverse transcriptase polymerase chain reaction (RT-qPCR) analysis, we show that human fibrochondrocytes rapidly dedifferentiate during monolayer expansion on standard tissue culture flasks, representing a significant limit to clinical use of this cell population for meniscal repair. Previously, we have characterized and described the feasibility of a tailored biomimetic surface (C6S surface) for reversing dedifferentiation of monolayer-expanded rat meniscal cells. The surface is comprised of major meniscal extracellular matrix (ECM) components in the inner region, namely collagen I/II (at a 2:3 ratio) and chondroitin-6-sulfate. We thus have further evaluated the effects of the C6S surface, alongside a number of other tailored surfaces, on cell adhesion, proliferation, matrix synthesis and relevant marker gene expression (collagen I, -II, aggrecan and Sox-9 etc) of passaged human fibrochondrocytes in 2D (coated glass coverslips) and 3D (surface-modified polymeric scaffolds) environments. We show that the C6S surface is permissive for cell adhesion, proliferation and ECM synthesis, as demonstrated using DNA quantification, 1,9-dimethylmethylene blue (DMMB) assay, histology and immunohistochemistry. More importantly, RT-qPCR analyses corroborate the feasibility of the C6S surface for reversing phenotypic changes, especially the downregulation of collagen II, of dedifferentiated human fibrochondrocytes. Furthermore, human fibrochondrocyte redifferentiation was enhanced by hypoxia in the 3D cultures, independent of hypoxia inducible factor (HIF) transcriptional activity and was shown to potentially involve the transcriptional activation of Sox-9.

Additive and synergistic effects of bFGF and hypoxia on leporine meniscus cell-seeded PLLA scaffolds

Injuries to avascular regions of menisci do not heal and result in significant discomfort to patients. Current treatments, such as partial meniscectomy, alleviate these symptoms in the short term but lead to premature osteoarthritis as a result of compromised stability and changes in knee biomechanics. Thus, tissue engineering of the meniscus may provide an alternative treatment modality to overcome this problem. In this experiment, a scaffold-based tissue-engineering approach was utilized to regenerate the meniscus. Meniscus cells were cultured on poly-L-lactic acid scaffolds in normoxic (approximately 21% oxygen) or hypoxic (approximately 2% oxygen) conditions in the presence or absence of the growth factor, basic fibroblast growth factor (bFGF). At t = 4 weeks, histological sections of constructs showed presence of collagen and glycosaminoglycan (GAG) in all groups. Immunohistochemical staining showed the presence of collagen I in all groups and collagen II in groups cultured under hypoxic conditions. bFGF in the culture medium significantly increased cell number/construct by 25%, regardless of culture conditions. For GAG/construct, synergistic increases were observed in constructs cultured in hypoxic conditions and bFGF (two-fold) when compared to constructs cultured in normoxic conditions. Compressive tests showed synergistic increases in the relaxation modulus and coefficient of viscosity and additive increases in the instantaneous modulus for constructs cultured under hypoxic conditions and bFGF, when compared to constructs cultured under normoxic conditions. Overall, these results demonstrate that bFGF and hypoxia can significantly enhance the ability of meniscus cells to produce GAGs and improve the compressive properties of tissue-engineered meniscus constructs in vitro.

A comparison of primary and passaged chondrocytes for use in engineering the temporomandibular joint

OBJECTIVE

This study examines the tissue engineering potential of passaged (P3) and primary (P0) articular chondrocytes (ACs) and costal chondrocytes (CCs) from skeletally mature goats for use in the temporomandibular joint (TMJ).

DESIGN

These four cell types were assembled into scaffoldless tissue engineered constructs and cultured for 4 wks. The constructs were then tested for cell, collagen, and glycosaminoglycan (GAG) content with biochemical assays, and collagen types I and II with enzyme-linked immunosorbent assays. Constructs were also tested under tension and compression to determine biomechanical properties.

RESULTS

Both primary and passaged CC constructs had greater GAG/wet weight than AC constructs. Primary AC constructs had significantly less total collagen and contained no collagen type I. AC P3 constructs had the largest collagen I/collagen II ratio, which was also greater in passaged CC constructs relative to primary groups. Primary AC constructs were not mechanically testable, whereas passaged AC and CC constructs had significantly greater tensile properties than primary CC constructs.

CONCLUSIONS

Primary CCs are considerably better than primary ACs and have potential use in tissue engineering when larger quantities of collagen type II are desired. The poor performance of the ACs, in this study, which contradicts the results seen with previous studies using immature bovine ACs, may thus be attributed to the animals' maturity. However, CC P3 cells appear particularly well suited for tissue engineering fibrocartilage of the TMJ due to the high quantity of collagen and GAG, and tensile and compressive mechanical properties.

Passage and reversal effects on gene expression of bovine meniscal fibrochondrocytes

The knee meniscus contains a mixed population of cells that exhibit fibroblastic as well as chondrocytic characteristics. Tissue engineering studies and future therapies for the meniscus require a large population of cells that are seeded on scaffolds. To achieve this, monolayer expansion is often used as a technique to increase cell number. However, the phenotype of these cells may be significantly different from that of the primary population. The objective of this study was to investigate changes in meniscal fibrochondrocytes at the gene expression level over four passages using quantitative real-time reverse transcriptase polymerase chain reaction. Cells from the inner two-thirds of bovine medial menisci were used. Four extracellular matrix (ECM) molecules, commonly found in the meniscus, were investigated, namely collagen I, collagen II, aggrecan and cartilage oligomeric matrix protein (COMP). In addition, primary and passaged meniscus fibrochondrocytes were placed on surfaces coated with collagen I or aggrecan protein to investigate whether any gene expression changes resulting from passage could be reversed. Collagen I expression was found to increase with the number of passages, whereas collagen II and COMP expression decreased. Collagen I and aggrecan surface coatings were shown to downregulate and upregulate collagen I and COMP expression levels, respectively, in passaged cells. However, decreases in collagen II expression could not be reversed by either protein coating. These results indicate that although monolayer expansion results in significant changes in gene expression in meniscal fibrochondrocytes, protein coatings may be used to regain the primary cell expression of several ECM molecules.