Enriching a cellulose hydrogel with a biologically active marine exopolysaccharide for cell-based cartilage engineering.

The development of biologically and mechanically competent hydrogels is a prerequisite in cartilage engineering. We recently demonstrated that a marine exopolysaccharide, GY785, stimulates the in vitro chondrogenesis of adipose stromal cells. In the present study, we thus hypothesized that enriching our silated hydroxypropyl methylcellulose hydrogel (Si-HPMC) with GY785 might offer new prospects in the development of scaffolds for cartilage regeneration. The interaction properties of GY785 with growth factors was tested by surface plasmon resonance (SPR). The biocompatibility of Si-HPMC/GY785 towards rabbit articular chondrocytes (RACs) and its ability to maintain and recover a chondrocytic phenotype were then evaluated in vitro by MTS assay, cell counting and qRT-PCR. Finally, we evaluated the potential of Si-HPMC/GY785 associated with RACs to form cartilaginous tissue in vivo by transplantation into the subcutis of nude mice for 3 weeks. Our SPR data indicated that GY785 was able to physically interact with BMP-2 and TGFß. Our analyses also showed that three-dimensionally (3D)-cultured RACs into Si-HPMC/GY785 strongly expressed type II collagen (COL2) and aggrecan transcripts when compared to Si-HPMC alone. In addition, RACs also produced large amounts of extracellular matrix (ECM) containing glycosaminoglycans (GAG) and COL2. When dedifferentiated RACs were replaced in 3D in Si-HPMC/GY785, the expressions of COL2 and aggrecan transcripts were recovered and that of type I collagen decreased. Immunohistological analyses of Si-HPMC/GY785 constructs transplanted into nude mice revealed the production of a cartilage-like extracellular matrix (ECM) containing high amounts of GAG and COL2. These results indicate that GY785-enriched Si-HPMC appears to be a promising hydrogel for cartilage tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.

Cartilage tissue engineering: From hydrogel to mesenchymal stem cells.

Articular cartilage does not repair itself spontaneously. To promote its repair, the transfer of stem cells from adipose tissue (ATSC) using an injectable self-setting cellulosic-hydrogel (Si-HPMC) appears promising. In this context, the objective of this work was to investigate the influence of in vitro chondrogenic differentiation of ATSC on the in vivo cartilage formation when combined with Si-HPMC. In a first set of experiments, we characterized ATSC for their ability to proliferate, self renew and express typical mesenchymal stem cell surface markers. Then, the potential of ATSC to differentiate towards the chondrogenic lineage and the optimal culture conditions to drive this differentiation were evaluated. Real-time RT-PCR and histological analysis for sulphated glycosaminoglycans and type II collagen revealed that 3-dimensional culture and hypoxic condition favored ATSC chondrogenesis regarding mRNA expression level and the corresponding proteins production. In order to assess the phenotypic stability of chondrogenically-differentiated ATSC, real-time RT-PCR for specific terminal chondrogenic markers and alkaline phosphatase activity assay were performed. In addition to promote chondrogenesis, our culture conditions seem to prevent the terminal differentiation of ATSC. Histological examination of ATSC/Si-HPMC implants suggested that the in vitro chondrogenic pre-commitment of ATSC in monolayer is sufficient to obtain cartilaginous tissue in vivo.

Nasal chondrocytes and fibrin sealant for cartilage tissue engineering.

Hybrid constructs associating a biodegradable matrix and autologous chondrocytes hold promise for the treatment of articular cartilage defects. In this context, our objective was to investigate the potential use of nasal chondrocytes associated with a fibrin sealant for the treatment of articular cartilage defects. The phenotype of primary nasal chondrocytes (NC) from human (HNC) and rabbit (RNC) origin were characterized by RT-PCR. The ability of constructs associating fibrin sealant and NC to form a cartilaginous tissue in vivo was investigated, firstly in a subcutaneous site in nude mice and secondly in an articular cartilage defect in rabbit. HNC express type II collagen and aggrecan, the two major hallmarks of a chondrocytic phenotype. Furthermore, when injected subcutaneously into nude mice within a fibrin sealant, these chondrocytes were able to form a cartilage-like tissue. Our data indicate that RNC also express type II collagen and aggrecan and maintained their phenotype in three-dimensional culture within a fibrin sealant. Moreover, treatment of rabbit articular cartilage defects with autologous RNC embedded in a fibrin sealant led to the formation of a hyalin-like repair tissue. The use of fibrin sealant containing hybrid autologous NC therefore appears as a promising approach for cell-based therapy of articular cartilage.