Biological roles of carboxymethyl-chitin associated for the growth factor production

Influence of carboxymethyl chitin on stability and biocompatibility of 3D nanohydroxyapatite/gelatin/carboxymethyl chitin composite for bone tissue engineering

A novel three-dimensional (3D) scaffold has been developed from the unique combination of nanohydroxyapatite/gelatin/carboxymethyl chitin (n-HA/gel/CMC) for bone tissue engineering by using the solvent-casting method combined with vapor-phase crosslinking and freeze-drying. The surface morphology and physiochemical properties of the scaffold were investigated by dissolvability test, infrared absorption spectra (IR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), mechanical testing, and soaking in simulated body fluid (SBF). An optimized (composition and processing parameters) ratio of n-HA:gel:CMC (1:2:1), exhibited ideal porous structure with regular interconnected pores (75-250 μm) and higher mechanical strength. Result suggested that the divalent (Ca(++)), carboxyl (COO(-)), amino (NH4(+)), and phosphate (PO4(3-)) groups created favorable ionic interactions which facilitated structural stability and integrity of the composite scaffold. The SBF soaking experiment confirmed the apatite nucleation ability, induced by CMC incorporation. Furthermore, hemocompatibility (hemolysis, platelet adhesion, and protein adsorption) and biocompatibility with MG63 osteoblast cells (MTT assay, cell morphology, and confocal studies from within the 3D scaffold) indicated that the structural and dimensional stability of composite scaffold provided an optimal mechanosensory environment for enhancement of cell adhesion, proliferation, and network formation. The n-HA/gel/CMC composite, therefore, may serve as a promising composite scaffold for guided bone regeneration.

Carboxymethyl-chitin promotes chondrogenesis by inducing the production of growth factors from immune cells

Many techniques have been tested for their ability to restore cartilage defects, but several problems still remain in the complete healing of injured cartilage. In our previous study, we found that a carboxymethyl-chitin/beta-tricalcium phosphate (CM-chitin/beta-TCP) composite induced cartilage regeneration in the osteochondral defects of rabbits in vivo. We also found that CM-chitin stimulated peritoneal exudate cells (PEC) in mice and induced several kinds of inflammatory cytokines and transforming growth factor beta-1 (TGF-beta1). In this study, we examined whether CM-chitin is responsible for the induction of chondrogenesis via the production of TGF-beta1 in vitro. The murine pluripotent cell line C3H10T1/2 was maintained as a micromass culture in conditioned medium prepared from PEC stimulated with and without CM-chitin. CM-chitin-conditioned medium induced RNA expression of the chondrogenic-factor Sox9 and the matrix proteins aggrecan, Col2a1, and Comp. Their expression levels were decreased in the presence of anti-TGF-beta1 antibody. The micromass tissues cultured in CM-chitin conditioned medium at day 21 were clearly stained by Toluidine blue or Alcian blue (histological staining) and collagen II antibody (immunohistological staining), showing the expression of acidic glycosaminoglycan and type II collagen. Similar results were observed in micromass tissue stimulated with TGF-beta1 as a positive control. However, no chondrogenesis occurred when CM-chitin was added directly to a C3H10T1/2 cell culture. These results indicated that CM-chitin is a potent inducer of chondrogenesis via the induction of TGF-beta1 in immune cells.