Interstitial flow upregulates matrix synthesis and attenuates NF-kB signaling in a novel perfusion bioreactor for articular cartilage tissue engineering

The present study is focused on designing an easy-to-use novel perfusion system for articular cartilage (AC) tissue engineering and using it to elucidate the mechanism by which interstitial shear upregulates matrix synthesis by articular chondrocytes (AChs). Porous chitosan-agarose (CHAG) scaffolds were synthesized, freeze-dried, and compared to bulk agarose (AG) scaffolds. Both scaffold types were seeded with osteoarthritic human AChs and cultured in a novel perfusion system for one week with a shear-inducing medium flow velocity of 0.33 mm/s corresponding to an average surficial shear of 0.4 mPa and a CHAG interstitial shear of 40 mPa. While there were no statistical differences in cell viability for perfusion vs. static cultures for either scaffold type, CHAG scaffold cultures exhibited 3.3-fold higher (p<0.005) cell viability compared to AG scaffold cultures. Effects of combined superficial and interstitial perfusion for CHAG showed 150- and 45-fold (p<0.0001) increases in total collagen (COL) and 13- and 2.2-fold (p<0.001) increases in glycosaminoglycans (GAGs) over AG’s scaffold non-perfusion and perfusion cultures, respectively, and a 1.5-fold and 3.6-fold (p<0.005) increase over non-perfusion CHAG cultures. Contrasting CHAG perfusion and static cultures, chondrogenic gene comparisons showed a 3.5-fold increase in collagen type II/type I (COL2A1/COL1A1) mRNA ratio (p<0.05), and a 1.3-fold increase in aggrecan mRNA. Observed effects are suggested to be the result of inhibiting the inflammatory NF-κB signal transduction pathway as confirmed by a further study that indicated a reduction by 3.2-fold (p<0.05) upon exposure to perfusion. Our results demonstrate that the presence of pores plays a critical role in improving cell viability and that interstitial flow caused by medium perfusion through the porous scaffolds enhances the expression of chondrogenic genes and ECM components through the downregulation of NF-κB1.

CaCO3–Chitosan Composites Granules for Instant Hemostasis and Wound Healing

Excessive bleeding induces a high risk of death and is a leading cause of deaths that result from traffic accidents and military conflict. In this paper, we developed a novel porous chitosan–CaCO3 (CS–CaCO3) composite material and investigated its hemostatic properties and wound healing performance. The CS–CaCO3 composites material was prepared via a wet-granulation method. Granulation increases the infiltrating ability of the CS–CaCO3 composites material. The improved water absorption ability was enhanced to 460% for the CS–CaCO3 composites material compared to the CaCO3 or chitosan with only one single component. The coagulation studies in vivo illustrated that the blood clotting time was greatly reduced from 31 s for CaCO3 to 16 s for the CS–CaCO3 composite material. According to the results of the wound healing experiments in rats, it was found that the CS–CaCO3 composite material can promote wound healing. The CS–CaCO3 composite material could accelerate wound healing to a rate of 9 days, compared with 12 days for the CaCO3. The hemostatic activity, biocompatibility, and low cost of CS–CaCO3 composite material make it a potential agent for effective hemostatic and wound healing materials.