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