Dynamic Hydrostatic Pressurization Differentially Regulates Extracellular Matrix Elaboration by Bovine Inner and Outer Annulus Fibrosus Cells Seeded on 3-D Polymer Scaffolds

Current surgical treatments for intervertebral disc (IVD) degeneration result in decreased mobility of the spine [1]. A tissue engineering approach may provide an alternative that restores both IVD structure and function. The IVD is comprised of three distinct regions: the outer annulus fibrosus (OA), inner annulus fibrosus (IA), and the nucleus pulposus (NP). Each of the cell populations within these regions possess unique phenotypic properties that are greatly influenced by environmental factors, such as the surrounding 3-D extracellular matrix (ECM) and mechanical loading (i.e., hydrostatic pressurization) [2]. As such, both the 3-D scaffold and in vitro culture conditions may have marked effects on the development of tissue-engineered IVD constructs. Although the influence of mechanical loading on IVD cells and explants has been investigated, no prior studies have examined the impact of hydrostatic pressurization on OA and IA cells in 3-D culture. Therefore, the objective of this study was to determine the effects of dynamic hydrostatic pressurization on OA and IA cells seeded on 3-D fibrous poly(glycolic acid)-poly(L-lactic acid) (PGA-PLLA) scaffolds. We hypothesized that the application of hydrostatic pressure would promote increased production of type II collagen and chondroitin sulfate proteoglycan in both OA- and IA-seeded constructs.