The effects of scaffold thickness on tissue engineered cartilage in photocrosslinked poly(ethylene oxide) hydrogels

The thickness of human articular cartilage has been reported to vary from less than 0.5 up to 7 mm. Hence, tissue engineered cartilage scaffolds should be able to span the thickness of native cartilage to fill defects of all shapes and sizes. In this study, we demonstrate the potential for using photopolymerization technology to encapsulate chondrocytes in poly(ethylene oxide) hydrogels, which vary in thickness from 2 to 8 mm. Chondrocytes, encapsulated in an 8 mm thick, photocrosslinked hydrogel and cultured in vitro for 6 weeks, remained viable and produced cartilaginous tissue throughout the construct comparable to a 2 mm thick gel as seen both histologically and biochemically. In addition, the total collagen and glycosaminoglycan contents per wet weight of the 8 mm thick cell-polymer construct were 0.13 +/- 0.01 and 0.25 +/- 0.03%, respectively, and did not vary significantly as a function of spatial position in the construct. The histological evidence and the biochemical content were similar in all constructs of varying thickness. The results suggest that photocrosslinked hydrogels are promising scaffolds for tissue engineering cartilage as cell viability is readily maintained; uniform cell seeding is easy to achieve: and the biochemical content of the extracellular matrix is not compromised as the scaffold thickness is increased from 2 to 8 mm.