In vitro formation of neocartilage in photocrosslinked poly(ethylene oxide) hydrogels

In tissue engineering cartilage, photopolymerization provides many benefits including rapid polymerization times under physiological conditions with temporal and spatial control over the polymerization. In situ forming hydrogels are attractive for their high water content and tissue-like elastic properties. We are interested in using photocrosslinkable macromers based on poly(ethylene oxide) to encapsulate chondrocytes in a three-dimensional hydrogel matrix to support cell proliferation and extracellular matrix production. In this study, we demonstrated that chondrocytes (at a concentration of 100×10⁶ cells/cc) in a 10% (w/w) macromer solution containing a cytocompatible photoinitiating system polymerized in the form of a ~2 mm thick disk survived the photoencapsulation process and remained healthy in the hydrogel network. The biochemical content of the hydrogels was also assessed at 4, 6, and 8 weeks in vitro to determine the cellular activity. An increase in glycosaminoglycan (GAG) and total collagen contents was observed over time, and at 8 weeks the neocartilage was comprised of 0.4±0.09% total collagen and 1.34±0.10% GAG per wet weight of the construct. In addition, we demonstrated that photocrosslinkable hydrogels may overcome some of the limitations of other materials in obtaining uniform cell seeding and the production of thick cartilaginous tissue. In this study, chondrocytes were photoencapsulated in a thick 8 mm hydrogel and remained healthy throughout the construct both radially and longitudinally, and the cells produced a uniform GAG content as seen histologically