Controlling the spatial distribution of ECM components in degradable PEG hydrogels for tissue engineering cartilage

TLDR

The degradation rate and mass loss profiles of a scaffold are critical design parameters for supporting new tissue growth. This study prepared degradable PEG hydrogels by copolymerizing PEG‑LA‑DA with nondegradable PEGDM to investigate their properties. Chondrocytes were photoencapsulated in PEGDM/PEG‑LA‑DA gels of varying degradability (50:50, 25:75, 15:85) and cultured for six weeks, after which the resulting tissue was analyzed biochemically and histologically. Six‑week cultures showed that gels with higher degradable crosslink content (75–85%) had nearly twice the DNA and significantly more collagen than 50% gels, and immunohistochemistry revealed that type II collagen was pericellular in 50% gels but distributed throughout the tissue in more degradable gels, demonstrating that degradation governs ECM deposition and distribution. © 2002 Wiley Periodicals, Inc., J Biomed Mater Res 64A: 70–79, 2003.

Abstract

Abstract In developing a scaffold to support new tissue growth, the degradation rate and mass loss profiles of the scaffold are important design parameters. In this study, hydrogels were prepared by copolymerizing a degradable macromer, poly(lactic acid)‐ b ‐poly(ethylene glycol)‐ b ‐poly(lactic acid) endcapped with acrylate groups (PEG‐LA‐DA) with a nondegradable macromer, poly(ethylene glycol) dimethacrylate (PEGDM). The resulting hydrogels exhibited a range of degradation behavior and mass loss profiles. Chondrocytes were photoencapsulated in gels formulated with 50:50, 25:75, and 15:85 (mol % PEGDM: mol % PEG‐LA‐DA) and cultured for 6 weeks in vitro . The neocartilaginous tissue formed was examined biochemically and histologically. After 6 weeks, the DNA content in gels with 75 and 85% degradable crosslinks was nearly twice that of the DNA content in the 50% gels. The total collagen content was significantly higher in the 85% gel [2.4 ± 0.8% wet weight (ww)] compared to the 50% gel (0.22 ± 0.29% ww). In examining the neocartilaginous tissue with immunohistochemistry, type II collagen was localized in the pericellular region in the 50% gel; however, when increased degradation was incorporated into the gel, type II collagen was found throughout the neotissue. In summary, the important role of hydrogel degradation in controlling and influencing the deposition and distribution of extracellular matrix molecules was demonstrated and quantified. © 2002 Wiley Periodicals, Inc., J Biomed Mater Res 64A: 70–79, 2003