Aging of a regenerative biologic scaffold (AlloDerm native tissue matrix) during storage at elevated humidity and temperature.

Tissue products will age upon storage. Although a number of tissue products have been used for tissue repair and regeneration for more than a decade, no study has been published on the aging of tissue products and its potential effect on product function. This study investigated aging-caused changes in a regenerative biologic scaffold (AlloDerm native tissue matrix) upon storage at accelerated conditions. Tissue matrix was stored at elevated humidity (33%, 75%, and 85% relative humidity [RH]) and temperature (40 +/- 2 degrees C). The study measured the accumulation of advanced glycation end-products (Maillard products), and the changes of tissue structure, tissue stability, and mechanical properties as well as in vitro fibroblast repopulation. Tissue products stored at 75% RH and 85% RH changed significantly, including collagen condensation and cross-linking, increased breaking strength, and decreased elasticity. The aged products became less stable, as demonstrated by lower denaturation temperature, lower denaturation enthalpy, and higher susceptibility to nonspecific proteolytic action. In comparison, changes were nondetectable in control products stored at 2 degrees C to 8 degrees C, or very small in tissue products stored at 33% RH and 40 degrees C. Changes of tissue structure and stability were correlated highly with the formation of Maillard products, suggesting a role of Maillard reactions in tissue aging during storage. Calorimetric analysis revealed that tissue products stored at 2 degrees C to 8 degrees C and at 33% RH and 40 degrees C were in the glassy state, whereas the products stored at 75% RH, 85% RH, and 40 degrees C were not in the glassy state, suggesting a role of the glassy state in preserving tissue products during storage. Aging did not affect in vitro fibroblast proliferation on tissue matrix, and further tests are needed to investigate how aging may affect in vivo performance of the tissue product.