Modulation of collagen proteolysis by chemical modification of amino acid side-chains in acellularized arteries

In this study, we have examined the effects of specific chemical modifications of amino acid side-chains on the in vitro degradation of "native" collagen obtained from acellular matrix (ACM)-processed arteries. Two monofunctional epoxides of different size and chemistry were used to modify lysine, with or without methylglyoxal modification of arginine. Biochemical, thermomechanical, tensile mechanical, and multi-enzymatic (collagenase, cathepsin B, acetyltrypsin, and trypsin) degradation analyses were used to determine the effects of modifications. Collagen solubilization by enzymes was found to depend upon the size and chemistry of epoxides used to modify lysine residues. In general, the solubilization of native ACM collagen by collagenase, cathepsin B, trypsin, and acetyltrypsin was either unaltered or decreased after modification with glycidol. In contrast, n-butylglycidylether (n-B) treatment increased solubilization by all enzymes. Subsequent arginine modification significantly reduced collagen solubilization by acetyltrypsin for glycidol-treated ACM arteries, whereas increased collagen solubilization was observed for n-B-treated ACM arteries with all enzymes. Gel chromatographic analyses of collagen fragments solubilized by trypsin revealed that both the amount and sites of cleavage were altered after lysine and arginine modification. The ability to modulate the enzymatic degradation of tissue-derived materials as demonstrated in this study may facilitate the design of novel engineering scaffolds for tissue regeneration or collagen-based drug delivery systems.