Influence of Mechanical Load on Enzymatic Cleavage of Native Collagen

It has been hypothesized that collagen fibrils in native tissue are “strain-stabilized” and thus protected (to some extent) from enzyme attack by the application of mechanical load. If true, collagen and its complement native enzymes (MMPs) could comprise the basis of “smart” structure which is intrinsically load-adaptive. If strain protection of collagen significantly reduces the activity of bacterial collagenase (BC-Clostridium Histolyticum), then benchtop “sculpting” of collagenous matrix for tissue engineering may be practical. In this investigation, we have quantified the enzymatically-induced creep of uniaxially-loaded (0.25 N) and unloaded control bovine corneal tissue strips (∼6.0 mm × 0.7 mm × 17 mm) which were exposed to BC (0.05 mM). Experimental and control strips were loaded for 15 minutes (initial creep-in) then exposed to the BC at which point the controls were unloaded. After 35 minutes of degradation, unloaded controls were re-loaded and the dynamic strain was recorded. All unloaded control specimens were significantly compromised mechanically compared to experimentals and could not hold the applied load for more than a few minutes following reloading. From the data is clear that strain protects the loaded fibrils. How that protection is manifested remains an open question.