Correlation of High-Speed Tensile Strength with Collagen Content in Control and Lathyritic Rat Skin

Severity of lacerative skin injury depends on the applied load and the resistance of the tissue. At low (static) rates of loading there is a high degree of correlation between skin tensile strength and the degree of collagen crosslinking, with little added strength due to collagen interactions with the glycosaminoglycan matrix. We examined the effects of high (ballistic) rates of loading in order to determine the contributions to strength made by both the degree of collagen crosslinking and the collagen-matrix interaction. Tensile failure experiments were conducted using the dorsal skin of rats 1.5-6 months of age. Test specimen orientations were cut parallel and transverse to the body axis at cephalad and caudad locations on the dorsum. Tensile strength was measured at nominal strain rates of 30%/sec (low speed) and 6000%/sec (high speed) using both control and lathyrogen fed rats. Biochemical analyses were conducted to determine the amount of total and crosslinked (insoluble) collagen. In low-speed tests, there was a significant correlation ( r ⩾ 0.900) between collagen content and skin tensile strength measured both transverse and parallel to the spine. The degree of correlation was higher with insoluble ( r = 0.973) collagen content than with total ( r = 0.901) collagen. The effect of a lathyrogen diet produced a significant ( P < 0.001) reduction (two- to threefold) in tensile strength compared to control. In both high- and low-speed groups, tensile strength was greatest in the transverse samples with a significant correlation to collagen content ( r ⩾ 0.858). In the high-speed experiments, the skin tensile strength was significantly ( P < 0.001) increased (two- to threefold) compared to low-speed results at each age tested. Because this increase occurred in identical tissues, these data support our hypothesis that the more dynamic strength properties of skin involve the influence of matrix interactions with collagen.