The contractile properties of wound granulation tissue

A systematic examination of the contractile properties of wound granulation tissue is presented. Shortening of and tension generated by granulation tissue in the presence of 30 mM diphenhydramine HCl have been measured. Analysis of the stress (load per unit area)/strain (extent of shortening) results from isotonic shortening studies showed that over the range of 0 to 2.5% shortening there was an approximately linear relationship between stress and strain with a high modulus of elasticity. At lower stresses, wide variations in the amount of shortening occurred with little change in stress. Our interpretation of these findings is that diphenhydramine HCl caused an active shortening of the granulation tissue by 2.5% of its length and contractions greater than this were the result of secondary effects such as coiling and bending of the strips. It is shown that the granulation tissue would have to shorten by 2% once every 3 days to account for observed in vivo rates of contraction for large human wounds and once every 13 hr for rapidly contracting experimental rabbit wounds. The time course of the development of isometric tension by the granulation tissue is shown to be consistent with the proposal that each contractile cell contributes equally to the overall tension developed and that each cell is individually activated by a critical concentration of diphenhydramine HCl which is transported through the tissue by diffusion.