Effects of X-radiation on Growth and Function of the Repair Blastema (Granulation Tissue)

Abstract

Closure and healing of open wounds of mammalian skin is due mainly to a rapid approximation of the wound due to contraction. Contraction depends on the proliferative growth of a repair blastema (‘granulation tissue’) from vascular and connective tissues. Thus, wound contraction is cellular in origin and probably due to contractility of cells of the blastema. Pre-operative local irradiation of intact skin given immediately before wounding caused dose-dependent reductions in the rate of wound contraction, largely by delaying and inhibiting growth of the repair blastema. When the dose was fractionated, evidence of recovery of sublethal damage [(D₂−D₁)≃250 rads] was obtained. The effect of pre-operative irradiation was decreased by increasing the time between irradiation and wounding. Pre-operative local irradiation of the skin, partly shielded by a lead grid or by a lattice of lead discs, with large single doses (4–8 kR), caused no reduction in the rate of wound contraction and showed that spatial discontinuity of blastemal tissues did not prevent integration of function. Partial shielding of the margin or base of a freshly-made wound during irradiation showed that the sphincter-like concentration of blastema produced at the periphery of an open wound principally effected contraction. When the radiation was given post-operatively to a contracting wound (i.e. after the repair blastema had developed) the rate of contraction was not decreased. The bearing of the radiobiological findings on the mechanism of wound contraction and their relevance to combined treatment by radiotherapy and surgery is discussed.