Wound Healing in the Mitral Valve Koichi Tamura MD, Michael Jones MD, Izumi Yamada MD, Victor J. Ferrans MD Light and electron microscopic studies were made of the healing of wounds produced surgically in the anterior mitral leaflet in young sheep (n = 11). All animals developed severe mitral regurgitation. Two types of granulation tissue were associated with wound healing. The first consisted of myxoid tissue that extended from the valvular spongiosa and fibrosa. The second consisted of spindle-shaped cells arranged in parallel and resembled that caused by reactive fibrosis in regurgitant mitral valves. Capillaries and arterioles were first found in the middle portion of the leaflet at eight weeks, and extended into the proximal area of the wound at 12 weeks. Thus, the healing of mitral valvular wounds is slow and requires 8-12 weeks for the formation of a dense scar and for restoration of the endothelial lining. Progression of healing is associated with the phenotypic modulation of connective tissue cells from fibroblasts to myofibroblasts and with neovascularization of the leaflets.

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