Studies on Inflammation and Wound Healing: Angiogenesis and Collagen Synthesis Stimulated in Vivo by Resident and Activated Wound Macrophages

Wound inflammatory cells were harvested by aspiration of fluid from the "dead space" of subcutaneous rabbit wounds and transplanted into the cornea where, compared with suitable controls, they stimulated healing (i.e., angiogenesis, fibroplasia, and new collagen synthesis, which led to formation of visible, vascularized scar tissue). Analysis of the data and the literature supports the conclusions that: (1) inflammatory cells control the continuation of the repair process after the immediate effects of injury subside; (2) macrophages, as opposed to granulocytes, appear to be the major contributors; (3) activated by their presence in the wound, macrophages release substances that stimulate fibroplasia, collagen synthesis, and angiogenesis in vivo; and (4) tissue injury is not a maximum stimulus to repair, since endotoxin-treated macrophages have increased capacity to stimulate collagen synthesis and angiogenesis. A hypothesis is offered to explain the notorious clinical discrepancy between the extent of injury and the extent of repair.