Microvasculature in hypertrophic scars and the effects of pressure.

The fine structure of the microvasculature was compared among eight samples of normal skin, 79 granulation tissues, 48 hypertrophic scars, 11 hypertrophic scars treated with mechanical pressure, and 13 mature scars. Increased synthesis activity is suggested in endothelial cells from granulation tissues, is less in hypertrophic scars, and low in mature scars. In hypertrophic scars most of the microvessels appear partially or completely occluded. Endothelial cell nuclei are crenated, many villous projections from the endothelial cell membranes exist on the blood side, and endothelial cell junctions are often complex, although no large gaps are observed. In all the granulation tissues studied fibrin polymer is present, occurring intraluminally and interstitially, which may be related to endothelial cell proliferation. Therapeutic mechanical pressure over 1 to 3 months effects striking changes in endothelial and perivascular satellite cells. Rented areas appear in endothelial cell cytoplasm. A few such areas were found in cases of nontreated hypertrophic scars but in no other group. Pressure-treated scars also demonstrate degenerating perivascular satellite cells, which also are observed in a few cases of mature scars but in no other group. A previously published theory that hypoxia is related to generation of the hypertrophic scar, and that pressure probably increases hypoxia, resulting in long-term focal degeneration of selective cells, appears further supported by the present findings.