Clonal characteristics of cutaneous scars and implications for atherogenesis

Atherosclerotic plaques in man have monoclonal characteristics. One possible explanation for this observation is that clonal selection occurs as cells proliferate at sites of intimal injury. To test whether such clonal selection could occur during the formation of an intimal 'scar', the clonal characteristics of human cutaneous scars were studied with the use of glucose-6-phosphate dehydrogenase (G-6-PD) as a cellular marker. Scars from 7 black women heterozygous for the A and B isoenzymes of G-6-PD were divided into 870 portions consisting of contiguous normal skin, scar margin, outer scar, and inner scar. Portions were further divided into surface and deeper portions of scar. In 4 of the 7 cases, significant differences were observed between the mean percentage of total activity in the B isoenzyme band in portions of scar and portions of skin. Significant differences between surface and deeper portions of both skin and scar were also observed in 5 cases. The variance of isoenzyme values from portions of scars was not significantly greater than that within portions of skin. It is concluded that the results are consistent with clonal selection occurring during the healing of skin wounds. However, the magnitude of the difference (no greater than a 5.7% B isoenzyme difference) is far too small to even partially explain the marked differences in isoenzyme patterns observed between atherosclerotic plaques and uninvolved aortic wall. The results do not support the idea that the monoclonality of human atherosclerotic plaques is due to clonal selection following the healing of an intimal injury.