Contributions of electron microscopy to the study of the hypertrophic scar and related lesions.

Prior to 1969, only one study of the hypertrophic scar had been done using electron microscopy, and that one used electron diffraction. Since that time, studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been integral in establishing not only the characteristics of this lesion but in formulating the reasons why the scar develops and how it resolves. The first SEM studies demonstrated a homogeneous, dense dermal matrix which supported the conclusion that the hypertrophic scar and keloid reflected excess collagen. These same studies were integral in identifying the collagen nodule as the basic anatomical unit of these lesions. SEM and TEM studies have been complimentary. The TEM studies revealed the first evidence of the phenomenon of occluded microvessels; but, their significance was not established until later quantitative studies. A hierarchy of fibroblasts was first demonstrated by TEM. Later, evidence came from several different investigators, through tissue culture and molecular differentiation, that the previously observed different electron microscopic features may reflect different fibroblast types of cells. Finally, the degenerative (or apoptotic) events, involving fibroblast-type cells and microvessels have been revealed by TEM studies, and supported by SEM observations. This phenomenon has been presented as a major factor in formation of the nodules, and, also, in the natural resolution of the hypertrophic scar and keloid.