ELECTRON MICROSCOPIC STUDIES OF NORMAL AND ABNORMAL ELASTIC FIBERS OF SKIN

[摘要] Formation of the dermal elastic fiber proceeded in much the same way as the collagen fiber in its early developmental stages. At the outset, protofilaments, equivalent in dimension to tropocollagen, were precipitated extracel-lularly by the fibroblasts. The subsequent aggregation of these protofilaments and deposition of the dense matrix substances made them thicker, denser fibrils, called skeleton fibrils. Individual skeleton fibrils were surrounded by a dense granular substance and other cytoplasmic organelles which derived from near-by fibroblasts by means of secretion and ecdysis. When these skeleton fibrils aggregated to form mature elastic fibers, the dense granular substances were compressed between them and formed dense granular septa. In the mature dermal elastic fiber, individual skeleton fibrils had coalesced with each other and were visible only at the periphery and frayed ends. In the body of the mature elastic fibers, they were discernible as moderately dense fasicles of irregular widths, cemented by denser granular substances. The skeleton fibrils may be the main resilient component of the elastic fiber, the dense granular septa serving as buffers between them. The majority of the elastic-stain positive material in pseudoxanthoma elasticum is composed of an increased number of elastic fibers, though most of them were severely damaged by calcification. An admixture of degenerated collagen and degraded elastin (as seen in actinic elastosis was also observed, but to a minor degree. Fibroblasts, collagen, and initial stages of elastic fiber formation appeared normal. Small newly-formed, elastic fibers did not show a great deposit of calcium sallts; abnormalities increased as they grew into large, stubby of bizarre-shaped elastic fibers. The only visible abnormality in these affected fibers was the calcification, which was either very dense, crystalline, lamellae-shaped, or granular. Normal-appearing elastin was always found along the periphery of affected fibers. An abnormal genetic factor influences the abnormal metabolism of calcium, the production of the calcinophilic building material of the elastic fibers, and/or the deficiency of enzymes essential to the incorporation and integrity of elastic fibers.