Adult human skin maintained in organ culture. II. The ultrastructure of the cellular compartment of connective tissue.

Dermal cells maintained in cultured human skin explants for up to 10 weeks were studied by electron microscopy. Common findings in the cell organelles were: 1) altered nuclear shapes and numerous nuclear bodies; 2) reduced rough endoplasmic reticulum; 3) a prominent Golgi complex; and 4) an increasing number of free ribosomes, mitochondria, glycogen granules, lysosomes and lipid droplets. The individual types of dermal cells showed various cytoplasmic changes according to duration of the culture. The fibroblasts displayed a moderately developed rough endoplasmic reticulum. The macrophages were filled up with lysosomes and residual bodies. The mast cells showed typical as well as atypical granules. The smooth muscle cells had a variable content of myofilaments. The pericytes and the smooth muscle cells, both surrounded by a basal lamina, became increasingly difficult to discern from each other as a consequence of the decreasing number of myofilaments in the latter. The endothelial cells were recognized because of the preserved blood vessel architecture. Besides the above-mentioned cell types, two other types appeared with the culture time. The unidentifiable cells were characterized by dense zones of the cell membrane and an adjacent extracellular basal lamina-like material. This cell type may be derived from the pericytes of the small blood vessels. The primitive cells had a large rounded nucleus and a cytoplasm with few organelles. This cell type is assumed to represent a precursor cell common to various cell types.