Report on the differentiation of vascular wall smooth muscle cells with the aid of immunofluorescence

Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: I. Normal development

Myometrial development from the prenatal to adult period was examined in rats and mice 1) by histologic and immunocytochemical methods with anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells; and 2) by morphometric procedures to assess quantitatively the expression of cellular orientation in the emerging inner circular myometrial layer. Uterine mesenchymal cells initially were uniformly vimentin-positive, undifferentiated, and randomly oriented during the late fetal period. By the early neonatal period, three mesenchymal layers became recognizable histologically, the middle one of which (prospective circular myometrium) developed distinct circular orientation and differentiated into a layer composed of actin-positive smooth muscle cells. The cells of the inner mesenchymal layer initially exhibited radial orientation. By 10 days postpartum, the outer longitudinal mesenchymal layer differentiated into bundles of smooth muscle cells representing the longitudinal myometrium. The inner mesenchymal layer remained vimentin-positive and differentiated into the randomly ordered endometrial stroma. The cells of the middle and outer mesenchymal layers that were destined to form myometrium initially expressed vimentin throughout and then coexpressed vimentin and actin, but with time vimentin staining disappeared in the maturing smooth muscle cells as they expressed actin.

Leiomyosarcoma of the pulmonary artery. A light and electronmicroscopical study

A 25-year-old man with chest pain and shortness of breath was found to have a primary sarcoma of the pumonary artery. On light- and electronmicroscopy and immunofluorescence microscopy the lesion was found to be composed of cells of smooth muscle origin. It was diagnosed as leiomyosarcoma. The cross and microscopic features of the tumor are described and the morphologic characteristics of previously reported vascular sarcomas are briefly reviewed.

A simple method for differentiating vascular smooth muscle cells and fibroblasts in tissue culture

The morphologic differentiation of vascular smooth muscle cells and fibroblasts in tissue culture is difficult if not impossible. By direct immunofluorescence, it is possible to distinguish between vascular smooth muscle cells and fibroblasts after 6 to 10 days in tissue culture. Microfilaments appear from the 6th to the 10th day. After an incubation period of 30 minutes with antibody against smooth muscle actomyosin at room temperature, microfilaments are demonstrable in smooth muscle cells. In contrast, fibroblasts, if incubated for the same period, show strong nuclear fluorescence and a primary fluorescence of the cytoplasm, but filaments are not visible. If fibroblasts are incubated with antiactomyosin for one hour at 37 degrees C, however microfilaments are easily detectable. With this method it is possible to differentiate in a simple manner vascular smooth muscle cells from fibroblasts in a heterologous tissue culture.

Changes in myosin distribution in dedifferentiating and redifferentiating smooth muscle cells in tissue culture

Isolated smooth muscle cells and fibroblasts from the newborn guinea-pig vas deferens were grown in culture. In the first 2 days, all cells characterized as smooth muscle by phase-contrast microscopy reacted intensely with fluoresceinated antibodies against smooth muscle myosin. The fluorescence was in the form of particles (termed here "myosin aggregates"), which were often aligned to give the cell a striated appearance. After 3-5 days, coarse fluorescent fibrils were also visible. These were termed "attachment fibrils" ("A-fibrils") since they were thought to represent myosin in microfilament bundles. Between 6 and days in culture, the smooth muscle cells began to dedifferentiate morphologically. At this time, the "myosin aggregates" became clumped and less intensely fluorescent. "A-fibrils" also decreased in fluorescence intensity. By 8 days in culture, the dedifferentiated cells had undergone intense proliferation and gave only a minimal reaction with myosin antibodies. However, when a confluent monolayer of cells formed on day 9 or 10, they immediately began to redifferentiate ultrastructurally and to regain immunofluorescence in both "myosin aggregates" and "A-fibrils". Throughout the entire culture period, cells characterized as fibroblasts by phase contrast microscopy gave only a weak reaction with fluoresceinated antibodies to myosin showing "A-fibrils" but no "myosin aggregates".

[Arteriosclerosis: morbid anatomy (author's transl)]

Pathology is a variant of physiology with obstacles. No arterial wall is absolutely impermeable. The basic form of arteriosclerosis results from a disturbance of the lifelong flow of humors ab intima in adventitiam et ex centro in peripheriam (author's "Perfusion theory"). Special forms develop from this basic form. Analysis of postmortem material with special reference to the so-called risk factors allowed us to establish connections between some of these factors and arteriosclerosis, while some other connections, e.g. with smoking, were called in question. It is pointed out that prospective treatment of arteriosclerosis will begin only when the cluster of risk factors can be broken down.