The Smooth Muscle Cell

Abstract

A B S T R A C TThese studies have examined the ability of smooth muscle cells from developing aorta of the prepubertal rat to utilize amino acids in the synthesis and secretion of connective tissue proteins. Prepubertal rats, previously given either an alcohol carrier or estradiol-17-beta, were each given an intravenous injection of proline-SH. The animals were sacrificed after 15 and 30 man, and 4 hr. Light and electron microscope radioautographs of the aortic smooth muscle and of the myometrial cells demonstrated that the aortic cells, in both groups of animals, and the myometrial cells, in the estrogen-stimulated animals, took up the proline and rapidly secreted it in both collagen and elastic fibers within 4 hr. In contrast, the myometrial cells of the nonstimulated animal took up relatively small amounts of proline and retained most of the amino acid within the cells. Electron microscope radioautographs demonstrated that the organelles involved in this activity were the rough endoplasmic reticulum and Golgi complex together with peripheral elements, presumed to be small vesicles. These studies have demonstrated that the smooth muscle cells of the developing aorta and of the estrogen-stimulated myometrinm have a capacity to synthesize and secrete proteins associated with the extracellular connective tissue matrix.

The smooth muscle cell. III. Elastin synthesis in arterial smooth muscle cell culture.

“…In a series of in vivo observations in the developing rat aorta, we were able to demonstrate, by autoradiographic exami- nation of [SH]proline incorporation, that smooth muscle cells incorporate proline into collagen and elastic fibers during growth and development (13). The ability to grow arterial smooth muscle cells in culture presented the opportunity to study the growth characteristics of these cells, and their FIGURE 4 SDS gel electrophoresis of radioactive tropoelastin fraction purified from cell extracts of smooth muscle cells and human gingiva fibroblasts.…”

“…Our earlier studies in this series of investigations demonstrated that in many tissues the smooth muscle cell is a connective tissue synthetic cell similar to the fibroblast, the osteoblast, and the chondroblast (13). In the vascular system the arterial smooth muscle cell is principally responsible for the synthesis of the major connective tissue components of the vessel wall, namely the elastic fiber, collagen, and glycosaminoglycan (11,20).…”

Hypertrophy-induced increase of intermediate filaments in vascular smooth muscle.

“…It will be of interest to determine whether comparable changes in actin to myosin filament ratios and in the number and distribution of intermediate filaments also occur in more slowly progressing systemic hypertension as they did in response to the relatively rapid increase in distending pressure used in this and in Gabella's (28) study. It is apparent that just as an increase in the volume of the endoplasmic reticulum represents a relatively nonspecific response to a variety of forms of injury (1,25,49,57,58), including hypertension and hypertrophy, an absolute and relative increase in the intermediate filaments of smooth muscle can also occur in response to a variety of interventions, such as cell culture (11)(12)(13)(45)(46)(47) and pressure induced hypertrophy (present study and reference 28) . Therefore, continued assessment of ultrastructural changes that are secondary to …”

“…Intermediate filaments are very numerous in cultured vascular (45)(46)(47) and other smooth muscles (11)(12)(13)60). In previous studies of normal adult vascular smooth muscle, occasional cells were found containing massive quantities ofintermediate filaments that appeared to displace the normal actin and myosin filament lattice (50,52) .…”

Cytokines and growth factors positively and negatively regulate interstitial collagen gene expression in human vascular smooth muscle cells.

“…1 VSMCs themselves can synthesize various matrix materials, including collagen types I and III, elastin, certain glycosaminoglycans, and microfibrillar proteins. 2 " 5 Therefore, inappropriate production of extracellular matrix constituents by VSMCs likely accounts for excessive formation of the collagenous matrix characteristic of advanced human atheromata and certain other arterial hyperplastic lesions. Knowledge of the regulation of collagen synthesis by these vascular cells would increase understanding of the pathophysiological mechanisms that underlie atherogenesis and might also indicate points in this process susceptible to therapeutic intervention.…”