Functional and structural vascular lesions have been observed in the organs involved in scleroderma. The etiology of these vascular changes is poorly understood. The ability to isolate, characterize, and maintain endothelial cells in vitro provides a target cell population to study endothelial damage in scleroderma. The present report describes the effect of scleroderma serum on endothelial, smooth muscle, and fibroblast cell types. Sera from patients with scleroderma (31/52) and Raynaud's syndrome (11/19) contain cytotoxic activity, specific for endothelial cells, which is nondialyzable, heat-stable, and elutes with albumin on gel-filtration chromatography.

A previous study of low density lipoprotein metabolism by cultured cells focused on the metabolism of normal lipoproteins in vitro by fibroblasts isolated from diabetic patients. No abnormalities were found. We have followed the opposite approach. Using normal human fibroblasts as test cells we compared the metabolism in vitro of low density lipoproteins isolated from diabetic patients before and after metabolic control. We found a significant decrease (p less than 0.02) in internalization and degradation of low density lipoproteins isolated from diabetic patients before metabolic control when compared with those isolated from normal control subjects or from the same patients after metabolic control. The observed changes were mainly apparent in intracellular degradation. To evaluate whether the observed differences in low density lipoprotein behaviour were correlated with lipid or apolipoprotein composition, we measured cholesterol, triglyceride, apolipoprotein B and total protein levels in the low density lipoproteins tested. A significant decrease (p less than 0.05) of the triglyceride/protein ratio was found in post-control low density lipoproteins suggesting that a high triglyceride content may interfere with low density lipoprotein metabolism. The present study represents the first observation that metabolic control in diabetes mellitus can alter low density lipoprotein-cell interaction and suggests a possible mechanism for the enhanced incidence of atherosclerosis in diabetic patients.

Human preputial skin fibroblasts were cloned in vitro, and studies in 21 clones were shown to exhibit a 3-fold difference in collagen synthesis; this heterogeneity of phenotypic expression was conserved over multiple population doublings. When the clones were exposed to sera from 10 scleroderma patients, selective growth of high-collagen-producing fibroblasts was observed. Prostaglandin E2 abrogated the selective effect of scleroderma serum on high-collagen-producing fibroblast clones. Besides enhanced collagen synthesis, these clones of normal fibroblasts shared an insensitivity to feeding schedule with fibroblasts from scleroderma skin. These data raise the possibility that scleroderma represents a process of selection of fibroblasts programmed to produce increased amounts of collagen.

To explore the mechanism of increased collagen synthesis by scleroderma skin fibroblasts in vitro, control and scleroderma fibroblasts were compared in confluent monolayer cultures growth-arrested by serum deprivation; responses to optimal mitogenic doses of platelet-derived growth factor, fibroblast growth factor, epidermal growth factor and nerve growth factor were compared. Plateletderived growth factor had a selective mitogenic effect on control skdn fibroblasts not observed with scleroderma skin fibroblasts. None of the factors studied had a selective effect on collagen synthesis independent of cell replication; scleroderma and control fibroblasts responded similarly. Therefore, the growth factors studied may not be involved in generating the activated scleroderma fibroblast directly; platelet-derived growth factor may play an indirect role in fibroblast replication in human fibrotic disorders.More than a decade ago, it was observed that fibroblasts from involved skin of patients with scleroderma synthesized increased levels of collagen in vitro (1, 2); today the mechanism remains unknown (3-6). During this period, observations ofthe pathogenesis of scleroderma have focused on vascular and microvascular lesions; on evidence of endothelial damage; on platelet adhesion, aggregation, and release; and on the subsequent activation both of smooth muscle cells to produce the intimal proliferation and of interstitial fibroblasts to produce fibrosis (7-10). A unifying hypothesis would propose the presence offactors released from plasma or platelets which act as stimuli to fibrosis; among such factors, the potent mitogen, plateletderived growth factor (PDGF), is released during endothelial injury and platelet adhesion to the subendothelium (11). Therefore, the influence of PDGF on skin fibroblast collagen synthesis was studied.Endothelial damage and platelet interaction with the exposed subendothelium, resulting in release of platelet-derived mitogenic factors (including PDGF), have been proposed, at least indirectly, to play a role in the evolution of the scleroderma vascular lesion. Events preceding endothelial injury are poorly understood; altered immunity leading to humoral or lymphocyte/monocyte mediators ofinjury has been proposed with supporting evidence (12). If PDGF is the direct mediator of fibroblast activation in scleroderma, the enhanced collagen synthesis of scleroderma fibroblasts should be accompanied by increased cell replication at some stage in the process. Thus, a PDGF mechanism in scleroderma would imply replication offibroblast populations instead of, or in addition to, the selective stimulation ofcollagen synthesis per cell; in earlier studies, increased collagen synthesis per cell was observed in vitro without evidence of increased cell replication (1, 2). If PDGF is the mediator of fibroblast activation in scleroderma, its action should account for the initial observations of increased collagen synthesis per cell.A second characteristic of scleroderma fibroblasts in culture has been ...

Peripheral lymphocytes from 3 scleroderma patients with systemic disease and from 3 normal controls were examined for frequencies of chromosomal aberration and sister chromatid exchange (SCE). Significant increases in the levels of chromosomal anomaly and SCE were found for all 3 patients. These results are discussed in terms of the diagnostic potential of SCE in scleroderma and the possible etiologic role of cytogenetic instability in this disease.Cytogenetic studies of scleroderma patients by Emerit and her coworkers have shown increased frequencies of chromosome breakage and rearrangement in cell cultures of blood, skin, and aponeurosis (1,2: for review, see 3.4). This increase was shown to be three times the aberration level in normal controls and was observed in 95% of all patients examined. These findings have been confirmed by other groups (5,6). Observations of spontaneous mitoses from bone marrow (without cultivation in vitro) verify that increased chromosomal damage occurs in vivo and is not an artifact of culture (7). This phenomenon has not been