Effects of transforming growth factor-beta on collagen synthesis by normal rat kidney epithelial cells.

The effects of transforming growth factor-beta (TGF-beta) on the growth of and collagen production by NRK52E cells, a clonal line established from normal rat kidney epithelial cells, have been characterized. NRK52E cells were grown in the absence or presence of TGF-beta for 4 days followed by incubation for 24 hours in serum-free medium containing [3H]proline. The secreted and cell-associated collagens produced by control and experimental cultures were isolated by limited pepsin digestion and differential salt fractionation. TGF-beta inhibited proliferation by about 50% but did not affect overall culture morphology. Both protein and collagen synthesis were increased in experimental cultures, but the increase in total collagen production exceeded that of total protein synthesis. Although NRK52E cells grown in the presence of TGF-beta continued to produce the same types of collagen (types I, III, IV, and V), their relative amounts were changed. In the experimental cultures, type I collagen production was increased eightfold, types III and V collagen levels were increased two-fold, but type IV production was only slightly enhanced. In addition to increasing total collagen production by about fivefold, TGF-beta increased the ratio of type I to type III about threefold but minimally affected the ratio of secreted to cell-associated molecules. These findings establish that TGF-beta specifically affects collagen production in NRK52E cells and that these alterations differ in many ways from the affects of epidermal growth factor. Because TGF-beta increased total collagen expression, these results provide additional evidence implicating this growth factor as a positive mediator of matrix accumulation in renal disease.

Effects of epidermal growth factor on collagen synthesis by an epithelioid cell line derived from normal rat kidney.

Studies were performed to characterize the effects of both acute and chronic exposure to epidermal growth factor (EGF) on collagen biosynthesis by NRK52E cells, an epithelioid line established from normal rat kidney. Both conditions of exposure to EGF stimulated cell growth. Qualitative analysis revealed that NRK52E cells continued to synthesize types I, III, IV, and V collagens under all circumstances. However, both acute and chronic exposure to EGF increased two- to fourfold the amounts of collagenous proteins secreted by NRK52E cells, but decreased by 40 to 80% the amounts of collagenous material derived from the cell layers. Quantitative evaluation of type I and type III molecules confirmed that both conditions of exposure to EGF resulted in substantial increases in the amounts of these types of collagen secreted by the cells. However, analysis of the cell-associated types I and III molecules revealed that, while prolonged exposure to EGF significantly decreased the production of both types of collagen, acute exposure minimally affected type I collagen levels, but decreased type III production greater than 40%. Thus, conditions of acute exposure resulted in a slight increase in the total amount of type I collagen produced, but a slight decrease in the amount of type III collagen synthesized. In contrast, chronic exposure to EGF decreased the total amount of both collagen types synthesized, with type III being decreased to a greater extent (approximately 70%) than was type I (approximately 50%). Thus, the ratio of type III to type I collagen produced by NRK52E cells was decreased under both conditions of exposure to EGF. Therefore, these studies establish that EGF can modify matrix production in an epithelioid line of renal origin.

Synthesis of type III collagen by cultured kidney epithelial cells.

Studies have been performed to evaluate both the relative amounts and molecular forms of the collagens synthesized by an established line of cultured rat kidney epithelial (clone NRK52E) cells. The collagens secreted into the culture medium and extracted from the cell layers of cultured NRK52E cells were isolated after limited pepsin digestion and differential salt fractionation. Greater than 95% of the collagenous proteins synthesized by NRK52E cells were found to be associated with the cells and not secreted. Polyacrylamide gel electrophoresis under denaturing conditions of the NRK52E cell collagens indicated the presence of components exhibiting properties corresponding to those of the chains present in types I, III, IV and V collagen. Analysis of each fraction by carboxymethyl-trisacryl chromatography revealed that approximately two-thirds of the total collagen synthesized by NRK52E cells was type III. Of the remaining collagen types I, IV and V molecules represented 20%, 4% and 10% respectively, of the total produced. Essentially all of the type I collagen produced by NRK52E cells was recovered as the type I-trimer, whereas the type V molecules synthesized by NRK52E cells had the molecular compositions of [alpha 1(V)]2 alpha 2(V) and alpha 1(V)alpha 2(V)alpha 3(V). These data establish the relative proportions and molecular forms of the collagens synthesized by cultured NRK52E cells. Furthermore, these findings suggest that NRK52E cells may be a useful in vitro model for investigating the regulation of changes in collagen biosynthesis occurring under situations of renal epithelial cell injury.

Carotid-cavernous fistula: a complication of maxillofacial trauma.

Fistulas of the internal carotid-cavernous sinus are an unusual arteriovenous malformation. Two types exist: (1) spontaneous fistulas and (2) traumatic fistulas. This paper deals with the traumatic variety which is seen more commonly in men as a direct result of severe maxillofacial injury. Recent anatomic studies are correlated with the physical findings associated with carotid-cavernous fistula, ie, headache, chemosis, exophthalmos, pulsatile bruit, and multiple cranial nerve paralyses. A case report illustrates these findings. The differential diagnosis which varies from tumors, to cavernous sinus thrombosis, to intraorbital aneurysm is discussed. The role of angiography in diagnosis is described. Present management consists of intracranial ligation of the internal carotid artery with use of a muscle embolus to occlude the fistula and selective ligation of the cervical carotid.