Glomerular cell culture

Glomerular cell culture has now become a widely used research technique. At the present time procedures are available to obtain isolated glomeruli from nearly all species. The isolation of individual cells has proven problematical. This is due to the lack of defined markers. Thus, it is not yet possible to determine the presence and relative degree of contamination by other glomerular or even nonglomerular, cell types. The importance of dealing with individual cell types, or defined mixtures, is exemplified by the variable results obtained in the assessment of prostaglandin synthesis within and between species. Several important bites of information have, nevertheless, evolved from glomerular cell culture experiments. The sites of synthesis of basement membrane components, as well as their composition, have been determined. Confirmation of the existence of a bone marrow-derived mesangial cell population and some of their properties has been obtained. The response of mesangial cells to, as well as their production of, various mediators has been shown. Finally, clear evidence for interspecies differences and similarities has been documented. Areas of controversy remain, including whether contractile mesangial cells are phagocytic, the presence of C3b receptors on epithelial cells, the amounts and types of certain extracellular matrix products synthesized by the various cell types, and the best methods for separation and culture of the individual glomerular cell types. There remain many fruitful areas for research. Fundamental questions such as the appropriate basal medium and supplements, the type of substrate, and the means to separate the individual cell types remain as unanswered or partially answered questions. When isolated cells are reliably obtained, the study of biosynthetic products in the resting and stimulated states must be again addressed. At that point, the effect of various and deliberate combinations of the glomerular cell types on the biosynthetic or proliferative responses will require further studies. For instance, although contractility mediated by receptors for angiotensin II has been assumed to be a specific property of mesangial cells, recent work shows that epithelial cells also respond to angiotensin II. In addition, the handling of immune complexes by various cells needs to be further investigated. Similarly, the pharmacologic response of the diverse populations of glomerular cells represents another area of study that has just begun. Finally, these data will provide the backdrop on which the analysis of various induced and genetic diseases can be performed. These studies are premature until all of the components of the assay system, including glomerular cells, are as pure and well characterized as possible.