Glomerular cells in vitro versus the glomerulus in vivo

Abstract

Early data on glomerular physiology and pathophysiology were largely based on morphological studies and on functional studies of either glomeruli in vivo or isolated glomeruli. The introduction of glomerular cell culture in the late seventies and early eighties has allowed a more specific approach to the role of individual glomerular cell types in the mediation of renal pathology [1–3]. Over the last five years there has been a tremendous increase in studies dealing with cultured glomerular cells. For example, the number of abstracts on mesangial cells in culture that have been presented at the annual meeting of the American Society of Nephrology has increased from about 10 in 1988 to about 150 in 1992. In contrast, only about 25 studies dealt with glomerular epithelial cells last year, and very few with glomerular endothelial cells, which is likely a reflection of the ease at which these cells can be grown out of isolated glomeruli. As discussed in several recent papers, these in vitro studies have shown that glomerular cells have a wide range of synthetic activities and response patterns [this issue of Kidney International, 1–8]. Based on the in vitro characterization of the capabilities of glomerular cells, physiological or pathological pathways have been suggested that may be operative in vivo . However, when working with cells isolated from glomeruli and when attempting to extrapolate to the in vivo situation, several issues need to be addressed. First, what type of cells has been obtained and how do their morphological characteristics compare to those observed in vivo ? Second, is there evidence to suggest that cultured cells exhibit the same synthetic profile as they do in vivo or do they synthesize products that can not be detected in vivo under normal or pathological circumstances? Third, are the responses of cultured glomerular cells comparable to those observed in vivo or do they show response patterns that are restricted to the petri dish? In the following review we will discuss these three issues by way of example rather than by attempting to give a complete overview. Finally, we will restrict our discussion to glomerular mesangial and epithelial cells, since too little information is available on glomerular endothelial cells either in culture or in vivo .