Cell surface markers in normal and diseased kidney
Cell surface receptors such as adhesion molecules and connexins are involved in interactions between cells and their surroundings. They play important roles in the normal function of healthy tissues and in the responses of cells to injury. In many cases aberrant repair mechanisms are thought to result in disease and this thesis will assess the expression of cell adhesion molecules (principally the pi integrins) and the connexin43 gap junction protein in normal and diseased kidney The expression of pi integrins on normal human mesangial cells was localised using the alkaline phosphatase anti-alkaline phosphatase immunochemical technique (APAAP) and Western blotting. Expression of mRNA coding for integrins was also assessed using reverse-transcription polymerase chain reaction (RT-PCR). Human mesangial cells in culture expressed the a2, a3, av, pi av and P3 integrin chains. Messenger RNA was detected for these integrin subunits plus the al, a4, a5 and a6 chains. Normal human kidney sections were stained using APAAP and monoclonal antibodies towards a wide range of integrin chains. Within the glomerulus, mesangial cells express al, a2 and pi, epithelial cells a3, av and pi and endothelial cells al, a5 and pi. Tubules express a2, a3, a6, av and pi and the interstitium al and pi. In renal biopsies from patients with IgA disease the main alterations in integrin expression were upregulation of a2, a3, av and pi on damaged tubules, with increased pi expression and de novo a5 and av staining within areas of interstitial damage. These changes were replicated in a wide range of other renal pathologies and correlate with the degree of tubulointerstitial histological damage. Connexin43 (Cx43) is distributed extensively on normal human kidney, particularly on glomerular epithelial cells and intra- and extra-glomerular endothelium. Human mesangial cells in vitro express Cx43 protein and its coding mRNA. There is, however, no expression of Cx43 by the mesangium in vivo. In biopsies from patients with inflammatory renal disease there is strong expression of Cx43 on infiltrating inflammatory cells, in areas of interstitial damage and on damaged tubules. The pattern of Cx43 expression in inflammatory renal disease was very similar to that of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1. The work in this thesis has demonstrated the large repertoire of cell surface receptors expressed on normal kidney. The principal alterations in diseased kidney are found within the tubulointerstitum. The potential relevance of these changes in the pathogenesis of renal disease are discussed and possible future avenues of research are suggested.