Changes in cell-cycle protein expression during experimental mesangial proliferative glomerulonephritis

Abstract

A characteristic response to mesangial cell injury is proliferation, which is closely linked to mesangial matrix accumulation and the progression of glomerular disease. Cell proliferation in non-renal cells in vitro is regulated at the level of the cell-cycle by specific cyclins and their catalytic partners, cyclin dependent kinases (CDK). Cyclin kinase inhibitors (CKI) prevent proliferation by inhibiting cell-cycle progression. However, the expression of cell-cycle regulatory proteins in the kidney and in renal disease is unknown. To determine this we studied the expression of cell-cycle proteins in vivo in normal rats and rats with experimental mesangial proliferative glomerulonephritis (Thy1 model). Normal quiescent rat glomeruli have a differential expression for CKI's, where p27Kip1 is highly expressed, and the levels for p21 (Cip1, Waf1, Sdi1, Cap20) (p21) are low. The onset of mesangial cell proliferation in Thy1 glomerulonephritis is associated with a reduction in p27Kip1 levels when mesangial cell proliferation is maximal. Mesangial cell proliferation in vivo is also associated with an increase in glomerular expression of cyclin A, and an increase in expression and activity for CDK2. The resolution of mesangial cell proliferation was associated with a return to baseline levels for p27Kip1, while the expression for p21 increased substantially. Furthermore, mesangial cell p21 expression was maintained following the resolution of proliferation. These results provide evidence for a complex interplay of cell-cycle regulatory proteins during the glomerular response to injury in vivo. The marked increase in CDK2 expression during mesangial cell proliferation and the sustained increase in p21 expression following the resolution of mesangial cell proliferation suggests that the in vivo expression of certain cell-cycle proteins may differ from that described in non-renal cells in vitro.

Role of differential and cell type-specific expression of cell cycle regulatory proteins in mediating progressive glomerular injury in human IgA nephropathy

“…[3][4][5]8,10,23 In contrast, we detected a dramatic upregulation of E2F1 in mesangial cells in all IgAN subgroups, with the highest levels of 18.973.0 positive mesangial cells per GCS in glomeruli of subgroup C (Figures 1a and 2a-c). This pattern correlated well with the proliferation index (PI), but not with the glomerulosclerosis score (GS score) and the index of glomerular lesion (IGL), suggesting a role for E2F1 overexpression in mediating mesangial cell proliferation.…”

“…1,2 In the experimental model of mesangial proliferative anti-Thy1.1 nephritis, increased expression of cyclins A, D1 and cyclin-dependent kinase 2 (CDK2) by mesangial cells in association with decreased high endogenous levels of CDK inhibitor (CKI) p27 kip1 by glomerular epithelial cells (GECs), were required for mesangial cell proliferation. [3][4][5] The increased glomerular activity of CDK2 could be inhibited by the CDK antagonist roscovitine resulting in decreased cell proliferation and extracellular matrix production. 6 In contrast, CKIs (p21 waf1 and p27 kip1 ) were persistently increased in passive Heyman nephritis (PHN), a model of experimental membranous nephropathy, in which glomerular epithelial cells (GECs) are the target of complement-mediated injury.…”

Podocyte Biology and Response to Injury

“…toration of normal podocyte number (118). This contrasts with mesangial and glomerular endothelial cells, which readily proliferate in response to many forms of injury (127). There is a large body of literature showing that podocyte proliferation correlates closely with its state of differentiation, which may provide important clues into the mechanisms underlying the lack of proliferation (128).…”

The Rapamycin derivative RAD inhibits mesangial cell migration through the CDK-inhibitor p27KIP1

“…8,24 Utilizing cultured MC from wt, p21 CIP1 -null, p27 KIP1 -null, and p21 CIP1 /p27 KIP1 -double-null mice, we demonstrated that the CDK-inhibitor p27 KIP1 , but not p21 CIP1 plays a critical role in mediating the antimigratory properties of RAD in vitro. The lack of p27 KIP1 in MMC prevented the antimigratory effect of RAD up to a concentration of 10 nM, while higher RAD concentrations were able to inhibit MMC migration in Boyden chamber assays, but to a much lesser extent than in wt-MMC.…”

“…We have previously shown that p27 KIP1 and p21 CIP1 expression is altered during glomerular repopulation in the anti-Thy1 model. 8 The potent antiproliferative rapamycin derivative RAD is a new promising immunosuppressive drug for the treatment of organ and kidney transplantation, and more recently, has been shown to inhibit proliferation via G1/S arrest in inflammatory renal disease. 9 Although RAD and rapamycin are generally considered to lack nephrotoxicity of the calcineurin inhibitors cyclosporine and tacrolimus, we (unpublished results) and others 10 have recently demonstrated detrimental long term effects on the glomerular architecture when RAD therapy was given during the early proliferative/migratory phase of anti-Thy1 nephritis.…”