Mesenchymal stem cell therapy promotes renal repair by limiting glomerular podocyte and progenitor cell dysfunction in adriamycin-induced nephropathy.

We previously reported that in a model of spontaneously progressive glomerular injury with early podocyte loss, abnormal migration, and proliferation of glomerular parietal epithelial progenitor cells contributed to the formation of synechiae and crescentic lesions. Here we first investigated whether a similar sequence of events could be extended to rats with adriamycin (ADR)-induced nephropathy. As a second aim, the regenerative potential of therapy with bone marrow-derived mesenchymal stem cells (MSCs) on glomerular resident cells was evaluated. In ADR-treated rats, decrease of WT1(+) podocyte number due to apoptosis was associated with reduced glomerular expression of nephrin and CD2AP. As a consequence of podocyte injury, glomerular adhesions of the capillary tuft to the Bowman's capsule were observed, followed by crescent-like lesions and glomerulosclerosis. Cellular components of synechiae were either NCAM(+) parietal progenitor cells or nestin(+) podocytes. In ADR rats, repeated injections of MSCs limited podocyte loss and apoptosis and partially preserved nephrin and CD2AP. MSCs attenuated the formation of glomerular podocyte-parietal epithelial cell bridges and normalized the distribution of NCAM(+) progenitor cells along the Bowman's capsule, thereby reducing glomerulosclerosis. Finding that MSCs increased glomerular VEGF expression and limited microvascular rarefaction may explain the prosurvival effect by stem cell therapy. MSCs also displayed anti-inflammatory activity. Coculture of MSCs with ADR-damaged podocytes showed a functional role of stem cell-derived VEGF on prosurvival pathways. These data suggest that MSCs by virtue of their tropism for damaged kidney and ability to provide a local prosurvival environment may represent a useful strategy to preserve podocyte viability and reduce glomerular inflammation and sclerosis.

The role of chemokines in progressive renal disease.

Tubulointerstitial damage followed by scarring and progressive loss of renal function is common to many forms of chronic proteinuric nephropathies. The severity of tubulointerstitial injury and in particular interstitial macrophage infiltration strongly correlate with the risk of renal failure. Proteins filtered through the glomerular capillary in excessive amount activate proximal tubular cells to upregulate chemokines mainly via activation of NF-kappaB-dependent pathway. Chemokines secreted toward the basolateral compartment of tubular epithelial cells incite local recruitment of mononuclear cells, that in turn interact with resident renal cells and extracellular matrix to create a proinflammatory microenvironment that amplifies tubulointerstitial inflammation and promotes renal scarring. The association between proteinuria and interstitial accumulation of inflammatory cells via activation of transcription factors and overexpression of chemokines has been established both experimentally and in human proteinuric nephropathies. Blocking leukocyte recruitment by interfering with transcription factor activity or chemokines and their receptors is envisioned as a strategy to retard kidney disease progression.