Type IV Collagen Induces Podocytic Features in Bone Marrow Stromal Stem Cells In Vitro

Abstract

Bone marrow-derived stromal stem cells (BMSC) can differentiate along a variety of mesenchymal lines, including mesangial cells. For determining whether BMSC can be induced to differentiate along podocytic lines in vitro, canine BMSC were cultured on plastic, type I collagen, and NC1 hexamers of type IV collagen from normal and Alport canine glomerular basement membrane. Results were compared with a mouse podocyte cell line. In the case of the podocyte line, differentiation occurred on all three matrices as indicated by the expression of synaptopodin and CD2-associated protein (CD2AP) and organization of myosin heavy chain IIA into a linear pattern. BMSC proliferated equally well on all matrices, but cells that were grown on type IV collagen NC1 hexamers became larger and stellate. Evidence for podocytic differentiation occurred on all three collagen matrices as indicated by the redistribution of myosin IIA to a linear pattern and expression of synaptopodin, CD2AP, and ␣-actinin. A punctate distribution of CD2AP was seen only in cells that were grown on normal and Alport glomerular basement membrane NC1 hexamers. Differentiated podocytes expressed the ␣1, ␣2, and ␣5 chains of type IV collagen but at higher levels in cells that were grown on NC1 hexamers. Similar results were obtained in BMSC for the ␣1 and ␣2 chains only. The ␣3, ␣4, and ␣6 chains were never detected in the podocyte line or BMSC. These results indicate that BMSC undergo a degree of podocytic differentiation in vitro and greater when grown on type IV collagen NC1 hexamers than type I collagen. Alport and normal NC1 hexamers seem equally permissive to BMSC growth and differentiation, suggesting that these processes are not influenced specifically by the ␣3/␣4/␣5 network. BMSC may be useful in the development of stem cell-based reconstitution of glomeruli that are damaged by disease and for gene therapy of genetic glomerular diseases such as Alport syndrome.

Cellular Origins of Type IV Collagen Networks in Developing Glomeruli

“…31 Immortalized podocytes also synthesize more ␣5(IV) collagen when cultured on NC1 hexamers of collagen IV purified from normal canine GBM. 32 Taking together all of the previous reports and our results presented here, there is now highly compelling evidence that podocytes synthesize GBM collagen ␣3␣4␣5(IV). However, the finding that collagen ␣1␣2␣1(IV) originates from both glomerular endothelial cells and podocytes, but collagen ␣3␣4␣5(IV) comes from podocytes alone, was unexpected.…”

Podocyte Number in Children and Adults

“…Other lines of evidence suggest that new podocytes may arise from bone marrow. [62][63][64] In this study, WT-1+PECs (parietal podocytes) were observed near the vascular pole in most glomeruli in children and adults, and some WT-1+cells were occasionally observed in the tunica intima and the tunica media of arterioles in the JGA. Whether any of these cells give rise to new podocytes deserves additional attention.…”

Bone marrow-derived mesenchymal stem cells ameliorate nephrosis through repair of impaired podocytes

“…Similarly, in vitro co-culture of BMSC and podocytes treated with doxorubicin showed elevated endothelial growth factor and reduced injury in podocytes [17]. Another study indicates that BMSC undergo a degree of podocytic differentiation in vitro [46]. In another study [47] using a model of autosomally-recessive Alport syndrome mice, Prodromidi et al showed that a) an apparent podocyte phenotype was showed in mice transplanted with bone marrow, b) the podocyte defect was rectified and c) glomerular scarring and interstitial fibrosis were also significantly decreased.…”