Bone-marrow-derived stem cells repair basement membrane collagen defects and reverse genetic kidney disease

Type IV collagen is a predominant component of basement membranes, and glomeruli of a kidney filter ≈70-90 liters of plasma every day through a specialized glomerular basement membrane (GBM). In Alport syndrome, a progressive disease primarily affecting kidneys, mutations in GBM-associated type IV collagen genes (COL4A3, COL4A4, or COL4A5) lead to basement membrane structural defects, proteinuria, renal failure, and an absence of all three GBM collagen triple helical chains because of obligatory posttranslational assembly requirements. Here, we demonstrate that transplantation of wild-type bone marrow (BM) into irradiated COL4A3^-/- mice results in a possible recruitment of BM-derived progenitor cells as epithelial cells (podocytes) and mesangial cells within the damaged glomerulus, leading to a partial restoration of expression of the type IV collagen α3 chain with concomitant emergence of α4 and α5 chain expression, improved glomerular architecture associated with a significant reduction in proteinuria, and improvement in overall kidney histology compared with untreated COL4A3^-/- mice or irradiated COL4A3^-/- mice with BM from adult COL4A3^-/- mice. The α3(IV) collagen produced by BM-derived podocytes integrates into the GBM and associates with other α-chains to form type IV collagen triple helical networks. This study demonstrates that BM-derived stem cells can offer a viable strategy for repairing basement membrane defects and conferring therapeutic benefit for patients with Alport syndrome.