Molecular phenotypes of the human kidney: Myoid stromal cells/telocytes and myoepithelial cells

The connective stromal and epithelial compartments of the kidney have regenerative potential and phenotypic flexibility. A few studies have shown that cells appertaining to both compartments can exhibit myoid phenotypes. The purpose of our study was to investigate the myoid pattern of kidney and its association with the kidney niches containing stromal cells/telocytes (SC/TCs). We performed an immunohistochemical study using a panel of endothelial, myoid, mesenchymal and stem/progenitor markers, namely CD31, CD34, CD105 (endoglin), CD117/c-kit, nestin, desmin, α-smooth muscle actin (α-SMA) and the heavy chain of smooth muscle myosin (SMM). We used histologically normal kidney samples, obtained after nephrectomy, from nine adult patients. The capsular SC/TCs had a strong CD34 and partial nestin and CD105 immunopositivity. Subcapsular and interstitial SC/TCs expressed c-kit, nestin, CD105, but also α-SMA and SMM, therefore having a myoid phenotype. The endothelial SC/TCs phenotype was CD31+/CD34+/CD105+/nestin±/SMM±/α-SMA±. All three myoid markers were expressed in periendothelial SC/TCs. We also found a scarce expression of nestin in parietal epithelial cells of Bowman's capsule, and in podocytes. In epithelial cells, we found a positive expression for CD31, CD117/c-kit, desmin, CD34, SMM, and CD105. In epithelial tubular cells, we found a predominant basal expression of the myoid markers (SMM and desmin). In conclusion, myoepithelial tubular cells, myoid endothelial cells and myoid SC/TCs are normal constituents of the kidney.