Characterization and Ischemic Response of Telecytes in the Mouse Renal Medulla

Abstract

Telocytes are currently defined as a novel type of interstitial (stromal) cells with very long and thin prolongations, and these cells can produce exosomes to transmit signals to different cells such as vascular smooth muscle cells, tubular cells and telocytes themselves. So far it remains unclear whether telocytes are present in the renal medulla and whether they are able to regulate renal medullary function. In the present study, we first characterized telocytes in the kidney, in particular, in the renal medulla, given that the renal medullary interstial cells (RMICs) are able to sense pressure and release bioactive lipids lowering arterial blood pressure. Using two selective markers of telocytes, CD34 and c‐kit for immunohistochemical analysis, we found that telocytes are present in the renal medullary interstitium between tubules, vessels or tubular‐blood vessels. Compared to the renal cortex, telocytes are more enriched in the renal medulla. Their long prolongations could be seen in the interstitium along the tubules or blood vessels. Using confocal microscopy, colocalization of CD34 and c‐kit are mainly detected around different tubules or vessels, but not in tubular or vascular cells. Electron microscopy found that many renal medullary telocytes had at least 3 prolongations, where a number of telopods were shown. In some interstitial space with enriched telopods, moreover, a large number of exosomes could be found. We also isolated and cultured telocytes, which were purified from renal medullary interstitial cells used in our laboratories by MiniMACS Cell Separator with anti‐c‐kit antibody beads‐loaded column. In culture, these cells showed typical telocyte features such as more than 3 prolongations, telopods and project connections between cells. Confocal microscopy showed that most cells through MiniMacs column could be double stained by antibodies against c‐kit and CD34, but the original renal medullary institial cells had much fewer cells stained, which was also confirmed by flow cytometry. In a group of mice with 2 kidney‐1 clip (2K1C) hypertensive model, we found that compared to the unclipped kidney, the clipped kidney had largely increased CD34 and c‐kit staining in the renal medullary interstitium, but not much in the renal cortex. These results suggest that telocytes are present in the renal medullary interstitium and in response to chronic ischemia produced by partially clipping renal artery, telocytes are increased. Given that exosomes are substantially enriched in the renal medulla of 2K1C mice, telocytes may be one of the important source for these exosomes that have antihypertensive action (Supported by NIH grants DK054927 and DK120491).