Renal interstitial fibroblasts coproduce erythropoietin and renin under anaemic conditions

Abstract

Background Erythrocyte mass contributes to maintaining systemic oxygen delivery and blood viscosity, with the latter being one of the determinants of blood pressure. However, the physiological response to blood pressure changes under anaemic conditions remain unknown. Methods and Findings We show that anaemia decreases blood pressure in human patients and mouse models. Analyses of pathways related to blood pressure regulation demonstrate that anaemia enhances the expression of the gene encoding the vasopressor substance renin in kidneys. Although kidney juxtaglomerular cells are known to continuously produce renin, renal interstitial fibroblasts are identified in the present study as a novel site of renin induction under anaemic hypotensive conditions in mice and rats. Notably, some renal interstitial fibroblasts are found to simultaneously express renin and the erythroid growth factor erythropoietin in the anaemic mouse kidney. Antihypertensive agents but not hypoxic stimuli induced interstitial renin expression, suggesting that blood pressure reduction triggers interstitial renin induction in anaemic mice. The interstitial renin expression was also detected in injured fibrotic kidneys of the mouse and human, and the renin-expressing interstitial cells in murine fibrotic kidneys were identified as myofibroblasts originating from renal interstitial fibroblasts. Since the elevated expression levels of renin in fibrotic kidneys along with progression of renal fibrosis were well correlated to the systemic blood pressure increase, the renal interstitial renin production seemed to affect systemic blood pressure. Interpretation Renal interstitial fibroblasts function as central controllers of systemic oxygen delivery by producing both renin and erythropoietin. Funding Grants-in-Aid from Japan Society for the Promotion of Science (JSPS) KAKENHI (17K19680, 15H04691, and 26111002) and the Takeda Science Foundation.

Effects of Roxadustat on Erythropoietin Production in the Rat Body

“…In contrast, severe hypoxia and ROX stimulate Epo production through renal erythropoietin producing (REP) cells [ 34 , 39 , 40 , 41 , 42 , 43 , 44 ] and increase the plasma Epo concentration. Our immunohistochemistry showed that both ROX and severe hypoxia increase Epo production by interstitial cells but not by tubular cells.…”

Gene expression changes related to bone mineralization, blood pressure and lipid metabolism in mouse kidneys after space travel

“…Because blood pressure and fluid volume are principally controlled by the renin-angiotensin-aldosterone system (RAAS), [32][33][34] we investigated the expression of RAAS-related genes. Of renal RAAS-related genes, the expression of Ren1 and Ace2 (encoding renin and angiotensin-converting enzyme 2, respectively) genes was altered by space travel, whereas that of Agtr1 and Ace (encoding angiotensin receptor 1 and angiotensin-converting enzyme 1, respectively) genes was not b a s i c r e s e a r c h 3a).…”

Efficient isolation of interstitial fibroblasts directly from mouse kidneys or indirectly after ex vivo expansion

“…This protocol describes how to efficiently isolate living interstitial fibroblasts from mouse kidneys and expand them in ex vivo cultivation. Because a subset of interstitial fibroblasts in the renal cortex, which are referred to as renal erythropoietin (Epo)-producing (REP) cells, play key roles in Epo production, renin production and kidney fibrosis ( Obara et al., 2008 ; Souma et al., 2013 , 2016 ; Suzuki and Yamamoto, 2016 ; Miyauchi et al., 2021 ), this protocol features the manipulation of REP cells. This protocol was established using a genetically modified mouse line in which REP cells were efficiently labeled with the tdTomato red fluorescent protein via the transgene expression of Cre recombinase under the control of mouse Epo gene regulatory regions ( Yamazaki et al., 2013 ; Suzuki et al., 2016 ).…”

“…Following this protocol, we collected approximately 3000 primary REP cells on average from the kidneys of an adult REP cell-labeled mouse ( Yamazaki et al., 2013 ). Sufficient amounts (1×10 5 cells) of cells for reverse transcription-quantitative PCR (RT-qPCR) analyses were collected by repeating steps 1–19 of this protocol ( Souma et al., 2013 ; Miyauchi et al., 2021 ). Alternatively, to conduct RT-qPCR analyses with a small number of REP cells, a CellAmp Whole Transcriptome Amplification Kit (Takara, Cat# 3734) was successfully used.…”

“…For complete details on the use and execution of this protocol, please refer to Sato et al. (2019a) and Miyauchi et al. (2021) .…”