Hormones – Cytokines – Signaling
Kidney International (1999) 55, 808–820; doi:10.1046/j.1523-1755.1999.055003808.x
Human, rat, and mouse kidney cells express functional erythropoietin receptors
CHRISTOF WESTENFELDER, DIANA L BIDDLE and ROBERT L BARANOWSKI
Division of Nephrology, VA and University of Utah Medical Centers, Salt Lake City, Utah, USA
Correspondence: Christof Westenfelder, M.D., Section of Nephrology (111 N), VA Medical Center, 500 Foothill Boulevard, Salt Lake City, Utah 84148, USA. E-mail: Westenfelder@pol.net
Received 23 June 1998; Revised 15 September 1998; Accepted 22 September 1998.
Abstract
Cells of human, rat, and mouse kidney express functional erythropoietin receptors.
Background
Erythropoietin (EPO), secreted by fibroblast-like cells in the renal interstitium, controls erythropoiesis by regulating the survival, proliferation, and differentiation of erythroid progenitor cells. We examined whether renal cells that are exposed to EPO express EPO receptors (EPO-R) through which analogous cytokine responses might be elicited.
Methods
Normal human and rat kidney tissue and defined cell lines of human, rat, and mouse kidney were screened, using reverse transcription-polymerase chain reaction, nucleotide sequencing, ligand binding, and Western blotting, for the expression of EPO-R. EPO's effects on DNA synthesis and cell proliferation were also examined.
Results
EPO-R transcripts were readily detected in cortex, medulla, and papilla of human and rat kidney, in mesangial (human, rat), proximal tubular (human, mouse), and medullary collecting duct cells (human). Nucleotide sequences of EPO-R cDNAs from renal cells were identical to those of erythroid precursor cells. Specific 125I-EPO binding revealed a single class of high- to intermediate-affinity EPO-Rs in each tested cell line (kD 96 pM to 1.4 nM; Bmax 0.3 to 7.0 fmol/mg protein). Western blots of murine proximal tubular cell membranes revealed an EPO-R protein of approximately 68 kDa. EPO stimulated DNA synthesis and cell proliferation dose dependently.
Conclusion
This is the first direct demonstration, to our knowledge, that renal cells possess EPO-Rs through which EPO stimulates mitogenesis. This suggests currently unrecognized cytokine functions for EPO in the kidney, which may prove beneficial in the repair of an injured kidney while being potentially detrimental in renal malignancies.
Keywords:
EPO, mitogenesis, erythropoiesis, injury repair, renal malignancies
Abbreviations:
EGF, epithelial growth factor; EPO, erythropoietin; EPO-R, erythropoietin receptor; HCT, human proximal tubule cells; HMC, human mesangial cells; HMCD, human medullary collecting duct cells; IGF, insulin-like growth factor; MCT, murine tubular cells; MTT, 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide); NCS, newborn calf serum; OCIM, human erythroleukemia cell line; PBS, phosphate buffered saline; rHuEPO, recombinant human erythropoietin; RMC, rat mesangial cells; RT-PCR, reverse transcription-polymerase chain reaction
