Expression of Platelet-Derived Growth Factor (PDGF) in the Epididymis and Analysis of the Epididymal Development in PDGF-A, PDGF-B, and PDGF Receptor β Deficient Mice

The platelet-derived growth factor (PDGF) family of ligands and receptors play a pivotal role in the development of various organs. The critical importance of the PDGF-mediated signaling during embryonic development and adult physiology of the kidney and the common mesonephric origin of the epididymis and kidney prompted us to investigate the immunohistochemical localization of PDGF A- and B-chain and PDGF receptor (PDGFR) α- and β-subunit in rat and mouse epididymis, the expression profiles of the corresponding mRNAs, and the consequences of a loss-of-function mutation at the PDGF-A, PDGF-B, and PDGFR-β loci on mouse epididymis phenotypic appearance. Prenatally, PDGF-A and PDGFR-α immunohistochemical staining was seen in both species, whereas PDGF-B and PDGFR-β were absent. The cellular localization of PDGF-A within the epithelium and the α-receptor in the mesenchyme in either mouse or rat before birth suggests that the PDGF-A/PDGFR-α system might be involved in the epididymal epithelial-mesenchymal interaction during the fetal period of life. Postnatally, PDGF A- and B-ligand and PDGFR α- and β-subunit were confined in the epithelium. The identity of PDGF and PDGFR proteins were further confirmed by immunoblotting. In line with the immunohistochemical studies, PDGF-A and PDGFR-α mRNAs were seen by reverse transcription–polymerase chain reaction in rat and mouse tissue before birth, whereas PDGF-B and PDGFR-β were almost not detectable. During the first days of life, PDGF-B and PDGFR-β genes started to appear, and the overall trend in mRNA expression throughout postnatal development showed that the transcripts levels for PDGF-A, PDGF-B, PDGFR-β, and PDGFR-α were constant with the only exception of a progressive decrease of PDGFR-α in adult rats. The PDGF-A null mutation strongly influenced the epididymal phenotype starting from puberty; only fetal PDGF-B and PDGFR-β −/− mice were available, and no differences were seen in the epididymis of these animals, compared with wild-type littermates. Taken together, these data indicate that the PDGF system is highly expressed in the epididymis and suggest that PDGF could be involved in the maintenance of morphological structure and functional control of this organ.