A developmental study on the expression of PDGFalphaR immunoreactive cells in the brain of postnatal rats

The platelet-derived growth factor-alpha receptor (PDGFalphaR) has been found specifically expressed in oligodendrocyte precursor cells (OPCs), whereas another membrane protein, NG2, has been widely applied to characterize developing and matured OPCs. In order to investigate whether PDGFalphaR expression is consistent to NG2 in identifying OPCs, we utilized techniques of immunohistochemistry and Western blot to study the PDGFalphaR expression and distribution in rat postnatal brain from a series of ages P0 (postnatal day 0) to P540, and further compared it with NG2. Results showed that PDGFalphaR immunoreactive (PDGFalphaR+) cells existed in both the gray and white matter of the postnatal rat brain, although these cells displayed different features in distinct regions and developmental stages. PDGFalphaR did not express in oligodendrocytes, astrocytes or neurons (indicated by non-co-localization with CC1 and NF200, respectively). Western blot analysis revealed that the expression of PDGFalphaR in the cerebral cortex and hippocampus increased from P0 to P7 and then decreased gradually. PDGFalphaR+ cells displayed similar characteristics as of NG2+ cells in the morphology, distribution and electrophysiology. Like NG2+ cells, the density of PDGFalphaR+ cells had an increase at P7 and a late age-dependent decline, except a lower value from P7 to P540 in cerebral cortex, hippocampus and corpus callosum. PDGFalphaR+ cells exhibited number consistent with NG2+ cells at early developmental stages and were approximately 75% as numerous as NG2+ cells at old age. PDGFalphaR+/NG2- cells were not found. In conclusion, our findings suggest that both PDGFalphaR and NG2 are markers of developing OPCs. PDGFalphaR is specific to the NG2+ OPCs and mainly plays an important role at early developmental stages of OPCs. Aging had an effect on the morphological feature, number and developmental regulation of OPCs in rat CNS. However, further work will be necessary to determine if PDGFalphaR-/NG2+ cells may still maintain the biological characteristics of OPCs or they are other subpopulation of OPCs.