Regulation of PDGF-BB signaling in placental pericytes by soluble PDGFRβ isoforms: implications for fetoplacental vascular development.

Vascular remodeling within the developing fetus and placenta is essential for supporting the growth and function of emerging tissues and organs. Pericytes (PCs) play a central role in stabilizing and maturing microvascular networks by extending along endothelial cells (ECs) and reinforcing vessel integrity. In the placenta, as in other organs, PC-EC communication is mediated in part by platelet-derived growth factor-BB (PDGF‑BB) signaling, which governs PC differentiation, proliferation, migration, and survival, ultimately enabling their recruitment and retention along capillaries. In this study, we identified progressive PC investment along feto‑placental capillaries in both murine and human tissues across gestation, supported by morphological and molecular evidence. Placental PCs displayed phenotypic heterogeneity comparable to that observed in the brain and heart, suggesting conserved diversity across organ systems. In addition to characterizing PC dynamics, we examined the expression of recently identified soluble PDGF Receptor-β (sPDGFRβ) isoforms. These variants were detected at the protein and transcript levels in mouse and human placentas, as well as in a murine trophoblast‑embryonic stem cell (TESC) differentiation model that recapitulates aspects of early placental vascular development. Within this model, sPDGFRβ expression was independent of ADAM10 activity and exogenous growth factors during early vessel formation but was markedly upregulated during hypoxia. To assess how elevated sPDGFRβ might influence PDGF‑BB signaling, we exposed TESC‑derived vascular networks to excess PDGF‑BB with or without a sPDGFRβ mimetic. PDGF‑BB alone reduced full‑length PDGFRβ levels while increasing receptor phosphorylation, consistent with known ligand‑induced regulatory mechanisms. Inclusion of the sPDGFRβ mimetic shifted these responses toward baseline, suggesting a potential modulatory or feedback role for soluble receptor variants. Together, these findings demonstrate that PCs are progressively recruited to placental capillaries and exhibit diverse phenotypes during development, and that soluble PDGFRβ isoforms may modulate PDGF‑BB signaling in a manner sensitive to oxygen tension. Understanding these mechanisms provides insight into the regulation of placental vascular maturation and may inform strategies to improve human health by targeting disorders rooted in impaired placental development.