Pericytes (PCs) are essential for regulating endothelial cell (EC) behavior and vascular development. This study used PDGF-B and PDGFR-β knockout mice to investigate the role of PCs in brain angiogenesis. The absence of PCs led to EC hyperplasia, increased capillary diameter, abnormal EC morphology, and altered junctional proteins, resulting in increased vascular permeability. These changes were observed as early as embryonic day (E) 11.5 and persisted through development. VEGF-A levels were upregulated, contributing to vascular abnormalities and edema in late gestation. The study also found that PCs influence EC number and morphology, but not microvessel density or branching. The lack of PCs may lead to increased VEGF-A levels, which further disrupts vascular architecture and promotes vascular leakage. The findings suggest that PCs play a critical role in maintaining normal vascular development and function, and their absence can lead to severe vascular and systemic abnormalities. The study highlights the complex interplay between PCs, VEGF-A, and other factors in vascular development and disease.Pericytes (PCs) are essential for regulating endothelial cell (EC) behavior and vascular development. This study used PDGF-B and PDGFR-β knockout mice to investigate the role of PCs in brain angiogenesis. The absence of PCs led to EC hyperplasia, increased capillary diameter, abnormal EC morphology, and altered junctional proteins, resulting in increased vascular permeability. These changes were observed as early as embryonic day (E) 11.5 and persisted through development. VEGF-A levels were upregulated, contributing to vascular abnormalities and edema in late gestation. The study also found that PCs influence EC number and morphology, but not microvessel density or branching. The lack of PCs may lead to increased VEGF-A levels, which further disrupts vascular architecture and promotes vascular leakage. The findings suggest that PCs play a critical role in maintaining normal vascular development and function, and their absence can lead to severe vascular and systemic abnormalities. The study highlights the complex interplay between PCs, VEGF-A, and other factors in vascular development and disease.