The Microenvironment That Regulates Vascular Wall Stem/Progenitor Cells in Vascular Injury and Repair

Figure 1

Proposed model of microenvironment in vascular stem cells niche. The vessel wall comprises an inner layer (intima), a thicker media layer (smooth muscle cells), and an outer layer (adventitia). The intima is mainly composed of a monolayer of endothelial cells (ECs), including mature and terminally differentiated cells (pink) and also endothelial progenitor cells (EPCs) (blue), which can proliferate, migrate, and differentiate into ECs to replace injured ECs in vascular repair. The adventitia is a dynamic layer in active communication with the other vessel wall layers, and it contains various cell types among others, including PCs (CD34⁺/SCa-1⁺ progenitor cells), mesenchymal stem cells (MSCs), macrophages, fibroblasts, adipocytes, pericytes, lymphocytes (B cells and T cells), and NK cells surrounding the neural fibers, lymphatic vessels, and secreted signaling molecules in adventitia.