Objective   To study the patterns of the presence and distribution of pericytes in granulation tissue of wound repair and the related significance.     Methods   Granulation tissue samples were collected from mice suffered from full-thickness skin excision on 1

3

5

7

and 9 d after injury. Single and double immunohistochemical staining

electron microscopy

and quantitative analysis of morphology were applied to study the presence and distribution of pericytes during angiogenesis of granulation tissues. Meanwhile

in vitro transforming growth factor-β1 (TGF-β1)-induced differentiation of 10T1/2 cell

a progenitor of pericyte

was assessed in 3-dimensional extracellular matrix (ECM) gel.     Results   Pericytes were found in the early stage of wound repair. The number of pericytes positive to staining was higher than that of endothelial cells in the new microvessels. The number of capillaries and pericytes in granulation kept increasing till 5 d after the injury. The pericytes stimulated with TGF-β1 were able to form cell cords and clumps in vivo and cell cord- or lumina-like structure in ECM gel in vitro.     Conclusion   Pericytes participate in the early angiogenesis in the wound healing and the formed cell cord or lumina structure may play a crucial or guiding role in angiogenesis.