Figure S1. Expression of the Fibroblast Marker CD34 and Pdgfra, the Smooth Muscle Cell Marker a-Smooth Muscle Actin and the ImmuneCell Marker CD45 across Old and Young Murine Dermis, Related to Figure 1(A) Immunohistochemistry of Pdgfra and CD34 on young and old skin sections. Both Pdgfra and CD34 are expressed in cells throughout the dermis in young skin(upper panel) and old skin (lower panel).(B) Immunohistochemistry of CD34 and a- smooth muscle actin on young and old skin sections. The a-smooth muscle actin + arrector pili muscle (indicated witharrows) is negative for CD34 in young skin (upper panel) and old skin (lower panel).(C) CD45 staining in young and old skin. We did not observe a notable increase in CD45+ immune cells in old dermis. E, epidermis; H, hair follicle; D, dermis;S, subdermis.