Figure 1.

The structure of mouse skin. A. A scheme of skin structure illustrates two lipid bio-membranes, colored in yellow. The outer bio-membrane of the ceramide-enriched epidermis is the water-proofing component of skin: ceramide-based lipids of the stratum corneum generate a highly ordered gel phase membrane with restricted mobility, called the epidermal barrier [31]. Junctions between keratinocytes and regulated water flow through aquaporins comprise a key “active” component of the epidermal barrier, reactive on acute time scales; on a slower time scale (days), the lipid composition of the stratum corneum changes as the superficial layers are sloughed and renewed [36]. The thickness of the dermal white adipose tissue (dWAT) is regulated by interaction with microbes, ambient temperature and the stage of the hair cycle, and by genetics, diet and sex [1], [2]. In between lies the dermis, laced with two vascular beds to allow adjustable blood volumes to control heat loss. At the right, for comparison, an H&E stained cross section of mouse skin (panniculus carnosus muscle layer; pan carn). Four adipose depots with different functions were collected for evaluation of vascular density (sites of each depot shown on left; B); dWAT, inguinal (“subcutaneous”) white adipose tissue (iWAT), brown adipose tissue (BAT) and visceral white adipose tissue (vWAT). Sections of each type were stained for podocalyxin, a vascular-associated antigen (C–F), and the density of vessels quantified (G). Sections of each were also stained with smooth muscle actin (SMA) to reveal pericyte-supported blood vessels, perilipin (PLN) to outline adipocytes and DAPI (Nuc) to counter-stain nuclei (H). The scale bar shown is 50 μM and applies to all panels C-F.