Fig. 2: Rete ridges support epidermal thickening.
From: Rete ridges form via evolutionarily distinct mechanisms in mammalian skin
a, Representative H&E stains of mature skin from across Mammalia: bottlenose dolphin, Yucatan miniaturized ‘hairless’ pig, domestic pig, Mangalitsa pig, human, North American grizzly bear, rhesus macaque, naked mole rat, common marmoset and 6 mo mouse skin. b, Representative images of hair density from across Mammalia. c, Rete ridges drive epidermal thickening in mammalian skin. Quantification of trunk skin histology for epidermal thickness (with rete ridges, if applicable) (left), ratio of rete ridge to inter-ridge thickness (middle) and rete ridge density (per mm) (right) in the bottlenose dolphin (n = 3), Yucatan miniaturized pig (n = 1), 6–7 mo adult domestic pig (n = 10), Mangalitsa pig (n = 3), human (n = 13), North American grizzly bear dorsal rump (n = 11), rhesus macaque (n = 6), naked mole rat (n = 8), common marmoset (n = 6) and adult mouse (n = 15) are shown. Replicates in a are the same as in c. Shared letters indicate no significant difference (P > 0.05), and different letters indicate significant difference (P < 0.05) according to one-way analysis of variance plus Tukey’s HSD (exact P values are provided in the source data). For a–c, see Extended Data Fig. 2a for visual representations of anatomical sites for all species and Methods for more detail. d, Rete ridges increase epidermal thickness in non-furry skin. Left, quantification of hair density images from adult mice (n = 10), rhesus macaques (n = 6), grizzly bears (n = 11), Mangalitsa pigs (n = 3), 7 mo domestic pigs (n = 3) and adult humans (n = 8). Hair density was imaged and quantified as in b, except for human samples (see Methods for complete details). Right, correlation between epidermal thickness (with rete ridges, if applicable) and hair density. The correlation statistic shown is the adjusted coefficient of determination, P = 2.407 × 10−11. e, LEF1 is broadly expressed in fetal mammalian epidermis. Representative immunostains of GW12 human skin stained for KRT15 and LEF1 (left, n = 1) and GW15 marmoset trunk skin stained for ITGA6 and LEF1 (right, n = 3) are shown. f, Epidermal LEF1 controls hair density by regulating placode formation in trunk skin. Representative immunostains of P0 wild-type (WT) (left, n = 3) and P0 K14-Cre;Lef1fl/fl (Lef1-eKO) (centre, n = 3) mouse trunk skin for ITGA6 and LEF1 are shown. Right, representative image of P21 WT (top, n = 3) and P21 Lef1-eKO (bottom, n = 3) female littermates. Histology scale bars, 100 μm (a,e,f); scale bar, 1 mm (b); littermate scale bar, 1 cm (f). DC, dermal condensate. Photograph in b was reproduced with permission from Tania Issa. Cetacean illustrations in were obtained from the National Oceanic and Atmospheric Agency (NOAA) Fisheries Species Directory entries for bottlenose dolphin. Other illustrations in a–f were created using BioRender. Thompson, S. (2026) https://BioRender.com/8rd8cz9.
