PDGF receptor signal mediates the contribution of Nestin-positive cell lineage to subcutaneous fat development.

The beiging of white adipose tissue (WAT) is expected to improve systemic metabolic conditions; however, the regulation and developmental origin of this process remain insufficiently understood. In the present study, the implication of platelet-derived growth factor receptor alpha (PDGFRα) was examined in the beiging of inguinal WAT (ingWAT) of neonatal mice. Using in vivo Nestin expressing cell (Nestin+) lineage tracing and deletion mouse models, we found that, in the mice with Pdgfra gene inactivation in Nestin+ lineage (N-PRα-KO mice), the growth of inguinal WAT (ingWAT) was suppressed during neonatal periods as compared with control wild-type mice. In the ingWAT of N-PRα-KO mice, the beige adipocytes appeared earlier that were accompanied by the increased expressions of both adipogenic and beiging markers compared to control wild-type mice. In the perivascular adipocyte progenitor cell (APC) niche of ingWAT, many PDGFRα+ cells of Nestin+ lineage were recruited in Pdgfra-preserving control mice, but were largely decreased in N-PRα-KO mice. This PDGFRα+ cell depletion was replenished by PDGFRα+ cells of non-Nestin+ lineage, unexpectedly resulting in an increase of total PDGFRα+ cell number in APC niche of N-PRα-KO mice over that of control mice. These represented a potent homeostatic control of PDGFRα+ cells between Nestin+ and non-Nestin+ lineages that was accompanied by the active adipogenesis and beiging as well as small WAT depot. This highly plastic nature of PDGFRα+ cells in APC niche may contribute to the WAT remodeling for the therapeutic purpose against metabolic diseases.

Dysregulation of Amphiregulin stimulates the pathogenesis of cystic lymphangioma.

Along with blood vessels, lymphatic vessels play an important role in the circulation of body fluid and recruitment of immune cells. Postnatal lymphangiogenesis commonly occurs from preexisting lymphatic vessels by sprouting, which is induced by lymphangiogenic factors such as vascular endothelial growth factor C (VEGF-C). However, the key signals and cell types that stimulate pathological lymphangiogenesis, such as human cystic lymphangioma, are less well known. Here, we found that mouse dermal fibroblasts that infiltrate to sponges subcutaneously implanted express VEGF-D and sushi, Von Willebrand factor type A, EGF, and pentraxin domain containing 1 (SVEP1) in response to PDGFRß signal. In vitro, Pdgfrb knockout (ß-KO) fibroblasts had reduced expression of VEGF-D and SVEP1 and overproduced Amphiregulin. Dysregulation of these three factors was involved in the cyst-like and uneven distribution of lymphatic vessels observed in the ß-KO mice. Similarly, in human cystic lymphangioma, which is one of the intractable diseases and mostly occurs in childhood, fibroblasts surrounding cystic lymphatics highly expressed Amphiregulin. Moreover, fibroblast-derived Amphiregulin could induce the expression of Amphiregulin in lymphatic endothelial cells. The dual source of Amphiregulin activated EGFR expressed on the lymphatic endothelial cells. This exacerbation cascade induced proliferation of lymphatic endothelial cells to form cystic lymphangioma. Ultimately, excessive Amphiregulin produced by fibroblasts surrounding lymphatics and by lymphatic endothelial cells per se results in pathogenesis of cystic lymphangioma and will be a fascinating therapeutic target of cystic lymphangioma.