Prolactin delays hair regrowth in mice

Abstract

Mammalian hair growth is cyclic, with hair-producing follicles alternating between active (anagen) and quiescent (telogen) phases. The timing of hair cycles is advanced in prolactin receptor (PRLR) knockout mice, suggesting that prolactin has a role in regulating follicle cycling. In this study, the relationship between profiles of circulating prolactin and the first post-natal hair growth cycle was examined in female Balb/c mice. Prolactin was found to increase at 3 weeks of age, prior to the onset of anagen 1 week later. Expression of PRLR mRNA in skin increased fourfold during early anagen. This was followed by upregulation of prolactin mRNA, also expressed in the skin. Pharmacological suppression of pituitary prolactin advanced dorsal hair growth by 3 . 5 days. Normal hair cycling was restored by replacement with exogenous prolactin for 3 days. Increasing the duration of prolactin treatment further retarded entry into anagen. However, prolactin treatments, which began after follicles had entered anagen at 26 days of age, did not alter the subsequent progression of the hair cycle. Skin from PRLR-deficient mice grafted onto endocrine-normal hosts underwent more rapid hair cycling than comparable wild-type grafts, with reduced duration of the telogen phase. These experiments demonstrate that prolactin regulates the timing of hair growth cycles in mice via a direct effect on the skin, rather than solely via the modulation of other endocrine factors.

Calcineurin/Nfatc1 signaling links skin stem cell quiescence to hormonal signaling during pregnancy and lactation

“…Since multiple hormones change during pregnancy and lactation, Stat5 activation in bulge SCs could be due to Prl or another molecular factor. To test whether p-Stat5 activity is downstream from Prl signaling, we reduced systemic Prl levels with bromocriptine (BRC), a dopamine agonist that depletes secretion of pituitary Prl (Craven et al 2006;Larsen and Grattan 2010). We confirmed that treatment of mice with a low dose of BRC during pregnancy diminished serum Prl levels to nonpregnant levels while still permitting successful lactation (Fig.…”

“…2A). This finding was particularly interesting given that Prl signaling has previously been implicated in the regulation of hair growth (Craven et al 2001(Craven et al , 2006Foitzik et al 2003Foitzik et al , 2006). However, a role for Prl signaling in the regulation of bulge SC activity has not been reported.…”

“…3A; data not shown) despite the expression of Prlr in the bulge (Fig. 2E) and the hair cycling phenotype of Prlr-null mice during the native hair cycle (Craven et al 2001(Craven et al , 2006. Outside the epithelium, p-Stat5 was detected in the DP throughout the native hair cycle (Fig.…”

“…Prl receptors (Prlrs) are expressed within the HF in both mice and humans, and Prl can induce follicle death in cultured skin tissue from both species (Foitzik et al 2003(Foitzik et al , 2006. Exogenous Prl delays hair growth in murine skin associated with inhibition of Prl secretion during the native hair cycle (Craven et al 2006), and Prlr knockout mice exhibit precocious hair growth during native hair cycling and in skin grafts (Craven et al 2001(Craven et al , 2006, indicating a functional role for Prl signaling in the skin. Despite these findings, whether Prl signaling acts directly on follicular SCs to regulate hair growth under native conditions or during pregnancy is not clear.…”

Biology of Human Hair: Know Your Hair to Control It

“…Prolactin is implicated in hair growth regulation in both mice and human [112][113][114]. Similarly, melatonin has been reported to promote hair growth in animals and in humans, where topical application of melatonin induced hair, probably through induction of anagen [115].…”