Interesting find. There's quite of bit of research out there on prolactin and hair cycle effects. This is a bit dated, but will include as relevant:
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Prolactin and its receptor are expressed in murine hair follicle epithelium, show hair cycle-dependent expression, and induce catagen.
Authors:
Foitzik K; Department of Dermatology, University Hospital Hamburg-Eppendorf, University of Hamburg, Hamburg, Germany.
Krause K
Nixon AJ
Ford CA
Ohnemus U
Pearson AJ
Paus R
Source:
The American Journal Of Pathology [Am J Pathol] 2003 May; Vol. 162 (5), pp. 1611-21.
Publication Type:
Journal Article; Research Support, Non-U.S. Gov't
Language:
English
Journal Info:
Publisher: Elsevier Country of Publication: United States NLM ID: 0370502 Publication Model: Print Cited Medium: Print ISSN: 0002-9440 (Print) Linking ISSN: 00029440 NLM ISO Abbreviation: Am. J. Pathol. Subsets: Core Clinical (AIM); MEDLINE
Imprint Name(s):
Publication: 2011-: New York : Elsevier
Original Publication: Philadelphia [etc.] American Assn. of Pathologists [etc.]
MeSH Terms:
Cell Cycle/*physiology
Hair/*growth & development
Hair Follicle/*physiology
Prolactin/*genetics
Receptors, Prolactin/*genetics
Animals ; Base Sequence ; DNA Primers ; Epithelial Cells/cytology ; Epithelial Cells/physiology ; Female ; Gene Expression Regulation ; Hair/cytology ; HairFollicle/cytology ; Humans ; Keratinocytes/cytology ; Keratinocytes/physiology ; Mice ; Mice, Inbred C57BL ; Models, Animal ; Placental Lactogen/genetics; Polymerase Chain Reaction ; Skin/cytology ; Skin Physiological Phenomena
Abstract:
Here, we provide the first study of prolactin (PRL) and prolactin receptor (PRLR) expression during the nonseasonal murine hair cycle, which is, in contrast to sheep, comparable with the human scalp and report that both PRL and PRLR are stringently restricted to the hair follicle epithelium and are strongly haircycle-dependent. In addition we show that PRL exerts functional effects on anagen hair follicles in murine skin organ culture by down-regulation of proliferation in follicular keratinocytes. In telogen follicles, PRL-like immunoreactivity was detected in outer root sheath (ORS) keratinocytes. During early anagen (III to IV), the developing inner root sheath (IRS) and the surrounding ORS were positive for PRL. In later anagen stages, PRL could be detected in the proximal IRS and the inner layer of the ORS. The regressing (catagen) follicle showed a strong expression of PRL in the proximal ORS. In early anagen, PRLR immunoreactivity occurred in the distal part of the ORS around the developing IRS, and subsequently to a restricted area of the more distal ORS during later anagen stages and during early catagen. The dermal papilla (DP) stayed negative for both PRL and PRLR throughout the cycle. Telogen follicles showed only a very weak PRLR staining of ORS keratinocytes. The long-form PRLR transcript was shown by real-time polymerase chain reaction to be transiently down-regulated during early anagen, whereas PRL transcripts were up-regulated during mid anagen. Addition of PRL (400 ng/ml) to anagen hair follicles in murine skin organ culture for 72 hours induced premature catagen development in vitro along with a decline in the number of proliferating hair bulb keratinocytes. These data support the intriguing concept that PRL is generated locally in the hair follicle epithelium and acts directly in an autocrine or paracrine manner to modulate the hair cycle.
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