Background/Purpose: Estradiol (E2), one of the three forms of estrogen, is pro-fibrotic in the skin because it positively influences ECM production in the dermis. In addition to the direct influence that E2 has on ECM production, E2 also induces pro-fibrotic mediators such as TGFβ1 in a wound healing model^{1 2}. Yet, few experiments discuss E2-induced pro-fibrotic mediator production or the transcriptional regulation of these protein(s). Since TGFβ1 is central in the development of organ fibrosis, especially in systemic sclerosis (SSc), delineating the regulation of TGFβ isoforms is important in understanding disease pathogenesis and developing potential therapeutics. Therefore, we investigated which ECM components are directly stimulated by E2-induced TGFβ signaling and the important regulatory proteins for TGFβ transcription and translation.

Methods: We received skin samples from healthy donors of various ages who underwent skin-resection procedures in the Division of Plastic Surgery at the Medical University of South Carolina under an approved IRB protocol. The ex-vivo human skin model organ culture was used as previously described³. Human primary dermal fibroblasts were isolated from human dermal tissue using the outgrowth method⁴. For experimentation, we used 6-well tissue culture dishes with 4-3mm punches/well or fibroblasts plated at 1.5-2.0 x 10⁵ cells/well in serum-free, phenol red-free DMEM. Steady-state mRNA levels were measured using quantitative PCR (qPCR) and signals normalized to B2M and GAPDH levels. Primary dermal fibroblasts were transfected with siRNA targeted to early growth response 1 (EGR1) or control prior to vehicle or E2 treatment.

Results: We report that the transcription of TGFβ1, TGFβ2 and collagen 22A1 (Col22A1), the TGFβ responsive gene, are induced in response to E2 stimulation in vitro and ex vivo. Mechanistically, Col22A1 induction is blocked by the TGFβ receptor inhibitor SB-431542 despite E2 stimulation. Additionally, blocking E2-induced MAPK activation and EGR1 transcription inhibit TGFβ1, TGFβ2 and Col22A1 transcription.

Conclusion: We conclude that E2-induced dermal fibrosis occurs in part through induction of TGFβ1, TGFβ2 and Col22A1 which is regulated though EGR1 and the MAPK pathway. Dermal fibrosis is a feature of pro-fibrotic diseases, such as SSc, emphasizing the necessity to understand the underlying mechanism of fibrosis. Here, we suggest a cell signaling mechanism for E2-induced fibrosis and TGFβ regulation. Based on the realization that E2-induced TGFβ1 and TGFβ2 directly increase Col22A1 and contribute to ECM accumulation, therapies that inhibit E2 signaling may reduce dermal fibrosis and present a novel therapeutic alternative in pro-fibrotic diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/investigation-of-the-cellular-mechanism-for-estradiol-induced-dermal-fibrosis/