Impact of Sex Hormones on Human Skin Immunity in Health and Hidradenitis Suppurativa (SIAP) (SIAP)

Impact of Sex Hormones on Human Skin Immunity in Health and Hidradenitis Suppurativa

Sex hormones are major regulators of skin immunity. Pregnancy represents a unique physiological state of profound hormonal remodeling. In late pregnancy, maternal levels of estrogens, progesterone, and other hormones increase dramatically, offering an unparalleled model to study the impact of sex hormones on skin immunity. Hidradenitis suppurativa (HS) provides a clinically relevant model to examine how sex hormones modulate skin inflammation.

Study Overview

• Status: Not yet recruiting
• Conditions: Skin Immunity
• Intervention / Treatment: Procedure: Blood sample, skin microbiota and biopsy

Detailed Description

Sex hormones are major regulators of skin immunity. Recent work from Belkaid's laboratory in mice demonstrated that testosterone negatively regulated skin innate lymphoid cells (ILC2), leading to a reduction in dendritic cell accumulation and decreased activation in males, along with reduced tissue immunity. These findings highlight that sex-related differences in skin immunity emerge primarily after sexual maturation, driven by fluctuating hormone levels. However, whether these mechanisms are conserved in humans remains unknown.

Pregnancy represents a unique physiological state of profound hormonal remodeling. In late pregnancy, maternal levels of estrogens, progesterone, and other hormones increase dramatically, offering an unparalleled model to study the impact of sex hormones on skin immunity. Understanding maternal skin immunity is of particular importance, as the maternal immune system must balance tolerance to the fetus with protection against pathogens. Perturbation in this balance can have lasting effects on both maternal and child health. Faced with the dramatic increase in inflammatory and autoimmune disorders affecting children globally, understanding maternal immunity is of fundamental importance.

Hidradenitis suppurativa (HS) provides a clinically relevant disease model to examine how sex hormones modulate skin inflammation. HS is a chronic inflammatory skin disease with strong sex dimorphism: it affects predominantly women (70%) in Europe but is often more severe in men. In women, HS severity varies with the menstrual cycle and is frequently altered during pregnancy, suggesting a hormonal component in disease modulation. Yet, the mechanisms linking sex hormones, pregnancy, and skin immune responses in HS remain unexplored.

By systematically comparing men, non-pregnant women, and pregnant women, in both health and HS, this study will map immune cell populations in the skin and determine how sex hormones; testosterone, estrogens, and progesterone; shape cutaneous immunity at steady state and during inflammation.

• Study Type: Observational
• Enrollment (Estimated): 240

Contacts and Locations

• Study Contact: Name: Clarisse GANIER, PhD; Phone Number: +33 0145688767; Email: clarisse.ganier@pasteur.fr
• Study Contact Backup: Name: Julia ABAD; Phone Number: +33 0140669760; Email: julia.abad@pasteur.fr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

As part of this study, adults (pregnant women, non-pregnant women, and men), healthy (not affected by HS) and affected by HS, will be recruited.

Description

Inclusion Criteria:

• Common criteria :
• Subject>18 years and <45 years,
• Written informed consent of the subject,
• Subject affiliated to the Assurance Maladie (French Health System) except Aide Médicale d'Etat (French State Medical Aid),
• Subject agrees that genomic analyses may be carried out on the samples
• Specific criteria :
• For pregnant women:Third trimester of pregnancy (between 29-37 weeks of amenorrhea).
• For HS subjects: Subject with hidradenitis suppurativa lesions at the sampling sites.

Exclusion Criteria:

• Common criteria :
• Subject immunocompromised,
• Subject under legal protection (guardianship or curatorship),
• Subject is unable to provide informed consent and to comply with the study requirements due to geographical, social, or psychiatric reasons,
• Subject in other research whose procedures may influence the immune system,
• Contraindication to any of medications listed in section 5.1 (antiseptic and local anesthetic used for biopsy(ies)),
• Subject whose health condition does not permit participation in study procedures.
• Specific criteria :
• For no HS subjects : Scarred skin at the biopsy site, Subject with pre-existing and/or still active inflammatory skin conditions, Subject experiencing early menopause (women) or andropause (men).

Study Plan

How is the study designed?

Number of groups / cohorts

6

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Healthy - Pregnant women; Adult woman, not affected by Hidradenitis Suppurativa, pregnant in her third trimester	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas
Healthy - Non-pregnant women; Adult woman, not affected by Hidradenitis Suppurativa	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas
Healthy - Men; Adult men, not affected by Hidradenitis Suppurativa	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas
Hidradenitis suppurativa - Pregnant women; Adult woman, affected by Hidradenitis Suppurativa, pregnant in her third trimester	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas
Hidradenitis suppurativa - Non-pregnant women; Adult woman, affected by Hidradenitis Suppurativa	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas
Hidradenitis suppurativa - Men; Adult men, affected by Hidradenitis Suppurativa	Procedure: Blood sample, skin microbiota and biopsy; Blood sample (maximum 40mL) Skin microbiota (collection of cells from the skin surface using a swab (non-invasive) Skin biopsy, in hormone-dependent areas and/or in a non-hormone-dependent areas

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the impact of sex hormones and pregnancy on skin immunity by comparing immune cell populations in different populations (pregnant women, non-pregnant women, and men) with or without hidradenitis suppurativa.	Percentage of key skin immune cells (ILC2, dendritic cells, Langerhans cells), according to sex, pregnancy, and pathological context (healthy vs HS).	4 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Defining the spatial organisation of skin cells in order to assess how pregnancy remodels cutaneous immune responses in health and HS inflammation.	Immune cell mapping in healthy vs. inflamed skin biopsies across hormonal states (e.g. pregnancy).	4 years
Exploring how sex hormones, which are massively increased during pregnancy, and circulating immune profiling impact skin function and immunity.	Measurement of sex hormones and composition of PBMCs (Peripheral Blood Mononuclear Cells) in the blood of pregnant women and in controls (men and non-pregnant women).	4 years
Revealing the influence of the skin microbiota on the host immune system adapting to pregnancy in healthy and HS conditions.	Skin microbial metatranscriptomic profiling at the latest stage of pregnancy and in controls (men and non-pregnant women) in healthy and HS conditions.	4 years

Collaborators and Investigators

• Sponsor: Institut Pasteur
• Investigators: Principal Investigator: Bénédicte OULES, MD-PhD, Assistance Publique - Hôpitaux de Paris

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): January 1, 2030
• Study Completion (Estimated): March 1, 2031

Study Registration Dates

• First Submitted: December 5, 2025
• First Submitted That Met QC Criteria: December 5, 2025
• First Posted (Estimated): December 18, 2025

Study Record Updates

• Last Update Posted (Actual): January 9, 2026
• Last Update Submitted That Met QC Criteria: January 8, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Pregnancy; Skin; Hormones; Maternal Immunity; Single Cell; Spatial-Omics
• Additional Relevant MeSH Terms: Investigative Techniques; Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Cytological Techniques; Cytodiagnosis; Environment and Public Health; Diagnostic Techniques, Surgical; Microbiota; Microbiological Phenomena; Biota; Biodiversity; Ecosystem; Environment; Ecological and Environmental Phenomena; Biological Phenomena; Biopsy; Blood Specimen Collection; Skin Microbiome
• Other Study ID Numbers: 2024-072; 2025-A00923-46 (Other Identifier: ID-RCB number)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No