AB0125 IL-25 PARTICIPATES IN KERATINOCYTE-DRIVEN DERMAL MATRIX TURNOVER AND IS REDUCED IN SYSTEMIC SCLEROSIS (SSc) EPIDERMIS

Background

Evidence shows that dysfunctional SSc keratinocytes contribute to fibrosis by altering dermal homeostasis (1, 2). Whether interleukin-25 (IL-25), an IL-17 family member regulating many epidermal functions (3), takes part in skin fibrosis is unknown.

Objectives

To investigate the role of IL-25 in skin fibrosis.

Methods

The expression of IL-25 was evaluated by immunofluorescence and in situ hybridization in 10 SSc and 7 healthy donors (HD) skin biopsies. Epidermal equivalents (EE) reconstituted by primary HD keratinocytes were used as a model to study transcriptomic changes induced by IL-25 in the epidermis. RNA expression profile in EE was characterized by RNAseq. The conditioned medium (CM) from primary SSc and HD keratinocytes primed with IL-25 was used to stimulate fibroblasts. IL-6, IL-8, MMP-1, type-I collagen (col-I), and fibronectin production by fibroblasts was assessed by ELISA.

Results

SSc epidermis expressed lower levels of IL-25 compared to HD. In EE, IL-25 regulated several molecular pathways related to wound healing and extracellular matrix (ECM) remodeling. Compared to control CM, the CM from IL-25-primed keratinocytes enhanced the fibroblast production of MMP-1, IL-6, IL-8, but not of Col-I nor fibronectin. However, IL-25 significantly reduced the production of Col-I when applied directly to fibroblasts and partially inhibit α-smooth muscle actin (α-SMA) expression promoted by TGFβ. The activation of keratinocytes by IL-25 was receptor-dependent and evident after a very short incubation time (10 min), largely mediated by IL-1, suggesting enhanced and specific release of preformed mediators.

Conclusion

These results show that IL-25 participates to skin homeostasis and its decreased expression in SSc may contribute to skin fibrosis by favoring ECM deposition over degradation.

References

[1]Russo B, Brembilla NC, Chizzolini C. Interplay between Keratinocytes and Fibroblasts: A Systematic Review Providing a New Angle for Understanding Skin Fibrotic Disorders. Frontiers in immunology. 2020; 11:648.

[2]Russo B, Borowczyk J, Boehncke WH, Truchetet ME, Modarressi A, Brembilla NC, et al. Dysfunctional keratinocytes increase dermal inflammation in systemic sclerosis. Results from tissue-engineered scleroderma epidermis. Arthritis & rheumatology. 2021.

[3]Borowczyk J, Shutova M, Brembilla NC, Boehncke WH. IL-25 (IL-17E) in epithelial immunology and pathophysiology. J Allergy Clin Immunol. 2021.

Acknowledgements

We thank Natacha Civic and Mylène Docquier (Genomics Platform) for performing the RNA sequencing; Nicolas Laudet (Bioimaging Core Facility) for quantification of immune-histology, François Prodon and Olivier Brun for microscope imaging (Bioimaging Core Facility), Marie Ebrahim Malek and Laura de Luca (Histology Core Facility) for contribution to tissue preparation (all at University Medical Center, Geneva, Switzerland).

Disclosure of Interests

Barbara Russo: None declared, Julia Borowczyk: None declared, Pietro Cacialli: None declared, Philippe Moguelet: None declared, Marie-Elise Truchetet Speakers bureau: Abbvie, Lilly, SOBI and Boehringer Ingelheim, Ali Modaressi: None declared, Nicolò Brembilla: None declared, Julian Bertrand: None declared, Wolf-Henning Boehncke Speakers bureau: Abbvie, Almirall, BMS, Celgene, Leo, Lilly, Novartis, and UCB, Carlo Chizzolini Speakers bureau: GSK, Roche, Boehringer Ingelheim

IL-17E, iNOS and Arginase1 as new biomarkers in the identification of neutrophilic dermatoses

Background

Neutrophilic dermatoses (ND) are a heterogeneous group of diseases, but can often have a relatively similar histological appearance.

Aim

To identify a combination of biomarkers allowing a better differentiation of ND types.

Methods

Biopsies were obtained from normal human skin (NS; n = 4), chronic plaque‐type psoriasis (PsO; n = 7), paradoxical psoriasis (PP; n = 8), generalized pustular psoriasis (GPP; n = 9), subcorneal pustular dermatosis of Sneddon–Wilkinson (SPD; n = 3), acute generalized exanthematous pustulosis (AGEP; n = 3), hidradenitis suppurativa (HS; n = 7), Sweet syndrome (SS; n = 8) and pyoderma gangrenosum (PG; n = 8). Samples were analysed by immunofluorescence using three biomarkers, interleukin (IL)‐17E, inducible nitric oxide synthase (iNOS) and arginase1, each one in combination with two cell markers, myeloperoxidase (MPO) and CD68, which allow the identification of neutrophils and macrophages, respectively.

Results

We found that SS is characterized by high expression of IL‐17E and iNOS in the epidermis, while PG exhibits low expression. The density of the neutrophil infiltrate helps to differentiate PP (high‐density infiltrate) from PsO (low‐density infiltrate). High expression of arginase1 in the granular layer of the epidermis is a hallmark of SPD. Finally, mature neutrophils and proinflammatory macrophages are readily detectable in PP, SPD and PG, whereas immature neutrophils and anti‐inflammatory macrophages are more frequent in GPP, AGEP, HS and SS.

Conclusions

The analysis of ND by immunofluorescence using IL‐17E, iNOS and arginase1 in combination with MPO and CD68 allows for characterization of differential expression patterns in the epidermis as well as the determination of the polarization status of the dermal neutrophils and macrophages. The appropriate markers may help in the differentiation of ND in clinical practice.

SAT0289 THE INS AND OUTS OF EPIDERMAL DYSFUNCTION IN SYSTEMIC SCLEROSIS (SSC): RESULTS FROM A NOVEL TISSUE ENGINEERED EPIDERMAL EQUIVALENT FROM SSC KERATINOCYTES

Background:

Skin fibrosis is a hallmark of systemic sclerosis (SSc). It is commonly accepted that vascular damage, immune system activation and, abnormal fibroblasts-to-myofibroblasts differentiation are pathological capital features. Nevertheless, recent evidence portrays a potential role of the epidermis in the pathogenesis of SSc skin fibrosis (1, 2). This new angle on skin fibrosis pathogenesis is particularly attractive as the epidermis is an easy to access therapeutic target.

Objectives:

To dissect the potential epidermal dysfunction in SSc and its effect on dermis homeostasis, using a novel epidermal equivalent reconstituted from SSc keratinocytes.

Methods:

Primary keratinocytes and fibroblasts cell lines were generated from skin biopsies obtained from 6 SSc and 6 healthy donors (HD), upon informed consent and ethical approval. Epidermal equivalents (EE) were generated from 4 SSc and 6 HD keratinocytes. Skin and EE expression of the mitotic marker Ki67, of the differentiation markers (K10, involucrin, filaggrin, loricrin), and activation markers (K6, K16) was evaluated by immunohistochemistry. The transcriptomic profile of SSc keratinocytes in monolayer or stratified in EE was identified by RNAseq analysis. EE conditioned medium was used to stimulate fibroblasts. The fibroblast production of interleukin (IL)-6, IL-8, matrix metalloproteinase (MMP)-1, type-I collagen (col-I), and fibronectin was assessed by ELISA.

Results:

Compared to HD, immunohistochemistry revealed that SSc epidermis is characterized by aberrant premature differentiation and enhanced expression of activation markers associated with a lower mitotic rate of basal keratinocytes. Of interest, EE reconstituted from SSc keratinocytes reproduced most of the abnormalities observed in SSc epidermis. RNAseq analysis revealed that SSc keratinocytes, either cultured in monolayer or in EE, have a distinct transcriptomic profile compared to their HD counterpart, characterized by the downregulation of genes from the HOX family.

The supernatant of EE enhanced the production of IL-6, IL-8, MMP-1, col-I, and fibronectin by HD fibroblasts (p<0.05). Except for col-I and fibronectin, this effect was 2-fold higher in the presence of supernatant from EE reconstituted by SSc keratinocytes. Neutralization experiments indicated that IL-1 was, at least in part, responsible for keratinocyte-dependent fibroblasts activation.

Conclusion:

We established a novel epidermal equivalent tissue engineered from SSc keratinocytes, that recapitulates thein vivocharacteristics of SSc epidermis. Our preliminary data suggest that SSc keratinocytes have an intrinsic altered program of differentiation, possibly due to the downregulation of some HOX genes. This altered phenotype is associated with increased production of mediators that stimulate fibroblasts production of inflammatory cytokines. In this scenario, we may hypothesize that SSc epidermis participates in modifying the dermis environment, favoring the development of chronic inflammation and fibrosis.

References

[1]Takahashi T, Asano Y, Sugawara K, Yamashita T, Nakamura K, Saigusa R, et al. Epithelial Fli1 deficiency drives systemic autoimmunity and fibrosis: Possible roles in scleroderma. J Exp Med. 20317;214(4):1129-51.

[2]Nikitorowicz-Buniak J, Shiwen X, Denton CP, Abraham D, Stratton R. Abnormally differentiating keratinocytes in the epidermis of systemic sclerosis patients show enhanced secretion of CCN2 and S100A9. J Invest Dermatol. 2014;134(11):2693-702.

Disclosure of Interests:

Barbara Russo: None declared, Julia Borowczyk-Michalowska: None declared, Wolf-Henning Boehncke Consultant of: WHB received honoraria as advisor or invited speaker from Abbvie, Almirall, BMS, Celgene, Leo, Lilly, Novartis, UCB., Speakers bureau: WHB received honoraria as advisor or invited speaker from Abbvie, Almirall, BMS, Celgene, Leo, Lilly, Novartis, UCB., Nicolò Brembilla: None declared, Carlo Chizzolini Consultant of: Boehringer Ingelheim, Roche