The Value of Negative-Pressure Wound Therapy and Flap Surgery in Hidradenitis Suppurativa – A Single Center Analysis of Different Treatment Options

Background

Hidradenitis suppurativa is manifested by painful abscesses and scarring of sweat glands. Axillary, inguinal and genital regions are mostly affected. Multiple options exist in the treatment of hidradenitis suppurativa. The aim of this retrospective, mono-center cohort study was to analyze the outcome of different treatment methods after radical excision of hidradenitis suppurativa.

Methods

We retrospectively evaluated the treatment strategy and recurrence rate of hidradenitis suppurativa. We included all eligible patients of legal age between February 2003 and October 2021, with the diagnosis of Hidradenitis suppurativa and the necessity for surgical treatment. All patients with surgical treatment and direct wound closure by suture were excluded. Bacterial load and flora were analyzed for primary and secondary reconstruction in combination with negative-pressure wound therapy. Patient data were analyzed for recurrence rate and remission time according to different reconstructive techniques.

Results

In 44 affected anatomical sites (n = 23 patients) we treated 15 patients with negative-pressure wound therapy. Bacterial load and flora were lower in the last wound swab of patients with multi-surgical procedures (22 localizations) compared to the first wound swab independent of the use of negative-pressure wound therapy.

Wound closure, independent of a direct and multi-stage procedure was achieved by local fasciocutaneous flaps (n = 12), secondary intention healing (n = 7), secondary intention healing with buried chip skin grafts (n = 10), or split-thickness skin grafts (n = 15). Radical excision combined with split-thickness skin grafts showed the lowest recurrence rate in the follow-up (16%; n = 4).

Conclusion

Radical excision of hidradenitis suppurativa as gold standard for surgical treatment combined with negative-pressure wound therapy as multi-stage procedures ultimately reduced bacterial load and flora in our study. The use of split-thickness skin grafts showed the lowest recurrence rate.

POS0328 ENGRAILED 1 COORDINATES CYTOSKELETAL ORGANIZATION TO PROMOTE MYOFIBROBLAST DIFFERENTIATION AND FIBROTIC TISSUE REMODELING

Background:

Engrailed 1 (EN1) is a homeodomain-containing transcription factor with essential roles in embryonic development. In most cell types, the expression of EN1 is restricted to embryonic development. However, under pathological conditions, EN1 can be re-expressed to promote phenotypical adaptation. En1 is transiently expressed in the developing dermis of murine embryos in a distinct fibroblast lineage and silenced before birth (1). Former EN1-expressing cells give rise to a subpopulation of fibroblasts that has a high capacity for extracellular matrix production in adult murine skin. The role of EN1 in systemic sclerosis (SSc) was previously not explored.

Objectives:

To study the role of EN1 in the pathological activation of fibroblasts in tissue fibrosis.

Methods:

Bulk RNA-Seq and EN1 or SP1 ChIP-Seq were performed from cultured human dermal fibroblasts. The expression of EN1 was inhibited by siRNA. Cytoskeletal drugs paclitaxel, vinblastin and ROCK inhibitor (Y27632) were used to modulate the cytoskeleton in EN1 knockdown or overexpressing dermal fibroblasts. The role of EN1 in fibroblast activation was evaluated by functional experiments with EN1 knockdown or overexpression in standard 2D culture systems as well as in 3D skin equivalent models. The role of EN1 in skin fibrosis was further studied in En1fl/fl X Col6Cre mice, with fibroblast-specific knockout of En1 in three complementary mouse models: overexpression of a constitutively active TGFß-receptor I (TBRICA), bleomycin-induced skin fibrosis and TSK1 mice.

Results:

Pathologically activated dermal fibroblasts from SSc patients express higher levels of EN1 compared with age and sex matched healthy individuals in the skin and in vitro. TGFβ induces EN1 expression in fibroblasts in a SMAD3-dependent manner both in cultured fibroblasts and in murine skin. Knockdown of EN1 prevents TGFβ-induced fibroblast activation, whereas overexpression of EN1 fosters the pro-fibrotic effects of TGFβ with increased expression of αSMA, stress fibers and collagen. RNA sequencing demonstrates that EN1 induces a pro-fibrotic gene expression profile functionally related to cytoskeleton organization and ROCK activation. In silico analyses of the promoters of En1 target genes coupled with siRNA-mediated knockdown demonstrated that EN1 regulates these pro-fibrotic target genes by modulating the activity of regulatory modules that contain transcription factors of the specificity protein (SP) family. Functional experiments with selective modulators of ROCK and of microtubule polymerization confirm the coordinating role of EN1 on ROCK activity and the re-organization of cytoskeleton during myofibroblast differentiation in both conventional culture systems and 3D skin equivalents. Consistently, mice with fibroblast-specific knockout of En1 demonstrate impaired fibroblast-to-myofibroblast transition, reduced dermal thickening and impaired collagen deposition in the TBRICA, bleomycin-induced and TSK1 models.

Conclusion:

We characterize the homeodomain transcription factor EN1 as a molecular amplifier of TGFβ signaling in myofibroblast differentiation that coordinates cytoskeletal organization in a SP-dependent manner. EN1 might thus be a novel candidate for molecular targeted therapies to interfere with myofibroblast differentiation in fibrotic diseases.

References:

[1]Rinkevich Y, Walmsley GG, Hu MS, Maan ZN, Newman AM, Drukker M, et al. Skin fibrosis. Identification and isolation of a dermal lineage with intrinsic fibrogenic potential. Science. 2015;348(6232):aaa2151.

Disclosure of Interests:

Andrea-Hermina Györfi: None declared, Alexandru-Emil Matei: None declared, Maximilian Fuchs: None declared, Aleix Rius Rigau: None declared, Xuezhi Hong: None declared, ZHU Honglin: None declared, Markus Luber: None declared, Christina Bergmann: None declared, Clara Dees: None declared, Ingo Ludolph: None declared, Raymund Horch: None declared, Oliver Distler Consultant of: Actellion, AbbVie, Acceleron Pharma, Anamar, Amgen, Blade Therapeutics, CSL Behring, ChemomAb, Ergonex, Glenmark Pharma, GSK, Inventiva, Italfarmaco, iQvia, Medac, Medscape, Lilly, Sanofi, Target BioScience, UCB, Bayer, Boehringer Ingelheim, Catenion, iQone, Menarini, Mepha, Novartis, Mitsubishi, MSD, Roche, Pfizer, Georg Schett: None declared, Meik Kunz: None declared, Jörg H.W. Distler Consultant of: Actelion, Active Biotech, Anamar, ARXX, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, JB Therapeutics, Medac, Pfizer, RuiYi and UCB., Grant/research support from: Anamar, Active Biotech, Array Biopharma, aTyr, BMS, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, Novartis, Sanofi-Aventis, RedX, UCB

Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure

The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca²⁺) gluconate (as 2.5% Ca²⁺gel and individually (2.84%) or commercially (10%) formulated Ca²⁺solution), magnesium (Mg²⁺) gluconate (2.84%) solution and aluminium (Al³⁺) solution (Hexafluorine®, pure and diluted) on the absorption of fluoride following HF exposure (1-3 min, 100 μl, 30%/0.64 cm²) through human skin was investigated in an ex-vivo diffusion cell model. Fluoride absorption was assessed over 6-24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride-binding decontamination agents (Ca²⁺, Mg²⁺, Al³⁺) or water alone without being significantly different. Ca²⁺ appeared slightly more effective than Mg²⁺ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride-binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.

Impact of physiologically relevant temperatures on dermal absorption of active substances - an ex-vivo study in human skin

Skin temperature plays a certain role in the dermal absorption of substances, but the extent and mechanisms of skin temperatures-induced modulation in ranges caused by physiological thermoregulation or environmental conditions are largely unknown. The influence of dermal temperature on the absorption of the model lipophilic compound (anisole) and the model hydrophilic compounds (1,4-dioxane, ethanol) through human skin was investigated at three dermal temperatures (25, 32 and 39 °C) in an ex-vivo diffusion cell model. The substances were applied to the skin and transdermal penetration was monitored. All substances showed temperature dependent variations in their penetration behavior (3 h: 25-39 °C: 202-275% increase in cumulative, transdermally penetrated amounts). The relative differences in absorption in relation to temperature were greatest within 45 min after exposure (25-39 °C: 347-653% rise in cumulated penetration), although absolute amounts absorbed were small (45 min vs. 3 h: 4.5-14.5%). Regardless of blood circulation, skin temperature significantly influences the amount and kinetics of dermal absorption. Substance-dependent, temperature-related changes of the lipid layer order or the porous pathway may facilitate penetration. The early-stage modulation of transdermal penetration indicates transappendageal absorption, which may be relevant for short-term exposures. For both, toxicological evaluation and perfusion cell studies, it is important to consider the thermal influence on absorption or to perform the latter at a standardized temperature (32±1 °C).

AB0172 PGC-1Α REGULATES AUTOPHAGY TO PROMOTE FIBROBLAST ACTIVATION AND TISSUE FIBROSIS

Background:

Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is the best studied member of the family of coactivators. PGC-1α was initially identified through its interaction with PPARγ in brown adipose tissue. Recent evidence further indicates that PGC-1α may also modulate the transcription of autophagy-related genes, which has recently been shown to be required for fibroblast-to-myofibroblast differentiation under fibrotic conditions. However, the role of PGC-1α in the pathogenesis of SSc has not been investigated.

Objectives:

The aim of the present study was to evaluate the role of the coactivator PGC-1α on autophagy and to evaluate its role in the pathologic activation of fibroblasts in SSc.

Methods:

Expression of PGC-1α was analyzed by RT-PCR, Western blot and immunofluorescence. Modulation of autophagy was analyzed by reporter studies by expression of autophagy related genes. The effects of PGC-1α knockdown on collagen production and myofibroblast differentiation were analyzed in cultured human fibroblasts and in two mouse models with fibroblast-specific knockout of PGC-1α.

Results:

PGC-1α overexpression was detected by immunohistochemistry in skin sections of SSc patients and in experimental fibrotic murine skin, particularly in fibroblasts. Knockdown of PGC-1α inhibited the stimulatory effects of TGFβ on fibroblast activation with impaired induction of collagen as compared to control fibroblasts. Fibroblasts specific knockout of PGC-1α ameliorates experimental fibrosis in bleomycin-induced and adTBR-induced murine dermal fibrosis with decreased dermal thickness, hydroxyproline and myofibroblast counts compared to wild-type fibrotic mice. Incubation of dermal fibroblasts with TGFβ activated autophagy in control fibroblasts with increased expression of the autophagy-related genes ATG7 and BECLIN-1, enhanced conversion of LC3 I to LC3 II and decreased ratios of ILC3 I EGFP to LC3 II RFP in LC3 reporter assays. The expression levels of ATG7, BECLIN-1 and ILC3 II of TGFβ-stimulated PGC-1α knockout fibroblasts decreased compare to TGFβ stimulated wild-type fibroblasts. The ratio of ILC3 I EGFP to LC3 II RFP of TGFβ-stimulated PGC-1α knockout fibroblasts in reporter assays were comparable to unstimulated fibroblasts.

Conclusion:

PGC-1α is upregulated in SSc and promotes autophagy to foster TGFβ-induced fibroblast activation. Targeting of PGC-1α prevents aberrant autophagy, inhibits fibroblast activation and tissue fibrosis.

References:

[1]Finck BN, Kelly DP. PGC-1 coactivators: inducible regulators of energy metabolism in health and disease. The Journal of clinical investigation. 2006 Mar; 116(3):615-622

[2]Lindholm D, Eriksson O, Makela J, Belluardo N, Korhonen L. PGC-1alpha: a master gene that is hard to master. Cellular and molecular life sciences: CMLS. 2012 Aug; 69(15):2465-2468.

[3]Li SY, Susztak K. The Role of Peroxisome Proliferator-Activated Receptor gamma Coactivator 1alpha (PGC-1alpha) in Kidney Disease. Semin Nephrol. 2018 Mar; 38(2):121-126.

[4]Vainshtein A, Tryon LD, Pauly M, Hood DA. Role of PGC-1alpha during acute exercise-induced autophagy and mitophagy in skeletal muscle. American journal of physiology Cell physiology. 2015 May 1; 308(9):C710-719.

[5]Zehender A LN, Stefanica A, Chen CW, Soare A, Wohlfahrt T, Rauber S, Bergmann C, Ramming A, Distler O, Schett G, Distler J. TGFβ Promotes Fibrosis By MYST1-Dependent Epigenetic Regulation of Autophagy [abstract]. Arthritis Rheumatol 2017; 69 (suppl 10).

Disclosure of Interests:

Yun Zhang: None declared, Katja Dreißigacker: None declared, Diana Distler: None declared, Andrea-Hermina Györfi: None declared, Christina Bergmann: None declared, xiang zhou: None declared, Lichong Shen: None declared, Ingo Ludolph: None declared, Raymund Horch: None declared, Andreas Ramming Grant/research support from: Pfizer, Novartis, Consultant of: Boehringer Ingelheim, Novartis, Gilead, Pfizer, Speakers bureau: Boehringer Ingelheim, Roche, Janssen, Georg Schett Speakers bureau: AbbVie, BMS, Celgene, Janssen, Eli Lilly, Novartis, Roche and UCB, Jörg Distler Grant/research support from: Boehringer Ingelheim, Consultant of: Boehringer Ingelheim, Paid instructor for: Boehringer Ingelheim, Speakers bureau: Boehringer Ingelheim

Scalp reconstruction: A 10-year retrospective study

Scalp reconstruction is a challenging task for the reconstructive surgeon. In consideration of the anatomical and cosmetic characteristics, the defect depth and size, an armamentarium of reconstructive procedures ranging from skin grafts over local flaps to free tissue transfer has been described. In this 10-year retrospective study, 85 operative procedures for scalp reconstruction were performed at our department. The underlying entity, defect size/depth, reconstructive procedure, complications, and mean hospital stay were analyzed. In most cases, scalp reconstruction was necessary after oncologic resection (67%) or radiation therapy (16%). A total of 85 operative procedures were performed for scalp reconstruction including local flaps (n = 50), free tissue transfer (n = 18), and skin grafts (n = 17). Regarding the complication rate, we could detect an overall major complication rate of 16.5% with one free flap loss. Briefly, local flaps are an adequate and safe procedure for limited scalp defects. In the case of extensive scalp defects affecting the calvarium, prior multiple surgical interventions and/or radiation, we prefer free tissue transfer.