Hypertrophic Scar

Exosome-Loaded GelMA Hydrogel as a Cell-Free Therapeutic Strategy for Hypertrophic Scar Inhibition

Purpose

Hypertrophic scar (HS) is a fibrotic proliferative disorder that arises from an abnormal wound healing process. It is a significant clinical challenge, primarily characterized by the excessive accumulation of extracellular matrix (ECM) and abnormal angiogenesis. This study introduces a novel injectable hydrogel system that integrates sustained-release Exosomes for targeted hypertrophic scar modulation. Exosomes (Exos) from adipose-derived stem cells (ASCs) are emerging as promising treatment for hypertrophic scar inhibition. But when treated independently, it must be applied regularly multiple times to maintain its optimal concentration. Gelatin Methacryloyl (GelMA) hydrogel is an ideal biomaterial candidate for engineering skin tissues because of its similarity to ECM, and importantly GelMA hydrogel can maintain drug concentrations via the encapsulation and sustained release of it, which enhances the potential of clinical applications.

Methods

The Exosome-Loaded GelMA Hydrogel (Exos-GelMA) hydrogel was fabricated and characterized for its pore size and biocompatibility. A rabbit ear HS model was established. Three skin defects on each ear were treated with GelMA hydrogel, Exos-GelMA hydrogel, or left untreated as a blank group. The effects of HS inhibition were assessed through Hematoxylin and Eosin (HE) staining, Masson's trichrome staining, and immunohistochemical staining of Collagen I (COL I), Collagen III (COL III), α-smooth muscle actin (α-SMA), as well as immunofluorescence staining of vascular endothelial growth factor (VEGF).

Results

The Exos-GelMA hydrogel demonstrated an appropriate pore size distribution, excellent biocompatibility, and enhanced fibroblast proliferation in vitro. In the rabbit ear HS model, the Exos-GelMA hydrogel significantly inhibited excessive collagen fiber deposition and the overexpression of the angiogenic factor VEGF. Quantitative analysis of immunohistochemical and immunofluorescence staining showed comparing to blank group the Exos-GelMA hydrogel significantly reduced COL I deposition by 43%, COL III deposition by 15%, α-SMA expression by 31%, and VEGF expression by 35% at 28 day.

Conclusion

In summary, the Exos-GelMA composite hydrogel exhibits significant potential for the prevention and treatment of HS. This study supports the feasibility of Exos-GelMA as a cell-free therapeutic approach for the management of HS.

The role of macrophages in hypertrophic scarring: molecular to therapeutic insights

Hypertrophic Scar (HS) is a common fibrotic disease of the skin, usually caused by injury to the deep dermis due to trauma, burns, or surgical injury. The main feature of HS is the thickening and hardening of the skin, often accompanied by itching and pain, which seriously affects the patient's quality of life. Macrophages are involved in all stages of HS genesis through phenotypic changes. M1-type macrophages primarily function in the early inflammatory phase by secreting pro-inflammatory factors, while M2-type macrophages actively contribute to tissue repair and fibrosis. Despite advances in understanding HS pathogenesis, the precise mechanisms linking macrophage phenotypic changes to fibrosis remain incompletely elucidated. This review addresses these gaps by discussing the pathological mechanisms of HS formation, the phenotypic changes of macrophages at different stages of HS formation, and the pathways through which macrophages influence HS progression. Furthermore, emerging technologies for HS treatment and novel therapeutic strategies targeting macrophages are highlighted, offering potential avenues for improved prevention and treatment of HS.

Investigating the causal relationship between skin microbiota and hypertrophic scar using bidirectional mendelian randomization

BACKGROUND

Hypertrophic scar (HS) is acknowledged as a pathological fibro-proliferative disease of the dermis, resulting from excessive connective tissue growth. HS significantly impacts patient quality of life due to both social and functional issues. Despite various treatments, therapeutic effectiveness remains limited, necessitating further exploration of underlying factors and mechanisms.

OBJECTIVE

The current study was designed to determine the causal relationship between skin microbiota and HS employing a bidirectional Mendelian randomization (MR) approach.

METHODS

We utilized genome-wide association study (GWAS) data from the PopGen cohort and the FinnGen database. Independent single nucleotide polymorphisms (SNPs) linked to the skin microbiota were identified as instrumental variables (IVs) chosen for the two-sample MR analysis. Key analytical approaches included inverse variance weighting (IVW), MR-Egger, simple median, simple mode, and weighted mode, with MR-Egger intercept test and Cochrane's Q test used to detect potential horizontal pleiotropy and heterogeneity.

RESULTS

The two-sample MR analysis identified significant causal relationships between specific skin microbiota features and HS. Notably, Enhydrobacter, Micrococcus, and Acinetobacter on moist skin exhibited protective effects against HS, whereas Finegoldia and Lactobacillales on dry skin were linked to an increased risk of HS. Sensitivity analyses verified the strength of these results, revealing no notable horizontal pleiotropy or heterogeneity.

CONCLUSION

Our research reveals a unidirectional causal relationship between certain skin microbiota and HS, suggesting that modulation of skin microbiota could be a novel therapeutic approach for HS management. These results emphasize the significance of considering skin microbiota in the pathogenesis and treatment of HS.

Slit1 Promotes Hypertrophic Scar Formation Through the TGF-β Signaling Pathway

Background and objectives: Slit1 is a secreted protein that is closely related to cell movement and adhesion. Few studies related to fibrosis exist, and the preponderance of current research is confined to the proliferation and differentiation of neural systems. Hypertrophic scars (HTSs) are delineated by an overproduction of the extracellular matrix (ECM) by activated fibroblasts, leading to anomalous fibrosis, which is a severe sequela of burns. However, the functionality of Slit1 in HTS formation remains unknown. We aimed to investigate whether Slit1 regulates fibroblasts through a fibrosis-related mechanism derived from post-burn HTS tissues and normal patient tissues. Methods: Human normal fibroblasts (HNFs) and hypertrophic scar fibroblasts (HTSFs) were extracted from normal skin and post-burn HTS tissues, with settings grouped according to the patient of origin. Cell proliferation was evaluated using a CellTiter-Glo Luminescent Cell Viability Assay Kit. Cell migration experiments were carried out using a μ-Dish insert system. Protein and mRNA expression levels were quantified by Western blot and quantitative real-time polymerase chain reaction. Results: We found increased expressions of Slit1 in HTS tissues and HTSFs compared to normal tissues and HNFs. The treatment of human recombinant Slit1 protein (rSlit1) within HNFs promoted cell proliferation and differentiation, leading to an upregulation in ECM components such as α-SMA, type I and III collagen, and fibronectin. The treatment of rSlit1 in HNFs facilitated cell migration, concurrent with enhanced levels of N-cadherin and vimentin, and a diminished expression of E-cadherin. Treatment with rSlit1 resulted in the phosphorylation of SMAD pathway proteins, including SMAD2, SMAD3, and SMAD1/5/8, and non-SMAD pathway proteins, including TAK1, JNK1, ERK1/2, and p38, in HNFs. Conclusions: Exogenous Slit1 potentiates the epithelial-mesenchymal transition and upregulates SMAD and non-SMAD signaling pathways in HNFs, leading to the development of HTS, suggesting that Slit1 is a promising new target for the treatment of post-burn HTS.

CircRNA_SLC8A1 alleviates hypertrophic scar progression by mediating the Nrf2-ARE pathway

BACKGROUND

Hypertrophic scar (HS) is associated with cosmetic defects, mobility, and functional impairments, pruritus, and pain. Previous circRNA microarray analysis identified reduced expression of circRNA_SLC8A1 in HS tissues. Therefore, this study aims to investigate the role of circRNA_SLC8A1 in modulating the abnormal behavior of HS-derived fibroblasts (HSFs) in vitro.

METHODS

RT-qPCR and FISH assays were used to assess the differential expression and localization of circRNA_SLC8A1 in normal and HS tissues. Following modulation of circRNA_SLC8A1 expression, CCK-8, flow cytometry, Transwell, and wound healing assays were employed to evaluate the effects of circRNA_SLC8A1 on the biological behaviors of HSFs. The Starbase database, dual-luciferase reporter assays, and Ago2-RIP assays were utilized to predict and validate the interaction between circRNA_SLC8A1 and downstream miRNAs.

RESULTS

CircRNA_SLC8A1 was found to be downregulated in HS tissues and was primarily localized in the cytoplasm. Overexpression of circRNA_SLC8A1 reduced cell viability, cell invasion, wound healing, and the expression of Vimentin, N-cadherin, Col I, and Col III, while enhancing apoptosis and E-cadherin expression in HSFs. CircRNA_SLC8A1 activates the Nrf2-ARE pathway by competitively binding to miRNA-27a-3p. miRNA-27a-3p and Nrf2 exhibited high and low expression, respectively in HS tissues, with an inverse correlation between their levels. Overexpression of miRNA-27a-3p counteracted the effects of circRNA_SLC8A1 in HSF proliferation, apoptosis, migration, EMT, collagen deposition, and Nrf2-ARE pathway activity.

CONCLUSION

CircRNA_SLC8A1 inhibits the proliferation, migration, EMT, and collagen deposition of HSF through competitive binding with miRNA-27a-3p, thereby activating the Nrf2-ARE pathway. The circRNA_SLC8A1/miRNA-27a-3p/Nrf2-ARE axis may offer a promising molecular target for HS therapy.

Comparison of Normal Human Skin and Hypertrophic Scar Tissue Samples of Different Ages, Locations, and Stages of Maturity

BACKGROUND

Scars disrupt the normal structure and function of the skin. The primary goal of plastic surgery is to prevent and reduce scarring. Therefore, we aimed to establish a comparison scheme between normal skin (NS) tissues of different ages and locations; hypertrophic scars (HTS) of different ages, locations, and maturities; and NS and HTS tissues to provide evidence on scar severity for improving treatment evaluation.

METHODS

Various methods including histology, immunohistochemistry, and immunofluorescence were employed to compare the general appearance, macrophage infiltration, fibroblast activity, degree of angiogenesis, and collagen fiber type and arrangement in human-sourced NS and HTS tissues of different ages, locations, and maturities in seven patients (three with NS and four with HTS) from the Department of Burn and Plastic Surgery of the Shandong Provincial Hospital from January 2019 to December 2020.

RESULTS

The thicknesses of the epidermis and dermis of NS tissues varied with age and location. The epidermis of the upper arms, face, and upper eyelids of NS tissues sequentially thickened, whereas the dermis was sequentially thinner. Several glandular structures were identified in the upper eyelids but rarely in the face and upper arms. Histological changes in HTS tissue of different ages, locations, and maturity occur as scar formation time is prolonged, accompanied by increased CD86 levels and fibrosis. As the scar matured, connexin and VEGFR2 expression decreased, indicating reduced inflammation, fibroblast activity, and angiogenesis. The comparison between NS and HTS tissue also revealed significant differences; the positive expression of VEGFR2 and total collagen in HTS tissue was higher than that in NS tissue.

CONCLUSIONS

We discovered significant differences among NS, HTS, and NS and HTS tissues of different ages, locations, and maturities. Further, this study may provide a basis for clarifying the treatment effect of different methods for HTS compared with those for NS, efficiently individualizing patients' treatment plans and ultimately shortening the scar treatment process.

Betamethasone transdermal administration combined with fractional Er:YAG lasers or microplasma radiofrequency technology improved hypertrophic scars: A retrospective study

OBJECTIVE

This retrospective study aims to compare the efficacy rates in treating hypertrophic scars among four distinct groups of patients who either underwent fractional Erbium: yttrium-aluminum-garnet (Er:YAG) laser or microplasma radiofrequency technology as standalone treatments or in combination with compound betamethasone transdermal administration.

METHOD

The study retrospectively examined 208 patients treated at our institution from April 2011 to December 2022 for hypertrophic scars, receiving no less than three treatments (with an interval of 8 weeks between each). The patients were categorized into four groups: the F group (treated with fractional Er:YAG laser), the F + B group (treated with fractional Er:YAG laser combined with compound betamethasone transdermal administration), the P group (treated with microplasma radiofrequency technology), and the P + B group (treated with microplasma radiofrequency technology combined with compound betamethasone transdermal administration). The therapeutic effects were evaluated based on the changes in the Vancouver Scar Scale (VSS) scores before and after treatment in these groups.

RESULTS

There was no statistically significant difference in the VSS scores among the four groups before treatment. After undergoing three sessions of the aforementioned four types of treatment, all groups showed a decrease in VSS scores, with average posttreatment VSS scores for the F group scored 5.15 ± 2.084, F + B group scored 3.7 ± 1.781, P group scored 4.41 ± 1.933, and P + B group scored 3.16 ± 1.775, respectively. With an increasing number of treatments, the total effective rate gradually increased in all four groups, and the combination treatment using compound betamethasone transdermal administration proved more effective than the standalone treatment.

CONCLUSION

All four treatments yielded favorable outcomes, with the combined therapy involving compound betamethasone transdermal administration proving more effective than the standalone treatments, meriting further clinical attention.