Background: Chronic nonhealing wounds remain a considerable challenge in clinical treatment due to excessive inflammation and impeded reepithelialization and angiogenesis. Therefore, the discovery of novel prohealing agents for chronic skin wounds are urgent and important. Amphibian-derived prohealing peptides, especially immunomodulatory peptides, provide a promising strategy for the treatment of chronic skin trauma. However, the mechanism of immunomodulatory peptides accelerating the skin wound healing remains poorly understood. Methods: The prohealing ability of peptide Andersonin-W1 (AW1) was assessed by cell scratch, cell proliferation, transwell, and tube formation. Next, full-thickness, deep second-degree burns and diabetic full-thickness skin wounds in mice were performed to detect the therapeutic effects of AW1. Moreover, the tissue regeneration and expression of inflammatory cytokines were evaluated by hematoxylin and eosin (H&E), enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry staining. Molecular docking, colocalization, and western blotting were used to explore the mechanism of AW1 in promoting wound healing. Results: We provide solid evidence to display excellent prohealing effects of AW1, identified as a short antimicrobial peptide in our previous report. At relative low concentration of nM, AW1 promoted the proliferation, migration, and scratch repair of keratinocyte, macrophage proliferation, and tube formation of HUVEC. AW1 also facilitated reepithelialization, granulation regeneration, and angiogenesis, thus significantly boosting the healing of full-thickness, deep second-degree burns and diabetic skin wounds in mice. Mechanistically, in macrophages, AW1 directly bound to Toll-like receptor 4 (TLR4) in the extracellular region and regulated the downstream nuclear factor‐κB (NF-κB) signaling pathway to facilitate the inflammatory factor secretion and suppress excessive inflammation induced by lipopolysaccharide (LPS). Moreover, AW1 regulated macrophage polarization to promote the transition from the inflammatory to the proliferative phase and then facilitated reepithelialization, granulation regeneration, and angiogenesis, thus exhibiting excellent therapeutic effects on diabetic skin wounds. Conclusions: AW1 modulates inflammation and the wound healing process by the TLR4/NF-κB molecular axis, thus facilitating reepithelialization, granulation regeneration, and angiogenesis. These findings not only provided a promising multifunctional prohealing drug candidate for chronic nonhealing skin wounds but also highlighted the unique roles of “small” peptides in the elucidation of “big” human disease mechanisms. Graphical

Acne vulgaris is one of the most prevalent skin conditions, affecting almost all teenagers worldwide. Multiple factors, including the excessive production of sebum, dysbiosis of the skin microbiome, disruption of keratinization within hair follicles, and local inflammation, are believed to trigger or aggravate acne. Immune activity plays a crucial role in the pathogenesis of acne. Recent research has improved our understanding of the immunostimulatory functions of microorganisms, lipid mediators, and neuropeptides. Additionally, significant advances have been made in elucidating the intricate mechanisms through which cutaneous innate and adaptive immune cells perceive and transmit stimulatory signals and initiate immune responses. However, our understanding of precise temporal and spatial patterns of immune activity throughout various stages of acne development remains limited. This review provides a comprehensive overview of the current knowledge concerning the immune processes involved in the initiation and progression of acne. Furthermore, we highlight the significance of detailed spatiotemporal analyses, including analyses of temporal dynamics of immune cell populations as well as single-cell and spatial RNA sequencing, for the development of targeted therapeutic and prevention strategies.

The combined use of peptides, nanomaterials, and hydrogels is a promising strategy for chronic skin wound healing, which remains a huge clinical challenge. Here, we optimized the RL-QN15 peptide, which was shown to be a pro-healing drug candidate in our previous research, to obtain the cyclic heptapeptide (Cy _RL-QN15 ) with considerable therapeutic potency against skin wounds. Furthermore, a Zn ²⁺ -crosslinked sodium alginate (ZA) hydrogel containing hollow polydopamine (HPDA) nanoparticles loaded with Cy _RL-QN15 (HPDAlCy _RL-QN15 /ZA hydrogel) was prepared and characterized, which significantly enhanced the pro-healing potency of Cy _RL-QN15 . At the cellular level, this nontoxic hydrogel accelerated the proliferation, migration, tube formation, and scratch healing of skin cells, regulated the secretion of cytokines from macrophages, directly scavenged free radicals, and decreased reactive oxygen species. Moreover, the HPDAlCy _RL-QN15 /ZA hydrogel significantly accelerated the healing of full-thickness skin wounds in type 2 diabetic mice by promoting the transition of macrophages to the M2 phenotype to reduce inflammation and cause re-epithelialization, formation of granulation tissue, deposition of collagen, and angiogenesis. Of note, the hydrogel also facilitated wound healing of diabetic patient skin cultured ex vivo. Overall, the HPDAlCy _RL-QN15 /ZA hydrogel presents a novel therapeutic strategy for clinical chronic skin wound (diabetic ulcer) healing.

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent of the keratinocyte-derived malignancies with actinic keratosis (AK) as a precancerous lesion. To comprehensively delineate the underlying mechanisms for the whole progression from normal skin to AK to invasive cSCC, we performed single-cell RNA sequencing (scRNA-seq) to acquire the transcriptomes of 138,982 cells from 13 samples of six patients including AK, squamous cell carcinoma in situ (SCCIS), cSCC, and their matched normal tissues, covering comprehensive clinical courses of cSCC. We identified diverse cell types, including important subtypes with different gene expression profiles and functions in major keratinocytes. In SCCIS, we discovered the malignant subtypes of basal cells with differential proliferative and migration potential. Differentially expressed genes (DEGs) analysis screened out multiple key driver genes including transcription factors along AK to cSCC progression. Immunohistochemistry (IHC)/immunofluorescence (IF) experiments and single-cell ATAC sequencing (scATAC-seq) data verified the expression changes of these genes. The functional experiments confirmed the important roles of these genes in regulating cell proliferation, apoptosis, migration, and invasion in cSCC tumor. Furthermore, we comprehensively described the tumor microenvironment (TME) landscape and potential keratinocyte-TME crosstalk in cSCC providing theoretical basis for immunotherapy. Together, our findings provide a valuable resource for deciphering the progression from AK to cSCC and identifying potential targets for anticancer treatment of cSCC.

The pursuit of developing groundbreaking pro‐regenerative therapies to expedite skin wound healing persists as a formidable challenge. Peptide RL‐QN15, emerges as a highly promising candidate for the first pro‐regenerative drug derived from amphibian skin, offering a glimmer of hope for innovative healing treatments. Yet, there is an urgent need for intensified research efforts to propel RL‐QN15 from a molecular entity to a viable drug candidate, particularly in unraveling the mechanisms underlying its exceptional pro‐healing efficacy. In the current research, our results revealed that RL‐QN15 significantly enhanced the proliferation, migration, stemness, and epithelial‐to‐mesenchymal transition of human epidermal stem cells (hESCs) through direct binding to the membrane frizzled 8 (FZD8) receptor. This interaction triggers the downstream Wnt/β‐catenin signaling pathway, leading to the up‐regulation of target genes MYC and CCND1. Furthermore, RL‐QN15 augmented the expression and secretion of matrix metalloproteinase‐3, which degrades E‐cadherin and activates the Wnt/β‐catenin pathway, thereby amplifying RL‐QN15's regulatory effects on hESCs. In summary, our findings have demonstrated that RL‐QN15 modulated the functions of ESCs to accelerate skin wound regeneration via the FZD8/β‐catenin axis. This research not only advances peptide RL‐QN15 from a molecular entity to a drug candidate by shedding light on the mechanisms involved with regulation of ESCs functions, but also presents compelling evidence implicating FZD8 as a novel therapeutic target for skin wound regeneration.