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. 2025 Aug 26;30:813. doi: 10.1186/s40001-025-03056-7

METTL14-mediated m6A methylation promotes macrophage M2 polarization via YTHDF1-Socs1 axis to accelerate skin wound healing

Jixun Zhang 1,✉, Chao Wang 1, Xinxin Dong 1
PMCID: PMC12381997  PMID: 40859253

Abstract

Background

Macrophage polarization plays a crucial role in the processes of inflammation, angiogenesis, and wound healing. N6-methyladenosine (m6A) RNA modification has been widely recognized as an abundant modification that regulates RNA expression. This work aimed to investigate the function of m6A modified Socs1 in skin wound healing.

Methods

A full-thickness skin wounds mouse model was established and treated with Socs1 overexpression. The wound healing process and the histological changes of skin tissues were detected. Ana-1 macrophages were treated with lipopolysaccharide (LPS) to mimic the inflammatory environment during the wound healing process. The macrophage polarization was detected by immunofluorescence staining of specific biomarkers and production of inflammatory factors was measured using ELISA kits. Angiogenesis and fibroblast proliferation and migration were measured by the co-culture system of Ana-1 with dermal microvascular endothelial cells (DMECs) or dermal fibroblasts (DFs). The m6A modification of Socs1 mRNA was measured by m6A mRNA immunoprecipitation.

Results

Socs1 expression was upregulated during wound healing process and M2 polarization of macrophages. Socs1 overexpression accelerated mouse skin wound healing and enhanced the formation of granulation tissue in wound tissues. Co-culture with Socs1-overexpressed macrophages increased angiogenesis of DMECs and enhanced the viability and migration of DFs. METTL14 regulates Socs1 expression in Ana-1 cells and increased the m6A methylation of Socs1 mRNA by recruiting YTHDF1.

Conclusion

Socs1 regulates the M2 macrophages polarization and accelerates wound healing, which is modulated by METTL14-mediated m6A modification of Socs1 mRNA through YTHDF1 recruitment in macrophages.

Keywords: Wound healing, M6A methylation, METTL14, M2 macrophages, Angiogenesis, Inflammation

Introduction

Skin acts as the primary barrier that protects the internal organs and tissues from external damage, including the ultraviolet radiation, extreme temperatures, mechanical injury, and microbial infection [1]. Wounds to the skin frequently occur in daily life, as well as following the surgery and traumatic events, increasing the risk of severe internal injuries [1, 2]. The skin is composed of two layers: the dermis and the epidermis. The epidermis is the thin outer layer that mainly comprises keratinocytes and small number of other cells such as Merkel cells, melanocytes, and Langerhans cells, and it contributes to some of the mechanical properties of the skin [3]. The dermis is the inner skin layer that provides structural support, elasticity, and nutrition. It is mainly composed of fibroblasts, immune cells, and an extracellular matrix (ECM) rich in collagen, as well as keratinizing structures, lymphatic vessels, blood vessels, nerves, and glands [3]. When tissue damage occurs, various cell types in dermis and epidermis participate in and coordinate precise processes, including the hemostasis, tissue growth, inflammatory response, re-epithelialization, vascular formation, and ECM remodeling [4].

Macrophages are critical immune cells that participate in the response to infections and regulate the pathological processes during wound healing. Macrophages produce growth factors and cytokines and engage in phagocytic activities to orchestrate fibrosis, inflammation and skin repair [5, 6]. During wound healing, macrophages transition from the predominantly pro-inflammatory form (M1 phenotype) present at early stage upon injury to an anti-inflammatory form (M2 phenotype) that appears later to promote wound closure [7]. Therefore, the transformation of macrophages is regarded as a pivotal process and ideal target for the repair of wounded tissues.

N6-methyladenosine (m6A) RNA modification is well-recognized as an abundant modification of eukaryotic mRNAs and long noncoding RNAs (lncRNAs) and has been widely studied in various cellular processes and diseases [8]. Recent studies have uncovered the mechanisms by which m6A modification controls the transportation, translation, and stability of RNAs [9–11]. The m6A methylation of mRNAs is regulated by a specific methyltransferase complex, in which methyltransferase like 3 (METTL3) and 14 (METTL14) form the central catalytic complex [12]. Moreover, after METTLs initiate m6A methylation, a number of co-factors, including the YTH (YT521-B homology) domain family of proteins (YTHDFs), recognize the m6A-modified RNA to regulate RNA processing [13]. Studies demonstrate that FTO-mediated m6A demethylation inhibits YTHDF2-dependent mRNA decay, upregulating STAT1 and PPARγ expression and activating NF-κB signaling, thereby promoting the concurrent activation of both M1 and M2 macrophages [14]. Furthermore, other RNA epigenetic modifications contribute to M2 macrophage polarization. For example, ADAR1 catalyzes A-to-I editing of pre-miR-21, attenuating mature miR-21 production and subsequently enhancing IL-10 expression to drive M2 macrophage activation [15].

The suppressor of cytokine signaling (Socs) family of proteins are important regulators of inflammatory responses [16]. Socs family members bind to signaling proteins via the SH2 domain and induce their ubiquitination and degradation of these proteins, thereby disrupting intracellular cytokine signaling transduction [17]. Studies have reported that Socs1and Socs3 mediate the polarization of macrophages to M2 phenotype and alleviate the neuroinflammation following traumatic brain injury [18]. In this study, we investigated the effects of Socs1 on wound healing using in vitro and in vivo models. We observed that Socs1 overexpression promoted the wound healing process and was modulated by METTL14-mediated m6A methylation through the recruitment of YTHDF. Our findings provide further evidence of the role of m6A methylation in wound healing and suggest a novel and promising strategy for accelerating the wound healing process.

Materials and methods

Murine skin wound model

All animal procedures were performed according to the guidelines of the Animal Care Committee of The Second Hospital, Cheeloo College of Medicine, Shandong University (MDL2023-01-18-02), and all experimental protocols were performed with the approval of The Second Hospital, Cheeloo College of Medicine, Shandong University. This study was conducted in accordance with the Declaration of Helsinki. BALB/c mice aged 8-weeks and weighing approximately 20 g were obtained from Huafukang Laboratory Co., Ltd. The mice were divided into experimental groups, anesthetized by intraperitoneal injection of pentobarbital sodium (30 mg/kg), and then shaved. A full-thickness skin wound with diameter of 1 cm was created on the back of each mouse. For treatment, vectors encapsulated by lentivirus (LV) and siRNAs were subcutaneously injected into the tissues around wound site. The LV-Socs1 and LV-METTLE14 with titer of 1 × 109 TU/mL were purchased from GenePharma. Wound images were captured using a digital camera on days 0, 4, and 8. Clinical trial number: not applicable.

Histological analysis

On the 8th day, the mice were anesthetized by intraperitoneal injection of pentobarbital sodium, and then sacrificed by cervical dislocation while under anesthesia. After that, skin tissues at the wound sites were collected. The tissues were fixed in 4% paraformaldehyde (PFA), dehydrated, and embedded in paraffin to create tissue slices. Hematoxylin–eosin (HE) staining (Beyotime, China) and Masson’s trichrome staining (Beyotime, China) were performed to observe pathological changes and collagen deposition, respectively. The expression of CD31 protein was examined by immunohistochemical (IHC) with anti-CD31 antibody (Abcam, USA).

Immunofluorescence (IF) staining

Macrophage polarization was evaluated by staining for the M1 marker iNOS and M2 marker CD163. The paraffin-embedded tissue samples were rehydrated in ethanol, penetrated with 0.2% Triton X-100, and incubated with anti-iNOS and anti-CD163 primary antibody overnight at 4 °C, followed by incubation with secondary antibody. Nuclei were stained with DAPI (Thermo, USA). Images were captured using a fluorescence microscope (Leica, Germany).

Cell line and treatment

Mouse macrophage Ana-1, mouse dermal microvascular endothelial cells (DMECs), and mouse dermal fibroblasts (DFs) were obtained from Procell Co., Ltd (China) and cultured in RPMI 1640 (Hyclone, USA) containing 10% fetal bovine serum (FBS, Gibco, USA) and 1% penicillin–streptomycin, DMEC-specific culture medium (Procell), and DF-specific culture medium (Procell) in a 37 °C incubator with 5% CO2. Macrophages polarization was induced by stimulation with lipopolysaccharide (LPS) at 1 μg/mL for 24 h.

Cell transfection

The Socs1 overexpression vectors, METTL14 overexpression vectors, METTL14 with R298P mutation, siMETTL14, siYTHDF, and negative control vectors (NC) were synthesized by GenePharma (China) and transfected using Lipofectamine 2000 reagent. Briefly, cells were seeded into 6-well plates to reach 70% confluence. The siRNA (2 µg) or overexpression vectors (5 µg) and Lipofectamine 2000 reagent were diluted in 50 µl OptiMEM medium separately and incubated for 5 min. Then, the oligonucleotides and Lipofectamine 2000 were mixed and incubated for 20 min, followed by incubation with cells at 37 °C for 48 h.

Cell co-culture

Cell co-culture was performed in Transwell chambers (Corning, USA). Ana-1 cells were stimulated with LPS and transfected with the indicated vectors, then placed in the apical chambers. DMECs or DFs were seeded into basolateral chambers. Cell culture medium was added, and the cells were incubated for 34 h.

Tube formation assay

The in vitro vascular formation was evaluated by tube formation assay. In brief, Matrigel (BD Bioscience, USA) was coated onto the bottom of 96-well plate and incubated at 37 °C for 30 min for polymerization. DMECs were then suspended in culture medium (2 × 104 cells/well) and seeded onto the Matrigel. After incubation for 6 h, images of the tubes were captured using a light microscope (Leica, Germany).

Wound healing assay

DFs were seeded into 6-well plates and cultured until they reached 80% confluence. Wounds were then created using a sterile 200 µl pipette tip. Cells were washed with PBS to remove debris and cultured in serum- free medium for 24 h. Images of wounds were captured at 0 and 24 h after scratching.

Western blotting assay

Ana-1 cells were lysed using RIPA lysis buffer (Beyotime, China) to extract total proteins. After quantification with BCA assay kit, 50 µg proteins were loaded and separated in SDS-PAGE gel and then blotted onto polyvinylidene fluoride membranes. The blots were blocked in 5% non-fat milk and incubated overnight at 4 °C with primary antibodies against Socs1, METTL14, and YTHDF. Next day, the membranes were incubated with secondary anti-mouse or anti-rabbit antibodies and visualized using an ECL solution.

Quantitative polymerase chain reaction (qPCR) assay

Total RNA was extracted from cells and tissues using TRIzol reagent (Thermo, USA) and reverse-transcribed to cDNA using PrimeScript RT reagent Kit (Takara, Japan). Gene quantification was conducted using SYBR Green qPCR Mix (Transgen) and normalized to GPADH following the 2−ΔΔCt method.

Enzyme-linked immunosorbent assay (ELISA)

The production of tumor necrosis factor-α (TNF-α), transforming growth factor beta 1 (TGF-β1), vascular endothelial growth factor (VEGF), and interleukin 12 (IL-12) was measured using commercial mouse ELISA kits purchased from Biovision and Abcam, following the manufacturers’ protocols.

m6A mRNA immunoprecipitation (IP) and quantification

The PolyA + RNA was isolated from cells for RNA immunoprecipitation. Protein G beads (Thermo, USA) were incubated with an anti- N6-methyladenosine monoclonal antibody at 4 °C for 16 h with rotation. Next day, the antibody-conjugated beads were incubated with PolyA + RNA at 4 °C for 6 h with rotation. Subsequently, the beads were eluted and washed, and RNA was extracted using Trizol. The extracted RNA was analyzed by qPCR to measure the expression level of Socs1.

Statistics

Each experiment was conducted for at least three times and data were shown as means ± SD. Data were analyzed by SPSS software (Version 20.0) and comparison between two or more groups were analyzed by t test and one-way or two-way ANOVA followed by Tukey’s test. The p < 0.05 was regarded as significant difference.

Results

Socs1 expression is correlated with M2 polarization and accelerates wound healing in murine model

We established a murine wound healing model and observed elevated RNA level of Socs1 in healing skin on day 8 compared with day 0 (Fig. 1A), suggesting a potential correlation between Socs1 and tissue healing. Next, we inducted the polarization of macrophages and measured the expression of Socs1. The M2 macrophages expressed a notably higher level of Socs1 compared with the M1 type (Fig. 1B). To elucidate the specific function of Socs1 in M2 polarization and wound healing, we administrated LV-Socs1 treatment to the wounded mouse skin. The mice were sacrificed on day 8 and skin tissues were collected for subsequent experiments. As shown in Fig. 1C, D, LV-Socs1 notably elevated the level of Socs1 in skin tissues and significantly accelerated the healing process of skin wounds. The results from HE staining and Masson’s staining showed that Socs1 overexpression significantly enhanced the formation of granulation tissues (Fig. 1E) and increased the collagen deposition (Fig. 1F). In addition, the results from IHC staining showed increased CD31 expression, indicating enhanced vascular formation in wounded tissues (Fig. 1G). Additionally, we assessed the proportions of M1 and M2 macrophages in tissues by using IF staining of iNOS (M1 macrophage biomarker; red fluorescence) and CD163 (M2 macrophage biomarker; green fluorescence). It was shown that the proportion of M1 macrophages decreased, while that of M2 macrophages increased under Socs1 treatment (Fig. 1H). Moreover, we analyzed the production of cytokines to confirm the polarization of macrophages. Socs1 treatment notably elevated the production of VEGF and TGF-β1 by M2 macrophages while suppressing the production of IL-12 and TNF-α by M1 macrophages (Fig. 1I).

Fig. 1.

Fig. 1

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Socs1 expression is correlated with M2 polarization and accelerates wound healing in murine model. A Expression of Socs1 in skin tissues of mice at day 1 and day 8 was measured by qPCR. B The RNA level of Socs1 in M0, M1, and M2 macrophages was measured by qPCR. C–I The murine wound healing model established and treated with Socs1 overexpression vectors. Then, the RNA level of Socs1 in the skin tissues was measured by qPCR. D Images of wounds were shown. E HE staining of skin tissue was performed. F The collagen deposition in the skin tissues was measured by Masson’s trichrome staining. G CD31 expression in the skin tissues was measured by IHC staining. H IF staining was performed for iNOS (M1 macrophage biomarker; red fluorescence) and CD163 (M2 macrophage biomarker; green fluorescence) in the skin tissues. I The levels of IL-12, TNF-α, VEGF and TGF-β1 in skin tissues were measured by ELISA. **p < 0.01, ***p < 0.001

Socs1 promotes M2 polarization, DMEC angiogenesis and DF viability

We next determined the function of Socs1 in macrophage polarization, angiogenesis of DMECs and the migration of DFs. Ana-1 cells were treated with LPS to stimulate M1 polarization. As shown in Fig. 2A, the expression of the M2 biomarker CD163 in Ana-1 cells was notably suppressed by LPS but this suppression was reversed by Socs1 overexpression. Besides, the LPS-elevated production of IL-12 and TNF-α and the LPS-suppressed production of VEGF and TGF-β1 were reversed by Socs1 overexpression (Fig. 2B), suggesting that Socs1 promotes M2 macrophage polarization. Furthermore, we co-cultured the macrophages with DMECs or DFs to assess in vitro vascular formation by microvascular endothelial cells and fibroblast proliferation and migration. As shown in Fig. 2C, co-culture with LPS-stimulated Ana-1 suppressed the tube formation ability of DMECs compared with those co-cultured with PBS-treated Ana-1 cells, However, overexpression of Socs1 in Ana-1 cells recovered the angiogenesis ability of co-cultured DMECs. Moreover, co-culture with LPS-treated Ana-1 cells suppressed fibroblast viability, which was reversed by Socs1 overexpression (Fig. 2D). The results from the wound—healing assay and Transwell assay showed a decreased number of migrated DFs upon co-culture with LPS-stimulated Ana-1 cells, whereas overexpression of Socs1 in LPS-stimulated Ana-1 cells abolished these effects (Fig. 2E, F). These data indicated that the Socs1-promoted M2 polarization enhanced the angiogenesis ability of dermal microvascular endothelial cells and the viability of dermal fibroblasts.

Fig. 2.

Fig. 2

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Socs1 promotes angiogenesis and DF migration. A and B Ana-1 cells were treated with LPS and subjected to the of Socs1. A The expression of CD163 was measured by IF staining (green fluorescence). B The production of TNF-α and IL-12, TGF-β, and VEGF was measured by ELISA. C DMECs were co-cultured with Ana-1 cells that treated with LPS and subjected to the overexpression of Socs1. The in vitro angiogenesis of DMECs was detected by the tube formation. D–F DFs were co-cultured with Ana-1 cells that treated with LPS and subjected to the overexpression of Socs1. Then, D cell proliferation was measured by CCK-8 assay and cell migration was checked by E the wound healing assay and F the Transwell assay. **p < 0.01

METTL14 regulates m6A modification of Socs1 in macrophages through YTHDF1

Subsequently, we evaluated whether Socs1 could be regulated by METTL14. We observed that both siMETTL14-1 and siMETTL14-2 effectively downregulated the RNA level of METTL14 in Ana-1 cells (Fig. 3A). The results from m6A RIP experiment and western blotting assay showed that depletion of METTL14 significantly decreased the level of m6A on Socs1 mRNA (Fig. 3B) and the protein level of Socs1 (Fig. 3C), suggesting that METTL14 may modulate Socs1 expression by regulating m6A modification. Next, we measured the Socs1 protein degradation by using CHX to block protein synthesis. The protein level of Socs1 was notably decreased at 6 h after CHX treatment in control cells and siMETTL14-2-treated cells, whereas siMETTL14-1 effectively decreased the Socs1 protein level within 3 h (Fig. 3D), indicating that the knockdown of METTL14 with siMETTL14-1 could suppress the Socs1 RNA stability. The R298P is a pivotal site in METTL14 that mediates m6A modification. We expressed wild type METTL14 or R298P mutant METTL14 in Ana-1 cells to determine whether METTL14 regulates Socs1 expression via m6A modification. Both wild-type METTL14 and the R298P mutant METTL14 significantly upregulated the protein level of METTL14 in Ana-1 cells, but the R298P mutant failed to upregulate Socs1 expression (Fig. 3E). Moreover, depletion of YTHDF1, the reader of m6A modification, suppressed the expression of Socs1 (Fig. 3F), and reversed the METTL14-upregulated Socs1 protein level (Fig. 3G). These data demonstrated that METTL14 regulates the m6A modification of Socs1 via YTHDF1.

Fig. 3.

Fig. 3

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METTL14 regulates m6A modification of Socs1 in macrophages through YTHDF1. A–C Ana-1 cells were transfected with siMETTL14-1 or siMETTL14-2. A The RNA level of METTL14 in Ana-1 cells was measured by qPCR assay. B The enrichment of m6A modification on Socs1 mRNA was measured by m6A RIP. C The protein level of Socs1 was detected by western blotting assay. D Ana-1 cells were transfected with siMETTL14-1 or siMETTL14-2 and treated with CHX, an inhibitor of protein synthesis, then protein level of Socs1 at 0, 3, 6, and 12 h was assessed by western blotting assay. E The Ana-1 cells were overexpressing wild type or R298P mutated METTL14, then protein levels of METTL14 and Socs1 were checked by western blotting assay. F The Ana-1 cells were transfected with siYTHDF1. Then the protein levels of Socs1 and YTHDF1 were checked by western blotting assay. G The Ana-1 cells were transfected with METTL14 overexpression vectors and siYTHDF1. then protein level of Socs1 was checked by western blotting assay

METTL14/YTHDF1/Socs1 axis modulates M2 polarization, angiogenesis and fibroblasts viability

We conducted rescue experiments using LPS-stimulated macrophages that overexpressed METTL14 by knocking down Socs1 and YTHDF1. The transfected macrophages were then co-cultured with DMECs or DFs. We found that METTL14 overexpression elevated the expression of the M2 macrophage biomarker CD163, suppressed the production of TNF-α and IL-12, and increased the production of TGF-β and VEGF, while depletion of Socs1 and YTHDF1 reversed these effects (Fig. 4A, B). Moreover, knockdown of Socs1 and YTHDF1 in macrophages abolished the METTL14 overexpression-induced tube formation ability of the co-cultured DMECs (Fig. 4C). The enhanced proliferation (Fig. 4D) and migration (Fig. 4E, F) of DFs co-cultured with METTL4-overexpressed Ana-1 cells were significantly retarded by siSocs1 and siYTHDF1. These data indicated that Socs1 and YTHDF1 mediate the METTL14-regualted M2 polarization, DMEC angiogenesis and fibroblasts viability.

Fig. 4.

Fig. 4

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METTL14/YTHDF1/Socs1 axis modulates M2 polarization, angiogenesis and fibroblast viability. A and B Ana-1 cells were treated with LPS, subjected to the overexpression of Socs1, or the depletion of Socs1 or YTHDF1. A The expression of CD163 was measured by IF staining (green fluorescence). B The production of TNF-α and IL-12, TGF-β and VEGF was measured by ELISA. C DMECs were co-cultured with Ana-1 cells that received indicated treatment. The in vitro angiogenesis of DMECs was detected by tube formation assay. D–F DFs were co-cultured with Ana-1 cells that received indicated treatment. Then, D cell proliferation was measured by CCK-8 assay and cell migration was checked by E wound healing assay and F and Transwell assay. **p < 0.01, ***p < 0.001

METTL14/YTHDF1/Socs1 axis enhances in vivo wound healing

Subsequently, we verified the METTL14-regulated m6A modification of Socs1 in a mouse skin damage model. After creating skin wounds, LV-METTL14 vectors, siYTHDF1, and siSocs1 were injected around the wounds. We found that METTL14 accelerated the healing process of skin wounds, whereas the suppression of YTHDF1 and Socs1 retarded the wound repair (Fig. 5A). The results from HE staining and Masson’s staining showed that METTL14 overexpression promoted the formation of granulation tissue (Fig. 5B) and collagen deposition (Fig. 5C). Moreover, the CD31 expression and angiogenesis in wounded skin tissues were elevated by METTL14, and these effects were then suppressed by the depletion of YTHDF1 and Socs1 (Fig. 5D).

Fig. 5.

Fig. 5

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METTL14/YTHDF1/Socs1 axis enhances in vivo wound healing. Mice with skin wounds were treated with METTL14 overexpression vectors, siSocs1, or siYTHDF1. A Images of the wounds at day 4 and day 8 were shown. B HE staining of the skin tissue was performed. C The collagen deposition in skin tissues was measured by Masson’s trichrome staining. D CD31 expression in the skin tissues was measured by IHC staining

Discussion

Insufficient wound healing is correlated with damaged skin barrier, tissue infection, necrosis, and other severe systemic and local consequences, which affect the life quality and is a waste of time and money [19]. Therefore, it is essential to develop novel and efficient methods to improve the wound healing process. In this study, we found that Socs1 was significantly elevated in mouse skin during the wound healing process and was highly expressed in M2 macrophages compared to the M1 type. Overexpression of Socs1 accelerated the healing of wounded skin, increased tissue granulation formation and collagen deposition, and enhanced the production of TGF-β and VEGF. Macrophage polarization plays a critical role in inflammation and wound healing [20, 21]. Regulating this process is of profound significance for improving wound healing and has been widely studied [22, 23]. Anti-inflammation is a pivotal event in the wound healing process [24]. The M2 phenotype of macrophages primarily exhibits anti-inflammatory effects and produces keratinocyte growth factor and epidermal growth factor to stimulate the proliferation of keratinocytes and fibroblasts, as well as the production of ECM proteins and collagen, thereby enhancing tissue granulation and epithelialization at wound sites [25]. These findings support the notion that Socs1 may promote the wound healing process by regulating macrophage polarization and inflammation.

Angiogenesis is an imperative process during wound healing due to its function in recovering blood supply which consequently supports the necessary exchange of nutrients and oxygen [26]. The proliferation and migration of DMECs and DFs represent the activity of angiogenesis and have been widely used in in vitro studies of wound healing [3]. We found that overexpression of Socs1 in Ana-1 cells enhanced M2 polarization which was initially blocked by LPS stimulation. Co-culturing with these polarized macrophages promoted the vascular formation of DMECs and the proliferation and migration of DFs. These findings suggest that the promoting effects of Socs1 on skin wound healing are closely correlated with M2 polarization of macrophages. Consistent with this finding, the M2 phenotype has been shown to enhance angiogenesis and fibroblasts migration [23].

The various forms of RNA modifications influence the stemness of epidermal progenitor cells and tissue homeostasis [27]. Studies over the past decade have demonstrated that m6A functions as a chemical mark on mRNA, facilitating the grouping of numerous gene transcripts for mRNA translation during cell differentiation and upon response to intracellular and environmental signaling [28]. A study indicated that changes in m6A modification on lncRNA Pvt1 regulated the stemness and differentiation of epidermal progenitor cells, and depletion of m6A methyltransferase impairs the self-renewal and wound healing capacity of skin [29]. Nevertheless, research on m6A modification in skin wound repair remains limited and is critically needed [30]. In this work, we investigated whether m6A modification is correlated with the functions of Socs1 during the repair process of wounded skin tissues. We found that METTL14 regulates the expression of Socs1 in macrophages, stimulating angiogenesis, proliferation and migration of co-cultured DMECs and DFs. A previous study indicated that ablation of METTL14 in myeloid cells intensified the bacterial infection induced macrophage responses, leading to sustained inflammation response and increased mortality in mice [31]. This METTL14 ablation suppressed YTHDF1 binding and impeded m6A methylation of Socs1, resulting in excessive activation of TLR4/NF-κB signaling in macrophages both in vitro and in vivo [31]. Consistent with these findings, our in vitro experiments identified that METTL14 recruits the YTHDF1 toSocs1 mRNA and enhance the m6A modification level. This regulation affects the M2 polarization of Ana-1 cells and consequently promotes angiogenesis, fibroblast migration, collagen deposition, and in vivo wound healing.

While our study demonstrates that the METTL14/YTHDF1 axis upregulates Socs1 to promote M2 polarization, recent reports suggest METTL14/YTHDF2 may suppress M2 polarization [32, 33]. This discrepancy could stem from: (1) differential roles of YTHDF1 (translation promotion) versus YTHDF2 (mRNA decay) in m6A-mediated regulation; (2) Under specific conditions, opposing functions of Socs1 in different signaling pathways. Our findings highlight the complexity of m6A machinery in macrophage polarization, warranting further investigation into METTL14’s substrate-specific effects and temporal regulation during wound healing.

While our findings demonstrate that METTL14-mediated m6A modification significantly enhances wound closure in mice, it is important to note that wound healing mechanisms differ substantially between rodents and humans. Notably, Rodent skin is elastic and loosely attached to underlying structures, enabling wound closure primarily through contraction mediated by the panniculus carnosus or striated muscle activation, whereas human skin heals via granulation tissue formation and re-epithelialization [14].This fundamental difference suggests that while our study establishes a proof-of-concept for m6A regulation in macrophage polarization during wound repair, the translational potential requires validation in human-relevant models.

Conclusion

To summarize, this work elucidates that Socs1 regulates the M2 polarization of macrophages and accelerates wound healing. The regulation of Socs1 is achieved through the METTL14—regulated m6A modification on its mRNA. Specifically, METTL14 recruits YTHDF1 in macrophages to perform this modification. This study demonstrates that the METTL14—regulated Socs1 may have potential application value in the treatment of wound healing.

Acknowledgements

The data used and/or analyzed during the current study available from the corresponding author on reasonable request.

Author contributions

Conception and design: Jixun Zhang and Chao Wang. Method: Jixun Zhang. Data Collection: Jixun Zhang. Manuscript Writing: Jixun Zhang. All authors contributed to the article and approved the submitted version.

Funding

None.

Data availability

Data is provided within the manuscript or supplementary information files.

Declarations

Ethics approval and consent to participate

All animal procedures were performed according to the guidelines of the Animal Care Committee of The Second Hospital, Cheeloo College of Medicine, Shandong University (MDL2023-01–18-02), and all experimental protocols were performed with the approval of The Second Hospital, Cheeloo College of Medicine, Shandong University. This study was conducted in accordance with the Declaration of Helsinki.

Consent for publication

All the authors have approved the manuscript and agree with submission to your esteemed journal.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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