Water-Responsive Self-Contractive Silk-Based Skin Anti-Aging Tensioners with Customizable Biofunctions.

Skin anti-aging treatments have become increasingly popular. Currently, the prevalent treatment method involves implanting skin tension regulation threads (skin lifting threads) under the skin, and radiofrequency treatments. In this study, inspired by the natural supercontraction of spider silk, the molecular structure of silk fibroin fibers is modulated into an oriented configuration. This modification endows silk proteins with water-responsive self-contraction capabilities, leading to the development of innovative self-contracting silk-based skin tensioners (SSSTs). To align with clinical requirements, skin tension regulation materials are functionalized by testing for their self-contraction, near-infrared laser heating function, and bacteriostatic properties. The SSSTs exhibited remarkable self-contraction properties, drug-loading and sustained-release capabilities, notable antibacterial effects, controllable degradation, and good biocompatibility. Moreover, the near-infrared light heating function effectively increased subcutaneous temperature, demonstrating its potential for enhancing and prolonging skin lifting effects. Therefore, SSSTs can be applied for skin tension regulation to improve and delay skin aging. The results may pave the way for novel strategies in skin rejuvenation, with broad implications for the field of skin anti-aging.

The efficacy of low-level laser therapy for the healing of second-degree burn wounds on lower limbs of glucocorticoid-dependent patients.

This study was designed to investigate the effect of 630 ~ 650-nm red light on treating second-degree burns on lower limbs of glucocorticoid-dependent patients. Sixty-two glucocorticoid-dependent patients with the second-degree burns on lower limbs were divided into the control group (n = 25) and the observation group (n = 37) according to the treatment sequence and the patients' willingness. The patients in both groups were conventionally treated with 1% sulfadiazine silver cream dressing, with the only difference that the observation group received an additional 630-650-nm red light irradiation for 20 min before dressing. Each group was observed for 21 days, and observation ended if the wound healing was terminated. The wound healing rates, wound secretions, marginal response, and pain/itching levels were monitored and assessed. Compared with the control group, the observation group showed higher wound healing rate, fewer wound secretions, and more relief in marginal response. Clinical observation showed that 630-650-nm red light could effectively reduce wound purulent drainage/discharge, relieve the marginal response as well as pain, and promote wound healing.

The burden of skin and subcutaneous diseases: findings from the global burden of disease study 2019.

Background: The small number of existing integrative studies on the global distribution and burden of all types of skin and subcutaneous diseases hinders relevant comparisons. Objective: This study aimed to determine the latest distribution, epidemiological differences, and factors potentially influencing each skin and subcutaneous disease and the policy implications. Methods: Data on the skin and subcutaneous diseases were obtained from the Global Burden of Disease Study 2019. The incidence, disability-adjusted life years (DALYs), and deaths due to skin and subcutaneous diseases in 204 countries and regions from 1990 to 2019 were analyzed and stratified by sex, age, geographical location, and sociodemographic index (SDI). The annual age-standardized rate of change in the incidence was obtained to evaluate temporal trends. Results: Of 4,859,267,654 (95% uncertainty interval [UI], 4,680,693,440-5,060,498,767) new skin and subcutaneous disease cases that were identified, most were fungal (34.0%) and bacterial (23.0%) skin diseases, which accounted for 98,522 (95% UI 75,116-123,949) deaths. The burden of skin and subcutaneous diseases measured in DALYs was 42,883,695.48 (95%UI, 28,626,691.71-63,438,210.22) in 2019, 5.26% of which were years of life lost, and 94.74% of which were years lived with disability. The highest number of new cases and deaths from skin and subcutaneous diseases was in South Asia. Globally, most new cases were in the 0-4-year age group, with skin and subcutaneous disease incidence slightly higher in men than in women. Conclusion: Fungal infections are major contributors to skin and subcutaneous diseases worldwide. Low-middle SDI states had the highest burden of skin and subcutaneous diseases, and this burden has increased globally. Targeted and effective management strategies based on the distribution characteristics of each country are, thus, required to reduce the burden of skin and subcutaneous diseases.

Infected Diabetic Wound Regeneration Using Peptide-Modified Chiral Dressing to Target Revascularization.

Revascularization plays a critical role in the healing of diabetic wounds. Accumulation of advanced glycation end products (AGEs) and refractory multidrug resistant bacterial infection are the two major barriers to revascularization, directly leading to impaired healing of diabetic wounds. Here, an artfully designed chiral gel dressing is fabricated (named as HA-LM2-RMR), which consists of l-phenylalanine and cationic hexapeptide coassembled helical nanofibers cross-linked with hyaluronic acid via hydrogen bonding. This chiral gel possesses abundant chiral and cationic sites, not only effectively reducing AGEs via stereoselective interaction but also specifically killing multidrug resistant bacteria rather than host cells since cationic hexapeptides selectively interact with negatively charged microbial membrane. Surprisingly, the HA-LM2-RMR fibers present an attractive ability to activate sprouted angiogenesis of Human Umbilical Vein Endothelial Cells by upregulating VEGF and OPA1 expression. In comparison with clinical Prontosan Wound Gel, the HA-LM2-RMR gel presents superior healing efficiency in the infected diabetic wound with respect to angiogenesis and re-epithelialization, shortening the healing period from 21 days to 14 days. These findings for chiral wound dressing provide insights for the design and construction of diabetic wound dressings that target revascularization, which holds great potential to be utilized in tissue regenerative medicine.

HSP70 alleviates sepsis-induced cardiomyopathy by attenuating mitochondrial dysfunction-initiated NLRP3 inflammasome-mediated pyroptosis in cardiomyocytes.

Background: Sepsis-induced cardiomyopathy (SIC) is an identified serious complication of sepsis that is associated with adverse outcomes and high mortality. Heat shock proteins (HSPs) have been implicated in suppressing septic inflammation. The aim of this study was to investigate whether HSP70 can attenuate cellular mitochondrial dysfunction, exuberated inflammation and inflammasome-mediated pyroptosis for SIC intervention. Methods: Mice with cecal ligation plus perforation (CLP) and lipopolysaccharide (LPS)-treated H9C2 cardiomyocytes were used as models of SIC. The mouse survival rate, gross profile, cardiac function, pathological changes and mitochondrial function were observed by photography, echocardiography, hematoxylin-eosin staining and transmission electron microscopy. In addition, cell proliferation and the levels of cardiac troponin I (cTnI), interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) were determined by Cell Counting Kit-8, crystal violet staining and enzyme-linked immunosorbent assay. Moreover, mitochondrial membrane potential was assessed by immunofluorescence staining, and dynamin-related protein 1 and pyroptosis-related molecules [nucleotide-binding domain, leucine-rich-repeat containing family pyrin domain-containing 3 (NLRP3), caspase-1, gasdermin-D (GSDMD), gasdermin-D N-terminal (GSDMD-N)] were measured by western blotting, immunoprecipitation and immunoblotting. Finally, hsp70.1 knockout mice with CLP were used to verify the effects of HSP70 on SIC and the underlying mechanism. Results: Models of SIC were successfully established, as reduced consciousness and activity with liparotrichia in CLP mice were observed, and the survival rate and cardiac ejection fraction (EF) were decreased; conversely, the levels of cTnI, TNF-α and IL-1ß and myocardial tissue damage were increased in CLP mice. In addition, LPS stimulation resulted in a reduction in cell viability, mitochondrial destabilization and activation of NLRP3-mediated pyroptosis molecules in vitro. HSP70 treatment improved myocardial tissue damage, survival rate and cardiac dysfunction caused by CLP. Additionally, HSP70 intervention reversed LPS-induced mitochondrial destabilization, inhibited activation of the NLRP3 inflammasome, caspase-1, GSDMD and GSDMD-N, and decreased pyroptosis. Finally, knockout of hsp70.1 mice with CLP aggravated cardiac dysfunction and upregulated NLRP3 inflammasome activity, and exogenous HSP70 significantly rescued these changes. It was further confirmed that HSP70 plays a protective role in SIC by attenuating mitochondrial dysfunction and inactivating pyroptotic molecules. Conclusions: Our study demonstrated that mitochondrial destabilization and NLRP3 inflammasome activation-mediated pyroptosis are attributed to SIC. Interestingly, HSP70 ameliorates sepsis-induced myocardial dysfunction by improving mitochondrial dysfunction and inhibiting the activation of NLRP3 inflammasome-mediated pyroptosis, and such a result may provide approaches for novel therapies for SIC.

Chiral Hydrogel Accelerates Re-Epithelization in Chronic Wounds via Mechanoregulation.

Chronic wounds, such as diabetic foot ulcers (DFU), are a serious clinical problem. It is a challenge for the conventional wound dressings to achieve the desirable therapeutic efficacy due to the lack of biomimetic structural environment for rapid re-epithelization. Inspired by the naturally existing chiral structures in skin, a novel amino acid-based chiral hydrogel dressing is developed, consisting of left-handed or right-handed helical fibers self-assembled by l/d-phenylalanine derivatives. Compared to the levorotatory chiral hydrogel (LH), the dextral chiral hydrogel (DH) shows the ability to enhance cell adhesion, proliferation, and migration, and strongly promotes diabetic wound healing and re-epithelialization with a drug-free mode. Interestingly, the dextral chiral hydrogel is able to actively increase adsorption of type I collagen and promote proliferation and migration of keratinocyte in an integrin and YAP-mediated manner. This study not only provides a novel strategy for treatment of chronic wounds by utilizing dextral chiral hydrogel dressings, but also unveils the molecular mechanism for effect of dextral chiral structures on the promoted proliferation of keratinocyte.

Effect of a subset of adipose-derived stem cells isolated with liposome magnetic beads to promote cartilage repair.

This study aimed to investigate the ability of CD146+ subset of ADSCs to repair cartilage defects. In this study, we prepared CD146+ liposome magnetic beads (CD146+ LMB) to isolate CD146+ ADSCs. The cells were induced for chondrogenic differentiation and verified by cartilage-specific mRNA and protein expression. Then a mouse model of cartilage defect was constructed and treated by filling the induced cartilage cells into the damaged joint, to evaluate the function of such cells in the cartilage microenvironment. Our results demonstrated that the CD146+ LMBs we prepared were uniform, small and highly stable, and cell experiments showed that the CD146+ LMB has low cytotoxicity to the ADSCs. ADSCs isolated with CD146+ LMB were all CD146+ , CD105+ , CD166+ and CD73+ . After chondrogenic induction, the cells showed significantly increased expression of cartilage markers Sox9, collagen Ⅱ and aggrecan at protein level and significantly increased Sox9, collagen Ⅱ and aggrecan at mRNA level, and the protein expression and mRNA expression of CD146+ ADSCs group were higher than those of ADSCs group. The CD146+ ADSCs group showed superior tissue repair ability than the ADSCs group and blank control group in the animal experiment, as judged by gross observation, histological observation and histological scoring. The above results proved that CD146+ LMB can successfully isolate the CD146+ ADSCs, and after chondrogenic induction, these cells successfully promoted repair of articular cartilage defects, which may be a new direction of tissue engineering.

HSPA1A Protects Cells from Thermal Stress by Impeding ESCRT-0-Mediated Autophagic Flux in Epidermal Thermoresistance.

Thermoresistance is a physiological phenomenon relevant to noninvasive laser treatments for skin esthetics and tumor removal, although the underlying mechanism remains elusive. We hypothesized that HSPA1A may regulate autophagy by reducing ESCRT-0 and/or STAM2 levels, which could lead to thermal protection from cell death. In this study, we showed that thermoresistance was induced in mouse epidermal tissue and HaCaT cells by heating at 45 °C for 10 minutes. Moreover, HSPA1A levels were increased in thermoresistant mouse epidermis and HaCaT cells. HSPA1A was highly involved in protecting cells from thermal cytotoxicity, as evidenced by the knockdown or overexpression assays of the HSPA1A gene. In addition, ESCRT-0 and STAM2 levels were dramatically decreased in thermoresistant cells, which was mediated by HSPA1A binding to STAM2, particularly through HSPA1A amino acids 395‒509. Furthermore, the loss of ESCRT-0 and/or STAM2 in response to HSPA1A-STAM2 binding regulated autophagy by impeding autophagosome‒lysosome fusion and abolishing autophagic flux in cellular thermoresistance, significantly reducing thermal cytotoxicity and promoting cell survival. To our knowledge, it is previously unreported that HSPA1A-ESCRT-0 and/or STAM2 modulates heat-induced resistance by inhibiting autophagic flux. In summary, the results of this study demonstrate that the mechanisms of thermoresistance may have clinical relevance for noninvasive or minimally invasive thermal therapeutics.

Biomimicking Antibacterial Opto-Electro Sensing Sutures Made of Regenerated Silk Proteins.

Surgical sutures play an important role across a wide range of medical treatments and a wide variety exist, differing in strength, size, composition, and performance. Recently, increasing interest has been paid to bioactive and electronic sutures made of synthetic polymers, owing to their ability to reduce inflammation as well as medically and/or electronically facilitate wound healing. However, integrating sensing capabilities into bioactive sutures without adversely affecting their mechanical strength, biocompatibility, and/or bioactivity remains challenging. In this work, a set of biomimicking, antibacterial, and sensing sutures based on the regenerated silk fibroin is designed and fabricated. These sensing sutures, inspired by the "core-shell" multilayered structure of natural spider-silk fibers, are hierarchically structured and heterogeneously functionalized to allow for the integration of multiple, clinically favorable functions into one suture device. These functions included: reducing inflammation and bacterial infection in wound sites, measuring tension of both the tissue and suture, and aiding tissue healing via multi-modal controlled drug and growth factor release. Critically, these functions are coupled with real-time optical and electronic monitoring capabilities. This approach provides greater insight into multifunctional sutures with inherent sensing capabilities and offers enormous potential in both therapeutic and diagnostic applications.

SUMO-specific protease 2 (SENP2) suppresses keratinocyte migration by targeting NDR1 for de-SUMOylation.

A key member of the sentrin/small ubiquitin-like modifier (SUMO)-specific protease (SENP) family, SENP2 has been shown to implicate embryonic development, fatty acid metabolism, atherosclerosis, and neurodegenerative diseases. However, other biologic functions of SENP2 and its specific targets are incompletely understood. Here, we uncovered a novel role of SENP2 in negative regulation of keratinocyte migration, a process crucial to wound epithelialization. Defects in this function are often associated with the clinical phenotypes of chronic nonhealing wounds. Mechanistically, SENP2 as a specific de-SUMOylase targets NDR1 (nuclear Dbf2-related 1), also called STK38 (serine-threonine kinase 38), for de-SUMOylation and SUMO conjugation of NDR1 on Lys-465 attenuates its inhibition of p38/ERK1/2 activation by decreasing the association of NDR1 with MEK kinase 1/2. Significantly, low-level laser (LLL) irradiation increases NDR1 SUMOylation and subsequent p38/ERK1/2 activation via down-regulation of SENP2, leading to faster keratinocyte migration. Our findings fill the gaps that linger in the basic mechanisms underlying LLL therapy.-Xiao, N., Li, H., Yu, W., Gu, C., Fang, H., Peng, Y., Mao, H., Fang, Y., Ni, W., Yao, M. SUMO-specific protease 2 (SENP2) suppresses keratinocyte migration by targeting NDR1 for de-SUMOylation.

Application of 460 nm visible light for the elimination of Candida albicans in vitro and in vivo.

The aim of the present study was to investigate the eradicating effects of 460 nm blue light (BL) on Candida albicans in vitro and in C. albicans­infected skin wounds in a mouse model. In the present study, the antifungal effects of irradiation with BL on C. albicans in vitro and in vivo were investigated. C. albicans colonies and cell numbers were investigated using the spread plate method and flow cytometry respectively following treatment with BL irradiation. In order to determine whether BL can eradicate C. albicans cells within biofilms, an in vitro C. albicans biofilm model was established, and the effect of BL was subsequently investigated using a confocal laser scanning microscope and a Live/Dead staining kit. Furthermore, a mouse skin wound infection model infected with C. albicans was established. Wound healing rates and histological examinations were determined 0, 3, 7, 10 and 14 days post­wounding. The results revealed that C. albicans was eradicated by BL in a dose­dependent manner, with a minimum fluence of 60 J/cm2. Irradiation with BL almost completely eradicated C. albicans when the light fluence was 240 J/cm2. C. albicans inside biofilms was also eradicated and biofilms were destroyed following BL irradiation at 240 J/cm2. In addition, BL was revealed to significantly suppress C. albicans infection in vivo. Irradiation with BL promoted the wound healing of C. albicans infected­skin wounds in a mouse model. In conclusion, the results of the present study demonstrated that 460 nm BL may eradicate planktonic and biofilm C. albicans in vitro, and represents a novel therapeutic strategy for the treatment of C. albicans infections in vivo.

Subacute effects of rose Bengal/Green light cross linking on rabbit thin corneal stability and safety.

BACKGROUND AND PURPOSE: The purpose of this study was to investigate the subacute effects of Rose Bengal (RB) and 532 nm green light-induced photochemical crosslinking (RB-PCL) on rabbit thin corneal stability and safety in vivo. MATERIALS AND METHODS: Rabbit thin corneal models with 250 µm thickness were created by photorefractive keratectomy surgery. Photochemical crosslinking with green light (wavelength 532 nm) at an illumination intensity of 0.4 W/cm2 for 250 s (100 J/cm2 ) was performed, followed by antibiotic treatment and slit lamp monitoring for four weeks. At the end of week four, corneal biomechanical stiffness, biochemical resistance to collagenase digestion, and corneal cellular morphology were assessed. The penetration depth of RB into the corneal stromal was measured by confocal microscopy. RESULTS: At the end of week 4, RB-PCL had increased corneal tensile strength by an average 2.5-fold and had extended the corneal collagenase digestion time from 10.17 ± 2.93 to 15.83 ± 2.64 days. RB penetrated approximately 90 µm into the corneal stroma. RB-PCL did not alter the corneal endothelial and stromal morphology at the cellular or subcellular levels, according to electron microscopic examination. CONCLUSIONS: RB and 532 nm green light irradiation effectively induced crosslinking in rabbit thin cornea, by increasing both the biomechanical stiffness and the biochemical resistance without evidence of morphological damage to the corneal endothelium or stroma. This study demonstrated the efficacy of RB-PCL in strengthening thin cornea at four weeks after the treatment, providing a potential and possibly better option for treating corneal ectasia disorders in cases where corneal thickness is less than 400 µm. Lasers Surg. Med. 50:324-332, 2018. © 2017 Wiley Periodicals, Inc.

Photochemical Cross-Linking for Penetrating Corneal Wound Closure in Enucleated Porcine Eyes.

PURPOSE: To compare the efficacy of photochemical-induced tissue cross-linking (PCL), utilizing Rose Bengal (RB) and 532 nm green light irradiation (RB-PCL), with standard sutures for closure of penetrating corneal incision in porcine cadaver eyes. METHODS: A full-thickness penetrating incision, 3 mm in length parallel to the limbus and perpendicular to the corneal surface, was made in the enucleated porcine cornea. Photochemical cross-linking was performed with tropical RB application and irradiation of 532 nm green light (0.6 W/cm2) for 200, 250, and 300 seconds at laser fluences of 120, 150, and 180 J/cm2, respectively, which was compared with the standard 10-0 nylon suture group. Following treatment, intraocular pressure to the point where wound leakage occurred (IOPL) was measured. Corneal central thickness and surface temperature before and after PCL treatment were recorded. Optical coherence tomography (OCT) and scanning electron microscopy (SEM) were utilized to evaluate wound closure. RESULTS: The mean corneal central thickness was increased from 812.0 ± 47.0 to 838.0 ± 45.6 µm after the incision as a result of cornea aqueous humor infiltration. RB penetrated approximately 140 µm into the porcine corneal stroma. The mean IOPL for untreated blank group after incision was 4.27 ± 0.36 mmHg. Increased laser fluences produced increased IOPL of 27.02 ± 3.01 (PCL120), 31.60 ± 3.67 (PCL150) and 36.73 ± 3.25 mmHg (PCL180), which were statistically different from the control intact group. The mean IOPL in the sutured cornea was 57.30 ± 4.59 mmHg. The average surface temperature difference before and after PCL treatment was 2.03 ± 0.45-2.47 ± 0.79°C. OCT demonstrated not only complete but also improved closure in comparison with disorganized collagen fibers after conventional suturing, which is further confirmed by SEM. CONCLUSIONS: Complete and clinically relevant seal of full-thickness porcine corneal incision was achieved using PCL method ex vivo, which provides potential application of this technique in ocular wound closure.

Involvements of γδT Lymphocytes in Acute and Chronic Skin Wound Repair.

Wound healing involves three stages including inflammation, proliferation, and tissue remodeling. The underlying mechanisms remain to be further elucidated. The inflammation is characterized by spatially and temporally changing patterns of various leukocyte subsets. It is regarded as the most crucial stage since the inflammatory response is instrumental to supplying various factors and cytokines that orchestrate healing events. As a subtype of T lymphocytes, γδ T cells play an important role in skin homeostasis, tumor immunosurveillance, and wound repair. However, either the dynamics of γδ T cells in healing process or the anticipated association of γδ T cells with chronic or refractory wounds were not well understood. In this study, we determine the dynamics of γδ T cells and γδ T cell-produced effectors during acute and chronic wound repair by establishing a third-degree burn model in mice skin or human skin from diabetic patients. Our data show that the involvement of γδ T cells in acute and chronic skin wound healing. The protein levels and mRNA expressions of γδ T cell-produced effectors were increased in acute healing model, whereas those effectors were decreased in chronic repair, suggesting γδ T cells are essential for wound repair. This study probes into the significant relevance of γδ T cells with effective wound repair and provides new enlightenments for the mechanisms of the formation of chronic and/or refractory wounds.

Cisplatin and photodynamic therapy exert synergistic inhibitory effects on small-cell lung cancer cell viability and xenograft tumor growth.

Lung cancer is the leading cause of cancer death worldwide. Small-cell lung cancer (SCLC) is an aggressive type of lung cancer that shows an overall 5-year survival rate below 10%. Although chemotherapy using cisplatin has been proven effective in SCLC treatment, conventional dose of cisplatin causes adverse side effects. Photodynamic therapy, a form of non-ionizing radiation therapy, is increasingly used alone or in combination with other therapeutics in cancer treatment. Herein, we aimed to address whether low dose cisplatin combination with PDT can effectively induce SCLC cell death by using in vitro cultured human SCLC NCI-H446 cells and in vivo tumor xenograft model. We found that both cisplatin and PDT showed dose-dependent cytotoxic effects in NCI-H446 cells. Importantly, co-treatment with low dose cisplatin (1 µM) and PDT (1.25 J/cm2) synergistically inhibited cell viability and cell migration. We further showed that the combined therapy induced a higher level of intracellular ROS in cultured NCI-H446 cells. Moreover, the synergistic effect by cisplatin and PDT was recapitulated in tumor xenograft as revealed by a more robust increase in the staining of TUNEL (a marker of cell death) and decrease in tumor volume. Taken together, our findings suggest that low dose cisplatin combination with PDT can be an effective therapeutic modality in the treatment of SCLC patients.

Reactive Oxygen Species Mediated Prostaglandin E2 Contributes to Acute Response of Epithelial Injury.

Reactive oxygen species (ROS) generated after tissue injury play a crucial role during wound healing through initiating acute inflammation, clarifying infection and dead tissue, and mediating various intracellular signal transduction. Prostaglandin E2 (PGE2) has been identified as one of the major factors responsible for inflammation and tissue repair. In this study, we tested our hypothesis that ROS produced by damaged human keratinocytes induces the synthesis of PGE2. In vitro epithelial wounding model was used to observe the production of ROS and secretion of PGE2 as well as the involved signal pathway. The mechanical injury caused the rapid production of ROS in in vitro cultured keratinocytes, which was significantly blocked by an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase. The increased intracellular ROS caused by mechanical injury stimulates PGE2 production in a time-dependent manner via the activation of cyclooxygenase-2 (COX-2), which was stimulated by phosphorylation of extracellular signal-regulated protein kinase (ERK). These results indicate ROS-induced ERK activation leading to the activation of COX-2 and the synthesis of PGE2 in human keratinocytes responding to mechanical injury in the acute phase.

Low molecular weight chitosan-coated silver nanoparticles are effective for the treatment of MRSA-infected wounds.

Silver nanoparticles (AgNPs) are being widely applied as topical wound materials; however, accumulated deposition of silver in the liver, spleen, and other main organs may lead to organ damage and dysfunction. We report here that low molecular weight chitosan-coated silver nanoparticles (LMWC-AgNPs) are effective against methicillin-resistant Staphylococcus aureus (MRSA), have better biocompatibility, and have lower body absorption characteristics when compared with polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) and silver nanoparticles without surface stabilizer (uncoated-AgNPs) in a dorsal MRSA wound infection mouse model. LMWC-AgNPs were synthesized by reducing silver nitrate with low molecular weight chitosan as a stabilizer and reducing agent, while PVP-AgNPs were synthesized using polyvinylpyrrolidone as a stabilizer and ethanol as a reducing agent. AgNPs with different surface stabilizers were identified by UV-visible absorption spectrometry, and particle size was determined by transmission electron microscopy. UV-visible absorption spectra of LMWC-AgNPs, PVP-AgNPs and uncoated-AgNPs were similar and their sizes were in the range of 10-30 nm. In vitro experiments showed that the three types of AgNPs had similar MRSA-killing effects, with obvious effect at 4 µg/mL and 100% effect at 8 µg/mL. Bacteriostatic annulus experiments also showed that all the three types of AgNPs had similar antibacterial inhibitory effect at 10 µg/mL. Cell counting kit-8 assay and Hoechst/propidium iodide (PI) staining showed that LMWC-AgNPs were significantly less toxic to human fibroblasts than PVP-AgNPs and uncoated-AgNPs. Treatment of mice with MRSA wound infection demonstrated that the three types of AgNPs effectively controlled MRSA wound infection and promoted wound healing. After continuous application for 14 days, LMWC-AgNPs-treated mice showed significantly reduced liver dysfunction as demonstrated by the reduced alanine aminotransferase and aspartate aminotransferase levels and liver deposition of silver, in comparison to mice treated with uncoated-AgNPs or PVP-AgNPs. Our results demonstrated that LMWC-AgNPs had good anti-MRSA effects, while harboring a better biocompatibility and lowering the body's absorption characteristics.

Inhibition of IRF8 Negatively Regulates Macrophage Function and Impairs Cutaneous Wound Healing.

The inflammatory response is essential for normal cutaneous wound healing. Macrophages, as critical inflammatory cells, coordinate inflammation and angiogenesis phases during wound healing. It has been reported that the transcription factor interferon regulatory factor 8 (IRF8), a member of the IRF family, plays a critical role in the development and function of macrophages and is associated with inflammation. However, the role of IRF8 in cutaneous wound healing and its underlying mechanism remain elusive. Through immunohistochemical (IHC) staining, we showed that IRF8 is involved in the wound repair process in mice and patients. Furthermore, we ascertain that the repression of IRF8 by small interfering RNA (siRNA) leads to delayed wound healing. To explore the mechanism by which IRF8 impacts wound healing, we observed its effect on macrophage-related mediators by IHC or real-time PCR. The results demonstrated that the inhibition of IRF8 decreases the mRNA expression of inflammatory mediators associated with M1 macrophage (il-1b, il-6, inos, and tnf-a) but no impact on M2 macrophage-related mediators (arg-1, mrc-1, and il-10) and the number of macrophages in the wounds. Furthermore, the inhibition of IRF8 induced apoptosis in the wounds. In summary, this study demonstrates that the down-regulation of IRF8 in the wound leads to impaired wound healing possibly through the regulation of macrophage function and apoptosis in skin wound.