1α,25-dihydroxyvitamin D3-eluting nanofibrous dressings induce endogenous antimicrobial peptide expression

Increased LL37 in psoriasis and other inflammatory disorders promotes LDL uptake and atherosclerosis

Patients with chronic inflammatory disorders such as psoriasis have an increased risk of cardiovascular disease and elevated levels of LL37, a cathelicidin host defense peptide that has both antimicrobial and proinflammatory properties. To explore whether LL37 could contribute to the risk of heart disease, we examined its effects on lipoprotein metabolism and show that LL37 enhanced LDL uptake in macrophages through the LDL receptor (LDLR), scavenger receptor class B member 1 (SR-B1), and CD36. This interaction led to increased cytosolic cholesterol in macrophages and changes in expression of lipid metabolism genes consistent with increased cholesterol uptake. Structure-function analysis and synchrotron small-angle x-ray scattering showed structural determinants of the LL37-LDL complex that underlie its ability to bind its receptors and promote uptake. This function of LDL uptake is unique to cathelicidins from humans and some primates and was not observed with cathelicidins from mice or rabbits. Notably, Apoe-/- mice expressing LL37 developed larger atheroma plaques than did control mice, and a positive correlation between plasma LL37 and oxidized phospholipid on apolipoprotein B (OxPL-apoB) levels was observed in individuals with cardiovascular disease. These findings provide evidence that LDL uptake can be increased via interaction with LL37 and may explain the increased risk of cardiovascular disease associated with chronic inflammatory disorders.

Electrospun fiber-based immune engineering in regenerative medicine

Immune engineering, a burgeoning field within regenerative medicine, involves a spectrum of strategies to optimize the intricate interplay between tissue regenerative biomaterials and the host tissue. These strategies are applied across different types of biomaterials and various disease models, which encompasses finely modulating the immune response at the levels of immune cells and factors, aiming to mitigate adverse effects like fibrosis and persistent inflammation that may arise at the injury site and consequently promote tissue regeneration. With the continuous progress in electrospinning technology, the immunoregulatory capabilities of electrospun fibers have gained substantial attention over the years. Electrospun fibers, with their extracellular matrix-like characteristics, high surface-area-to-volume ratio, and reliable pharmaceutical compound capacity, have emerged as key players among tissue engineering materials. This review specifically focuses on the role of electrospun fiber-based immune engineering, emphasizing their unique design strategies. Notably, electrospinning actively engages in immune engineering by modulating immune responses through four essential strategies: (i) surface modification, (ii) drug loading, (iii) physicochemical parameters, and (iv) biological grafting. This review presents a comprehensive overview of the intricate mechanisms of the immune system in injured tissues while unveiling the key strategies adopted by electrospun fibers to orchestrate immune regulation. Furthermore, the review explores the current developmental trends and limitations concerning the immunoregulatory function of electrospun fibers, aiming to drive the advancements in electrospun fiber-based immune engineering to its full potential.

Induction of Endogenous Antimicrobial Peptides to Prevent or Treat Oral Infection and Inflammation

Antibiotics are often used to treat oral infections. Unfortunately, excessive antibiotic use can adversely alter oral microbiomes and promote the development of antibiotic-resistant microorganisms, which can be difficult to treat. An alternate approach could be to induce the local transcription and expression of endogenous oral antimicrobial peptides (AMPs). To assess the feasibility and benefits of this approach, we conducted literature searches to identify (i) the AMPs expressed in the oral cavity; (ii) the methods used to induce endogenous AMP expression; and (iii) the roles that expressed AMPs may have in regulating oral inflammation, immunity, healing, and pain. Search results identified human neutrophil peptides (HNP), human beta defensins (HBD), and cathelicidin AMP (CAMP) gene product LL-37 as prominent AMPs expressed by oral cells and tissues. HNP, HBD, and LL-37 expression can be induced by micronutrients (trace elements, elements, and vitamins), nutrients, macronutrients (mono-, di-, and polysaccharides, amino acids, pyropeptides, proteins, and fatty acids), proinflammatory agonists, thyroid hormones, and exposure to ultraviolet (UV) irradiation, red light, or near infrared radiation (NIR). Localized AMP expression can help reduce infection, inflammation, and pain and help oral tissues heal. The use of a specific inducer depends upon the overall objective. Inducing the expression of AMPs through beneficial foods would be suitable for long-term health protection. Additionally, the specialized metabolites or concentrated extracts that are utilized as dosage forms would maintain the oral and intestinal microbiome composition and control oral and intestinal infections. Inducing AMP expression using irradiation methodologies would be applicable to a specific oral treatment area in addition to controlling local infections while regulating inflammatory and healing processes.

Electrospun Nanofibers for Wound Management

Electrospun nanofibers show great potential in biomedical applications. This mini review article traces the recent advances in electrospun nanofibers for wound management via various approaches. Initially, we provide a short note on the four phases of wound healing, including hemostasis, inflammation, proliferation, and remodeling. Then, we state how the nanofiber dressings can stop bleeding and reduce the pain. Following that, we discuss the delivery of therapeutics and cells using different types of nanofibers for enhancing cell migration, angiogenesis, and re-epithelialization, resulting in the promotion of wound healing. Finally, we present the conclusions and future perspectives regarding the use of electrospun nanofibers for wound management.

Identification of metabolic pathways underlying FGF1 and CHIR99021-mediated cardioprotection

Acute myocardial infarction is a leading cause of death worldwide. We have previously identified two cardioprotective molecules — FGF1 and CHIR99021— that confer cardioprotection in mouse and pig models of acute myocardial infarction. Here, we aimed to determine if improved myocardial metabolism contributes to this cardioprotection. Nanofibers loaded with FGF1 and CHIR99021 were intramyocardially injected to ischemic myocardium of adult mice immediately following surgically induced myocardial infarction. Animals were euthanized 3 and 7 days later. Our data suggested that FGF1/CHIR99021 nanofibers enhanced the heart’s capacity to utilize glycolysis as an energy source and reduced the accumulation of branched-chain amino acids in ischemic myocardium. The impact of FGF1/CHIR99021 on metabolism was more obvious in the first three days post myocardial infarction. Taken together, these findings suggest that FGF1/CHIR99021 protects the heart against ischemic injury via improving myocardial metabolism which may be exploited for treatment of acute myocardial infarction in humans.

•

FGF1/CHIR confer cardioprotection in myocardial infarction animals

•

FGF1/CHIR enhance the capability of ischemic hearts to produce energy via glycolysis

•

FGF1/CHIR reduce the abundance of branched chain amino acids in ischemic hearts

•

This study reveals a novel approach to correct metabolic disorders in ischemic hearts

Codelivery of 1α,25-Dihydroxyvitamin D3 and CYP24A1 Inhibitor VID400 by Nanofiber Dressings Promotes Endogenous Antimicrobial Peptide LL-37 Induction

Surgical site infections represent a significant clinical problem. Herein, we report a nanofiber dressing for topical codelivery of immunomodulating compounds including 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) and VID400, a CYP24A1 inhibitor in a sustained manner, for inducing the expression of the endogenous cathelicidin antimicrobial peptide (CAMP) gene encoding the hCAP18 protein, which is processed into the LL-37 peptide. Nanofiber wound dressings with coencapsulation of 1,25(OH)₂D₃ and VID400 were generated by electrospinning. Both 1,25(OH)₂D₃ and VID400 were coencapsulated into nanofibers with loading efficiencies higher than 90% and exhibited a prolonged release from nanofiber membranes longer than 28 days. Incubation with 1,25(OH)₂D₃/VID400-coencapsulated poly(ϵ-caprolactone) nanofiber membranes greatly induced the hCAP18/LL-37 gene expression in monocytes, neutrophils, and keratinocytes in vitro. Moreover, the administration of 1,25(OH)₂D₃/VID400-coencapsulated nanofiber membranes dramatically promoted the hCAP18/LL-37 expression in dermal wounds created in both human CAMP transgenic mice and human skin tissues. The 1,25(OH)₂D₃- and VID400-coencapsulated nanofiber dressings enhanced innate immunity via the more effective induction of antimicrobial peptide than the free drug alone or 1,25(OH)₂D₃-loaded nanofibers. Together, 1,25(OH)₂D₃/VID400-embedded nanofiber dressings presented in this study show potential in preventing surgical site infections.

Cathelicidin hCAP18/LL-37 promotes cell proliferation and suppresses antitumor activity of 1,25(OH)2D3 in hepatocellular carcinoma

Cathelicidin hCAP18/LL-37 can resist infection from various pathogens and is an essential component of the human immune system. Accumulating evidence has indicated that hCAP18/LL-37 plays a tissue-specific role in human cancer. However, its function in hepatocellular carcinoma (HCC) is poorly understood. The present study investigated the effects of hCAP18/LL-37 on HCC in vitro and in vivo. Results showed that hCAP18/LL-37 overexpression significantly promoted the proliferation of cultured HCC cells and the growth of PLC/PRF-5 xenograft tumor. Transcriptome sequencing analyses revealed that the PI3K/Akt pathway was the most significant upregulated pathway induced by LL-37 overexpression. Further analysis demonstrated that hCAP18/LL-37 stimulated the phosphorylation of EGFR/HER2 and activated the PI3K/Akt pathway in HCC cells. Furthermore, stronger EGFR/HER2/Akt signals were observed in the PLC/PRF-5^LL-37 xenograft tumor. Interestingly, even though the expression of hCAP18/LL-37 was significantly downregulated in HCC cells and tumors, 1,25(OH)₂D₃ treatment significantly upregulated the hCAP18/LL-37 level both in HCC cells and xenograft tumors. Moreover, 1,25(OH)₂D₃ together with si-LL-37 significantly enhanced the antitumor activity of 1,25(OH)₂D₃ in the PLC/PRF-5 xenograft tumor. Collectively, these data suggest that hCAP18/LL-37 promotes HCC cells proliferation through stimulation of the EGFR/HER2/Akt signals and appears to suppress the antitumor activity of 1,25(OH)₂D₃ in HCC xenograft tumor. This implies that hCAP18/LL-37 may be an important target when aiming to improve the antitumor activity of 1,25(OH)₂D₃ supplementation therapy in HCC.

Our Initial Experience In The Customized Treatment Of Donor Site And Burn Wounds With A New Nanofibrous Temporary Epidermal Layer

Recently, electrospinning technology has gained increasing attention for wound care. SpinCare™ electrospun polymer nanofibrous temporary epidermal layer is one of the latest developments in the market. Our objective was to explore the potential use of the new SpinCare™ system for treating burns and wounds. We conducted a single-center prospective observational trial, treating 10 patients with superficial to partial thickness wounds including burn wounds with a nanofibrous dressing. Treatment was evaluated, including procedures, place of injury, treatment times, ease of use etc. Ten superficial to deep dermal wounds were treated successfully. Inexperienced users learned the handling of the device quickly. Covering difficult-to-access wound surfaces was challenging. One leading problem is that the product is nearly opaque once applied on the moist wound. We introduced a standardized 3-day treatment protocol. After application, wounds were covered with a silicon layer for 2 days. The nanofibrous dressing appeared to be suitable following enzymatic debridement in burn wounds. Because there is a risk of wounds drying out under the dressing, the application should probably be limited to superficial and partial thickness wounds if not combined with other treatment options. The electrospun polymer nanofibrous temporary epidermal layer shows promising results in the treatment of superficial to partial thickness wounds including burns. However, minor improvements might help to optimize its usage and thus take full advantage of all existing treatment options.

LL-37-Induced Autophagy Contributed to the Elimination of Live Porphyromonas gingivalis Internalized in Keratinocytes

Porphyromonas gingivalis (P. gingivalis), one of the most important pathogens of periodontitis, is closely associated with the aggravation and recurrence of periodontitis and systemic diseases. Antibacterial peptide LL-37, transcribed from the cathelicidin antimicrobial peptide (CAMP) gene, exhibits a broad spectrum of antibacterial activity and regulates the immune system. In this study, we demonstrated that LL-37 reduced the number of live P. gingivalis (ATCC 33277) in HaCaT cells in a dose-dependent manner via an antibiotic-protection assay. LL-37 promoted autophagy of HaCaT cells internalized with P. gingivalis. Inhibition of autophagy with 3-methyladenine (3-MA) weakened the inhibitory effect of LL-37 on the number of intracellular P. gingivalis. A cluster of orthologous groups (COGs) and a gene ontology (GO) functional analysis were used to individually assign 65 (10%) differentially expressed genes (DEGs) to an "Intracellular trafficking, secretion, and vesicular transport" cluster and 306 (47.08%) DEGs to metabolic processes including autophagy. Autophagy-related genes, a tripartite motif-containing 22 (TRIM22), and lysosomal-associated membrane protein 3 (LAMP3) were identified as potentially involved in LL-37-induced autophagy. Finally, bioinformatics software was utilized to construct and predict the protein-protein interaction (PPI) network of CAMP-TRIM22/LAMP3-Autophagy. The findings indicated that LL-37 can reduce the quantity of live P. gingivalis internalized in HaCaT cells by promoting autophagy in these cells. The transcriptome sequencing and analysis also revealed the potential molecular pathway of LL-37-induced autophagy.

Healing of Full-Thickness Murine Skin Wounds Containing Nanofibers Using Splints for Efficient Reepithelialization and to Avoid Contracture

Wound healing process is the outcome of a series of actions and combined with collaborative process involving concerted efforts of multiple cell types. The dynamic series of events constituting each of these overlapping rather than discrete stages of wound healing increases its complexity and the necessity to understand it. The contrasting mechanisms of wound healing employed by mouse (via wound contraction) and humans (via reepithelialization) puts forth the need of a model closely mimicking human wound-healing and hence comes the applicability of the mouse excisional wound splinting model. Use of silicone-based splints has demonstrated their effectiveness in aptly resembling the human reepithelialization mediated wound healing by preventing contraction during healing. The rising popularity of nanofiber-based treatments for wound healing through sustained release of factors/molecules promoting wound closure can be potentially implemented in association with this model to determine its efficacy in wound management in a more humanized way.

A mouse model for vitamin D-induced human cathelicidin antimicrobial peptide gene expression

In humans and other primates, 1,25(OH)2vitamin D3 regulates the expression of the cathelicidin antimicrobial peptide (CAMP) gene via toll-like receptor (TLR) signaling that activates the vitamin D pathway. Mice and other mammals lack the vitamin D response element (VDRE) in their CAMP promoters. To elucidate the biological importance of this pathway, we generated transgenic mice that carry a genomic DNA fragment encompassing the entire human CAMP gene and crossed them with Camp knockout (KO) mice. We observed expression of the human transgene in various tissues and innate immune cells. However, in mouse CAMP transgenic macrophages, TLR activation in the presence of 25(OH)D3 did not induce expression of either CAMP or CYP27B1 as would normally occur in human macrophages, reinforcing important species differences in the actions of vitamin D. Transgenic mice did show increased resistance to colonization by Salmonella typhimurium in the gut. Furthermore, the human CAMP gene restored wound healing in the skin of Camp KO mice. Topical application of 1,25(OH)2vitamin D3 to the skin of CAMP transgenic mice induced CAMP expression and increased killing of Staphylococcus aureus in a wound infection model. Our model can help elucidate the biological importance of the vitamin D-cathelicidin pathway in both pathogenic and non-pathogenic states.

The Skin and Intestinal Microbiota and Their Specific Innate Immune Systems

The skin and intestine are active organs of the immune system that are constantly exposed to the outside environment. They support diverse microbiota, both commensal and pathogenic, which encompass bacteria, viruses, fungi, and parasites. The skin and intestine must maintain homeostasis with the diversity of commensal organisms present on epithelial surfaces. Here we review the current literature pertaining to epithelial barrier formation, microbial composition, and the complex regulatory mechanisms governing the interaction between the innate immune system and microbiota in the skin and intestine. We also compare and contrast the skin and intestine—two different organ systems responsible creating a protective barrier against the external environment, each of which has unique mechanisms for interaction with commensal populations and host repair.

Eluted 25-hydroxyvitamin D3 from radially aligned nanofiber scaffolds enhances cathelicidin production while reducing inflammatory response in human immune system-engrafted mice

Vitamin D₃ modulates immune response, induces endogenous antimicrobial peptide production, and enhances innate immunity to defend against infections. These findings suggest that incorporating vitamin D₃ into medical devices or scaffolds could positively modulate host immune response and prevent infections. In the current study, we evaluated host responses and endogenous antimicrobial peptide production using 25-hydroxyvitamin D₃ (25(OH)D₃)-eluting radially aligned PCL nanofiber scaffolds in human immune system-engrafted mice. We transformed traditional 2D electrospun nanofiber membranes into radially aligned PCL nanofiber scaffolds using the concept of solid of revolution and an innovative gas-foaming technique. Such scaffolds can promote rapid cellular infiltration and neovascularization. The infiltrating immune cells within subcutaneously implanted 25(OH)D₃-containing scaffolds mainly consisted of human macrophages in the M1 phase (CCR7⁺), mice macrophages in the M2 phase (CD206⁺), and human cytotoxic T cells (CD8⁺) other than few human T-helper cells (CD4⁺). The 25(OH)D₃-eluting nanofiber scaffolds significantly inhibited the production of pro-inflammatory cytokines (TNF-α, IL-6), while accelerating the production of anti-inflammatory cytokines (IL-4, IL-10) within the scaffolds. Additionally, we observed increased expression of human cathelicidin LL-37 within the 25(OH)D₃-eluting scaffolds, while no LL-37 expression was observed in the control. Together, these findings support further work in the design of vitamin D₃-eluting medical devices or scaffolds for modulating immune response and promoting antimicrobial peptide production. This could potentially reduce the inflammatory response, prevent infections, and eventually improve success rates of implants. STATEMENT OF SIGNIFICANCE: Transplant failure of medical devices, grafts, scaffolds, and tissue-engineered constructs due to inflammation and infection causes not only economic losses but also sufferings of second operation to the patient. Positive modulation of the host response to implants, scaffolds, and tissue-engineered constructs is likely to reduce the failure rate. Vitamin D₃ plays an important role in modulating the immune response. It is able to not only reduce inflammation and induce endogenous antimicrobial peptide production but also prevent multidrug resistance and other side effects of traditional antibiotics. In this study, host responses to 25-hydroxyvitamin D₃ (25(OH)D₃)-eluting radially aligned PCL nanofiber scaffolds were evaluated in human immune system-engrafted mice. The 25(OH)D₃-eluting medical devices or scaffolds were able to modulate positive immune response and promote antimicrobial peptide production. This work presented an innate immunity-enhancing approach for reducing the inflammatory response and preventing infections, likely resulting in improvement of success rates of implants.

Innate Immune Dysfunction in Rosacea Promotes Photosensitivity and Vascular Adhesion Molecule Expression

Rosacea is a chronic skin disease characterized by photosensitivity, abnormal dermal vascular behavior, inflammation, and enhanced expression of the antimicrobial peptide LL-37. We observed that dermal endothelial cells in rosacea had an increased expression of VCAM1 and hypothesized that LL-37 could be responsible for this response. The digestion of double-stranded RNA from keratinocytes exposed to UVB blocked the capacity of these cells to induce adhesion molecules on dermal microvascular endothelial cells. However, a synthetic noncoding snoU1RNA was only capable of increasing adhesion molecules on endothelial cells in the presence of LL-37, suggesting that the capacity of UVB exposure to promote both double-stranded RNA and LL-37 was responsible for the endothelial response to keratinocytes. Sequencing of RNA from the endothelial cells uncovered the activation of Gene Ontology (GO) pathways relevant to the human disease, such as type I and II interferon signaling, cell-cell adhesion, leukocyte chemotaxis, and angiogenesis. Functional relevance was demonstrated as double-stranded RNA and LL-37 promoted adhesion and transmigration of monocytes across the endothelial cell monolayers. Gene knockdown of TLR3, RIGI, or IRF1 decreased monocyte adhesion in endothelial cells, confirming the role of the double-stranded RNA recognition pathways. These observations show how the expression of LL-37 can lead to enhanced sensitivity to UVB radiation in rosacea.