dECM restores macrophage immune homeostasis and alleviates iron overload to promote DTPI healing.

Due to its highly insidious and rapid progression, deep tissue pressure injury (DTPI) is a clinical challenge. Our previous study found that DTPI may be a skeletal muscle injury dominated by macrophage immune dysfunction due to excessive iron accumulation. Decellularized extracellular matrix (dECM) hydrogel promotes skeletal muscle injury repair. However, its role in polarizing macrophages and regulating iron metabolism in DTPI remains unclear. Here, porcine dECM hydrogel was prepared, and its therapeutic function and mechanism in repairing DTPI were investigated. The stimulus of dECM hydrogel toward RAW264.7 cells resulted in a significantly higher percentage of CD206+ macrophages and notably decreased intracellular divalent iron levels. In mice DTPI model, dECM hydrogel treatment promoted M1 to M2 macrophage conversion, improved iron metabolism and reduced oxidative stress in the early stage of DTPI. In the remodeling phase, the dECM hydrogel remarkably enhanced revascularization and accelerated skeletal muscle repair. Furthermore, the immunomodulation of dECM hydrogels in vivo was mainly involved in the P13k/Akt signaling pathway, as revealed by GO and KEGG pathway analysis, which may ameliorate the iron deposition and promote the healing of DTPI. Our findings indicate that dECM hydrogel is promising in skeletal muscle repair, inflammation resolution and tissue injury healing by effectively restoring macrophage immune homeostasis and normalizing iron metabolism.

Extracts of Portulaca oleracea promote wound healing by enhancing angiology regeneration and inhibiting iron accumulation in mice.

Objective: To investigate the role of Portulaca oleracea (POL) in promoting revascularization and re-epithelization as well as inhibiting iron aggregation and inflammation of deep tissue pressure injury (DTPI). Methods: The hydroalcoholic extract of POL (P) and aqueous phase fraction of POL (PD) were prepared based on maceration and liquid-liquid extraction. The number of new blood vessels and VEGF-A expression level were assessed using H&E stain and Western blot on injured muscle to examine the role of POL different extracts in vascularization. The iron distribution and total elemental iron of injured muscle were detected using laser ablation inductively coupled plasma mass spectrometry (ICP-MS) and Perls' staining to determine whether POL extracts can inhibit the iron accumulation. Besides, the ability of POL extracts to promote wound healing by combining re-epithelization time, inflammation degree and collagen deposition area were comprehensively evaluated. Results: In vitro, we observed a significant increase in HUVEC cell viability, migration rate and the number of the tube after P and PD treatment (P < 0.05). In vivo, administration of P and PD impacted vascularization and iron accumulation on injured tissue, evident from more new blood vessels, higher expression of VEGF-A and decreased muscle iron concentration of treatment groups compared with no-treatment groups (P < 0.05). Besides, shorter re-epithelization time, reduced inflammatory infiltration and distinct collagen deposition were associated with administration of P and PD (P < 0.05). Conclusion: POL extract administration groups have high-quality wound healing, which is associated with increased new blood vessels, collagen deposition and re-epithelization, along with decreased iron accumulation and inflammatory infiltration. Our results suggest that that POL extract is beneficial to repair injured muscle after ischemia-reperfusion, highlighting the potential of POL in the DTPI treatment.

Tazarotene-loaded PLGA nanoparticles potentiate deep tissue pressure injury healing via VEGF-Notch signaling.

BACKGROUND AND PURPOSE: New capillaries are essential for deep tissue pressure injury wound healing. Tazarotene is a recently discovered small molecule drug and functions to promote neovascularization and tissue repair. At present, the application of tazarotene in the repair of pressure injuries has not previously been investigated. This study used poly (lactic-co-glycolic acid) (PLGA) as nanoparticle carriers loaded with tazarotene (Ta/PLGA NPs) for drug delivery and to overcome shortcomings associated with the low water solubility, short half-life, easy photolysis and low bioavailability of tazarotene itself. METHODS: The physicochemical properties, drug release and bioactivity of Ta/PLGA NPs were examined in vitro by transmission electron microscope, spectrophotometry and cell assays. Mouse models of deep tissue pressure injuries (DTPI) were established and the therapeutic effects and mechanisms of Ta/PLGA NPs in local wound repair were studied. RESULTS: The results showed that Ta/PLGA NPs were of uniform size and distribution and were non-toxic both in vitro and in vivo. In vivo experiments suggested that Ta/PLGA NPs significantly promoted DTPI wound repair through activation of the VEGF/VEGFR-Notch1/DLL4 signaling pathway. CONCLUSION: This study highlights the potential clinical significance of implementation of tazarotene small molecule drugs in combination with effective biomaterial carriers for the treatment of chronic refractory wounds, such as DTPI.

Chitosan hydrogel encapsulated with LL-37 peptide promotes deep tissue injury healing in a mouse model.

BACKGROUND: LL-37 peptide is a member of the human cathelicidin family, and has been shown to promote the healing of pressure ulcers. However, the low stability of this peptide within the wound environment limits its clinical use. Chitosan (CS) hydrogel is commonly used as a base material for wound dressing material. METHODS: CS hydrogel (2.5% w/v) was encapsulated with LL-37. Cytotoxicity of the product was examined in cultured NIH3T3 fibroblasts. Effects on immune response was examined by measuring tumor necrosis factor-α (TNF-α) release from RAW 264.7 macrophages upon exposure to lipopolysaccharides. Antibacterial activity was assessed using Staphylococcus aureus. Potential effect on pressure ulcers was examined using a mouse model. Briefly, adult male C57BL/6 mice were subjected to skin pressure using magnets under a 12/12 h schedule for 21 days. Mice were randomized to receive naked LL-37 (20 µg), chitosan gel containing 20-µg LL-37 (LL-37/CS hydrogel) or hydrogel alone under the ulcer bed (n = 6). A group of mice receiving no intervention was also included as a control. RESULTS: LL-37/CS hydrogel did not affect NIH3T3 cell viability. At a concentration of 1-5 µg/ml, LL-37/CS inhibited TNF-α release from macrophage. At 5 µg/ml, LL-37/CS inhibited the growth of Staphylococcus aureus. The area of the pressure ulcers was significantly lower in mice receiving LL-37/CS hydrogel in comparison to all other 3 groups on days 11 (84.24% ± 0.25%), 13 (56.22% ± 3.91%) and 15 (48.12% ± 0.28%). Histological examination on days 15 and 21 showed increased epithelial thickness and density of newly-formed capillary with naked LL-37 and more so with LL-37/CS. The expression of key macromolecules in the process of angiogenesis (i.e., hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor-A (VEGF-A)) in wound tissue was increased at both the mRNA and protein levels. CONCLUSION: Chitosan hydrogel encapsulated with LL-37 is biocompatible and could promote the healing of pressure ulcers.