Bi-layered living cellular construct resulted in greater healing in an alloxan-induced diabetic porcine model

Recent advances in sodium alginate-based dressings for targeted drug delivery in the context of diabetic wound healing

Diabetic wounds pose a significant challenge in healthcare due to impaired healing and increased risk of complications. In recent years, various drug delivery systems with stimuli-responsive features have been developed to address these issues. These systems enable precise dosage control and tailored drug release, promoting comprehensive tissue repair and regeneration. This review explores targeted therapeutic agents, such as carboxymethyl chitosan-alginate hydrogel formulations, nanofiber mats, and core-shell nanostructures, for diabetic wound healing. Additionally, the integration of nanotechnology and multifunctional biomimetic scaffolds shows promise in enhancing wound healing outcomes. Future research should focus on optimizing the design, materials, and printing parameters of 3D-bio-printed wound dressings, as well as exploring combined strategies involving the simultaneous release of antibiotics and nitric oxide for improved wound healing.

Effects of a bioengineered allogeneic cellular construct on burn-related macrophage phenotype

Bioengineered allogeneic cellularised constructs (BACC) exert pro-healing effects in burn wounds and skew macrophage phenotype towards a predominately reparative phenotype. However, whether BACC can modulate the phenotype of dysregulated macrophages, like those present in burn wounds, is not known. To better understand the macrophage modulatory characteristics of the BACC, primary human macrophages were polarised to the M2b phenotype, an immunosuppressive phenotype relevant to burn wounds, by simultaneously exposing macrophages to polystyrene plate-coated immunoglobulin G and the endotoxin lipopolysaccharide (LPS). The resulting macrophage phenotype upregulated both inflammatory and reparative genes, and increased secretion of the M2b marker CCL1 compared to five different in vitro macrophage phenotypes. M2b macrophages were cultured with the BACC in the presence or absence of LPS to mimic infection, which is a common occurrence in burn wounds. The BACC caused up-regulation of reparative gene sets and down-regulation of pro-inflammatory gene sets, even when LPS was present in the cell culture media. Co-cultures were maintained for 1, 3, or 5 days in the presence of LPS, and by day 1 both non-activated macrophages and M2b macrophages exhibited signs of endotoxin tolerance, as demonstrated by a reduced secretion of tumour necrosis factor α (TNFα) in response to fresh LPS stimulus. The BACC was not able to prevent endotoxin tolerance, but reparative genes were upregulated in macrophages chronically exposed to LPS. These results suggest that the BACC can promote a reparative phenotype in dysregulated macrophages relevant to the pathophysiology of burns.

VEGF-delivering PEG hydrogels promote vascularization in the porcine subcutaneous space

For cell therapies, the subcutaneous space is an attractive transplant site due to its large surface area and accessibility for implantation, monitoring, biopsy, and retrieval. However, its poor vascularization has catalyzed research to induce blood vessel formation within the site to enhance cell revascularization and survival. Most studies focus on the subcutaneous space of rodents, which does not recapitulate important anatomical features and vascularization responses of humans. Herein, we evaluate biomaterial-driven vascularization in the porcine subcutaneous space. Additionally, we report the first use of cost-effective fluorescent microspheres to quantify perfusion in the porcine subcutaneous space. We investigate the vascularization-inducing efficacy of vascular endothelial growth factor (VEGF)-delivering synthetic hydrogels based on 4-arm poly(ethylene) glycol macromers with terminal maleimides (PEG-4MAL). We compare three groups: a non-degradable hydrogel with a VEGF-releasing PEG-4MAL gel coating (Core+VEGF gel); an uncoated, non-degradable hydrogel (Core-only); and naïve tissue. After 2 weeks, Core+VEGF gel has significantly higher tissue perfusion, blood vessel area, blood vessel density, and number of vessels compared to both Core-only and naïve tissue. Furthermore, healthy vital signs during surgery and post-procedure metrics demonstrate the safety of hydrogel delivery. We demonstrate that VEGF-delivering synthetic hydrogels induce robust vascularization and perfusion in the porcine subcutaneous space.