Wound splinting modulates granulation tissue proliferation

Polycaprolactone/gelatin-QAS/bioglass nanofibres accelerate diabetic chronic wound healing by improving dysfunction of fibroblasts

Worldwide, more than 25 % of patients with diabetes develop chronic diabetic wounds in their lifetime. Infection and dysfunctional fibroblasts represent two significant etiological factors contributing to impaired wound healing in patients with diabetes. It is therefore evident that the development of wound dressings with both anti-infective and DM fibroblast modulating functions has the potential for clinical applications. In this study, a PCL/gelatine-quaternary ammonium salts (QAS)/bioglass (BG) electrospun nanofibrous membrane was developed with physico-chemical and biological properties that not only meet the clinical requirements for wound dressings but also exhibit remarkable moisturising (water adsorption rate of 382.39 ± 4.36 %) and tear-resistance properties (a tear strength of ~5.5 MPa). The incorporation of QAS and BG has enhanced the biocompatibility and bioactivity of the nanofibres, while also imparting remarkable antimicrobial properties. The antibacterial efficacy of PGQ-BG against E. coli and S. aureus was found to be 92.8 ± 0.78 % and 99.3 ± 0.55 %, respectively. Moreover, it was demonstrated that PGQ-BG nanofibers exerted a promoting effect on the extracellular matrix (ECM) in dysfunctional fibroblasts and upregulated the expression level of α-smooth muscle actin (α-SMA), a marker of their differentiation to myofibroblasts in vitro and in vivo. Furthermore, the COL-III/COL-I ratio was significantly increased, indicating that PGQ-BG may also accelerate wound healing. The nanofibrous dressing reduced scar formation by increasing the COL-III/COL-I ratio. This is the first report of BG improving fibroblast dysfunction via COL-III and COL-I promotion in fibroblasts, both in vitro and in vivo. Therefore, this novel bioactive nanofibrous dressing represents an effective and safe therapeutic strategy for improving chronic wound healing in patients with diabetes.

The rat as an animal model in chronic wound research: An update

The increasing global prevalence of chronic wounds underscores the growing importance of developing effective animal models for their study. This review offers a critical evaluation of the strengths and limitations of rat models frequently employed in chronic wound research and proposes potential improvements. It explores these models in the context of key comorbidities, including diabetes, venous and arterial insufficiency, pressure-induced blood flow obstruction, and infections. Additionally, the review examines important wound factors including age, sex, smoking, and the impact of anesthetic and analgesic drugs, acknowledging their substantial effects on research outcomes. A thorough understanding of these variables is crucial for refining animal models and can provide valuable insights for future research endeavors.

Attachment-regulated signaling networks in the fibroblast-populated 3D collagen matrix

Fibroblasts in the attached collagen matrix are in a pro-survival, pro-proliferative state relative to fibroblasts in the released collagen matrix, such that matrix cell number increases in the former over time. Gene array data from attached vs. released matrices were analyzed for putative networks that regulated matrix cell number. Select networks then underwent augmentation and/or inhibition in order to determine their biologic relevance. Matrix stress-release was associated with modulation of signaling networks that involved IL6, IL8, NF-κB, TGF-β1, p53, interferon-γ, and other entities as central participants. Perturbation of select networks in multiple fibroblast strains suggested that IL6 and IL8 secretion may have been involved in preservation of matrix cell population in the released matrix, though there was variability in testing results among the strains. NF-κB activation may have contributed to the induction of population regression after matrix release.

Human mesenchymal stem cell grafts enhance normal and impaired wound healing by recruiting existing endogenous tissue stem/progenitor cells

Mesenchymal stem cells (MSCs) have been investigated as a clinical therapy to promote tissue repair. However, the disappearance of grafted cells soon after engraftment suggests a possible role as initiators of repair rather than effectors. We evaluated the relative contribution of grafted human MSCs and host stem/progenitor cells in promoting wound healing by using a novel asymmetric wound model in normal and impaired healing diabetic (db/db) mice to discriminate between the effect of direct engraftment and the subsequent systemic response. Experimental animals received paired wounds, with one wound receiving human mesenchymal stem cells (hMSCs) and the other wound receiving vehicle to assess local and systemic effects, respectively. Control animals received vehicle in both wounds. Grafted hMSCs significantly improved healing in both normal and impaired healing animals; produced significant elevation of signals such as Wnt3a, vascular endothelial growth factor, and platelet-derived growth factor receptor-α; and increased the number of pre-existing host MSCs recruited to the wound bed. Improvement was also seen in both the grafted and nongrafted sides, suggesting a systemic response to hMSC engraftment. Healing was enhanced despite the rapid loss of hMSCs, suggesting that mobilizing the host response is the major outcome of grafting MSCs to tissue repair. We validate that hMSCs evoke a host response that is clinically relevant, and we suggest that therapeutic efforts should focus on maximizing the mobilization of host MSCs.

Impaired therapeutic capacity of autologous stem cells in a model of type 2 diabetes

Endogenous stem cells in the bone marrow respond to environmental cues and contribute to tissue maintenance and repair. In type 2 diabetes, a multifaceted metabolic disease characterized by insulin resistance and hyperglycemia, major complications are seen in multiple organ systems. To evaluate the effects of this disease on the endogenous stem cell population, we used a type 2 diabetic mouse model (db/db), which recapitulates these diabetic phenotypes. Bone marrow-derived mesenchymal stem cells (MSCs) from db/db mice were characterized in vitro using flow cytometric cell population analysis, differentiation, gene expression, and proliferation assays. Diabetic MSCs were evaluated for their therapeutic potential in vivo using an excisional splint wound model in both nondiabetic wild-type and diabetic mice. Diabetic animals possessed fewer MSCs, which were proliferation and survival impaired in vitro. Examination of the recruitment response of stem and progenitor cells after wounding revealed that significantly fewer endogenous MSCs homed to the site of injury in diabetic subjects. Although direct engraftment of healthy MSCs accelerated wound closure in both healthy and diabetic subjects, diabetic MSC engraftment produced limited improvement in the diabetic subjects and could not produce the same therapeutic outcomes as in their nondiabetic counterparts in vivo. Our data reveal stem cell impairment as a major complication of type 2 diabetes in mice and suggest that the disease may stably alter endogenous MSCs. These results have implications for the efficiency of autologous therapies in diabetic patients and identify endogenous MSCs as a potential therapeutic target.

A review on static splinting therapy to prevent burn scar contracture: do clinical and experimental data warrant its clinical application?

BACKGROUND

Static splinting therapy is widely considered an essential part in burn rehabilitation to prevent scar contractures in the early phase of wound healing. However, scar contractures are still a common complication. In this article we review the information concerning the incidence of scar contracture, the effectiveness of static splinting therapy in preventing scar contractures, and specifically focus on the - possible - working mechanism of static-splinting, i.e. mechanical load, at the cellular and molecular level of the healing burn wound.

METHOD

A literature search was done including Pubmed, Cochrane library, CINAHL and PEDRO.

RESULTS

Incidence of scar contracture in patients with burns varied from 5% to 40%. No strong evidence for the effectiveness of static splinting therapy in preventing scar contracture was found, whereas in vitro and animal studies demonstrated that mechanical tension will stimulate the myofibroblast activity, resulting in the synthesis of new extracellular matrix and the maintenance of their contractile activity.

CONCLUSION

The effect of mechanical tension on the wound healing process suggests that static splinting therapy may counteract its own purpose. This review stresses the need for randomised controlled clinical trials to establish if static splinting to prevent contractures is a well-considered intervention or just wishful thinking.

Testing photobiomodulatory effects of laser irradiation on wound healing: development of an improved model for dressing wounds in mice

OBJECTIVE

To develop a suitable method for dressing skin wounds in BKS.Cg-m(+)/(+)Lepr(db) mice for subsequent use in laser irradiation of wounds. The healing of nonirradiated wounds (controls) was examined histologically to provide essential reference data.

BACKGROUND DATA

Dressing excisional skin wounds in mice has many advantages. However, previous studies using dressings such as Tegaderm W or OpSite, with or without adhesives, have shown that this is not easily achieved.

MATERIALS AND METHODS

In a pilot study, a full-thickness wound was made on the left flank in six diabetic and six nondiabetic mice, and five different methods were tried for dressing the wounds with Tegaderm HP to develop an optimized procedure. The optimized procedure was used in subsequent studies, with a total of 23 diabetic and 13 nondiabetic mice being controls for laser-irradiated mice. Measurements of healing outcomes from histologic sections of controls were statistically analyzed.

RESULTS

The optimized procedure used Tegaderm HP with Cavilon and Fixomull Stretch strips for the first dressing, and with Mastisol for subsequent dressings. Wound closure by contraction was retarded in a large proportion of diabetic mice (approximately 80%) and a small proportion of nondiabetic mice. These wounds, described as "splinted," healed mainly by epithelial regeneration and granulation tissue formation.

CONCLUSION

A simple, easy-to-perform procedure was developed for dressing wounds in diabetic and nondiabetic mice. It was found to cause splinting with wound healing mimicking that in human patients. This model is suitable for examining the effects of different therapies on wound healing, including lasers.

Keratinocyte-releasable factors increased the expression of MMP1 and MMP3 in co-cultured fibroblasts under both 2D and 3D culture conditions

Matrix metalloproteinases (MMPs) are key elements in extracellular matrix (ECM) degradation and scar remodeling during the wound-healing process. Our previous data revealed that keratinocyte-releasable factors significantly increased the expression of fibroblast MMPs in monolayer-cultured fibroblasts. In this study, we analyzed the differences in the MMP expressions of fibroblasts in a three-dimensional fibroblast-populated collagen gel (3D FPCG) from that in a two-dimensional monolayer-cultured fibroblasts when both co-cultured with keratinocytes. Differential mRNA and protein expression of fibroblasts were examined by microarray, RT-PCR, and western blot. Our results showed that fibroblasts co-cultured with keratinocytes in a 3D FPCG expressed significantly higher MMP1 and MMP3 at the gene and protein levels. Due to the physiological advantages of a 3D FPCG model to a 2D system, we concluded that the 3D FPCG model may provide a better means of understanding the fibroblast-keratinocyte cross-talk during the wound-healing process.

Modeling dermal granulation tissue with the linear fibroblast-populated collagen matrix: A comparison with the round matrix model

BACKGROUND

Wound contraction typically is not symmetrical; for example, a square-shaped wound will not yield a square scar. Interestingly, the round fibroblast-populated collagen matrix has been used as a model of wound contraction, even though contraction in this model is mostly symmetrical.

OBJECTIVE

We wanted to compare the round versus linear fibroblast-populated collagen matrix to see which would be a better model of dermal granulation tissue.

METHODS

Gross and microscopic morphology, contraction kinetics, cytoskeletal architecture, and apoptotic and proliferative indices were compared between the round versus the linear fibroblast-populated collagen matrix. A rat excisional wound model was used as an in vivo standard of healing.

RESULTS

The rate of contraction was similar between the two models, although the mode of contraction was grossly asymmetric in the linear while remaining symmetric in the round model. Cellular survival and proliferation were both dependent on matrix attachment in both models; this was analogous to the attachment-dependence of granulation tissue. In the attached (restrained) condition, the level of cellular organization was higher in the linear than in the round matrix; the tissue architecture of the linear matrix, moreover, mimicked that of the excisional wound model.

CONCLUSION

The round versus linear fibroblast-populated collagen matrix displayed a similar proliferative and survival response to matrix attachment. The latter model, however, demonstrated tissue organization with attachment and asymmetrical contraction after detachment analogous to that of the in vivo wound model. The linear fibroblast-populated collagen matrix appears to be the better model of dermal granulation tissue.