Skin Wound Contraction Research Articles

Guanidinylated bioactive chitosan-based injectable hydrogels with pro-angiogenic and mechanical properties for accelerated wound closure

Wound healing is a complex process involving the concerted action of many genes and signaling pathways, with angiogenesis being crucial for expediting wound closure. Dressings that possess pro-angiogenic properties are increasingly recognized as attractive candidates for wound care. Drawing inspiration from the active closure of wounds in embryos, we have developed a thermo-responsive hydrogel with mechanoactive properties, combining vascular regeneration and skin wound contraction to accelerate healing. The significant improvement in vascular reconstruction is attributed to the synergistic effect of arginine and deferoxamine (DFO) released from the hydrogels. Additionally, the contraction force of the hydrogel actively promotes skin closure in wounds. Remarkably, groups treated with hydroxybutyl chitosan methacrylate combined with arginine (HBC_m_Arg/DFO) exhibited increased vascularization, and greater wound maturity, leading to enhanced healing. These results highlight the synergistic impact of pro-angiogenic and mechanical properties of the HBC_m_Arg/DFO hydrogel in accelerating wound healing in rats.

Stretching Promotes Wound Contraction Through Enhanced Expression of Endothelin Receptor B and TRPC3 in Fibroblasts.

The conditioned medium from stretched keratinocyte was added to the fibroblast populated collagen lattice. Then, we analyzed the levels of endothelin receptor in the human hypertrophic scar tissue and stretched fibroblasts. To address the function of TRPC3, we have used an overexpression system with the collagen lattice. Finally, the TRPC3 overexpressing fibroblasts were transplanted to mouse dorsal skin, and the rate of skin wound contraction was assessed. Conditioned medium from stretched keratinocytes increased the rate of contraction of fibroblast populated collagen lattice. In human hypertrophic scar and stretched fibroblasts, endothelin receptor type B was increased. Cyclic stretching of TRPC3 overexpressing fibroblasts activated NFATc4, and stretched human fibroblasts showed more activation of NFATc4 in response to ET-1. The wound treated with TRPC3 overexpressing fibroblasts showed more contraction than control wound. These findings suggest that cyclical stretching of wounds have an effect on both keratinocytes and fibroblasts, where keratinocytes secret more ET-1, and fibroblasts develop more sensitivity to ET-1 by expressing more endothelin receptors and TRPC3.

Fibroblast-targeting polymeric nanovehicles to enhance topical wound healing through promotion of PAR-2 receptor-mediated endocytosis.

The level of collagen production critically determines skin wound contraction. If an intelligent skin drug delivery technology that enables collagen production in a specific wound skin area is developed, a breakthrough in wound healing treatment would be expected. However, such an intelligent drug delivery technology has not yet been developed as much as in the field of anticancer therapy. In this study, we propose a smart drug delivery system using polymeric nanovehicles (PNVs), in which the periphery is conjugated with a fibroblast-targeting collagen-derived peptide, KTTKS (Lys-Thr-Thr-Lys-Ser). We showed that surface engineering of PNVs with simultaneous PEGylation and peptide patching improved the dispersibility of PNVs, while promoting selective cellular uptake to fibroblasts via PAR-2 receptor-mediated endocytosis. In vitro collagen production and in vivo wound healing assays revealed that curcumin-loaded fibroblast-targeting PNVs significantly enhanced collagen production and wound healing activities, thus promising effective skin tissue regeneration.

Fabrication of SA/Gel/C scaffold with 3D bioprinting to generate micro-nano porosity structure for skin wound healing: a detailed animal in vivo study

Bioprinting has exhibited remarkable promises for the fabrication of functional skin substitutes. However, there are some significant challenges for the treatment of full-thickness skin defects in clinical practice. It is necessary to determine bioinks with suitable mechanical properties and desirable biocompatibilities. Additionally, the key for printing skin is to design the skin structure optimally, enabling the function of the skin. In this study, the full-thickness skin scaffolds were prepared with a gradient pore structure constructing the dense layer, epidermis, and dermis by different ratios of bioinks. We hypothesized that the dense layer protects the wound surface and maintains a moist environment on the wound surface. By developing a suitable hydrogel bioink formulation (sodium alginate/gelatin/collagen), to simulate the physiological structure of the skin via 3D printing, the proportion of hydrogels was optimized corresponding to each layer. These results reveal that the scaffold has interconnected macroscopic channels, and sodium alginate/gelatin/collagen scaffolds accelerated wound healing, reduced skin wound contraction, and re-epithelialization in vivo. It is expected to provide a rapid and economical production method of skin scaffolds for future clinical applications.

Inhibition of Skin Wound Contraction by Nanofibrillar Cellulose Hydrogel.

Although wound contraction is an essential part of healing, excessive contraction can compromise healing through induction of scarring and fibrosis. This in turn leads to development of wound contractures that limit elasticity and function. Major research efforts have focused on development of novel therapeutic approaches to gain inhibitory control over wound contraction. Despite these efforts, the need for cost-effective, clinically feasible, and effective agents to inhibit wound contraction remains. In this study, the authors investigated the effect of nanofibrillar cellulose hydrogel on wound contraction both in vitro and in vivo. Two different porcine full-thickness wounds (8-mm punch-biopsy wounds and 4 × 4-cm wounds covered with a 1:3-meshed split-thickness skin graft) were treated with or without nanofibrillar cellulose or carboxymethylcellulose (Purilon hydrogel), which was used as a reference treatment. Wound contraction was observed macroscopically, and histologic sections were taken at 14-day follow-up. Nanofibrillar cellulose hydrogel inhibited 70 percent of punch-biopsy wound contraction, whereas the carboxymethylcellulose hydrogel was ineffective. Importantly, application of nanofibrillar cellulose on split-thickness skin grafts did not inhibit epithelialization of the interstices or cell migration from the graft. The authors' results, although preliminary, indicate a potential for nanofibrillar cellulose hydrogel as a novel material for controlling excessive wound contraction.

Mast cell concentration and skin wound contraction in rats treated with Ximenia americana L.

To evaluate wound contraction and the concentration of mast cells in skin wounds treated with wild plum (Ximenia americana) essential oil-based ointment in rats. Sixty rats were submitted to two cutaneous wounds in the thoracic region, on the right and left antimeres. Thereon, they were divided into three groups: GX (wounds treated once a day with hydro alcoholic branch extract of Ximenia americana), GP (wounds that received vehicle), and GC (wounds without product application). Wounds were measured immediately after the injury as well as 4, 7, 14 and 21 days post-topical application of the extract. At these days, five rats from each group were euthanatized. Thereafter, samples were fixed in 10% formaldehyde and processed for paraffin embedding. Sections were stained with H.E, Masson's Trichrome and toluidine blue for morphological, morphometrical and histopathological analysis, under light microscopy. The degree of epithelial contraction was measured and mast cell concentrations were also evaluated with an image analyzer (Image Pro-plus®software) . The extract treated group showed lower mast cell concentrations in the 4th day of lesion, as compared to GP (GX<GP=GC, p=0.029), as well as with increased contraction at 7th and 14th days, respectively (7th and 14th days, GX > GP = GC; p<0.05) . Ointment containing 10% X. americana induces a decrease in mast cell concentration, at the beginning of the healing process, and promotes early skin wound contraction in rats.

Filamin A Mediates Wound Closure by Promoting Elastic Deformation and Maintenance of Tension in the Collagen Matrix

Cell-mediated remodeling and wound closure are critical for efficient wound healing, but the contribution of actin-binding proteins to contraction of the extracellular matrix is not defined. We examined the role of filamin A (FLNa), an actin filament cross-linking protein, in wound contraction and maintenance of matrix tension. Conditional deletion of FLNa in fibroblasts in mice was associated with ~4 day delay of full-thickness skin wound contraction compared with wild-type (WT) mice. We modeled the healing wound matrix using cultured fibroblasts plated on grid-supported collagen gels that create lateral boundaries, which are analogues to wound margins. In contrast to WT cells, FLNa knockdown (KD) cells could not completely maintain tension when matrix compaction was resisted by boundaries, which manifested as relaxed matrix tension. Similarly, WT cells on cross-linked collagen, which requires higher levels of sustained tension, exhibited approximately fivefold larger deformation fields and approximately twofold greater fiber alignment compared with FLNa KD cells. Maintenance of boundary-resisted tension markedly influenced the elongation of cell extensions: in WT cells, the number (~50%) and length (~300%) of cell extensions were greater than FLNa KD cells. We conclude that FLNa is required for wound contraction, in part by enabling elastic deformation and maintenance of tension in the matrix.

RECK-Mediated β1-Integrin Regulation by TGF-β1 Is Critical for Wound Contraction in Mice.

Fibroblasts are critical for wound contraction; a pivotal step in wound healing. They produce and modify the extracellular matrix (ECM) required for the proper tissue remodeling. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a key regulator of ECM homeostasis and turnover. However, its role in wound contraction is presently unknown. Here we describe that Transforming growth factor type β1 (TGF-β1), one of the main pro-fibrotic wound-healing promoting factors, decreases RECK expression in fibroblasts through the Smad and JNK dependent pathways. This TGF-β1 dependent downregulation of RECK occurs with the concomitant increase of β1-integrin, which is required for fibroblasts adhesion and wound contraction through the activation of focal adhesion kinase (FAK). Loss and gain RECK expression experiments performed in different types of fibroblasts indicate that RECK downregulation mediates TGF-β1 dependent β1-integrin expression. Also, reduced levels of RECK potentiate TGF-β1 effects over fibroblasts FAK-dependent contraction, without affecting its cognate signaling. The above results were confirmed on fibroblasts derived from the Reck +/- mice compared to wild type-derived fibroblasts. We observed that Reck +/- mice heal dermal wounds more efficiently than wild type mice. Our results reveal a critical role for RECK in skin wound contraction as a key mediator in the axis: TGF-β1—RECK- β1-integrin.

Conditioned medium from hypoxic bone marrow-derived mesenchymal stem cells enhances wound healing in mice.

Growing evidence indicates that bone marrow-derived mesenchymal stem cells (BM-MSCs) enhance wound repair via paracrine. Because the extent of environmental oxygenation affects the innate characteristics of BM-MSCs, including their stemness and migration capacity, the current study set out to elucidate and compare the impact of normoxic and hypoxic cell-culture conditions on the expression and secretion of BM-MSC-derived paracrine molecules (e.g., cytokines, growth factors and chemokines) that hypothetically contribute to cutaneous wound healing in vivo. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) analyses of normoxic and hypoxic BM-MSCs and their conditioned medium fractions showed that the stem cells expressed and secreted significantly higher amounts of basic fibroblast growth factor (bFGF),vascular endothelial growth factor A (VEGF-A) interleukin 6 (IL-6) and interleukin 8 (IL-8) under hypoxic conditions. Moreover, hypoxic BM-MSC-derived conditioned medium (hypoCM) vs. normoxic BM-MSC-derived conditioned medium (norCM) or vehicle control medium significantly enhanced the proliferation of keratinocytes, fibroblasts and endothelial cells, the migration of keratinocytes, fibroblasts, endothelial cells and monocytes, and the formation of tubular structures by endothelial cells cultured on Matrigel matrix. Consistent with these in vitro results, skin wound contraction was significantly accelerated in Balb/c nude mice treated with topical hypoCM relative to norCM or the vehicle control. Notably increased in vivo cell proliferation, neovascularization as well as recruitment of inflammatory macrophages and evidently decreased collagen I, and collagen III were also found in the hypoCM-treated group. These findings suggest that BM-MSCs promote murine skin wound healing via hypoxia-enhanced paracrine.

The mast cell stabilizer ketotifen prevents development of excessive skin wound contraction and fibrosis in red Duroc pigs

Skin wound healing in Yorkshire pigs closely approximates human wound healing. Conversely, red Duroc pigs form fibroproliferative, hypercontractile scars. As mast cells have been implicated in several fibrotic conditions, the present study used these models to evaluate the potential role of mast cells in wound contraction and fibrosis. Immediately following the creation of full-thickness excisional wounds, the mast cell stabilizer ketotifen was used to treat both Yorkshire and red Durocs. Control red Durocs showed significantly more wound contraction than Yorkshires, both before and after reepithelialization. Ketotifen treatment significantly reduced the first phase of contraction in red Duroc wounds to a level equivalent to Yorkshire wounds, but had no detectable effect on the postepithelialization phase of contraction. Cessation of drug treatment after 10 weeks did not lead to resumption of excessive contraction in red Durocs, indicating that ketotifen blocked rather than delayed such contraction during a critical phase of healing. Ketotifen treatment also reduced the deposition of collagen within the red Duroc wounds, but did not affect Yorkshire wound contraction or collagen deposition. These results suggest that ketotifen may be an effective treatment for the reduction of excessive wound contraction and fibrosis in human cutaneous injuries, without affecting the normal healing process.

Expression of smooth muscle actin in connective tissue cells participating in fracture healing in a murine model

The role of α-smooth muscle actin (SMA)-expressing fibroblasts in the contraction of skin wounds has been known for three decades. Recent studies have demonstrated that osteoblasts can also express the gene for this contractile muscle actin isoform and can contract a collagen-glycosaminoglycan analog of extracellular matrix in vitro. These findings provided rationale for the hypothesis that SMA-expressing cells contribute to fracture healing by drawing the bone ends together. To begin to test this hypothesis, immunohistochemistry was employed to evaluate the distribution of connective tissue cells expressing SMA in a mouse model of successful fracture healing. The results demonstrated that the majority of the cells comprising the mesenchymal tissue interposed between the fracture ends contained SMA after 7 and 21 days, supporting the working hypothesis. Most of the osteoblasts lining the surfaces of newly forming bone and the chondrocytes comprising the cartilaginous callus also expressed this contractile actin isoform. The maximal SMA expression extended from 7 to 21 days postfracture. The finding of high levels of SMA expression in connective tissue cells participating in fracture healing suggests that SMA-enabled contraction may be playing a role in the healing process. These results warrant further study of the specific SMA-dependent cell behavior.

Effects of Mometasone Furoate on Human Keratinocytes and Fibroblasts in vitro

The long-term treatment of inflammatory skin diseases with topical glucocorticoids is limited by their side effects such as skin atrophy, delayed wound healing and striae distensae. Mometasone furoate (MF) is a newly synthesized glucocorticoid with the advantage of increasing efficacy and reducing the number of adverse effects. The aim of our study was to compare the effects of MF and conventional fluorinated corticosteroids on a human keratinocyte cell line (HaCat) and human skin fibroblasts in vitro. Monolayer cultures of these cell lines were exposed to different concentrations of the active compounds for 5 days to analyze the influence on morphology and proliferation. Chemotaxis of HaCat cells and fibroblasts was studied in blind-well Boyden chambers using collagen type I and fibroblast-conditioned medium as a chemoattractant. Additionally, fibroblasts were used to investigate the contraction of collagen gels since lattice contraction appears to model the contraction of skin wounds. All glucocorticoids tested influenced fibroblast and keratinocyte proliferation in a dose-dependent manner, yet the effect was clearly more marked with fluorinated corticosteroids than with MF. Similar effects were obtained using the chemotaxis assay. At low concentrations (10^–9 M) MF exerted almost no influence, while the conventional fluorinated substances inhibited direct migration significantly. Contraction of collagen gels was inhibited completely by betamethasone valerate at high concentrations (10^–5– 10^–3 M), but only partially inhibited by MF at its highest concentration (10^–3 M). Although MF reveals high anti-inflammatory activity similar to that known for conventional fluorinated derivatives of corticosteroids, the study shows that MF has less effect in the tested in vitro systems. Therefore, it remains to be seen whether these data might indicate the possibility of a dissociation between the inflammatory activity and the inhibition of the biosynthetic capacities of fibroblasts and keratinocytes by modification of the steroidal structure of corticosteroids.

Midgestational excisional fetal lamb wounds contract in utero

Clinical observations and experimental data suggest that fetal wound healing is very different from adult wound healing. An understanding of the biology of scarless fetal wound healing has tremendous clinical potential for modulating postnatal wound problems. In this study, the fetal lamb model was used to assess excisional fetal skin wound contraction in utero. Full-thickness 9-mm punch biopsy wounds were created on fetal lambs at 100 days' gestation (term, 145 days). Half of the wounds remained exposed to amniotic fluid, whereas the other half were covered by a silastic patch to exclude amniotic fluid. Wounds were harvested 3, 7, or 14 days later and wound areas were calculated. Exposure to amniotic fluid retarded wound contraction significantly at 3 days, but by 14 days all wounds had completely contracted and reepithelialized. Myofibroblasts are an important cellular element of wound contraction. The presence of wound myofibroblasts was documented by both transmission electronmicroscopy and immunocytochemistry with antimuscle actin antibody. It is concluded that fetal lamb wounds contract in utero and exposure to amniotic fluid appears to retard fetal skin wound contraction only during the early healing process.

Contraction of collagen lattices by skin fibroblasts: drug-induced changes.

A range of dermatologically useful drugs were added to human skin fibroblasts cultured in collagen lattices to assess possible effects on the rate of lattice contraction. Vitamin C, Vitamin E, phenytoin, sodium salicylate, D-penicillamine and dibutyryl c-AMP had no significant effect. Chlorhexidine acetate at 10 micrograms/ml arrested contraction after 24 h but this was related to its cytotoxicity. The antibiotics griseofulvin (2-16 micrograms/ml) and cycloheximide (5-30 micrograms/ml) caused dose-related inhibitions of contraction without affecting fibroblast viability. Four corticosteroids at 10 micrograms/ml inhibited contraction, clobetasol propionate having the greatest effect. On the other hand 4 retinoids at 10(-5) M enhanced contraction by up to 20%. As lattice contraction appears to model the contraction of skin wounds and there are broad parallels between the effects shown here of antiseptics, corticosteroids and the retinoids, and their reported influence on healing wounds, the lattice system may be a useful pharmacological screen for new compounds.

Opioid component of the effect of the lacrimal glands on wound healing

Naloxone partially inhibited skin wound contraction and completely blocked acceleration of wound healing in rats with stimulated lacrimal glands. Endorphins were detected in lacrimal glands. Alteration of functional activity of the lacrimal glands produces a considerable effect on pain sensitivity and endorphin blood concentration. Opioid peptides have a considerable effect on the functioning of the lacrimal apparatus and are involved in injury-induced reactions, regulating pain sensitivity, structural homeostasis and producing an anti-stress effect.

A Systematic Study of Wound Contraction in Mammalian Skin

The phenomenon of wound contraction has been studied in the skin of rats, rabbits and guinea pigs with the aim of obtaining a standardized wound system to be used for biological assay of in vivo agonists and antagonists of granulation tissue contraction. The sex of the animal, the time of day of wounding, the size and the shape of the wounds all had no apparent influence on the wound contraction curves expressed as per cent of original area against time. The test animal's age and species did have a significant influence on contraction of skin wounds which by analogy with results obtained with rigid splints attached to the skin could be attributed to variations in the thickness, rigidity and fixation of the skin to deep tissues. The shape of the final scar was influenced by the position of the wound on the body surface. The major factor in this instance was considered to be tensile forces acting within the skin. Wound contraction curves in rats and rabbits showed three distinct phases, namely early closure, stationary and logarithmic closure. Guinea pigs lacked the early closure phase. The exact role of the panniculus carnosus in wound healing is considered to be worthy of detailed study.

A systematic study of wound contraction in mammalian skin

<h2>Summary</h2> The phenomenon of wound contraction has been studied in the skin of rats, rabbits and guinea pigs with the aim of obtaining a standardized wound system to be used for biological assay of <i>in vivo</i> agonists and antagonists of granulation tissue contraction. The sex of the animal, the time of day of wounding, the size and the shape of the wounds all had no apparent influence on the wound contraction curves expressed as per cent of original area against time. The test animal's age and species did have a significant influence on contraction of skin wounds which by analogy with results obtained with rigid splints attached to the skin could be attributed to variations in the thickness, rigidity and fixation of the skin to deep tissues. The shape of the final scar was influenced by the position of the wound on the body surface. The major factor in this instance was considered to be tensile forces acting within the skin. Wound contraction curves in rats and rabbits showed three distinct phases, namely early closure, stationary and logarithmic closure. Guinea pigs lacked the early closure phase. The exact role of the panniculuscarnosus in wound healing is considered to be worthy of detailed study.