Mechanisms of action of microdeformational wound therapy

Negative Pressure Wound Therapy for Chronic Wounds

ABSTRACT

Chronic wounds, including those caused by venous and arterial insufficiency, diabetic complications, and pressure-induced ulcers, pose significant treatment challenges. Negative pressure wound therapy has been increasingly used for managing these wounds. This treatment aims to promote wound healing, prepare the wound bed for further surgical intervention, minimize the risk of infection, and potentially shorten the time to wound healing. Considering variances in techniques applied in different regions globally, there is an emerging need to comprehensively evaluate the effectiveness of negative pressure wound therapy on chronic wounds. Unfortunately, detailed descriptions of the techniques applied to achieve negative pressure are often lacking in existing literature abstracts, posing challenges for direct comparisons. This review aims to analyze the application of negative pressure wound therapy in the treatment of chronic wounds, summarize its advantages and disadvantages, and further explore the potential value and future research direction of negative pressure wound therapy in the repair of chronic wounds.

The Evolution of Commercial Negative Pressure Wound Therapy Systems over the Past Three Decades

Significance: Since the introduction of the first commercial negative pressure wound therapy (NPWT) system nearly three decades ago, several key technological innovations have led to the wide adoption of the therapy. This is a review of the history and innovation of commercial NPWT systems for adjunctive management of open wounds. Recent Advances: Technical modifications have broadened NPWT options to include innovative dressing interfaces, tubing configurations, power sources, capability of topical wound solution instillation or irrigation, canister versus canister-free configurations, smart technology, and disposable versus larger reusable therapy units. While these options complicate product selection, they have greatly expanded the potential to manage a wide variety of wounds in patients who previously may not have been candidates for NPWT. Critical Issues: Basic yet mandatory requirements of NPWT include delivering an accurate level of negative pressure to the wound bed, maintaining a seal, removing wound surface exudate through the dressing interface, and patient adherence to prescribed therapy. Meeting these requirements is challenging in the face of variable wound types, wound locations, exudate levels, and exudate viscosity. While there are a growing number of marketed NPWT systems, each may have different characteristics and performance. Evaluating the functionality of each system and relevant accessories is complicated, especially as additional manufacturers enter the market. Understanding the key innovations and specific challenges they are intended to solve may aid health care providers in selecting appropriate NPWT technologies for patients. Future Directions: Evolving technology, including artificial intelligence, will likely play a major role in redefining NPWT safety, simplicity, and reliability.

From Time to Timer in Wound Healing Through the Regeneration

Hard-to-heal wounds are an important public health issue worldwide, with a significant impact on the quality of life of patients. It is estimated that approximately 1-2% of the global population suffers from difficult wounds, which can be caused by a variety of factors such as trauma, infections, chronic diseases like diabetes or obesity, or poor health conditions. Hard-to-heal wounds are often characterized by a slow and complicated healing process, which can lead to serious complications such as infections, pressure ulcers, scar tissue formation, and even amputations. These complications can have a significant impact on the mobility, autonomy, and quality of life of patients, leading to an increase in healthcare and social costs associated with wound care. The preparation of the wound bed is a key concept in the management of hard-to-heal wounds, with the aim of promoting an optimal environment for healing. The TIME (Tissue, Infection/Inflammation, Moisture, Edge) model is a systematic approach used to assess and manage wounds in a targeted and personalized way. The concept of TIMER, expanding the TIME model, further focuses on regenerative processes, paying particular attention to promoting tissue regeneration and wound healing in a more effective and comprehensive way. The new element introduced in the TIMER model is "Regeneration", which highlights the importance of activating and supporting tissue regeneration processes to promote complete and lasting wound healing. Regenerative therapies can include a wide range of approaches, including cellular therapies, growth factors, bioactive biomaterials, stem cell therapies, and growth factor therapies. These therapies aim to promote the formation of new healthy tissues, reduce inflammation, improve vascularization, and stimulate cellular proliferation to accelerate wound closure and prevent complications. Thanks to continuous progress in research and development of regenerative therapies, more and more patients suffering from difficult wounds can benefit from innovative and promising solutions to promote faster and more effective healing, improve quality of life, and reduce the risk of long-term complications.

Effectiveness of negative-pressure wound therapy to standard therapy in the prevention of complications after vascular surgery

Wound complications are common after vascular surgery and many may be preventable. Negative pressure wound therapy (NPWT) dressings may be able to reduce wound complications relating to closed incisions following vascular surgery and several devices are currently available along with a large body of literature. This review article will describe the use of NPWT dressings in vascular surgery. We will summarize the currently available systems, the likely mechanism of action of NWPT, the published studies to date and we will give our recommendations regarding the priorities for future research on this topic.

An Overview of Scaffolds and Biomaterials for Skin Expansion and Soft Tissue Regeneration: Insights on Zinc and Magnesium as New Potential Key Elements

The utilization of materials in medical implants, serving as substitutes for non-functional biological structures, supporting damaged tissues, or reinforcing active organs, holds significant importance in modern healthcare, positively impacting the quality of life for millions of individuals worldwide. However, certain implants may only be required temporarily to aid in the healing process of diseased or injured tissues and tissue expansion. Biodegradable metals, including zinc (Zn), magnesium (Mg), iron, and others, present a new paradigm in the realm of implant materials. Ongoing research focuses on developing optimized materials that meet medical standards, encompassing controllable corrosion rates, sustained mechanical stability, and favorable biocompatibility. Achieving these objectives involves refining alloy compositions and tailoring processing techniques to carefully control microstructures and mechanical properties. Among the materials under investigation, Mg- and Zn-based biodegradable materials and their alloys demonstrate the ability to provide necessary support during tissue regeneration while gradually degrading over time. Furthermore, as essential elements in the human body, Mg and Zn offer additional benefits, including promoting wound healing, facilitating cell growth, and participating in gene generation while interacting with various vital biological functions. This review provides an overview of the physiological function and significance for human health of Mg and Zn and their usage as implants in tissue regeneration using tissue scaffolds. The scaffold qualities, such as biodegradation, mechanical characteristics, and biocompatibility, are also discussed.

Endoscopic vacuum therapy: 2 methods of successful endosponge placement for treatment of anastomotic leak in the upper GI tract

Video 1Presentation of 2 methods of successful endosponge placement for treatment of anastomotic leak in the upper GI tract.

Experimental study of negative pressure wound therapy combined with platelet-rich fibrin for bone-exposed wounds

Aim: To evaluate the efficacy of negative pressure wound therapy (NPWT) combined with platelet-rich fibrin (PRF) in treating bone-exposed wounds and explore its possible mechanism. Materials & methods: A bone-exposed wound was created in a total of 32 healthy Sprague-Dawley rats, which were divided into either control group, NPWT group, PRF group or both (N + P group). The bone-exposed area, skin contraction rate and granulation coverage and the level of growth factors in granulation tissue were determined on days 4, 7 and 10. Results: The N + P group showed significantly higher wound closure rate than that achieved with others respectively. Four factors were significantly higher in N + P group than in the other three groups. Conclusion: Combination of NPWT and PRF can repair bone-exposed wounds effectively and accelerate wound healing.

Effects of negative pressure wound therapy on an axial congested rabbit skin flap model without any bare surface

One of the most important problems encountered in reconstructive surgery is partial or total flap loss, and venous congestion is the most common reason. It should be solved as early as possible. The purpose of this study is to investigate the effects of Negative pressure wound therapy (NPWT) on an ideal congested rabbit skin flap model without any open wound. The current study included 28 female, adult, New Zealand albino rabbits. Animals were divided into four groups according to the duration of NPWT to be applied. An axial pattern ideal congested skin flap was designed on the posterior surface of the ear. After surgical intervention on the right ears, we applied NPWT treatment for 2, 4, 6 and 8 days. The left ears were followed without any treatment. Samples were taken for edema, congestion and neo-angiogenesis examination. There was no significant difference between the NPWT applied group and control group in the 2nd, 4th, 6th, and 8th days for edema and neo-angiogenesis and no differences in the 2nd, 6th, and 8th days for congestion. NPWT group had a higher flap survival rate than the control group but without a significant difference. This study used an ideal congested rabbit skin flap model imitating venous congestion. Our findings illustrate that NPWT treatment does not have a significant effect on the congested skin flap model we utilized where a closed system was created maintaining a skin barrier without a bare surface of the flap. Level of Evidence: Level I, experimental study.

Endoscopic vacuum therapy for anastomotic leak in esophagectomy and total gastrectomy: a systematic review and meta-analysis

The curative treatment for esophageal and gastric cancer is primarily surgical resection. One of the main complications related to esophagogastric surgery is the anastomotic leak. This complication is associated with a prolonged length of stay, reduced quality of life, high treatment costs, and an increased mortality rate. The placement of endoluminal stents is the most frequent endoscopic therapy in these cases. However, since its introduction, endoscopic vacuum therapy has been shown to be a promising alternative in the management of this complication. This study primarily aims to evaluate the efficacy and safety of endoscopic vacuum therapy for the treatment of anastomotic leak in esophagectomy and total gastrectomy. A systematic review and meta-analysis was performed. Studies that evaluated the use of endoscopic vacuum therapy for anastomotic leak in esophagectomy and total gastrectomy were included. Twenty-three articles were included. A total of 559 patients were evaluated. Endoscopic vacuum therapy showed a fistulous orifice closure rate of 81.6% (rate: 0.816; 95% CI: 0.777-0.864) and, when compared to the stent, there is a 16% difference in favor of endoscopic vacuum therapy (risk difference [RD]: 0.16; 95% CI: 0.05-0.27). The risk for mortality in the endoscopic vacuum therapy was 10% lower than in endoluminal stent therapy (RD: -0.10; 95% CI: -0.18 to -0.02). Endoscopic vacuum therapy might have a higher rate of fistulous orifice closure and a lower rate of mortality, compared to intraluminal stenting.

Should Negative Pressure Therapy Replace Any Other Temporary Abdominal Closure Device in Open-Abdomen Management of Secondary Peritonitis?

AIM

To clarify the advantages of negative pressure therapy (NPT) compared to other methods of temporary abdominal closure (TAC) in the management of secondary peritonitis.

METHODS

We retraced the history of known methods of TAC, and analyzed their advantages and disadvantages. We evaluated as the NPT mechanisms, both from the macroscopic that bio-molecular point of view, well suits to manage this difficult condition.

RESULTS

The ideal TAC technique should be quick to apply, easy to change, protect and contain the abdominal viscera, decrease bowel edema, prevent loss of domain and abdominal compartment syndrome, limit contamination, allow egress of peritoneal fluid (and its estimation) and not result in adhesions. It should also be cost-effective, minimize the number of dressing changes and the number of surgical revisions, and ensure a high rate of early closure with a low rate of complications (especially entero-atmospheric fistula). For NPT, the reported fistula rate is 7%, primary fascial closure ranges from 33 to 100% (average 60%) and the mortality rate is about 20%. With the use of NPT as TAC, it may be possible to extend the window of time to achieve primary fascial closure (for up to 20-40 days).

CONCLUSION

NPT has several potential advantages in open-abdomen (OA) management of secondary peritonitis and may make it possible to achieve all the goals suggested above for an ideal TAC system. Only trained staff should use NPT, following the manufacturer's instructions when commercial products are used. Even if there was a significant evolution in OA management, we believe that further research into the role of NPT for secondary peritonitis is necessary.

Preconditioning with Foam-mediated External Suction on Flap Microvasculature and Perfusion in a Rodent Model

Foam-mediated external suction (FMES) has previously shown to improve tissue microcirculation. We hypothesized that preconditioning fasciocutaneous perforator flaps with FMES would augment perfusion and demonstrate greater capillary recruitment.

Topical negative-pressure wound therapy: emerging devices and techniques

Introduction: The treatment of chronic wounds constitutes a massive financial burden to society and our health-care system. Therefore, efficient wound care is of great importance to all kinds of medical fields. The implementation and modification of negative-pressure wound therapy can be seen as a major improvement in wound healing. Many different NPWT applications evolved trying to address various wound etiologies.Areas covered: This review aims to give an overview of various NPWT applications, show its effects on wound healing, and discuss future modifications.Expert opinion: NPWT as a delivery device for cold plasma, growth factors, or targeted stem cells to the wound bed and the ability to monitor the inflammatory activity, bacterial load and wound healing factors can be seen as possible future steps to individualized wound care. In addition, it requires high-quality experimental studies to develop the ideal foam in terms of microstructure, pore size, and material properties.

Microdeformational wound therapy: A novel option to salvage complex wounds associated with the Nuss procedure

BACKGROUND

Complex wounds associated with the Nuss procedure are a resource intensive complication that may lead to significant morbidity with potential removal of the implanted device and abandonment of the repair. We report our management technique of this complication utilizing microdeformational wound therapy (MDWT) that is safe, is efficacious and allows for salvage of the repair.

OPERATIVE TECHNIQUE

We defined a complex wound as a wound that became suppurative and drained in the postoperative period and failed to resolve with a trial of conventional wound management and antibiotics. Upon recognition of a complex wound, we recommend an initial operative wound debridement. This allows wound cultures, wound assessment and precise initiation of MDWT. It is not uncommon to have exposed hardware in the wound early in the course of therapy. Metal allergy must be excluded. The patient is transitioned to oral antibiotics following resolution of the acute process. MDWT is performed until the wounds are completely epithelialized with no clinical signs of drainage or infection. The average length of MDWT in our patients was 39 days. Following complete wound healing the patients are maintained on antibiotics until implant removal.

CONCLUSIONS

The use of microdeformational wound therapy in complex wounds associated with the Nuss procedure is a safe and effective modality. The technique may reduce the likelihood of implant removal with potential recurrent pectus excavatum.

TYPE OF STUDY

Operative technique.

LEVEL OF EVIDENCE

Level IV, case series with no comparison group.

Biomimetic coatings and negative pressure wound therapy independently limit epithelial downgrowth around percutaneous devices

Biomimetic material coatings and negative pressure wound therapy (NPWT) have been shown independently to limit the epithelial downgrowth rates in percutaneous devices. It was therefore hypothesized that these techniques, in combination, could further limit the clinically observed epithelial downgrowth around these devices. In this study, we evaluated the efficacy of two biomimetic coatings, collagen and hydroxyapatite (HA), to prevent downgrowth when used with continuous NPWT. Using an established single-stage surgical protocol, collagen (n = 10) and HA (n = 10) coated devices were implanted subdermally on the back of hairless guinea pigs. Five animals from each group were subjected to continuous ~90 mmHg NPWT. Four weeks post-implantation, animals were sacrificed, and the devices and surrounding tissues were harvested, processed, and downgrowth was computed and compared to historical porous titanium coated controls. Data showed a significant reduction in downgrowth in NPWT treated animals (p ≤ 0.05) when compared to the untreated porous titanium controls. HA coated devices, without the NPWT treatment, also showed significantly decreased downgrowth compared to the untreated porous titanium controls.

Role of endoscopic vacuum therapy in the management of gastrointestinal transmural defects

A gastrointestinal (GI) transmural defect is defined as total rupture of the GI wall, and these defects can be divided into three categories: perforations, leaks, and fistulas. Surgical management of these defects is usually challenging and may be associated with high morbidity and mortality rates. Recently, several novel endoscopic techniques have been developed, and endoscopy has become a first-line approach for therapy of these conditions. The use of endoscopic vacuum therapy (EVT) is increasing with favorable results. This technique involves endoscopic placement of a sponge connected to a nasogastric tube into the defect cavity or lumen. This promotes healing via five mechanisms, including macrodeformation, microdeformation, changes in perfusion, exudate control, and bacterial clearance, which is similar to the mechanisms in which skin wounds are treated with commonly employed wound vacuums. EVT can be used in the upper GI tract, small bowel, biliopancreatic regions, and lower GI tract, with variable success rates and a satisfactory safety profile. In this article, we review and discuss the mechanism of action, materials, techniques, efficacy, and safety of EVT in the management of patients with GI transmural defects.

The Role of Negative-Pressure Wound Therapy in Lower-Limb Reconstruction

Negative-pressure wound therapy (NPWT) has gained increasing popularity among clinicians since its introduction in 1997 as a potential aid to wound healing. Multiple benefits of NPWT have since been proven in studies, including increase in granulation tissue formation, decrease in bacterial load, and the improved survival of flaps. With our increasing use and greater understanding of the tissue and cellular changes that occur in a wound treated with NPWT, our lower-limb reconstructive practice has also evolved. Although controversial, the definite timing for lower-limb reconstruction has stretched from 72 hours to longer than 2 weeks as NPWT contains the wound within a sterile, closed system. It has also shown to decrease the rate of infection in open tibia fractures. Previously, a large number of critical defects of the lower limb would require free tissue transfer for definitive reconstruction. NPWT has reduced this rate by more than 50% and has allowed for less complicated resurfacing procedures to be performed instead.

Spatial-Temporal Changes of Mechanical Microenvironment in Skin Wounds During Negative Pressure Wound Therapy

Cell migration, proliferation, and differentiation are regulated by mechanical cues during skin wound healing. Negative pressure wound therapy (NPWT) reduces the healing period by optimizing the mechanical microenvironment of the wound bed. Under NPWT, it remains elusive how the mechanical microenvironment (e.g., stiffness, strain gradients) changes both in time and space during wound healing. To illustrate this, the healing time of full-thickness skin wounds under NPWT, with pressure settings ranging from -50 to -150 mm Hg, were evaluated and compared with gauze dressing treatments (control group), and three-dimensional finite element models of full-thickness skin wounds on days 1 and 5 after treatment were developed on the basis of MR 3D imaging data. Shear wave elastography (SWE) was applied to detect the stiffness of wound soft tissue on days 1 and 5, and nonlinear finite element analysis (FEA) was used to represent the spatial-temporal environment of the 3D strain field of the wound under NPWT vs the control group. Compared with the control group, NPWT with -50, -80, and -125 mm Hg promoted wound healing. SWE showed that the elastic modulus of wounded skin increased during healing. Meanwhile, the elastic modulus in wounded skin under NPWT was significantly smaller than in the control group. Strain and its gradient decreased under NPWT during wound healing, while no significant change was observed in the control group. This study, which is based on MR 3D imaging, shear wave elastography, and nonlinear FEA, provides an in-depth understanding of changes of the skin mechanical microenvironment under NPWT in the time-space dimension and the associated wound healing.

Study of negative pressure wound therapy as an adjunct treatment for acute burns in children (SONATA in C): protocol for a randomised controlled trial

BACKGROUND

Although negative pressure wound therapy (NPWT) is widely used in the management of several wound types, its efficacy as a primary therapy for acute burns has not yet been adequately investigated, with research in the paediatric population particularly lacking. There is limited evidence, however, that NPWT might benefit children with burns, amongst whom scar formation, wound progression and pain continue to present major management challenges. The purpose of this trial is to determine whether NPWT in conjunction with standard therapy accelerates healing, reduces wound progression and decreases pain more effectively than standard treatment alone.

METHODS/DESIGN

A total of 104 children will be recruited for this trial. To be eligible, candidates must be under 17 years of age and present to the participating children's hospital within 7 days of their injury with a thermal burn covering <5% of their total body surface area. Facial and trivial burns will be excluded. Following a randomised controlled parallel design, participants will be allocated to either an active control or intervention group. The former will receive standard therapy consisting of Acticoat™ and Mepitel™. The intervention arm will be treated with silver-impregnated dressings in addition to NPWT via the RENASYS TOUCH™ vacuum pump. Participants' dressings will be changed every 3 to 5 days until their wounds are fully re-epithelialised. Time to re-epithelialisation will be studied as the primary outcome. Secondary outcomes will include pain, pruritus, wound progression, health-care-resource use (and costs), ease of management, treatment satisfaction and adverse events. Wound fluid collected during NPWT will also be analysed to generate a proteomic profile of the burn microenvironment.

DISCUSSION

The study will be the first randomised controlled trial to explore the clinical effects of NPWT on paediatric burns, with the aim of determining whether the therapy warrants implementation as an adjunct to standard burns management.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12618000256279 . Registered on 16 February 2018.

MnSOD is implicated in accelerated wound healing upon Negative Pressure Wound Therapy (NPWT): A case in point for MnSOD mimetics as adjuvants for wound management

Negative Pressure Wound Therapy (NPWT), a widely used modality in the management of surgical and trauma wounds, offers clear benefits over conventional wound healing strategies. Despite the wide-ranging effects ascribed to NPWT, the precise molecular mechanisms underlying the accelerated healing supported by NPWT remains poorly understood. Notably, cellular redox status-a product of the balance between cellular reactive oxygen species (ROS) production and anti-oxidant defense systems-plays an important role in wound healing and dysregulation of redox homeostasis has a profound effect on wound healing. Here we investigated potential links between the use of NPWT and the regulation of antioxidant mechanisms. Using patient samples and a rodent model of acute injury, we observed a significant accumulation of MnSOD protein as well as higher enzymatic activity in tissues upon NPWT. As a proof of concept and to outline the important role of SOD activity in wound healing, we replaced NPWT by the topical application of a MnSOD mimetic, Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+, MnE, BMX-010, AEOl10113) in the rodent model. We observed that MnE is a potent wound healing enhancer as it appears to facilitate the formation of new tissue within the wound bed and consequently advances wound closure by two days, compared to the non-treated animals. Taken together, these results show for the first time a link between NPWT and regulation of antioxidant mechanism through the maintenance of MnSOD activity. Additionally this discovery outlined the potential role of MnSOD mimetics as topical agents enhancing wound healing.

Incorporating mechanical strain in organs-on-a-chip: Lung and skin

In the last decade, the advent of microfabrication and microfluidics and an increased interest in cellular mechanobiology have triggered the development of novel microfluidic-based platforms. They aim to incorporate the mechanical strain environment that acts upon tissues and in-vivo barriers of the human body. This article reviews those platforms, highlighting the different strains applied, and the actuation mechanisms and provides representative applications. A focus is placed on the skin and the lung barriers as examples, with a section that discusses the signaling pathways involved in the epithelium and the connective tissues.

Negative-Pressure Wound Therapy in a Pseudomonas aeruginosa Infection Model

BACKGROUND

Negative-pressure wound therapy (NPWT) is an effective strategy for the management of contaminated wounds, including those infected by Pseudomonas aeruginosa. We hypothesized that NPWT would reduce virulence factors as well as biofilm components and inhibit virulence-regulated gene expression in a model of P. aeruginosa wound infection.

METHODS

Wounds were created in anesthetized rabbits and P. aeruginosa was inoculated to the wound surface for 24 h. Wounds were treated with either NPWT or a sterile gauze dressing. Virulence factors including exotoxin A, rhamnolipid, and elastase were quantified by the enzyme-linked immunosorbent assay, orcinol, and elastin-Congo red methods, respectively. A biofilm component, eDNA, was quantified using a commercial kit. Virulence-regulated genes were determined by quantitative real-time polymerase chain reaction (RT-PCR). Biofilms were observed in vivo by staining with concanavalin A conjugated to Alexa Fluor® 647.

RESULTS

NPWT was more effective than the control treatment in reducing virulence factors and bacteria counts in vivo. A biofilm component, eDNA, was less abundant in the NPWT group. The results of the RT-PCR indicated that the expression levels of P. aeruginosa virulence-regulated genes and quorum-sensing population density-dependent systems were significantly inhibited by NPWT treatment.

CONCLUSION

NPWT reduced bacteria counts, virulence factors, and eDNA in a P. aeruginosa wound infection model in vivo. These beneficial effects are likely to be related to the reduced expression of virulence-regulated genes and the drainage induced by NPWT treatment. These findings may help clinicians to obtain a better understanding of the mechanism of NPWT for the treatment of infected wounds.

Instructive microenvironments in skin wound healing: Biomaterials as signal releasing platforms

Skin wound healing aims to repair and restore tissue through a multistage process that involves different cells and signalling molecules that regulate the cellular response and the dynamic remodelling of the extracellular matrix. Nowadays, several therapies that combine biomolecule signals (growth factors and cytokines) and cells are being proposed. However, a lack of reliable evidence of their efficacy, together with associated issues such as high costs, a lack of standardization, no scalable processes, and storage and regulatory issues, are hampering their application. In situ tissue regeneration appears to be a feasible strategy that uses the body's own capacity for regeneration by mobilizing host endogenous stem cells or tissue-specific progenitor cells to the wound site to promote repair and regeneration. The aim is to engineer instructive systems to regulate the spatio-temporal delivery of proper signalling based on the biological mechanisms of the different events that occur in the host microenvironment. This review describes the current state of the different signal cues used in wound healing and skin regeneration, and their combination with biomaterial supports to create instructive microenvironments for wound healing.

Negative pressure wound therapy reduces the motility of Pseudomonas aeruginosa and enhances wound healing in a rabbit ear biofilm infection model

Pseudomonas aeruginosa motility, virulence factors and biofilms are known to be detrimental to wound healing. The efficacy of negative pressure wound therapy (NPWT) against P. aeruginosa has been little studied, either in vitro or in vivo. The present study evaluated the effect of negative pressure (NP) on P. aeruginosa motility in vitro, and the effect of NPWT on virulence factors and biofilms in vivo. P. aeruginosa motility was quantified under different levels of NP (atmospheric pressure, − 75, − 125, − 200 mmHg) using an in vitro model. Swimming, swarming and twitching motility were significantly inhibited by NP (− 125 and − 200 mmHg) compared with atmospheric pressure (p = 0.05). Virulence factors and biofilm components were quantified in NPWT and gauze treated groups using a rabbit ear biofilm model. Biofilm structure was studied with fluorescence microscopy and scanning electron microscopy. Additionally, viable bacterial counts and histological wound healing parameters were measured. Compared with the control, NPWT treatment resulted in a significant reduction in expression of all virulence factors assayed including exotoxin A, rhamnolipid and elastase (p = 0.01). A significant reduction of biofilm components (eDNA) (p = 0.01) was also observed in the NPWT group. The reduction of biofilm matrix was verified by fluorescence- and scanning electron-microscopy. NPWT lead to better histologic parameters (p = 0.01) and decreased bacterial counts (p = 0.05) compared with the control. NPWT treatment was demonstrated to be an effective strategy to reduce virulence factors and biofilm components, which may explain the increased wound healing observed.

Negative pressure wound therapy promotes muscle-derived stem cell osteogenic differentiation through MAPK pathway

Negative pressure wound therapy (NPWT) has been revealed to be effective in the treatment of open fractures, although the underlying mechanism is not clear. This article aimed to investigate the effects of NPWT on muscle‐derived stem cell (MDSC) osteoblastic differentiation and the related potential mechanism. The cell proliferation rate was substantially increased in NPWT‐treated MDSCs in comparison with a static group for 3 days. There was no observable effect on the apoptosis of MDSC treated with NPWT compared with the control group for 3 days. The expression levels of HIF‐1α, BMP‐2, COL‐I, OST and OPN were increased on days 3, 7 and 14, but the expression level of Runx2 was increased on days 3 and 7 in the NPWT group. Pre‐treatment, the specific inhibitors were added into the MDSCs treated with NPWT and the control group. ALP activity and mineralization were reduced by inhibiting the ERK1/2, p38 and JNK pathways. The expression levels of Runx2, COL‐I, OST and OPN genes and proteins were also decreased using the specific MAPK pathway inhibitors on days 3, 7 and 14. There were no significant effects on the expression of BMP‐2 except on day 3. However, the expressions of the HIF‐1α gene and protein slightly increased when the JNK pathway was inhibited. Therefore, NPWT promotes the proliferation and osteogenic differentiation of MDSCs through the MAPK pathway.

Effects of negative-pressure wound therapy combinedwith microplasma on treating wounds of ulcer and the expression of heat shock protein 90

The effects of negative pressure wound therapy (NPWT) combined with microplasma on treating wounds of ulcer, and blood perfusion of wound-healing of interface, angiogenesis and the expressions of heat shock protein 90 (HSP90) were explored. We selected continuously 64 patients with wounds of ulcer. The patients were divided into the conventional treatment group (just medical foam dressing and 1% silver sulfadiazine cream for dressing changes) (n=20 cases), the NPWT group (n=22 cases) and the combination group (NPWT combined with microplasma) (n=22 cases), and compared the effects. It was found that in the 7 and 14 day combination group, maturity of granulation tissues and growth degree of epithelium were significantly higher than those in other two groups, and the areas of ulcer reduced significantly, the healing rate increased significantly (P<0.05). In the 7 and 14 day combination group, blood perfusion of wounds and density of new vessels were significantly higher than the other two groups (P<0.05). In the 7 and 14 day combination group, the expression of HSP90 was significantly higher than the other two groups (P<0.05). In conclusion, NPWT combined with microplasma can improve the healing of woulds of ulcers, and it is related to the upregulated expression of HSP90.

VAC therapy with long term continuous saline infusion for secondary septic peritonitis: A new strategy for the reduction of perioperative risks?

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The use of VAC therapy is amply demonstrated in the literature as an adjuvant in the open abdomen technique.

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Today VAC therapy have not a definite indication in secondary septic peritonitis.

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In our case, VAC therapy wasn’t a rescue treatment, but a preventive treatment of high-risk perioperative complications.

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A conservative approach led to the resolution of the septic shock and to the wound healing.

Background

The management of a septic peritonitis open abdomen is a serious problem for clinicians. Open surgery is associated with several complications such as bleeding and perforation of the bowel.

Case presentation

The authors report a case of a 59-years-old female who underwent a sigmoid resection with an latero-terminal (L-T) anastomosis for the perforation of a diverticulum. After a few days the patients developed a new widespread peritonitis. At the emergency re-laparotomy, surgeons found dehiscence of the posterior wall of the anastomosis with fecal contamination. At admission in ICU (Intensive Care Unit) the patient had open abdomen with dehiscence of cutaneous and subcutaneous layers.

Conclusion

Conservative therapy with antibiotic therapy and use of the Vacuum-Assisted Closure^® (VAC) Therapy with a long term continuous saline infusion led to the resolution of the septic shock and to the wound healing.

Evidence based review of negative pressure wound therapy

Vacuum-assisted closure, sometimes referred to as microdeformational wound therapy or most commonly negative pressure wound therapy (NPWT), has significantly improved wound care over the past two decades. NPWT is known to affect wound healing through four primary mechanisms (macrodeformation, microdeformation, fluid removal, and alteration of the wound environment) and various secondary mechanisms (including neurogenesis, angiogenesis, modulation of inflammation, and alterations in bioburden) which are described in this review. In addition, the technique has many established uses, for example in wound healing of diabetic and pressure ulcers, as well as burn and blast wounds. This therapy also has many uses whose efficacy has yet to be confirmed, for example the use in digestive surgery. Modifications of the traditional NPWT have also been established and are described in detail. This therapy has various considerations and contraindications which are summarized in this review. Finally, future perspectives, such as the optimal cycling of the treatment and the most appropriate interface material, are touched upon in the final segment. Overall, despite the fact that questions remain to be answered about NPWT, this technology is a major breakthrough in wound healing with significant potential use both in the hospital but also in the community.

Deconstructing negative pressure wound therapy

Since its introduction 20 years ago for the treatment of chronic wounds, negative pressure wound therapy use has expanded to a variety of other wound types. Various mechanisms of action for its efficacy in wound healing have been postulated, but no unifying theory exists. Proposed mechanisms include induction of perfusion changes, microdeformation, macrodeformation, exudate control and decreasing the bacterial load in the wound. We surmise that these different mechanisms have varying levels of dominance in each wound type. Specifically, negative pressure wound therapy is beneficial to acute open wounds because it induces perfusion changes and formation of granulation tissue. Post-surgical incisional wounds are positively affected by perfusion changes and exudate control. In the context of chronic wounds, negative pressure wound therapy removes harmful and corrosive substances within the wounds to affect healing. When skin grafts and dermal substitutes are used to close a wound, negative pressure wound therapy is effective in promoting granulation tissue formation, controlling exudate and decreasing the bacterial load in the wound. In this review, we elucidate some of the mechanisms behind the positive wound healing effects of negative pressure wound therapy, providing possible explanations for these effects in different wound types.

Negative Pressure Wound Therapy in Maxillofacial Applications

Negative pressure wound therapy has greatly advanced the field of wound healing for nearly two decades, by providing a robust surgical adjunct technique for accelerating wound closure in acute and chronic wounds. However, the application of negative pressure wound therapy in maxillofacial applications has been relatively under utilized as a result of the physical articulations and contours of the head and neck that make it challenging to obtain an airtight seal for different negative pressure wound therapy systems. Adapting negative pressure wound therapies for maxillofacial applications could yield significant enhancement of wound closure in maxillofacial applications. The current review summarizes the basic science underlying negative pressure wound therapy, as well as specific maxillofacial procedures that could benefit from negative pressure wound therapy.

Integrin-mediated regulation of epidermal wound functions

During cutaneous wound healing, keratinocyte proliferation and migration are critical for re-epithelialization. In addition the epidermis secretes growth factors, cytokines, proteases, and matricellular proteins into the wound microenvironment that modify the extracellular matrix and stimulate other wound cells that control the inflammatory response, promote angiogenesis and facilitate tissue contraction and remodeling. Wound keratinocytes express at least seven different integrins-the major cell adhesion receptors for the extracellular matrix-that collectively control essential cell-autonomous functions to ensure proper re-epithelialization, including migration, proliferation, survival and basement membrane assembly. Moreover, it has become evident in recent years that some integrins can regulate paracrine signals from wound epidermis that stimulate other wound cells involved in angiogenesis, contraction and inflammation. Importantly, it is likely that abnormal integrin expression or function in the epidermis contributes to wound pathologies such as over-exuberant healing (e.g., hypertrophic scar formation) or diminished healing (e.g., chronic wounds). In this review, we discuss current knowledge of integrin function in the epidermis, which implicates them as attractive therapeutic targets to promote wound healing or treat wound pathologies. We also discuss challenges that arise from the complex roles that multiple integrins play in wound epidermis, which may be regulated through extracellular matrix remodeling that determines ligand availability. Indeed, understanding how different integrin functions are temporally coordinated in wound epidermis and which integrin functions go awry in pathological wounds, will be important to determine how best to target them clinically to achieve maximum therapeutic benefit. Graphical abstract In addition to their well-characterized roles in keratinocyte adhesion, migration and wound re-epithelialization, epidermal integrins play important roles in modifying the wound microenvironment by regulating the expression and secretion of growth factors, extracellular proteases, and matricellular proteins that stimulate other wound cells, including vascular endothelial cells and fibroblasts/myofibroblasts.

Role of negative pressure wound therapy in total hip and knee arthroplasty

Negative-pressure wound therapy (NPWT) has been a successful modality of wound management which is in widespread use in several surgical fields. The main mechanisms of action thought to play a role in enhancing wound healing and preventing surgical site infection are macrodeformation and microdeformation of the wound bed, fluid removal, and stabilization of the wound environment. Due to the devastating consequences of infection in the setting of joint arthroplasty, there has been some interest in the use of NPWT following total hip arthroplasty and total knee arthroplasty. However, there is still a scarcity of data reporting on the use of NPWT within this field and most studies are limited by small sample sizes, high variability of clinical settings and end-points. There is little evidence to support the use of NPWT as an adjunctive treatment for surgical wound drainage, and for this reason surgical intervention should not be delayed when indicated. The prophylactic use of NPWT after arthroplasty in patients that are at high risk for postoperative wound drainage appears to have the strongest clinical evidence. Several clinical trials including single-use NPWT devices for this purpose are currently in progress and this may soon be incorporated in clinical guidelines as a mean to prevent periprosthetic joint infections.

Mechanical cues in orofacial tissue engineering and regenerative medicine

Cleft lip and palate patients suffer from functional, aesthetical, and psychosocial problems due to suboptimal regeneration of skin, mucosa, and skeletal muscle after restorative cleft surgery. The field of tissue engineering and regenerative medicine (TE/RM) aims to restore the normal physiology of tissues and organs in conditions such as birth defects or after injury. A crucial factor in cell differentiation, tissue formation, and tissue function is mechanical strain. Regardless of this, mechanical cues are not yet widely used in TE/RM. The effects of mechanical stimulation on cells are not straight-forward in vitro as cellular responses may differ with cell type and loading regime, complicating the translation to a therapeutic protocol. We here give an overview of the different types of mechanical strain that act on cells and tissues and discuss the effects on muscle, and skin and mucosa. We conclude that presently, sufficient knowledge is lacking to reproducibly implement external mechanical loading in TE/RM approaches. Mechanical cues can be applied in TE/RM by fine-tuning the stiffness and architecture of the constructs to guide the differentiation of the seeded cells or the invading surrounding cells. This may already improve the treatment of orofacial clefts and other disorders affecting soft tissues.

Experimental study of fat grafting under negative pressure for wounds with exposed bone

BACKGROUND

The combination of fat grafting and negative pressure (VAC) therapy represents a synergistic interaction of all essential components for wound healing. The aim of this experimental study was to determine whether it could promote healing of wounds with exposed bone.

METHODS

Full-thickness wounds with denuded bone in Sprague-Dawley rats were treated with either polyurethane foam dressing, fat grafting alone, polyurethane foam dressing with VAC, or polyurethane foam dressing with VAC combined with a single, or two administrations of fat graft. Wound healing kinetics, tissue growth, cell proliferation (Ki-67) and angiogenesis (platelet endothelial cell adhesion molecule 1 and α-smooth muscle actin) were investigated. Messenger RNA levels related to angiogenesis (vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF)), profibrosis (platelet-derived growth factor A and transforming growth factor β), adipocyte expression (fatty acid-binding protein (FABP) 4 and peroxisome proliferator activated receptor γ), and extracellular matrix remodelling (collagen I) were measured in wound tissues.

RESULTS

Wounds treated by VAC combined with fat grafting were characterized by cell proliferation, neoangiogenesis and maturation of functional blood vessels; they showed accelerated granulation tissue growth over the denuded bone compared with VAC- or foam dressing-treated wounds. Fat grafting alone over denuded bone resulted in complete necrosis. Expression of angiogenesis markers (VEGF and b-FGF) and adipocyte expression factors (FABP-4) was upregulated in wounds treated with VAC combined with fat grafting.

CONCLUSION

Fat grafting with VAC therapy may represent a simple but effective clinical solution for a number of complex tissue defects, and warrants testing in clinical models.

SURGICAL RELEVANCE

The combination of fat grafting and vacuum therapy represents a synergistic interaction of regenerative cells, hospitable wound matrix and stimulating micromechanical forces. It could accelerate complex wound healing through cell proliferation, neoangiogenesis and maturation of functional blood vessels. The efficacy of a multimodal wound healing approach is established in this experimental model; it could easily be translated into clinical trials of treatment for difficult wounds.

Negative pressure wound therapy is associated with up-regulation of bFGF and ERK1/2 in human diabetic foot wounds

Chronic foot wounds are a leading cause of morbidity and hospitalization for patients with diabetes. Negative pressure wound therapy (NPWT) is known to promote healing of diabetic foot wounds, but the underlying molecular mechanisms remain elusive. We propose to gain molecular insights into the wound healing promoting signals underlying the effects of NPWT on diabetic foot wounds in humans. We assessed 30 patients with diabetic foot ulcers. Of these cases, 15 were treated with NPWT, while 15 patients were treated with traditional gauze therapy. Granulated tissue was harvested before and after treatment in both patient groups and histologically analyzed with hematoxylin & eosin as well as Masson's trichrome staining methods. Immunohistochemistry and Western blot analysis was performed to evaluate expression of basic fibroblast growth factor (bFGF) and extracellular signal-regulated kinase (ERK)1/2, previously associated with promoting cellular growth and/or wound healing. Unlike controls, the wounds in the NPWT-treated diabetic patients developed characteristic features of granulated tissue with increased collagen deposition. Immunohistochemical analysis also revealed an increase in bFGF levels in NPWT-treated patients. Western blot analysis further showed a significant up-regulation of bFGF and phosphorylated ERK1/2 protein levels in the NPWT-treated diabetic patients vs. controls. Our studies reveal that NPWT is associated with an up-regulation of bFGF and ERK1/2 signaling, which may be involved in promoting the NPWT-mediated wound healing response.

Noncontact, low-frequency ultrasound therapy enhances neovascularization and wound healing in diabetic mice

BACKGROUND

Chronic wounds are a major source of morbidity for patients and represent a significant health burden. Implementing noninvasive techniques that accelerate healing of these wounds would provide great benefit. Ultrasound appears to be an effective modality for the treatment of chronic wounds in humans. MIST Therapy is a noncontact, low-frequency ultrasound treatment delivered through a saline mist. A variety of mechanisms have been proposed to explain the efficacy of ultrasound therapy, but the underlying molecular and cellular pathways impacted by this technique remain unclear. The in vivo effect of noncontact, low-frequency ultrasound was therefore examined in a humanized excisional wound model.

METHODS

The treatment group received noncontact, low-frequency ultrasound therapy three times per week, whereas the control group received a standard dressing change. Wounds were photographed at regular intervals to calculate healing kinetics. Wound tissue was harvested and processed for histology, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

The MIST group demonstrated significantly accelerated wound healing, with 17.3 days to wound closure compared with 24 days in the controls (p < 0.05). This improvement became evident by day 9, with healing evidenced by significantly decreased mean wound area relative to original size (68 percent versus 80 percent; p < 0.01). Expression of markers of neovascularization (stromal cell-derived factor 1, vascular endothelial growth factor, and CD31) was also increased in the wound beds of noncontact, low-frequency ultrasound-treated mice compared with controls.

CONCLUSION

Noncontact, low-frequency ultrasound treatment improves neovascularization and wound closure rates in excisional wounds for diabetic mice, likely because of the stimulated release of angiogenic factors.

The role of mouse mast cell proteases in the proliferative phase of wound healing in microdeformational wound therapy

BACKGROUND

Stored in the secretory granules of cutaneous mouse mast cells are mouse mast cell proteases (mMCP-4, -5, and -6). Using transgenic mouse lines that lacked these enzymes, it was shown that mMCP-4 and mMCP-5 modulate the outcome of burn-induced skin injury. Whether or not these proteases also play a role in the repair of surgically damaged skin, with or without microdeformational wound therapy, remains to be determined.

METHODS

Wild-type C57BL/6 mice and transgenic C57BL/6 mouse lines lacking mMCP-4, -5, or -6 were subjected to surgical wounding of their skin. Wounds were splinted with a stabilizing patch, and the mice received either microdeformational wound therapy (n = 5) or occlusive dressing (n = 5) for 7 days. Wound healing parameters were assessed in the proliferative phase.

RESULTS

Cell proliferation in the wounded wild-type mice receiving microdeformational wound therapy was 60 ± 3 percent. Cell proliferation was only 35 ± 5 percent, 25 ± 5 percent, and 45 ± 4 percent for the treated mMCP-4-, mMCP-5-, and mMCP-6-null mice, respectively (p = 0.005). Blood vessel sprouting was higher in the control mice with microdeformational wound therapy (170 ± 40 vessels/high-power field) compared with mouse mast cell protease 6-null mice with microdeformational wound therapy (70 ± 20 vessels/high-power field; p = 0.005), and higher in the control mice with occlusive dressing (110 ± 30 vessels/high-power field) compared with mMCP-4-null mice with occlusive dressing (50 ± 20 vessels/high-power field; p = 0.01). Qualitatively, the granulation tissue of all the protease-deficient groups receiving microdeformational wound therapy was disrupted.

CONCLUSION

Results suggest that mouse mast cell proteases 4, 5, and 6 are mediators of the critical role mast cells play in microdeformational wound therapy in the proliferative phase of healing.

Mechanoregulation of Angiogenesis in Wound Healing

Significance: Mechanical forces are important regulators of cell and tissue function. Endothelial cells proliferate in response to tissue stretch and the mechanical properties of the environment direct capillary sprouting and growth. As the vascular network is a key factor in physiology and disease, control of the vascularity by means of mechanical forces could lead to the development of innovative therapeutic strategies. Recent Advances: Increased understanding of mechanobiology has stimulated translational research and allowed the development and optimization of clinical devices that exploit mechanical forces for the treatment of diseases, in particular in the field of wound healing. Stretching in distraction osteogenesis and tissue expansion induces neogenesis of well-vascularized tissues. In micro-deformational wound therapy, micro-mechanical distortions of the wound bed stimulate cell proliferation and angiogenesis by stretching resident cells to improve healing of difficult wounds. Relief from tension antagonizes proliferation and angiogenesis in primarily closed wounds allowing for better scar quality. Critical Issues: The integration of mechanobiology into traditional cell biology and pathophysiology in general is not yet complete and further research is needed to fill existing gaps, in particular in the complexity of in vivo conditions. Future Directions: Still largely unexplored approaches based on mechanical perturbation of the micro-/macro-environment can be devised to overcome the limits of current strategies in a broad spectrum of clinical conditions.

Stretch-induced intussuceptive and sprouting angiogenesis in the chick chorioallantoic membrane

Vascular systems grow and remodel in response to not only metabolic needs, but also mechanical influences as well. Here, we investigated the influence of tissue-level mechanical forces on the patterning and structure of the chick chorioallantoic membrane (CAM) microcirculation. A dipole stretch field was applied to the CAM using custom computer-controlled servomotors. The topography of the stretch field was mapped using finite element models. After 3days of stretch, Sholl analysis of the CAM demonstrated a 7-fold increase in conducting vessel intersections within the stretch field (p<0.01). The morphometric analysis of intravital microscopy and scanning electron microscopy (SEM) images demonstrated that the increase vessel density was a result of an increase in interbranch distance (p<0.01) and a decrease in bifurcation angles (p<0.01); there was no significant increase in conducting vessel number (p>0.05). In contrast, corrosion casting and SEM of the stretch field capillary meshwork demonstrated intense sprouting and intussusceptive angiogenesis. Both planar surface area (p<0.05) and pillar density (p<0.01) were significantly increased relative to control regions of the CAM. We conclude that a uniaxial stretch field stimulates the axial growth and realignment of conducting vessels as well as intussusceptive and sprouting angiogenesis within the gas exchange capillaries of the ex ovo CAM.

Effect of negative pressure wound therapy on wound healing

The efficacy of NPWT in promoting wound healing has been largely accepted by clinicians, yet the number of high-level clinical studies demonstrating its effectiveness is small and much more can be learned about the mechanisms of action. In the future, hopefully we will have the data to assist clinicians in selecting optimal parameters for specific wounds including interface material, waveform of suction application, and the amount of suction to be applied. Further investigation into specific interface coatings and instillation therapy are also needed. We believe that advances in mechanobiology, the science of wound healing, the understanding of biofilms, and advances in cell therapy will lead to better care for our patients.

Mechanotransduction and fibrosis

Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

Integrin Regulation of Epidermal Functions in Wounds

Significance: Integrins are bidirectional signaling receptors for extracellular matrix that regulate both inside-out signaling that controls keratinocyte-mediated changes to the wound microenvironment and outside-in signaling that controls keratinocyte responses to microenvironmental changes. As such, integrins represent attractive therapeutic targets for treatment of chronic wounds or general promotion of wound healing. Advances in wound management are particularly important as the elderly and diabetic populations within the United States continue to grow. Recent Advances: Although integrins are best known for mediating cell adhesion and migration, integrins in wound epidermis also control cell survival, proliferation, matrix remodeling, and paracrine crosstalk to other cellular compartments of the wound. Importantly, the concept of targeting integrins in the clinic has been established for treatment of certain cancers and other diseases, laying the groundwork for similar exploitation of integrins as targets to treat chronic wounds. Critical Issues: Despite their attractiveness as therapeutic targets, integrins have complex roles in wound healing that are impacted by both their own expression and a highly dynamic wound microenvironment that determines ligand availability. Therefore, identifying relevant integrin ligands in the wound and understanding both distinct and overlapping functions that different integrins play in the epidermis will be critical to determine their precise roles in wound healing. Future Directions: Future research should focus on gaining a thorough understanding of the highly coordinated functions of different integrins in wound epidermis, and on determining which of these functions go awry in pathological wounds. This focus should facilitate development of integrin-targeting therapeutics for treating chronic wounds.

Mechanoregulation of the Myofibroblast in Wound Contraction, Scarring, and Fibrosis: Opportunities for New Therapeutic Intervention

SIGNIFICANCE

Myofibroblasts are responsible for wound closure that occurs in healed acute wounds. However, their actions can result in disfiguring scar contractures, compromised organ function, and a tumor promoting stroma. Understanding the mechanisms regulating their contractile machinery, gene expression, and lifespan is essential to develop new therapies to control their function.

RECENT ADVANCES

Mechanical stress and transforming growth factor beta-1 (TGF-β1) regulate myofibroblast differentiation from mesenchymal progenitors. As these precursor cells differentiate, they assemble a contractile apparatus to generate the force used to contract wounds. The mechanisms by which mechanical stress promote expression of contractile genes through the TGF-β1 and serum response factor pathways and offer therapeutic targets to limit myofibroblast function are being elucidated.

CRITICAL ISSUES

Emerging evidence suggests that the integration of mechanical cues with intracellular signaling pathways is critical to myofibroblast function via its effects on gene expression, cellular contraction, and paracrine signaling with neighboring cells. In addition, while apoptosis is clearly one pathway that can limit myofibroblast lifespan, recent data suggest that pathogenic myofibroblasts can become senescent and adopt a more beneficial phenotype, or may revert to a quiescent state, thereby limiting their function.

FUTURE DIRECTIONS

Given the important role that myofibroblasts play in pathologies as disparate as cutaneous scarring, organ fibrosis, and tumor progression, knowledge gained in the areas of intracellular signaling networks, mechanical signal transduction, extracellular matrix biology, and cell fate will support efforts to develop new therapies with a wide impact.

How mechanical deformations contribute to the effectiveness of negative-pressure wound therapy

Negative-pressure wound therapy (NPWT) has significantly improved healing rates and patient comfort since its inception. However, a considerable number of questions have been raised regarding its mechanisms of action. Many health care workers and researchers have attempted to clarify the role of NPWT in wound healing. The purpose of this perspective article is to assemble some of the concepts that have been put forward in order to propose an integrated view of the mechanisms involved in NPWT. Particular emphasis will be placed on mechanically induced tissue deformations and their involvement in some of the key processes of wound healing, including nutrient and oxygen transport, blood vessel formation, and cellular proliferation and differentiation, mainly of myofibroblasts.