Wounds: Biology, Pathology, and Management

Human In Vitro Skin Models for Wound Healing and Wound Healing Disorders

Skin wound healing is essential to health and survival. Consequently, high amounts of research effort have been put into investigating the cellular and molecular components involved in the wound healing process. The use of animal experiments has contributed greatly to the knowledge of wound healing, skin diseases, and the exploration of treatment options. However, in addition to ethical concerns, anatomical and physiological inter-species differences often influence the translatability of animal-based studies. Human in vitro skin models, which include essential cellular and structural components for wound healing analyses, would improve the translatability of results and reduce animal experiments during the preclinical evaluation of novel therapy approaches. In this review, we summarize in vitro approaches, which are used to study wound healing as well as wound healing-pathologies such as chronic wounds, keloids, and hypertrophic scars in a human setting.

Pulmonary and systemic toxicity in rats following inhalation exposure of 3-D printer emissions from acrylonitrile butadiene styrene (ABS) filament

BACKGROUND

Fused filament fabrication 3-D printing with acrylonitrile butadiene styrene (ABS) filament emits ultrafine particulates (UFPs) and volatile organic compounds (VOCs). However, the toxicological implications of the emissions generated during 3-D printing have not been fully elucidated.

AIM AND METHODS

The goal of this study was to investigate the in vivo toxicity of ABS-emissions from a commercial desktop 3-D printer. Male Sprague Dawley rats were exposed to a single concentration of ABS-emissions or air for 4 hours/day, 4 days/week for five exposure durations (1, 4, 8, 15, and 30 days). At 24 hours after the last exposure, rats were assessed for pulmonary injury, inflammation, and oxidative stress as well as systemic toxicity.

RESULTS AND DISCUSSION

3-D printing generated particulate with average particle mass concentration of 240 ± 90 µg/m³, with an average geometric mean particle mobility diameter of 85 nm (geometric standard deviation = 1.6). The number of macrophages increased significantly at day 15. In bronchoalveolar lavage, IFN-γ and IL-10 were significantly higher at days 1 and 4, with IL-10 levels reaching a peak at day 15 in ABS-exposed rats. Neither pulmonary oxidative stress responses nor histopathological changes of the lungs and nasal passages were found among the treatments. There was an increase in platelets and monocytes in the circulation at day 15. Several serum biomarkers of hepatic and kidney functions were significantly higher at day 1.

CONCLUSIONS

At the current experimental conditions applied, it was concluded that the emissions from ABS filament caused minimal transient pulmonary and systemic toxicity.

​Primary closure versus delayed or no closure for traumatic wounds due to mammalian bite

BACKGROUND

Mammalian bites are a common presentation in emergency and primary healthcare facilities across the world. The World Health Organization recommends postponing the suturing of a bite wound but this has not been evaluated through a systematic review.

OBJECTIVES

To assess the effects of primary closure compared with delayed closure or no closure for mammalian bite wounds.

SEARCH METHODS

In July 2019 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

We included randomised controlled trials which compared primary closure with delayed or no closure for traumatic wounds due to mammalian bite.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles, abstracts and full-text publications, applied the inclusion criteria, and extracted data. We pooled data using a random-effects model, as appropriate. We used the Cochrane 'Risk of bias' tool and assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We found three trials (878 participants) that compared primary closure with no closure for dog bites and one trial (120 participants) that compared primary closure with delayed closure. No other mammalian bite studies were identified. The trials were from the UK (one trial), Greece (one trial) and China (two trials). Overall, participants from both sexes and all age groups were represented. We are uncertain whether primary closure improves the proportion of wounds which are infection-free compared with no closure, as the certainty of evidence for this outcome was judged to be very low (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.97 to 1.05; 2 studies, 782 participants; I2 = 0%). We downgraded the evidence by one level for high risk of bias and two levels for imprecision. There is no clinically important difference in cosmesis (acceptable physical/cosmetic appearance) of dog bite wounds when primary closure is compared with no closure (mean difference (MD) -1.31, 95% CI -2.03 to -0.59; 1 study, 182 participants). The certainty of evidence for this outcome was judged to be moderate (we downgraded our assessment by one level for imprecision). We are uncertain whether primary closure improves the proportion of dog bite wounds that are infection-free compared with delayed closure, as the evidence for this outcome was judged to be very low (RR 0.98, 95% CI 0.90 to 1.07; 1 study, 120 participants; I2 = 0%). We downgraded the evidence by one level for high risk of bias and two levels for imprecision. None of the four trials reported any adverse outcomes such as death or rabies but they were, in any case, unlikely to have been large enough to have satisfactory power to provide precise estimates for these. Important outcomes like time to complete wound healing, proportion of wounds healed, and length of hospital stay were not evaluated.

AUTHORS' CONCLUSIONS

All the studies we identified concerned dog bites. There is no high-certainty evidence to support or refute existing recommendations concerning primary closure for dog bites. The potential benefits and harms of primary closure compared with delayed or no closure for mammalian bites remain uncertain and more robust trials are needed.

The interaction of ceramide 1-phosphate with group IVA cytosolic phospholipase A2 coordinates acute wound healing and repair

The sphingolipid ceramide 1-phosphate (C1P) directly binds to and activates group IVA cytosolic phospholipase A₂ (cPLA₂α) to stimulate the production of eicosanoids. Because eicosanoids are important in wound healing, we examined the repair of skin wounds in knockout (KO) mice lacking cPLA₂α and in knock-in (KI) mice in which endogenous cPLA₂α was replaced with a mutant form having an ablated C1P interaction site. Wound closure rate was not affected in the KO or KI mice, but wound maturation was enhanced in the KI mice compared to that in wild-type controls. Wounds in KI mice displayed increased infiltration of dermal fibroblasts into the wound environment, increased wound tensile strength, and a higher ratio of type I:type III collagen. In vitro, primary dermal fibroblasts (pDFs) from KI mice showed substantially increased collagen deposition and migration velocity compared to pDFs from wild-type and KO mice. KI mice also showed an altered eicosanoid profile of reduced proinflammatory prostaglandins (PGE₂ and TXB₂) and an increased abundance of certain hydroxyeicosatetraenoic acid (HETE) species. Specifically, an increase in 5-HETE enhanced dermal fibroblast migration and collagen deposition. This gain-of-function role for the mutant cPLA₂α was also linked to the relocalization of cPLA₂α and 5-HETE biosynthetic enzymes to the cytoplasm and cytoplasmic vesicles. These findings demonstrate the regulation of key wound-healing mechanisms in vivo by a defined protein-lipid interaction and provide insights into the roles that cPLA₂α and eicosanoids play in orchestrating wound repair.

Impaired wound healing: facts and hypotheses for multi-professional considerations in predictive, preventive and personalised medicine

Whereas the physiologic wound healing (WH) successfully proceeds through the clearly defined sequence of the individual phases of wound healing, chronic non-healing wounds/ulcers fail to complete the individual stages and the entire healing process. There are many risk factors both modifiable (such as stress, smoking, inappropriate alcohol consumption, malnutrition, obesity, diabetes, cardio-vascular disease, etc.) and non-modifiable (such as genetic diseases and ageing) strongly contributing to the impaired WH. Current statistics demonstrate that both categories are increasingly presented in the populations, which causes dramatic socio-economic burden to the healthcare sector and society at large. Consequently, innovative concepts by predictive, preventive and personalised medicine are crucial to be implemented in the area. Individual risk factors, causality, functional interrelationships, molecular signature, predictive diagnosis, and primary and secondary prevention are thoroughly analysed followed by the expert recommendations in this paper.

Nutritional Support for Exercise-Induced Injuries

Nutrition is one method to counter the negative impact of an exercise-induced injury. Deficiencies of energy, protein and other nutrients should be avoided. Claims for the effectiveness of many other nutrients following injuries are rampant, but the evidence is equivocal. The results of an exercise-induced injury may vary widely depending on the nature of the injury and severity. Injuries typically result in cessation, or at least a reduction, in participation in sport and decreased physical activity. Limb immobility may be necessary with some injuries, contributing to reduced activity and training. Following an injury, an inflammatory response is initiated and while excess inflammation may be harmful, given the importance of the inflammatory process for wound healing, attempting to drastically reduce inflammation may not be ideal for optimal recovery. Injuries severe enough for immobilization of a limb result in loss of muscle mass and reduced muscle strength and function. Loss of muscle results from reductions in basal muscle protein synthesis and the resistance of muscle to anabolic stimulation. Energy balance is critical. Higher protein intakes (2-2.5 g/kg/day) seem to be warranted during immobilization. At the very least, care should be taken not to reduce the absolute amount of protein intake when energy intake is reduced. There is promising, albeit preliminary, evidence for the use of omega-3 fatty acids and creatine to counter muscle loss and enhance hypertrophy, respectively. The overriding nutritional recommendation for injured exercisers should be to consume a well-balanced diet based on whole, minimally processed foods or ingredients made from whole foods. The diet composition should be carefully assessed and changes considered as the injury heals and activity patterns change.

Fibromodulin-deficiency alters temporospatial expression patterns of transforming growth factor-β ligands and receptors during adult mouse skin wound healing

Fibromodulin (FMOD) is a small leucine-rich proteoglycan required for scarless fetal cutaneous wound repair. Interestingly, increased FMOD levels have been correlated with decreased transforming growth factor (TGF)-β1 expression in multiple fetal and adult rodent models. Our previous studies demonstrated that FMOD-deficiency in adult animals results in delayed wound closure and increased scar size accompanied by loose package collagen fiber networks with increased fibril diameter. In addition, we found that FMOD modulates in vitro expression and activities of TGF-β ligands in an isoform-specific manner. In this study, temporospatial expression profiles of TGF-β ligands and receptors in FMOD-null and wild-type (WT) mice were compared by immunohistochemical staining and quantitative reverse transcriptase-polymerase chain reaction using a full-thickness, primary intention wound closure model. During the inflammatory stage, elevated inflammatory infiltration accompanied by increased type I TGF-β receptor levels in individual inflammatory cells was observed in FMOD-null wounds. This increased inflammation was correlated with accelerated epithelial migration during the proliferative stage. On the other hand, significantly more robust expression of TGF-β3 and TGF-β receptors in FMOD-null wounds during the proliferative stage was associated with delayed dermal cell migration and proliferation, which led to postponed granulation tissue formation and wound closure and increased scar size. Compared with WT controls, expression of TGF-β ligands and receptors by FMOD-null dermal cells was markedly reduced during the remodeling stage, which may have contributed to the declined collagen synthesis capability and unordinary collagen architecture. Taken together, this study demonstrates that a single missing gene, FMOD, leads to conspicuous alternations in TGF-β ligand and receptor expression at all stages of wound repair in various cell types. Therefore, FMOD critically coordinates temporospatial distribution of TGF-β ligands and receptors in vivo, suggesting that FMOD modulates TGF-β bioactivity in a complex way beyond simple physical binding to promote proper wound healing.

Primary closure versus delayed closure for non bite traumatic wounds within 24 hours post injury

BACKGROUND

Acute traumatic wounds are one of the common reasons why people present to the emergency department. Primary closure has traditionally been reserved for traumatic wounds presenting within six hours of injury and considered 'clean' by the attending surgeon, with the rest undergoing delayed primary closure as a means of controlling wound infection. Primary closure has the potential benefit of rapid wound healing but poses the potential threat of increased wound infection. There is currently no evidence to guide clinical decision-making on the best timing for closure of traumatic wounds.

OBJECTIVES

To determine the effect on time to healing of primary closure versus delayed closure for non bite traumatic wounds presenting within 24 hours post injury. To explore the adverse effects of primary closure compared with delayed closure for non bite traumatic wounds presenting within 24 hours post injury.

SEARCH METHODS

In May 2013, for this first update we searched the Cochrane Wounds Group Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; and EBSCO CINAHL. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

Randomised controlled trials comparing primary closure with delayed closure of non bite traumatic wounds.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated the results of the searches against the inclusion criteria. No studies met the inclusion criteria for this review.

MAIN RESULTS

Since no studies met the inclusion criteria, neither a meta-analysis nor a narrative description of studies was possible.

AUTHORS' CONCLUSIONS

There is currently no systematic evidence to guide clinical decision-making regarding the timing for closure of traumatic wounds. There is a need for robust research to investigate the effect of primary closure compared with delayed closure for non bite traumatic wounds presenting within 24 hours of injury.

Primary closure versus delayed closure for non bite traumatic wounds within 24 hours post injury

BACKGROUND

Acute traumatic wounds are one of the common reasons why people present to the emergency department. Primary closure has traditionally been reserved for traumatic wounds presenting within six hours of injury and considered 'clean' by the attending surgeon, with the rest undergoing delayed primary closure as a means of controlling wound infection. Primary closure has the potential benefit of rapid wound healing but poses the potential threat of increased wound infection. There is currently no evidence to guide clinical decision-making on the best timing for closure of traumatic wounds.

OBJECTIVES

To determine the effect on time to healing of primary closure versus delayed closure for non bite traumatic wounds presenting within 24 hours post injury. To explore the adverse effects of primary closure compared with delayed closure for non bite traumatic wounds presenting within 24 hours post injury.

SEARCH STRATEGY

We searched the Cochrane Wounds Group Specialised Register (searched 14 July 2011); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3); Ovid MEDLINE (1950 to July Week 1 2011); Ovid MEDLINE (In-Process & Other Non-Indexed Citations, July 13, 2011); Ovid EMBASE (1980 to 2011 Week 27); and EBSCO CINAHL (1982 to 14 July 2011). There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

Randomised controlled trials comparing primary closure with delayed closure of non bite traumatic wounds.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated the results of the searches against the inclusion criteria. No studies met the inclusion criteria for this review.

MAIN RESULTS

Since no studies met the inclusion criteria, neither a meta-analysis nor a narrative description of studies was possible.

AUTHORS' CONCLUSIONS

There is currently no systematic evidence to guide clinical decision-making regarding the timing for closure of traumatic wounds. There is a need for robust research to investigate the effect of primary closure compared with delayed closure for non bite traumatic wounds presenting within 24 hours of injury.

Tissue repair: The hidden drama

As living beings who encounter every kind of traumatic event from paper cut to myocardial infarction, we must possess ways to heal damaged tissues. While some animals are able to regrow complete body parts following injury (such as the earthworm who grows a new head following bisection), humans are sadly incapable of such feats. Our means of recovery following tissue damage consists largely of repair rather than pure regeneration. Thousands of times in our lives, a meticulously scripted but unseen wound healing drama plays, with cells serving as actors, extracellular matrix as the setting, and growth factors as the means of communication. This article briefly reviews the cells involved in tissue repair, their signaling and proliferation mechanisms, and the function of the extracellular matrix, then presents the actors and script for the three acts of the tissue repair drama.

The role of furin in papillomavirus infection

Papillomaviruses represent a medically important virus family. Infection with a high-risk human papillomavirus type is a prerequisite for cervical carcinoma development. Infection by low-risk types may result in the generation of benign skin warts. It was recently found that infectious entry of these viruses is dependent upon a specific proteolytic event that occurs prior to viral endocytosis. Specifically, a proprotein convertase, furin or proprotein convertase 5/6, must cleave the minor capsid protein for infection to proceed. Here, an overview of what is currently known about this process is presented, and what we have learned about the papillomavirus lifecycle from these studies discussed. This work also has implications for further advances in papillomavirus vaccine development.