Experimental models and methods for cutaneous wound healing assessment.

Wound healing studies are intricate, mainly because of the multifaceted nature of the wound environment and the complexity of the healing process, which integrates a variety of cells and repair phases, including inflammation, proliferation, reepithelialization and remodelling. There are a variety of possible preclinical models, such as in mice, rabbits and pigs, which can be used to mimic acute or impaired for example, diabetic and nutrition-related wounds. These can be induced by many different techniques, with excision or incision being the most common. After determining a suitable model for a study, investigators need to select appropriate and reproducible methods that will allow the monitoring of the wound progression over time. The assessment can be performed by non-invasive protocols such as wound tracing, photographic documentation (including image analysis), biophysical techniques and/or by invasive protocols that will require wound biopsies. In this article, we provide an overview of some of the most often needed and used: (a) preclinical/animal models including incisional, excisional, burn and impaired wounds; (b) methods to evaluate the healing progression such as wound healing rate, wound analysis by image, biophysical assessment, histopathological, immunological and biochemical assays. The aim is to help researchers during the design and execution of their wound healing studies.

Comparison of collagen content in skin wounds evaluated by biochemical assay and by computer-aided histomorphometric analysis.

CONTEXT: The quantification of total collagen is of major importance in a wide range of research areas, including the study of cutaneous wound healing and new drugs trials. OBJECTIVE: The total collagen content in skin biopsies was compared by biochemical hydroxyproline assay and by two computer-aided histomorphometric analyses of histological sections. MATERIALS AND METHODS: Two methods were used to evaluate collagen formation: the hydroxyproline assay, as the gold standard and histomorphometric image analysis of the filled areas by corresponding stained collagen fibres, using picrosirius and Gomori's trichrome staining. The image analyses were determined by digital densitometry recognition using computer-aided ImageJ software. One-way ANOVA, simple linear regression and ANCOVA were applied for the statistical analysis and correlation. RESULTS: In a simple linear regression analysis carried out on the 14th day period after the induction of skin injury, three techniques, picrosirius red (F = 33.57, p = 0.00), Gomori's trichrome (F = 81.61, p = 0.00) and hydroxyproline content (F = 16.85, p = 0.00) were able to detect collagen production. After scale adjustment, there were no significant differences among either the slopes (F = 1.17, p = 0.32) or the intercepts (F = 0.69, p = 0.51) of the estimated regression lines. It seems that a highly significant correlation exists between the histomorphometrical analysis and hydroxyproline assay. DISCUSSION AND CONCLUSION: The morphometric analysis proved to be adequate and can be used as a simple, rapid, low-cost technology for evaluating total collagen in cutaneous wound specimens, compared with the gold standard hydroxyproline assay.

Physico-chemical characterization and tissue healing changes by Hancornia speciosa Gomes latex biomembrane.

Skin wounds have been a public health concern of high frequency, in addition to requiring intensive and expensive care. The natural rubber latex (NRL) from Hancornia speciosa Gomes has been used to treat many problems in traditional medicine and also present healing properties, antifungal and anti-inflammatory activity and antinociceptive effects. The purpose of this study was to characterize the new biomembrane from the NRL of H. speciosa (HS) by Fourier transform infrared (FTIR) and mechanical strength test and to investigate its biological properties by the cytotoxicity assay and in vivo healing activity. The results showed that the HS biomembrane exhibited characteristic bands of the main component cis-1,4-polyisoprene. Besides, its Young modulus was close to human skin with adhesive-compatible mechanical characteristics. The cytotoxicity assays revealed that the HS biomembrane was not toxic to fibroblast cells neither using agar diffusion test nor MTT assay. Furthermore, the HS biomembrane stimulated the inflammatory cells and the angiogenesis, increased significantly the collagenesis and improved the quality of heal until the remodeling phase induced by implants in mice. Thus, this biomembrane has proven to be a safe and biocompatible biomaterial with healing potential, becoming an effective and low-cost alternative for the treatment of skin wounds.

Hyaluronidase modulates inflammatory response and accelerates the cutaneous wound healing.

Hyaluronidases are enzymes that degrade hyaluronan an important constituent of the extracellular matrix. They have been used as a spreading agent, improving the absorption of drugs and facilitating the subcutaneous infusion of fluids. Here, we investigated the influence of bovine testes hyaluronidase (HYAL) during cutaneous wound healing in in vitro and in vivo assays. We demonstrated in the wound scratch assay that HYAL increased the migration and proliferation of fibroblasts in vitro at low concentration, e.g. 0.1 U HYAL enhanced the cell number by 20%. HYAL presented faster and higher reepithelialization in in vivo full-thickness excisional wounds generated on adult Wistar rats back skin already in the early phase at 2nd day post operatory compared to vehicle-control group. Wound closured area observed in the 16 U and 32 U HYAL treated rats reached 38% and 46% compared to 19% in the controls, respectively. Histological and biochemical analyses supported the clinical observations and showed that HYAL treated wounds exhibited increased granulation tissue, diminished edema formation and regulated the inflammatory response by modulating the release of pro and anti-inflammatory cytokines, growth factor and eicosanoids mediators. Moreover, HYAL increased gene expression of peroxisome proliferator-activated receptors (PPAR) γ and PPAR ß/δ, the collagen content in the early stages of healing processes as well as angiogenesis. Altogether these data revealed that HYAL accelerates wound healing processes and might be beneficial for treating wound disorders.

In vivo analgesic activity, toxicity and phytochemical screening of the hydroalcoholic extract from the leaves of Psidium cattleianum Sabine.

ETHNOPHARMACOLOGICAL RELEVANCE: Psidium cattleianum Sabine is extensively used in Brazilian traditional medicine to treat several diseases including painful disorders. Aim of the study to investigate the toxicity and the possible analgesic activities of the hydroalcoholic extract from the leaves of Psidium cattleianum Sabine (ELPCS), to support its use in folk medicine. To screen the major phytochemical constituents of this extract and evaluate their antioxidant activity. MATERIALS AND METHODS: ELPCS was assessed for its antioxidant activity using the DPPH model. Its analgesic activity was examined using mouse models of acetic acid-induced writhing and hot plate paw licking models. The major phytochemical constituents of the extract were screened; their toxicity on LLC-MK2 mammalian cells was evaluated. RESULTS: ELPCS exhibited significant peripheral analgesic activity at doses of 60, 80, 100, 200 and 400mg/kg in mice, but it did not display central analgesic activity and not was toxic to LLC-MK2 cell (LD50>400 µg/mL). The extract exhibited free radical scavenging activity as evidenced by IC50 values (15.9 µg/mL) obtained by the DPPH method. Phytochemical screening detected flavonoids, saponins, cardiac glycosides, anthraquinones, and tannins. CONCLUSIONS: The results of the experimental studies proved the analgesic activity of ELPCS and supported the traditional use of this plant.