Adriana P. Nascimento

Overweight induced by high-fat diet delays rat cutaneous wound healing

Prolonged wound healing is a complication that contributes to morbidity and mortality. Overweight people regularly undergo surgery and trauma, and often develop chronic wounds, but the effects of the adipose tissue excess on cutaneous wound healing are not well understood. This study tested the hypothesis that overweight induced by a high-fat diet impairs rat cutaneous wound healing. Male Wistar rats were fed with either a high-fat or a standard (control) diet. After 15 weeks, an excisional lesion was done and the animals were killed 21 d later. Wound contraction and re-epithelialization, blood pressure, glucose and retroperitoneal fat were evaluated. After killing, lesion and adjacent normal skin were formol-fixed and paraffin-embedded. Inflammatory infiltrate, myofibroblasts, collagen fibres and cellular proliferation were analysed and blood vessels were evaluated using stereological methods. There was no difference in blood pressure and glucose, but retroperitoneal fat increased in the high-fat diet group. Animals fed with the high-fat diet presented delayed wound contraction and re-epithelialization. It was found that 21 d after wounding, overweight induced by a high-fat diet increased the inflammatory infiltrate and delayed myofibroblastic differentiation, collagen deposition, epithelial and connective tissue cell proliferation, and angiogenesis. These findings support the hypothesis that a high-fat diet exerts negative effects on rat cutaneous wound healing, due mainly to the prolongation of the inflammatory phase.

Propranolol improves cutaneous wound healing in streptozotocin-induced diabetic rats.

Sympathetic nerve failure has been proposed as a contributing factor in impaired cutaneous wound healing in diabetes mellitus. Nevertheless, no studies have shown whether beta-adrenoceptor blockade through beta-blocker (e.g., propranolol) administration may alter healing of diabetic cutaneous lesions. This study evaluated macro- and microscopically the effects of propranolol administration on cutaneous wound healing in streptozotocin-induced diabetic rats. Acute diabetes was induced by a single intraperitoneal injection of streptozotocin 14 days before wounding. Animals were treated with propranolol (50 mg/kg) dissolved in drinking water; controls received water only. Administration of beta-receptor antagonist began 1 day before wounding and was continued daily until euthanasia. A full-thickness excisional lesion (1 cm(2)) was created. The wound area was measured weekly and the animals were killed 14 days after wounding. Lesions and adjacent skin were formalin-fixed and paraffin-embedded. Sections were stained with hematoxylin-eosin, Sirius red, and toluidine blue, and immunostained for CD-68, alpha-smooth muscle actin and proliferating cell nuclear antigen. The wound area was significantly smaller in the propranolol-treated group than in the control group 7 and 14 days after wounding. Inflammatory cell numbers and metalloproteinase-9 levels were reduced in the propranolol-treated group compared to the control group 14 days after wounding. Cell proliferation, mast cell number, collagen deposition, blood vessel density, and nitric oxide levels were increased in the propranolol-treated group compared to the control group 14 days after wounding. Propranolol administration improves cutaneous wound healing of hyperglycemic diabetic rats by reducing the local inflammatory response and improving subsequent phases of the repair process.

Low-dose propranolol improves cutaneous wound healing of burn-injured rats.

Background: Severe burns stimulate a hypermetabolic response that causes systemic complications. Propranolol, a nonselective β-blocker, reduces this response and increases survival. Nevertheless, few studies have shown the effects of propranolol on healing of severe burns. This study evaluated macroscopically and microscopically the effects of the administration of propranolol (low-dose) on cutaneous wound healing of burn-injured rats. Methods: A third-degree burn (10 percent total body surface area) was created in female Wistar rats. Beginning 1 week after burning, animals were treated daily with propranolol (n = 5) (6 mg/kg) dissolved in water until they were euthanized, whereas rats in the control group (n = 5) received only water. Wound area was measured weekly and animals were euthanized 63 days after burning. Lesions and adjacent skin were fixed in formalin and embedded in paraffin. Sections were stained with hematoxylin and eosin, Sirius red, and toluidine blue, and immunostained for CD68, α-smooth muscle actin, and proliferating cell nuclear antigen. Results: The wound area was greater in the control group than in the propranolol-treated group 21, 53, and 63 days after burning. All propranolol-treated animals presented more than 70 percent of reepithelialized wound area 63 days after burning, whereas control animals did not. The number of inflammatory cells and blood vessel density were greater in the control group than in the propranolol-treated group 63 days after burning. Cellular proliferation, myofibroblast density, collagen deposition, and active matrix metalloproteinase-2 levels were reduced in the control group compared with the propranolol-treated group 63 days after burning. Conclusion: Administration of (low-dose) propranolol improves healing of burned rats, reducing the local inflammatory response and improving subsequent healing phases.

Both obesity-prone and obesity-resistant rats present delayed cutaneous wound healing.

Diet-induced overweight rats exhibit delayed cutaneous healing; however, when receiving an obesogenic diet, some rats are susceptible to developing the overweight phenotype, whereas others are resistant. We investigated cutaneous healing in diet-induced obesity (DIO)-prone and diet-resistant (DR) rats. Male rats were fed with a standard (control) or a high-saturated fat (30 % fat, w/w) diet for 20 weeks. Then, the experimental group was subdivided into DIO (n 17) and DR (n 16) groups. An excision lesion was made, and the animals were killed 7 or 14 d later. The average body weight was 29 and 25 % higher in the DIO group compared with the C and DR groups. Retroperitoneal fat was higher in the DIO group than in the control and DR groups (518 and 92 %) and was higher in the DR group than in the control group (223 %). The DIO group presented glucose intolerance, and both the DIO and DR groups presented delayed wound contraction (50 %) and re-epithelialisation (20 %). Compared with the DR group, the DIO group displayed higher amounts of inflammatory cells as well as higher levels of lipid peroxidation (P < 0·05). Myofibroblastic differentiation and vessel remodelling were delayed in both the DIO and DR groups. Nitrite levels were lower in the DIO group (340 % less) than in the DR group. TNF-α expression was increased in the DIO group (130 %) compared with the DR group. Our results showed that DIO as well as DR rats present delays in cutaneous wound healing, even though the DR group does not have an overweight phenotype.

Insulin resistance impairs cutaneous wound healing in mice

Obesity is associated with significant changes in skin combined with metabolic alterations such as insulin resistance. Our aim was to investigate the effects of insulin resistance induced by a high‐fat diet on cutaneous wound healing. Male C57BL/6 mice were fed standard chow (SC group) or high‐fat chow (HFC group) for 30 weeks. On day 0 (28th week), an excisional wound was performed. After 14 days (30th week), the mice were euthanized. Starting from the 8th week, the HFC group had a higher body weight. The HFC group became intolerant to glucose, resistant to insulin, and presented increased plasma cholesterol and triglyceride levels. The wound area was greater in the HFC group. The inflammatory infiltrate and the amount of “fibroblast‐like” cells increased in superficial regions of the lesions in the HFC group. The collagen fibers were more organized and denser in the SC group. Hydroxyproline levels were lower in the HFC group. The nitric oxide synthase‐2‐positive cells were higher in the HFC group. Lipid peroxidation and protein carbonyl levels were higher in the HFC group. The expression levels of alpha‐smooth muscle actin and transforming growth factor‐β were higher in the HFC group. These findings support the hypothesis that insulin resistance leads to delayed cutaneous wound healing.

Ultrasound accelerates healing of normal wounds but not of ischemic ones

To examine the influence of therapeutic ultrasound (US) on repair of standard and ischemic cutaneous lesions, full‐thickness excisional wounds were made in rats and treated with a US 3 MHz, 0.5 W/cm2 pulsed duty cycle. We used five experimental groups: control (received US powered off on the day of surgery, and on the second and fourth day), control US (received US on the day of surgery, and on the second and fourth day), ischemic (received US powered off on the day of surgery, and on the second and fourth day), ischemic US 3X (received US on the day of surgery, and on the second and fourth day) and ischemic US 5X (received US in the day of surgery, first, second, third and fourth day). The control US group showed acceleration in wound contraction 7 days after wounding, an increase in collagen density, and only focal inflammatory areas. Neo‐epidermis formation was more advanced in the control US group than in the control one. Wound contraction was delayed in the ischemic group when compared with the control group as well as the ischemic US 3X group, was but slightly accelerated in the ischemic US 5X group when compared with the ischemic group 7 days after wounding. Reepithelialization was delayed in both ischemic US groups when compared with the ischemic group. The number of inflammatory cells was higher in both US ischemic groups. We conclude that US therapy accelerates wound healing in normal wounds and delays wound healing in ischemic wounds.

Deletion of the α2A/α2C-adrenoceptors accelerates cutaneous wound healing in mice

The α2‐adrenoceptors regulate the sympathetic nervous system, controlling presynaptic catecholamine release. However, the role of the α2‐adrenoceptors in cutaneous wound healing is poorly understood. Mice lacking both the α2A/α2C‐adrenoceptors were used to evaluate the participation of the α2‐adrenoceptor during cutaneous wound healing. A full‐thickness excisional lesion was performed on the dorsal skin of the α2A/α2C‐adrenoceptor knockout and wild‐type mice. Seven or fourteen days later, the animals were euthanized and the lesions were formalin‐fixed and paraffin‐embedded or frozen. Murine skin fibroblasts were also isolated from α2A/α2C‐adrenoceptor knockout and wild‐type mice, and fibroblast activity was evaluated. The in vivo study demonstrated that α2A/α2C‐adrenoceptor depletion accelerated wound contraction and re‐epithelialization. A reduction in the number of neutrophils and macrophages was observed in the α2A/α2C‐adrenoceptor knockout mice compared with wild‐type mice. In addition, α2A/α2C‐adrenoceptor depletion enhanced the levels of nitrite and hydroxyproline, and the protein expression of transforming growth factor‐β and vascular endothelial growth factor. Furthermore, α2A/α2C‐adrenoceptor depletion accelerated blood vessel formation and myofibroblast differentiation. The in vitro study demonstrated that skin fibroblasts isolated from α2A/α2C‐adrenoceptor knockout mice exhibited enhanced cell migration, α‐smooth muscle actin _protein expression and collagen deposition compared with wild‐type skin fibroblasts. In conclusion, α2A/α2C‐adrenoceptor deletion accelerates cutaneous wound healing in mice.

SLC40A1 and CP single nucleotide polymorphisms in porphyria cutanea tarda patients of mixed ancestry

Porphyria cutanea tarda (PCT) is a multifactorial disease; clinical expression depends on both genetic and acquired factors. Few studies have examined the connection between PCT and the regulation of iron metabolism genes other than the HFE gene. We selected five polymorphisms in the CYBRD1, CP, SLC40A1, and HAMP genes to determine whether these polymorphisms can act as genetic modulators in patients with sporadic PCT. None of the 29 patients carried the C282Y mutation.