Quantitative analysis of collagen accumulation during protein malnutrition

Risk factors for delayed healing at the free anterolateral thigh flap donor site

BACKGROUND

The free anterolateral thigh (ALT) flap has been widely used for various kinds of reconstructions. However, delayed healing at the donor site occasionally occurs due to wound dehiscence or the partial loss of grafted skin at the donor site. The aim of the present study was to identify reliable predictive factors for delayed healing at the donor site after the harvest of a free ALT flap.

METHODS

This study included 52 patients who underwent reconstructive procedures using free ALT flaps. The delayed healing group included patients with wounds at the donor site that had not healed over 3 weeks after surgery, and the normal healing group included patients who showed wound healing within 3 weeks after surgery. Multivariate logistic regression models were created to identify the risk factors for delayed healing at the ALT flap donor site.

RESULTS

Among the 52 patients, 24 (46.2%) showed delayed healing at the donor site, and 6 patients required additional operative treatment. A high preoperative body mass index (BMI), smoking, and skin grafting were found to be significantly associated with delayed healing at the ALT donor site. Of the 37 patients who underwent skin grafting, 23 (62%) experienced delayed healing at the donor site.

CONCLUSIONS

A high preoperative BMI, smoking, and skin grafting were risk factors for delayed healing at the free ALT donor site. Skin grafting at the ALT donor site should be avoided in patients with a high BMI or a habit of smoking.

First Chemosensor for Selective Detection and Quantification of L-4-Hydroxyproline in Collagen and Other Bio Samples

Amino pyridine-based rhodamine conjugate (APR) has been developed as a first chemosensor for selective detection and quantification of L-4-Hydroxyproline (Hyp). The "turn-on" fluorescence property of the chemosensor makes it unique for easy estimation of Hyp in collagen and biological samples.

Combination of BCAAs and glutamine enhances dermal collagen protein synthesis in protein-malnourished rats

Skin collagen decreases in protein-malnourished states. Amino acids regulate protein metabolism, glutamine stimulates collagen synthesis through the conversion process to proline and provides 75 % of the intracellular free proline in fibroblasts. However, the impact of these amino acids on collagen synthesis under malnutrition has not been examined. We investigated the effect of amino acids on dermal tropocollagen synthesis in protein-malnourished rats. The fractional synthesis rate (FSR, %/h) of dermal tropocollagen was evaluated by the incorporation of L-[ring-(2)H(5)]-phenylalanine after 4 h infusion of each amino acid and the stable isotope. None of the infused 12 single amino acids (glutamine, proline, alanine, arginine, glutamate, glycine, aspartate, serine, histidine, lysine, phenylalanine and threonine) significantly increased the FSR (P = 0.343, one-way ANOVA). In contrast, amino acid mixtures of essential amino acids + glutamine + arginine (EAARQ) and branched-chain amino acids + glutamine (BCAAQ) significantly increased the FSR compared to saline, but the branched-chain amino acids (BCAAs) and amino acid mixture of collagen protein (AAC) did not alter the FSR (saline, 0.96 ± 0.24 %/h; EAARQ, 1.76 ± 0.89 %/h; BCAAQ 1.71 ± 0.36 %/h; BCAAs, 1.08 ± 0.20 %/h and AAC 1.39 ± 0.35 %/h, P < 0.05, Tukey's test). Proline conversion from glutamine represented only 3.9 % of the free proline in skin, as evaluated by the primed-constant infusion of L-d7-proline and L-α-15N-glutamine in rats. These results suggested that the combination of BCAAQ is a key factor for the enhancement of skin collagen synthesis in protein-malnourished rats. The contribution of extracellular free glutamine on de novo proline synthesis and collagen synthesis is very low in vivo compared to the contribution in vitro.

Wound healing process in post-bariatric patients: an experimental evaluation

Bariatric surgery is the most effective treatment for morbid obesity. Despite this, side effects are recorded. One of them is redundant skin hanging from the patients' body causing both aesthetical and functional deformities. They can only be corrected with body contouring surgery, whose wound complication rate is very high in previously obese population. Despite several hypotheses, an adequate explanation is still awaited. The aim of our study was to evaluate the wound healing process in post-bariatric patients. Seven patients, six women and one man, were enrolled. They all were nonsmokers and nondiabetic. They all underwent biliopancreatic diversion (BPD). After 36 months, abdominoplasty was performed. Biochemical parameters before and after bariatric surgery were evaluated. The content of total protein and hydroxyproline was assessed in multiple scar biopsies before and after BPD. Abdominoplasty horizontal scar skin samples were subjected to histological evaluation with Weigert-Van Gieson stain for elastic fibers and connectivum. All biochemical parameters analyzed were reduced post-BPD compared to the preoperative period. Tissue proteins were significantly reduced after BPD both in their totality and as hydroxyproline and hydroxyproline/total tissue protein. Histological evaluation revealed abnormal dermal elastic and collagen fibers. The cause of aberrant healing in massive weight loss body contouring is likely multifactorial. A relationship between nutritional state, wound collagen accumulation, and elastic fiber content seems to be only partially involved. The high mechanical stress of tissues before BPD probably influences the wound healing process after BPD.

Male and female rats with severe protein restriction present delayed wound healing

Malnutrition remains a significant problem, not only in developing countries, but also in the developed world. The aim of this study was to investigate the effects of protein restriction on rat excisional cutaneous healing. Male and female rats (12 weeks old) were exposed to different degrees of protein restriction (23%, 12% (slight restriction), and 0% (severe restriction)) for 12 weeks. On week 9, a full-thickness excisional skin lesion was performed, and the lesion area was measured to evaluate wound contraction and re-epithelialization. Euthanasia was performed after 12 weeks, and the lesion and adjacent skin were removed, fixed in formalin, and embedded in paraffin. Sections were stained with hematoxylin-eosin, toluidine blue, picro-mallory, and sirius red, and were immunostained for alpha-smooth muscle actin. Animals (males and females) exposed to severe protein restriction (0% protein) presented impairment of wound contraction. Inflammatory cells were present in higher amounts in the protein-restricted groups than in the 23% group. Extracellular matrix was poorly deposited in the severely restricted group (0%), but only mildly disturbed in the slightly restricted group (12%). Neovascularization was disturbed in both restricted groups. Our study demonstrates that animals exposed to slight protein restriction present disturbed wound healing, but animals exposed to severe protein restriction present impaired wound healing.

Increased collagen deposition in an uncomplicated surgical wound compared to a minimal subcutaneous test wound

Little information is currently available concerning the relationship between results obtained in humans from surgical test wounds and results from wound models. Therefore, to evaluate human wound healing parameters, tubings of expanded polytetrafluoroethylene were implanted in a subcutaneous test wound in the arm of 47 volunteers and 20 patients undergoing hernia repair. The surgical patients also had implants left in the surgical wound cavity. After 10 days the deposition of collagen in the tubings as expressed by hydroxyproline content was 30% higher in the surgical wound than in the test wound, p < 0.05. The amount of collagen deposited in the tubing within the surgical wound did not correlate with measurements in the test wound, whereas a significant correlation of proline levels was found between the two sites, p < 0.05. Deposition of proline and total protein in the model was equivalent. In both wound types age negatively correlated with levels of protein, but not collagen. The variability of the results was 40% lower in the subcutaneous test wound than in the surgical wound. There was no significant difference in hydroxyproline deposition between the volunteers and the patients undergoing hernia repair. In patients undergoing minor surgery without signs of compromised healing the expanded polytetrafluoroethylene test wound in the arm reflects the deposition of non-collagenous protein, but not collagen, within the surgical wound.