Human hypertrophic scar‐like nude mouse model: Characterization of the molecular and cellular biology of the scar process

Hypertrophic scar (HTS) following thermal injury and other forms of trauma is a dermal fibroproliferative disorder that leads to considerable morbidity. Because of the lack of an ideal animal model, research is difficult. We have established an HTS model that involves transplanting human split‐thickness skin graft (STSG) or full‐thickness skin graft (FTSG) onto the backs of nude mice. The animals developed raised, firm, and reddish scars 2 months following transplantation. Histology and micromeasurement indicate raised, thickened engrafted skin with STSG and FTSG. In contrast, thickening was not observed with full‐thickness rat skin grafts used as controls. Masson's trichrome staining demonstrates increased accumulations of collagen fibrils in the dermis in both scars grafted with STSG and FTSG. Staining cells with toludine blue and an antibody for F4/80 showed an increase in the infiltration of mast cells and macrophages. Quantification of fibrocytes reveals increased fibrocytes. Moreover, STSG grafted skin had significantly more macrophages, mast cells, and fibrocytes than FTSG. Real‐time polymerase chain reaction analysis showed significantly elevated mRNA levels for type I collagen, transforming growth factor‐β, connective tissue growth factor and heat shock protein 47 in both types of engrafted skin. These data demonstrate that human skin grafted onto nude mice develops red raised and thickened scars having intrinsic properties that closely resemble HTS formation as seen in humans. Interestingly, STSG developed more scar than FTSG. Furthermore, inflammatory cells and bone marrow‐derived fibrocytes may play a critical role in HTS development in this animal model.     

Stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4 in the formation of postburn hypertrophic scar (HTS)

Recent data support the involvement of stromal cell-derived factor 1 (SDF-1) in the homing of bone marrow-derived stem cells to wound sites during skeletal, myocardial, vascular, lung, and skin wound repair as well as some fibrotic disorders via its receptor CXCR4. In this study, the role of SDF-1/CXCR4 signaling in the formation of hypertrophic scar (HTS) following burn injury and after treatment with systemic interferon α2b (IFNα2b) is investigated. Studies show SDF-1/CXCR4 signaling was up-regulated in burn patients, including SDF-1 level in HTS tissue and serum as well as CD14+ CXCR4+ cells in the peripheral blood mononuclear cells. In vitro, dermal fibroblasts constitutively expressed SDF-1 and deep dermal fibroblasts expressed more SDF-1 than superficial fibroblasts. Lipopolysaccharide increased SDF-1 gene expression in fibroblasts. Also, recombinant SDF-1 and lipopolysaccharide stimulated fibroblast-conditioned medium up-regulated peripheral blood mononuclear cell mobility. In the burn patients with HTS who received subcutaneous IFNα2b treatment, increased SDF-1/CXCR4 signaling was found prior to treatment which was down-regulated after IFNα2b administration, coincident with enhanced remodeling of their HTS. Our results suggest that SDF-1/CXCR4 signaling is involved in the development of HTS by promoting migration of activated CD14+ CXCR4+ cells from the bloodstream to wound sites, where they may differentiate into fibrocyte and myofibroblasts and contribute to the development of HTS.     

Systematic review and meta-analysis of methotrexate use and risk of cardiovascular disease

Inflammation predicts risk for cardiovascular disease (CVD) events, but the relation of drugs that directly target inflammation with CVD risk is not established. Methotrexate is a disease-modifying antirheumatic drug broadly used for the treatment of chronic inflammatory disorders. A systematic review and meta-analysis of evidence of relations of methotrexate with CVD occurrence were performed. Cohorts, case-control studies, and randomized trials were included if they reported associations between methotrexate and CVD risk. Inclusions and exclusions were independently adjudicated, and all data were extracted in duplicate. Pooled effects were calculated using inverse variance-weighted meta-analysis. Of 694 identified publications, 10 observational studies in which methotrexate was administered in patients with rheumatoid arthritis, psoriasis, or polyarthritis met the inclusion criteria. Methotrexate was associated with a 21% lower risk for total CVD (n = 10 studies, 95% confidence interval [CI] 0.73 to 0.87, p <0.001) and an 18% lower risk for myocardial infarction (n = 5, 95% CI 0.71 to 0.96, p = 0.01), without evidence for statistical between-study heterogeneity (p = 0.30 and p = 0.33, respectively). Among prespecified sources of heterogeneity explored, stronger associations were observed in studies that adjusted for underlying disease severity (relative risk 0.64, 95% CI 0.43 to 0.96, p <0.01) and for other concomitant medication (relative risk 0.73, 95% CI 0.63 to 0.84, p <0.001). Publication bias was potentially evident (funnel plot, Begg's test, p = 0.06); excluding studies with extreme risk estimates did not, however, alter results (relative risk 0.81, 95% CI 0.74 to 0.89). In conclusion, methotrexate use is associated with a lower risk for CVD in patients with chronic inflammation. These findings suggest that a direct treatment of inflammation may reduce CVD risk.     

Pulsatile insulin secretion in elderly patients with diabetes

Insulin pulsation is impaired in type 2 diabetes. GLP-1 increases pulsatile insulin secretion in these patients. We conducted these studies with the hypothesis that GLP-1 would enhance pulsatile insulin secretion and alter glucose metabolism in elderly patients with type 2 diabetes. Experiments were conducted in nine patients (age: 72+/-5 years; BMI: 27+/-3kg/m(2); diabetes duration: 7+/-3 years; HbA(1c): 6.6+/-0.9%). Subjects underwent three glucose clamp studies. The first was a euglycemic clamp to determine individual insulin clearance. In the second, GLP-1 was infused from 0-240min (0.75pM/kg/min) and glucose was maintained at fasting levels. The third was similar except that octreotide (30ng/kg/min) was infused with GLP-1 to suppress pulsatile insulin. Insulin and glucose were given to match levels during the second study. 3-(3)H-glucose was infused to allow calculation of hepatic glucose production and glucose disposal rates. There was no significant difference in measurements of pulsatile insulin secretion or hepatic glucose production and glucose disposal rates between the studies. Because there was no difference in pulsatile insulin between experiments, we could not test the effect of pulsatile insulin on glucose metabolism. Further studies are required to determine the impact of insulin pulses on glucose metabolism.     

Modeling the Parameters Involved in Preparation of PLA Nanoparticles Carrying Hydrophobic Drug Molecules Using Artificial Neural Networks

Purpose

Artificial neural networks (ANNs) are used to optimize a formulation of poly(lactic acid) (PLA) nanoparticles containing hydrophobic drug molecules through a study of the critical parameters affecting nanoparticle size.

Methods

We evaluate the effect of input variables, including concentrations of PLA and Tween 80, amplitude of ultrasound wave, and sonication time on the formation of PLA nanoparticles, which were prepared using a solvent evaporation method. Budesonide was used as a model hydrophobic drug. An ANN model was created using training data and evaluated for prediction capability using validation data.

Results

The ANN model demonstrated that reducing PLA concentration and increasing Tween 80 concentration provided optimum conditions for the preparation of small particle size. Additionally, the simultaneous use of high sonication time and amplitude has an adverse effect on particle diameter.

Conclusion

By defining the effects of each parameter on the size of PLA nanoparticles, this study demonstrated the feasibility of using an ANN model to optimize the conditions for achieving minimum particle size in hydrophobic drug-loaded PLA nanoparticles.