ABSTRACT
Objective: To develop an efficacious and efficient method for treating chronic wounds using "nanosheet" that improves the survival and localization of transplanted cells without prior seeding to optimally derive the regenerative potentials of uncultured stromal vascular fraction (SVF) cells. Approach: We propose a method whereby the wound is covered by uncultured SVF cells using the nanosheet [porous poly(d, l,-lactic acid)] (PDLLA) films) designed to hold cells in a single-cell layer. A chronic wound model was created on 12-month-old db/db mice by inflecting a full-thickness skin excision on their dorsum and was subsequently given either no treatment or a treatment with SVF cells alone (with Tegaderm dressing), nanosheet alone, or nanosheet with SVF cells. Results: The placement of the nanosheet improved the grafted cell retention rate at day 10 timepoint by 5 folds, and the wound area was the smallest in the wounds treated with SVF cells plus nanosheet in comparison to the other groups. Collagen deposition and epidermal growth factor were significantly higher in the wound beds treated with SVF cells with the nanosheet, offering some mechanistic insights. Innovation: Porous poly(d, l,-lactic acid acid) (PDLLA) films or "nanosheet" printed on the nanoscale (1-100 nm in thickness) as a cellular scaffold for cytotherapy for the treatment of chronic wounds. Conclusion: The use of the nanosheet is an effective way to improve the transplanted SVF cell retention and accelerate the overall wound closure.
ABSTRACT
Hypertrophic scarring is a major source of morbidity. Sex hormones are not classically considered modulators of scarring. However, based on increased frequency of hypertrophic scarring in patients on testosterone, we hypothesized that androgenic steroids induce abnormal scarring and developed a preclinical porcine model to explore these effects. Mini-swine underwent castration, received no testosterone (noT) or biweekly testosterone therapy (+T), and underwent excisional wounding. To create a delayed wound healing model, a subset of wounds were re-excised at 2 weeks. Scars from postoperative day 42 (POD42) and delayed wounds (POD28) were harvested 6 weeks after initial wounding for analysis via histology, bulk RNA-seq, and mechanical testing. Histologic analysis of scars from +T animals showed increased mean fibrosis area (16 mm2noT, 28 mm2+T; p = .007) and thickness (0.246 mm2noT, 0.406 mm2+T; p < .001) compared to noT. XX+T and XY+T scars had greater tensile burst strength (p = .024 and p = .013, respectively) compared to noT swine. Color deconvolution analysis revealed greater deposition of type I and type III collagen as well as increased collagen type I:III ratio in +T scars. Dermatopathologist histology scoring showed that +T exposure was associated with worse overall scarring (p < .05). Gene ontology analysis found that testosterone exposure was associated with upregulation of cellular metabolism and immune response gene sets, while testosterone upregulated pathways related to keratinization and laminin formation on pathway analysis. In conclusion, we developed a preclinical porcine model to study the effects of the sex hormone testosterone on scarring. Testosterone induces increased scar tissue deposition and appears to increase physical strength of scars via supraphysiologic deposition of collagen and other ECM factors. The increased burst strength seen in both XX and XY animals suggests that hormone administration has a strong influence on scar mechanical properties independent of chromosomal sex. Anti-androgen topical therapies may be a promising future area of research.
