Preparation of Reproducible and Responsive Scar Model and Histology Analysis

Local Silencing of Connective Tissue Growth Factor by siRNA/Peptide Improves Dermal Collagen Arrangements

Background

Collagen organization within tissues has a critical role in wound regeneration. Collagen fibril diameter, arrangements and maturity between connective tissue growth factor (CTGF) small interfering RNA (siRNA) and mismatch scrambled siRNA-treated wound were compared to evaluate the efficacy of CTGF siRNA as a future implement for scar preventive medicine.

Methods

Nanocomplexes of CTGF small interfering RNA (CTGF siRNA) with cell penetrating peptides (KALA and MPG^∆NLS) were formulated and their effects on CTGF downregulation, collagen fibril diameter and arrangement were investigated. Various ratios of CTGF siRNA and peptide complexes were prepared and down-regulation were evaluated by immunoblot analysis. Control and CTGF siRNA modified cells-populated collagen lattices were prepared and rates of contraction measured. Collagen organization in rabbit ear 8 mm biopsy punch wound at 1 day to 8 wks post injury time were investigated by transmission electron microscopy and histology was investigated with Olympus System and TS-Auto software.

Conclusion

CTGF expression was down-regulated to 40% of control by CTGF siRNA/KALA (1:24) complexes (p < 0.01) and collagen lattice contraction was inhibited. However, down-regulated of CTGF by CTGF siRNA/MPG^∆NLS complexes was not statistically significant. CTGF KALA-treated wound appeared with well formed-basket weave pattern of collagen fibrils with mean diameter of 128 ± 22 nm (n = 821). Mismatch siRNA/KALA-treated wound showed a high frequency of parallel small diameter fibrils (mean 90 ± 20 nm, n = 563).

Conclusion

Controlling over-expression of CTGF by peptide-mediated siRNA delivery could improve the collagen orientation and tissue remodeling in full thickness rabbit ear wound.

Effect of freeze dried bovine amniotic membrane extract on full thickness wound healing

This study explored the feasibility of development of solubilized amniotic membrane extract (AME) as a potential wound healing substrate with improved efficacy. Bovine amniotic membrane was extracted using a mixture of acetic acid and 2-mercaptopropionic acid under sonication, which was followed by the frozen, and then lyophilized processes. The effects of AME on cell migration and growth properties were evaluated from 0 to 24 h of post injury using primary human foreskin fibroblast monolayer culture with one line scratch as an in vitro wound model. Its wound healing efficacy and scar preventive effects were investigated using whole thickness biopsy punch (8 mm) wound model obtained from rabbit ear. Intra dermal injections of AME fluid (10 μl of 1.2 μg/μl) on four wound sites were performed at 1 h pre injury, post 1, 2 and 3 day. The processes and levels of re-epithelialization and dermal regeneration were examined through histological assessment with H-E staining. In cell migration study conducted at 24 h post injury, AME (1.7 μg/ml) treated cells significantly increased wound closure with 54.9 % compared to control. Histological image analysis on AME treated wound sites at 36 days post injury showed properly developed epidermal basal cell layers and weave-like dermal collagen bundles, whereas those of untreated control skin showed over-proliferation of epidermis and aggregated collagen bundles with defected dermal regeneration. The results of this study verified the feasibility of dermal injections of freeze dried AME as a potential wound healing substrate which can promote epidermal and dermal regeneration, while avoiding undesirable hyper-proliferation of damaged tissue.