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Characteristics and Young's Modulus of Collagen Fibrils from Expanded Skin Using Anisotropic Controlled Rate Self-Inflating Tissue Expander

Manssor NA, Radzi Z, Yahya NA, Mohamad Yusof L, Hariri F, Khairuddin NH, et al.

Skin Pharmacol Physiol, 2016;29(2):55-62.
PMID: 26836267 DOI: 10.1159/000431328

Mechanical properties of expanded skin tissue are different from normal skin, which is dependent mainly on the structural and functional integrity of dermal collagen fibrils. In the present study, mechanical properties and surface topography of both expanded and nonexpanded skin collagen fibrils were evaluated. Anisotropic controlled rate self-inflating tissue expanders were placed beneath the skin of sheep's forelimbs. The tissue expanders gradually increased in height and reached equilibrium in 2 weeks. They were left in situ for another 2 weeks before explantation. Expanded and normal skin samples were surgically harvested from the sheep (n = 5). Young's modulus and surface topography of collagen fibrils were measured using an atomic force microscope. A surface topographic scan showed organized hierarchical structural levels: collagen molecules, fibrils and fibers. No significant difference was detected for the D-banding pattern: 63.5 ± 2.6 nm (normal skin) and 63.7 ± 2.7 nm (expanded skin). Fibrils from expanded tissues consisted of loosely packed collagen fibrils and the width of the fibrils was significantly narrower compared to those from normal skin: 153.9 ± 25.3 and 106.7 ± 28.5 nm, respectively. Young's modulus of the collagen fibrils in the expanded and normal skin was not statistically significant: 46.5 ± 19.4 and 35.2 ± 27.0 MPa, respectively. In conclusion, the anisotropic controlled rate self-inflating tissue expander produced a loosely packed collagen network and the fibrils exhibited similar D-banding characteristics as the control group in a sheep model. However, the fibrils from the expanded skin were significantly narrower. The stiffness of the fibrils from the expanded skin was higher but it was not statistically different.

Matched MeSH terms: Skin/ultrastructure
AFM analysis of collagen fibrils in expanded scalp tissue after anisotropic tissue expansion

Aziz J, Ahmad MF, Rahman MT, Yahya NA, Czernuszka J, Radzi Z

Int J Biol Macromol, 2018 Feb;107(Pt A):1030-1038.
PMID: 28939521 DOI: 10.1016/j.ijbiomac.2017.09.066

Successful use of tissue expanders depends on the quality of expanded tissue. This study evaluates the impact of anisotropic self-inflating tissue expander (SITE) on the biomechanics of skin. Two different SITE were implanted subcutaneously on sheep scalps; SITE that requires 30days for maximum expansion (Group A; n=5), and SITE that requires 21days for maximum expansion (Group B; n=5). Control animals (n=5) were maintained without SITE implantation. Young's Modulus, D-periodicity, overlap and gap region length, diameter, and height difference between overlap and gap regions on collagen fibrils were analyzed using atomic force microscopy. Histology showed no significant differences in dermal thickness between control and expanded skin of groups A and B. Furthermore, most parameters of expanded skin were similar to controls (p>0.05). However, the height difference between overlap and gap regions was significantly smaller in group B compared to both control and group A (p<0.01). Strong correlation was observed between Young's Modulus of overlap and gap regions of the control and group A, but not group B. Results suggest that a relatively slower SITE can be useful in reconstructive surgery to maintain the biomechanical properties of expanded skin.

Matched MeSH terms: Skin/ultrastructure
Fulltext Molecular Mechanisms of Stress-Responsive Changes in Collagen and Elastin Networks in Skin

Aziz J, Shezali H, Radzi Z, Yahya NA, Abu Kassim NH, Czernuszka J, et al.

Skin Pharmacol Physiol, 2016;29(4):190-203.
PMID: 27434176 DOI: 10.1159/000447017

Collagen and elastin networks make up the majority of the extracellular matrix in many organs, such as the skin. The mechanisms which are involved in the maintenance of homeostatic equilibrium of these networks are numerous, involving the regulation of genetic expression, growth factor secretion, signalling pathways, secondary messaging systems, and ion channel activity. However, many factors are capable of disrupting these pathways, which leads to an imbalance of homeostatic equilibrium. Ultimately, this leads to changes in the physical nature of skin, both functionally and cosmetically. Although various factors have been identified, including carcinogenesis, ultraviolet exposure, and mechanical stretching of skin, it was discovered that many of them affect similar components of regulatory pathways, such as fibroblasts, lysyl oxidase, and fibronectin. Additionally, it was discovered that the various regulatory pathways intersect with each other at various stages instead of working independently of each other. This review paper proposes a model which elucidates how these molecular pathways intersect with one another, and how various internal and external factors can disrupt these pathways, ultimately leading to a disruption in collagen and elastin networks.

Matched MeSH terms: Skin/ultrastructure
Physicochemical modulation of skin barrier by microwave for transdermal drug delivery

Wong TW, Nor Khaizan A

Pharm Res, 2013 Jan;30(1):90-103.
PMID: 22890987 DOI: 10.1007/s11095-012-0852-z

PURPOSE: To investigate mechanism of microwave enhancing drug permeation transdermally through its action on skin.
METHODS: Hydrophilic pectin-sulphanilamide films, with or without oleic acid (OA), were subjected to drug release and skin permeation studies. The skins were untreated or microwave-treated, and characterized by infrared spectroscopy, Raman spectroscopy, thermal, electron microscopy and histology techniques.
RESULTS: Skin treatment by microwave at 2450 MHz for 5 min promoted drug permeation from OA-free film without incurring skin damage. Skin treatment by microwave followed by film loaded with drug and OA resulted in permeation of all drug molecules that were released from film. Microwave exerted spacing of lipid architecture of stratum corneum into structureless domains which was unattainable by OA. It allowed OA to permeate stratum corneum and accumulate in dermis at a greater ease, and synergistically inducing lipid/keratin fluidization at hydrophobic C-H and hydrophilic O-H, N-H, C-O, C=O, C-N regimes of skin, and promoting drug permeation.
CONCLUSION: The microwave technology is evidently feasible for use in promotion of drug permeation across the skin barrier. It represents a new approach in transdermal drug delivery.

Matched MeSH terms: Skin/ultrastructure