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Biomechanical Effects of Unidirectional Expansion Using Anisotropic Expanders in Horse Skin Tissue

Al-Majhali SH, Khairuddin NH, Abdul Razak IS, Radzi Z, Rahman MT, Sapalo JT, et al.

J Equine Vet Sci, 2021 04;99:103399.
PMID: 33781409 DOI: 10.1016/j.jevs.2021.103399

The use of a self-inflating tissue expander is a technique to stretch cutaneous tissues for potential use in reconstructive skin surgeries. This study investigates the mechanical properties of horse skin stretched by the subcutaneous implantation of anisotropic tissue expanders at the forehead, right shoulder, and dorsomedial part of the cannon region of the right forelimb in six (n = 6) horses. After 14 days of skin expansion, expanded and normal (control) skin samples were harvested and their mechanical properties of elastic modulus (EM), maximum force (MF), maximum stress (MSs) and maximum strain (MSr) were evaluated using uniaxial tension test. The expanded skin from shoulder area has higher EM, MSs, MSr and MF than the normal skin when compared to the forehead and lower forelimb. Statistically, there was a significant (P= .02) mean difference for MSs between the expanded shoulder and lower forelimb skin, but the pairwise comparison of EM, MSr and MF showed no significant difference between the locations. The overall effect of locations on EM and MSs was statistically significant (P < .05), however, there was no overall effect of horse factor, treatment factor (normal and expanded skin) and location interaction on the EM, MSS, MF and MSr. In conclusion, the expanded skin from the frontal head and the distal limb are less elastic (stiffer) compared to that of the expanded skin of the shoulder, thus anatomical location of the skin has some degree of effect on EM and MSs.

Matched MeSH terms: Tissue Expansion Devices*
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: Tissue Expansion Devices*
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: Tissue Expansion Devices*
Fulltext Histological changes of immediate skin expansion of the distal limb of rats

Ali AK, Abubakar AA, Kaka U, Radzi Z, Khairuddin NH, Yusoff MSM, et al.

Vet World, 2018 Dec;11(12):1706-1711.
PMID: 30774262 DOI: 10.14202/vetworld.2018.1706-1711

Aim: Tissue expansion is an applicable technique to reconstruct many surgical defects. The aim of this research was to evaluate the histological changes caused by immediate skin tissue expansion in rats as an animal model.
Materials and Methods: Immediate skin tissue expansion in 18 adult female rats was performed using three different sizes (small, medium, and big) of polymethylmethacrylate tissue expanders at the dorsal surface of the metatarsal area of the right limb. The contralateral limb was served as the control. The tissue expanders were surgically implanted and kept for 15 days.
Results: The immediate skin expansion resulted in histological changes such as the increased thickness of the epidermal layer, the reduction of the dermal layer, an elevated number of fibroblast as well as increased vascularity. Furthermore, skin adnexal structures such as hair follicles and sebaceous glands were farther apart.
Conclusion: The rat skin was able to rapidly adjust and compensate against a specific range of immediate mechanical expansion. The histological changes suggest that the tissues were prepared to withstand the increased external forces, in addition to create possibly additional skin in a relatively short-term period.

Matched MeSH terms: Tissue Expansion Devices
Fulltext Inflammatory Responses in Oro-Maxillofacial Region Expanded Using Anisotropic Hydrogel Tissue Expander

Ali Salim KM, Abd Jalil A, Radzi Z, Ismail SM, Czernuszka JT, Rahman MT

Materials (Basel), 2020 Oct 06;13(19).
PMID: 33036128 DOI: 10.3390/ma13194436

OBJECTIVE: Reconstruction of oral and facial defects often necessitate replacement of missing soft tissue. The purpose of tissue expanders is to grow healthy supplementary tissue under a controlled force. This study investigates the inflammatory responses associated with the force generated from the use of anisotropic hydrogel tissue expanders.
METHODS: Sprague Dawley rats (n = 7, body weight = 300 g ± 50 g) were grouped randomly into two groups-control (n = 3) and expanded (n = 4). Anisotropic hydrogel tissue expanders were inserted into the frontal maxillofacial region of the rats in the expanded group. The rats were sacrificed, and skin samples were harvested, fixed in formalin, and embedded in paraffin wax for histological investigation. Hematoxylin and eosin staining was performed to detect histological changes between the two groups and to investigate the inflammatory response in the expanded samples. Three inflammatory markers, namely interleukin (IL)-1α, IL-6, and tumor necrosis factor-α (TNF-α), were analyzed by immunohistochemistry.
RESULT: IL-1-α expression was only observed in the expanded tissue samples compared to the controls. In contrast, there was no significant difference in IL-6, and TNF-α production. Histological analysis showed the absence of inflammatory response in expanded tissues, and a negative non-significant correlation (Spearman's correlation coefficient) between IL-1-α immune-positive cells and the inflammatory cells (r = -0.500). In conclusion, tissues that are expanded and stabilized using an anisotropic self-inflating hydrogel tissue expander might be useful for tissue replacement and engraftment as the expanded tissue does not show any sign of inflammatory responses. Detection of IL-1-α in the expanded tissues warrants further investigation for its involvement without any visible inflammatory response.

Matched MeSH terms: Tissue Expansion Devices