In Vivo and ex Vivo Approaches to Studying the Biomechanical Properties of Healing Wounds in Rat Skin

Abstract

An evaluation of wound mechanics is crucial in reflecting the wound healing status. The present study examined the biomechanical properties of healing rat skin wounds in vivo and ex vivo. Thirty male Sprague-Dawley rats, each with a 6 mm full-thickness circular punch biopsied wound at both posterior hind limbs were used. The mechanical stiffness at both the central and margins of the wound was measured repeatedly in five rats over the same wound sites to monitor the longitudinal changes over time of before wounding, and on days 0, 3, 7, 10, 14, and 21 after wounding in vivo by using an optical coherence tomography-based air-jet indentation system. Five rats were euthanized at each time point, and the biomechanical properties of the wound tissues were assessed ex vivo using a tensiometer. At the central wound bed region, the stiffness measured by the air-jet system increased significantly from day 0 (17.2%), peaked at day 7 (208.3%), and then decreased progressively until day 21 (40.2%) as compared with baseline prewounding status. The biomechanical parameters of the skin wound samples measured by the tensiometer showed a marked reduction upon wounding, then increased with time (all p < 0.05). On day 21, the ultimate tensile strength of the skin wound tissue approached 50% of the normal skin; while the stiffness of tissue recovered at a faster rate, reaching 97% of its prewounded state. Our results suggested that it took less time for healing wound tissues to recover their stiffness than their maximal strength in rat skin. The stiffness of wound tissues measured by air-jet could be an indicator for monitoring wound healing and contraction.

Marker-Free Tracking of Facet Capsule Motion Using Polarization-Sensitive Optical Coherence Tomography

“…Polarization-sensitive optical coherence tomography (PS OCT) is non-destructive, reflection-based imaging modality that has been shown 2, 9, 14 to provide depth-resolved structural characteristics of biological tissues. The current study shows the use of phase retardance images produced by polarization-sensitive optical coherence tomography (PS OCT) for providing the means for marker-free, high-resolution 3D motion tracking of the lumbar facet capsular ligament (FCL).…”

“…Optical coherence tomography (OCT) is a non-destructive, depth-resolved, back-scattering/reflection-based imaging technique that has been used previously in mechanical investigations of wound healing 9 , tissue folding 14 , and thermal denaturation of collagen 2, 11 . Importantly, Filas et al 13, 14 used OCT images of the embryonic chick heart with microspheres as markers to track tissue deformation, and Li et al 20 used OCT for gross strain and strain rate estimates based on heart wall thickness changes.…”

TGF-β1 Pretreatment Improves the Function of Mesenchymal Stem Cells in the Wound Bed

“…Despite the recent progress in evaluating MSC based therapies for wound healing, the distinct interaction of MSCs with the mechanical and chemical cues present in wound bed is not fully understood and this currently limits the extensive use of MSCs in clinical capacity. Previous studies have reported that wound stiffness increases dramatically during the healing process and modifies the function of underlying cells, e.g., fibroblasts, in both normal and pathological conditions (Goffin et al, 2006; López et al, 2010; Liu et al, 2010a; Chao et al, 2013; Klingberg et al, 2013; Darby et al, 2014). In addition to the biochemical signals present in the wound milieu, such mechanical cues e.g., matrix elasticity, can also affect the MSC function profoundly (Engler et al, 2006; Kilian et al, 2010; Tse and Engler, 2011; MacQueen et al, 2013).…”

High myopia induced by form deprivation is associated with altered corneal biomechanical properties in chicks

“…In this study, we incorporated optical coherence tomography (OCT)[ 26 , 27 ] into our indentation system[ 28 ], and we used this novel OCT-indentation system to determine the impact of FD-induced high myopia on in-situ corneal biomechanical properties (CB), while IOP was maintained constant at one of three values in the physiological range. This system was designed with attention to the anatomical features of our target animal model, the chicken; namely: 1) the indenter probe was miniaturized (1 mm diameter) because of the steep corneal curvature in our small animals; 2) crystalline lens surface was used as a reference (see details in Methods ), to avoid confounding error due to eyeball movement during corneal indentation[ 29 ]; and 3) time-domain OCT (TD-OCT) was incorporated, to provide fast, high-resolution tracking of corneal and crystalline lens surfaces during indentation at different IOPs.…”