title: Microtopography and stretch activated mechanotransduction in dermal fibroblasts and epithelia
Creators: name: Jarangdej, Nuttaporn
Publisher: name: University of Glasgow
Year: 2023

description: Mechanical forces are key contributors to regulating cell function, development, homeostatic turnover, and repair of tissues. To date, the dynamic interactions between cell mechanics and their microenvironment. This study aims to reproduce a biomaterial scaffold that can carry dermal fibroblast and/or epithelia, combined with applied tissue engineering approaches to manipulate the mechanosensitive elements of cells to function for skin regeneration and wound healing. The major focus of this study provide insight into the mechanisms underlying the deformation of cell nuclei which have an impact on transcription factor control, cell memory, and behaviours. In an attempt to offer an effective biocompatible scaffold, one particular challenge lies in the delivery of functional mechanical stimuli to potential translational outcomes and promote regenerative characteristics of skin grafting and wound healing. This research project highlights how mechanical and biochemical microenvironments link the nuclear reorganization which reflects to functional consequences under mechanical regulation, imposed on nuclear overall shape and transcriptional activities. Two ways of delivering mechanical signals have been used to convey force to nuclear regulation which connect to the cytoskeleton and/or nucleoskeleton including; I) Externally applied force applications to activate cell growth or motility, with active stretch via microtopographic patterns and loading passive stretch by pulling on the cells. II) Adjusting nuclear force internally via the expression and activity of nuclear membrane proteins (i.e. emerin and binding partners; lamin A/C and BAF). The read-out of measuring at the end of dynamic changes in actin polymerisation direct to the nuclear entry of mechanosensitive transcription factor (TF), myocardin-related factor A (MRTF-A) have been addressed. As a result of the response of dermal fibroblasts to mechanical stimuli, immunofluorescent staining of n/c ratio showed that have significant enhanced nuclear import of MRTF-A by~2.0-fold and ~1.3-fold increased subjected to 4.2% unidirectional stretch and 5% cyclic stretch (0.05Hz, 90°grooves), respectively. However, the cells under lower mechanical force promoted the nuclear export of MRTF-A. Immunoblot results revealed that nuclear accumulation of MRTF-A in cell-lacking emerin to the range between 0.3-fold to 0.5-fold decreased confirmed by two knockout clones. The impact of reduced mechanical tension contributes to the nuclear mechanical properties and histone modification. Assessing the alteration of acetylation status of histones via HDAC3 gene expression was examined using real-time qPCR, with a significant decrease of half expression in knockout models of emerin both in BJ1 and HEK293 cells. With the stated results, the analysis of cell-induced environment deformations can imply chromatin remodelling and thus regulate cell behaviours. Increased mechanical properties lead to chromatin condensation and influence on cell contractility or even differentiation while, low mechanical forces link to chromatin unfold or decondensation with hyperproliferation. To conclude, this study represents the cell-based tissue-engineered platform which improved delivery via a biocompatible scaffold to offer an alternative artificial tissue layer for enhancing translational qualities in skin regeneration and wound healing. The results suggest condition favours with dynamic microenvironment to regulate cell behaviour specified to mechanical properties for cell contraction or proliferation. In addition to this, the work illustrates how mechanotransduction of cells sense and convert mechanical signals into changes in intracellular biochemistry and nuclear regulation including transcription factor translocation, TF activity, and chromatin reorganisation.