Prof Wen Wang

Wen Wang
PhD, CEng, FIMechE, FHEA, FAIMBE, FREng

Professor of Biomedical Engineering
Vice-Principal and Executive Dean for Science and Engineering

School of Engineering and Materials Science
Queen Mary University of London
+44 (0)20 7882 3031
www.sems.qmul.ac.uk/staff/wen.wang/
Centre for Bioengineering

Research

Cell biomechanics, Biofluids, Flow and solute transport in tissues, Cardiovascular disease, Arterial haemodynamics, Microcirculation

Interests

My work focuses on vascular bioengineering and biomaterial mechanics, including studies on the endothelial glycocalyx, vascular stem cells and progenitor cells, transmembrane and transcapillary exchange. Working at the interface between biomedical engineering, biomaterials and cell mechanics, I have led a number of multidisciplinary projects in the UK, as well as international projects between the UK, US, China and Japan. Due to limitation of the space, I will only present our research on the vascular endothelial glycocalyx. We have a number of other projects, including microcapsules as vehicles for drug delivery and vascular stem cells in collaboration with colleagues in Medical Schools at Queen Mary and King's College London. Details of these studies can be found in our publication lists.

Studies on the glycocalyx

a) its spatial distribution and temporal development on the endothelial cell membrane;
b) mechanical properties of the glycocalyx;
c) effects of fluid shear stress on its distribution on the cell membrane; and
d) its stability and interplay with the cytoskeletal actin network.

The endothelial glycocalyx is a carbohydrate–protein layer that lines the luminal surface of the endothelium. It anchors to the cell membrane via its core proteins that share extended link to the actin cytoskeleton. Those protein domains and the attached carbohydrates are susceptible to pathological changes, contributing to vascular diseases.


a) Spatio-temporal development of the glycocalyx

We observe the spatial distribution of the endothelial glycocalyx layer using laser-scanning confocal microscopy. Cells after different days in culture are studied to evaluate the temporal development of the glycocalyx layer. Comparisons are made between the controls and enzyme-treated groups.

Our in vitro results using confocal microscopy show the development of the endothelial glycocalyx over time. The growth appears to initiate from the edge of cells and takes up to two weeks to cover the apical region of the cell membrane (i.e. region above the nucleus). The mechanism underlining this spatial distribution and temporal change needs further investigation, but it seems functionally beneficial as the glycocalyx layer covers the intercellular gaps for the endothelium to fulfil its role as a selective semi-permeable membrane for the circulating blood. Our three-dimensional reconstructed images, although limited by the confocal resolution in the z-direction, indicate that the thickness of the glycocalyx layer is approximately 1 μm. This finding agrees reasonably well with previous studies.


b) Mechanical property of the glycocalyx

we have investigated mechanical properties of the glycocalyx layer using AFM nano-indentation. The Young's modulus of the glycocalyx is calculated by analysing testing results on the HUVEC cell membrane with and without the glycocalyx layer.

Indentation of the cell membrane of the initial 200 nm (after bending of the cantilever is deducted) enables us to estimate the Young's modulus of the glycocalyx layer by comparing the change in the cell membrane Young's modulus with and without the glycocalyx. We can simplify the flexible glycocalyx layer on a deformable cell membrane to a two springs in series system. Our results suggest that the cell membrane Young's modulus without the glycocalyx layer is approximately 2.13 kPa (average of day 14 and 21), and with the glycocalyx layer, the overall Young's modulus is approximately 0.34 kPa (average of day 14 and 21 control groups). This leads to the Young's modulus of the glycocalyx layer alone to be approx. 0.39 kPa.


c) Shear stress-induced redistribution of the glycocalyx

We study the effects of shear stress on the spatial distribution of the glycocalyx on endothelial cell membranes, using a flow chamber. Two parameters are used to characterize the spatial distribution of the glycocalyx: (a) the percentage area of the cell membrane covered by the glycocalyx layer and (b) the fluorescence intensity ratio between the apical and edge regions of endothelial cells. They give quantitative measures of the observed changes in the distribution of the glycocalyx following shear exposure. Comparisons are made at different time points after shear stimulation to study the redistribution of the glycocalyx on the cell membrane. Further studies are carried out to analyse the recovery of the glycocalyx layer following its enzyme degradation in either static or shear flow conditions.


d) Stability of the glycocalyx

We investigate the contribution of the actin cytoskeleton to the structural stability of the glycocalyx in vitro. Specifically, we establish two states of actin depolymerisation with the use of cytochalasin D (CD). One is rapid depolymerisation which quickly disrupts the actin using a high concentration of CD, and the other is prolonged actin disruption by employing a low CD concentration to persistently depolymerise the actin cytoskeleton.