Korpela, S. | Search bioRxiv

bioRxiv2021

Cerebrospinal fluid amyloid beta and glial fibrillary acidic protein concentrations in Huntingtons disease

IntroductionHuntingtons disease (HD) is a genetic incurable lethal disease. Biomarkers are needed for objective assessment of disease progression. Evidence supports both complex protein aggregation and astrocyte activation in HD. This study assesses the 42 amino acid long amyloid beta (A{beta}42) and glial fibrillary acidic protein (GFAP) as potential biomarkers in the cerebrospinal fluid (CSF) of HD mutation carriers. MethodsCSF was obtained from manifest HD patients (ManHD), premanifest HD-gene-expansion carriers (PreHD) and gene-negative controls (controls). Disease Burden Score (DBS) and Total Functional Capacity (TFC) were calculated. Protein concentrations were measured by enzyme-linked immunosorbent assays (ELISA) and intergroup differences were analysed using Mann-Whitney U test. Spearman correlations were calculated to assess disease stage association. Age-adjustment was included in the statistical tests. ResultsThe study enrolled 27 ManHD and 13 PreHD subjects. The number of controls differed in the analysis of A{beta}42 and GFAP (n = 19, and 8 respectively). A{beta}42 levels were higher in ManHD (mean 741 ng/l, SD 361) compared with PreHD (mean 468 ng/l, SD 184) (p = 0.025). Likewise GFAP concentration was higher in ManHD (mean 435 ng/l, SD 255) compared with both PreHD (mean 266 ng/l, SD 92.4)(p = 0.040) and controls (mean 208 ng/l, SD 83.7)(p = 0.011). GFAP correlated with DBS (r = 0.361, p = 0.028), TFC (r = - 0.463, p = 0.005), and 5-year risk of onset in PreHD (r = 0.694, p = 0.008). In contrast, there was no correlation between A{beta}42 concentration and DBS, TFC or 5-year risk of onset. ConclusionCSF A{beta}42 levels did not correlate with disease stage suggesting no A{beta}aggregation in HD. GFAP is a potential biomarker in HD with association to disease stage. Validation in larger HD cohorts and potential correlations with clinical phenotype would be of interest.

neuroscience↗

bioRxiv2021

The effect of substrate stiffness on tensile force transduction in the epithelial monolayers

In recent years, the importance of mechanical signaling and the cellular mechanical microenvironment in affecting cellular behavior has been widely accepted. Cells in epithelial monolayers are mechanically connected to each other and the underlying extracellular matrix (ECM), forming a highly connected mechanical system subjected to various mechanical cues from their environment, such as the ECM stiffness. Changes in the ECM stiffness have been linked to many pathologies, including tumor formation. However, our understanding of how ECM stiffness and its heterogeneities affect the transduction of mechanical forces in epithelial monolayers is lacking. To investigate this, we used a combination of experimental and computational methods. The experiments were conducted using epithelial cells cultured on an elastic substrate and applying a mechanical stimulus by moving a single cell by micromanipulation. To replicate our experiments computationally and quantify the forces transduced in the epithelium, we developed a new model that described the mechanics of both the cells and the substrate. Our model further enabled the simulations with local stiffness heterogeneities. We found the substrate stiffness to distinctly affect the force transduction as well as the cellular movement and deformation following an external force. Also, we found that local changes in the stiffness can alter the cells response to external forces over long distances. Our results suggest that this long-range signaling of the substrate stiffness depends on the cells ability to resist deformation. Furthermore, we found that the cells elasticity in the apico-basal direction provides a level of detachment between the apical cell-cell junctions and the basal focal adhesions. Our simulation results show potential for increased ECM stiffness, e.g. due to a tumor, to modulate mechanical signaling between cells also outside the stiff region. Furthermore, the developed model provides a good platform for future studies on the interactions between epithelial monolayers and elastic substrates. Author summaryCells can communicate using mechanical forces, which is especially important in epithelial tissues where the cells are highly connected. Also, the stiffness of the material under the cells, called the extracellular matrix, is known to affect cell behavior, and an increase in this stiffness is related to many diseases, including cancers. However, it remains unclear how the stiffness affects intercellular mechanical signaling. We studied this effect using epithelial cells cultured on synthetic deformable substrates and developed a computational model to quantify the results better. In our experiments and simulations, we moved one cell to observe how the substrate stiffness impacts the deformation of the neighboring cells and thus the force transduction between the cells. Our model also enabled us to study the effect of local stiffness changes on the force transduction. Our results showed that substrate stiffness has an apparent impact on the force transduction within the epithelial tissues. Furthermore, we found that the cells can communicate information on the local stiffness changes over long distances. Therefore, our results indicate that the cellular mechanical signaling could be affected by changes in the substrate stiffness which may have a role in the progression of diseases such as cancer.

cell biology↗