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Matrix strains induced by cells: Computing how far cells can feel.

ABSTRACT: Many tissue cells exert contractile forces that mechanically couples them to elastic matrices and that influence cell adhesion, cytoskeletal organization, and even cell differentiation. However, strains within the depths of matrices are often unclear and are likely relevant not only to the fact that some matrices such as so-called basement membranes are thin relative to cell dimensions but also to defining how far cells can 'feel'. Here we briefly present experimental results for cell spreading on thin, ligand-coated gels and for prestress in stem cells in relation to gel stiffness. We then introduce a finite element computation in which a cell is placed on an elastic matrix, while matrix elasticity and thickness are varied in order to compute and compare elastostatic deformations within the matrix. Average interfacial strains between cell and matrix show large deviations only when soft matrices are a fraction of the height and width of a cell, proving consistent with experiments. Three-dimensional (3D) cell morphologies that model stem cell-derived neurons, myoblasts, and osteoblasts show that a cylinder-shaped myoblast induces the highest strains, consistent with the prominent contractility of muscle. Groups of such cells show a weak crosstalk in matrix strains, but the cells must be much closer than a cell-width. Cells thus feel on length scales closer to that of adhesions than on cellular scales or higher.

SUBMITTER: Sen S

PROVIDER: S-EPMC2891090 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Matrix strains induced by cells: Computing how far cells can feel.

Sen Shamik S Engler Adam J AJ Discher Dennis E DE

Cellular and molecular bioengineering 20090301 1

Many tissue cells exert contractile forces that mechanically couples them to elastic matrices and that influence cell adhesion, cytoskeletal organization, and even cell differentiation. However, strains within the depths of matrices are often unclear and are likely relevant not only to the fact that some matrices such as so-called basement membranes are thin relative to cell dimensions but also to defining how far cells can 'feel'. Here we briefly present experimental results for cell spreading ...[more]

PMID: 20582230

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Project description:Pedigree relationships between every pair of individuals forms the elements of the additive genetic relationship matrix (A). Calculation of A -1 does not require forming and inverting A, and it is faster and easier than the calculation of A. Although A -1 is used in best linear unbiased prediction of genetic merit, A is used in population studies and post-evaluation procedures, such as breeding programs and controlling the rate of inbreeding. Three pedigrees with 20,000 animals (20K) and different (1, 2, 4) litter sizes, and a pedigree with 180,000 animals (180K) and litter size 2 were simulated. Aiming to reduce the computation time for calculating A, new methods [Array-Tabular method, ( T -1)-1 instead of T in Thompson's method, iterative updating of D in Thompson's method, and iteration by generation] were developed and compared with some existing methods. The methods were coded in the R programming language to demonstrate the algorithms, aiming for minimizing the computational time. Among 20K, computational time decreased with increasing litter size for most of the methods. Methods deriving A from A -1 were relatively slow. The other methods were either using only pedigree information or both the pedigree and inbreeding coefficients. Calculating inbreeding coefficients was extremely fast (<0.2 s for 180K). Parallel computing (15 cores) was adopted for methods that were based on solving A -1 for columns of A, as those methods allowed implicit parallelism. Optimizing the code for one of the earliest methods enabled A to be built in 13 s (faster than the 31 s for calculating A -1) for 20K and 17 min 3 s for 180K. Memory is a bottleneck for large pedigrees but attempts to reduce the memory usage increased the computational time. To reduce disk space usage, memory usage, and computational time, relationship coefficients of old animals in the pedigree can be archived and relationship coefficients for parents of the next generation can be saved in an external file for successive updates to the pedigree and the A matrix.

Project description:BackgroundThere is a high reported rate of sexual dysfunction among women with spina bifida, but little is known about the etiology of this or how sexual satisfaction could be improved.AimTo identify, through the words of women with spina bifida, perceived causes of diminished sexual satisfaction and recommendations to optimize partnered sexual encounters.MethodsIn this qualitative study, we conducted semi-structured individual interviews with 22 women with spina bifida (median age 26.5 years, range 16-52 years) who have had a romantic partner. Using Grounded Theory, interviews were independently coded by 3 reviewers. Disagreements were resolved by consensus.OutcomesWe identified overlapping themes of issues women experienced during sexual intimacy and strategies they learned to improve sexual encounters.Results7 salient themes emerged from the data: (i) fear of rejection with resulting difficulty setting boundaries and the risk of coercion; (ii) conflict between spontaneity and self-care in sexual encounters; (iii) worry about incontinence during sex; (iv) trial and error in learning optimal sexual positions; (v) decreased genital sensation; (vi) safety considerations; and (vii) sharing advice with other women with spina bifida.Clinical implicationsAs sexual satisfaction is influenced by physical features as well as psychological, interpersonal, and sociocultural factors, optimizing sexual satisfaction of women with spina bifida is best managed with a holistic approach utilizing a biopsychosocial model.Strengths & limitationsThe sample included women with a diverse range of functional impairments. Women were forthright with their comments and thematic saturation was reached. Recruitment was primarily from a single Midwestern institution, which may have limited sampled perspectives.ConclusionWhile women with spina bifida encounter challenges during sexual encounters, strategies focused on improving communication with partners and addressing specific physical considerations can potentially enhance their sexual experiences. Streur CS, Schafer CL, Garcia VP, et al. "I Tell Them What I Can Feel and How Far My Legs Can Bend": Optimizing Sexual Satisfaction for Women With Spina Bifida. J Sex Med 2020;17;1694-1704.

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Matrix strains induced by cells: Computing how far cells can feel.

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Matrix strains induced by cells: Computing how far cells can feel.

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