title: Collagen Substrate Stiffness Anisotropy Affects Cellular Elongation, Nuclear Shape, and Stem Cell Fate toward Anisotropic Tissue Lineage.
abstract: Rigidity of substrates plays an important role in stem cell fate. Studies are commonly carried out on isotropically stiff substrate or substrates with unidirectional stiffness gradients. However, many native tissues are anisotropically stiff and it is unknown whether controlled presentation of stiff and compliant material axes on the same substrate governs cytoskeletal and nuclear morphology, as well as stem cell differentiation. In this study, electrocompacted collagen sheets are stretched to varying degrees to tune the stiffness anisotropy (SA) in the range of 1 to 8, resulting in stiff and compliant material axes orthogonal to each other. The cytoskeletal aspect ratio increased with increasing SA by about fourfold. Such elongation was absent on cellulose acetate replicas of aligned collagen surfaces indicating that the elongation was not driven by surface topography. Mesenchymal stem cells (MSCs) seeded on varying anisotropy sheets displayed a dose-dependent upregulation of tendon-related markers such as Mohawk and Scleraxis. After 21 d of culture, highly anisotropic sheets induced greater levels of production of type-I, type-III collagen, and thrombospondin-4. Therefore, SA has direct effects on MSC differentiation. These findings may also have ramifications of stem cell fate on other anisotropically stiff tissues, such as skeletal/cardiac muscles, ligaments, and bone.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.
authors.forename: Anowarul
authors.initials: A
authors.lastname: Islam
authors.affiliation: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.
authors.forename: Mousa
authors.initials: M
authors.lastname: Younesi
authors.affiliation: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mbimba
authors.affiliation: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA. oxa@case.edu.|Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA. oxa@case.edu.|Department of Orthopaedics, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA. oxa@case.edu.
authors.forename: Ozan
authors.initials: O
authors.lastname: Akkus
mesh_terms: D000818:Animals; D016880:Anisotropy; D002417:Cattle; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism*; D048430:Cell Shape; D003094:Collagen / Q000737:chemistry*; D003599:Cytoskeleton / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*
chemical_list: D003094:Collagen
keywords: MSC differentiation; cellular alignment; collagen sheet stretch; substrate stiffness anisotropy