id,collection,dc.contributor.author,dc.contributor.firstReferee,dc.contributor.furtherReferee,dc.contributor.gender,dc.date.accepted,dc.date.accessioned,dc.date.available,dc.date.issued,dc.description.abstract[en],dc.format.extent,dc.identifier.uri,dc.identifier.urn,dc.language,dc.rights.uri,dc.subject.ddc,dc.subject[en],dc.title,dc.type,dcterms.accessRights.dnb,dcterms.accessRights.openaire,dcterms.format,refubium.affiliation "c8f99558-2994-48c7-97e8-df163eec384b","fub188/14","Xu, Xun","Lendlein, Andreas","Stricker, Sigmar","male","2019-03-19","2019-03-29T09:38:31Z","2019-03-29T09:38:31Z","2019","Stem cells hold a great potential for regenerative therapy due to their properties of self-renewal, differentiation potential, homing ability, pro-angiogenic secretion and immunoregulation. With the help of biomaterials, stem cells can potentially be adapted since the physicochemical properties of biomaterials are able to guide the regenerative therapy towards the desired goals and augment the therapeutic efficacy by modulating cell fate and the regeneration process. Therefore, the understanding of stem cell-material interaction and the underlying mechanism is essential for designing biomaterials that are qualified for regenerative applications. Different cell types or same type of stem cells derived from different species may differ in response to the physicochemical factors from the different materials and to the same material with different microstructures according to their size, phenotype and sensing approach. Here, rat bone marrow-derived MSCs, human adipose derived-MSCs and mouse iPSCs were used. The study of bone marrow derived-MSCs (Chapter 3.1) was focused on the intrinsic physicochemical properties of PEI and PEU with similar wettability. They both were applied as polymeric inserts to ensure that the MSCs were exclusively in contact with the target polymers, and served as culture vessels for long-term maintenance of MSCs in vitro. Previously, we have investigated the cell compatibility of different polymers including PEI and PEU with human bone marrow-derived MSCs. The cell shape was altered and the alignment of F-actin cytoskeleton was reorganized in a random way in PEU. Among the tested polymers, PEI could support the long-term maintenance of human MSC self-renewal state. Similarly, for rat MSCs, flat and enlarged shape with rearranged F-actin cytoskeleton was observed for cells growing on PEU, while cells on PEI and TCP shared a typical spindle-shaped morphology and F-actin orientation. Although cells could grow on both polymeric surfaces with the similar adhesion ratio and subsequent division rate, cells cultured on PEU exhibited lower cell density after 5 days culture, which may directly attribute to the higher apoptosis level and senescence ratio. In this context, PEI provided relatively better cell compatibility for rat MSC survival and growth. Regardless of implementing a human or rat system, among all the tested polymers, PEI proved to be or was observed to be the most appropriate polymer substrate for bone marrow-derived MSCs culture. Strikingly, compared to the cells growing in traditional culture conditions with TCP and the human MSCs growing in PEU and PEI, both substrates could trigger rat MSCs towards spontaneous adipogenesis. Besides the effects that different chemical compositions of polymeric surfaces have on cells, the stem cell-mediated reflection to the polymer surface or the entire microenvironment at the cell-material interface may also differ due to species or other issues. These issues may play a certain role in differentiation, however, they still need to be further clarified. In this thesis, for the study of human adipose-derived MSC response to micro-scale geometric cues (Chapter 3.2 and 3.3), microstructured substrates comprising arrays of square-shaped or round-shaped microwells were developed as a transitional model between 2D and 3D systems. Initially after seeding, cells were likely to roll into the microwells instead of adopting a random distribution. Post spreading, MSCs moved freely on both microstructured substrates without physical constraints. In spite of the free cell migration, different migration velocities were observed on different microstructured substrates. The cell morphologies were three-dimensionally modulated by the local curvature of microwell structure due to differences in focal adhesion and alterations of the cytoskeleton. In contrast to the substrate with round-shaped microwells, the substrate with square-shaped microwells promoted the secretion of angiogenic factor IL-6, proliferation and osteogenesis of MSCs. Such microwell shape-dependent modulatory effect was highly associated with ROCK signaling. Following ROCK inhibition, the differences in IL-6 secretion, proliferation and osteogenesis between cells on different substrates were diminished. These findings allow a better understanding of MSC response to geometric cues and highlight the possibility to control the fate and functions of MSCs through structured features via manipulation of ROCK signaling. This knowledge might help to direct stem cells towards desired orientations and functions through utilization of biomaterial surface structures. As indicated in Chapter 3.2 and 3.3, the distinct local curvature of square and round-shaped microwells was considered as a potential trigger and regulatory factor involved in modulation of MSC cellular response. In Chapter 3.4 and 3.5, a series of microroughness surfaces with local micro-scale curvature change were created. Surfaces with an appropriate microcurvature relevant to a single MSC size (PS-160) could effectively enhance the VEGF secretion and the pro-angiogenic effect of human adipose-derived MSCs via integrin-activation initiated intracellular signaling cascades (e.g FAK and ERK). The functional cardiomyogenic differentiation together with pro-angiogenic secretion of mouse iPSCs was boosted and mechanically memorized initially via cell compacting and later on via strengthening of cell-cell junctions by local curvatures fitting to EB diamension (PEI R2). We speculated that both mechanosensors E-cadherin and YAP might be the potential determinants. Further studies need to be carried out. Regardless of various MSC sources (adipose tissue- and bone marrow-derived) and different types of stem cells (MSCs and iPSCs), both 2.5D microstructuring with different local curvatures and polymeric substrates with different chemical components can modulate stem cell morphology and behavior, and provide the basis for development and future commercialization in tissue culture systems. This approach of induced and controlled endogenous regeneration using a polymeric biomaterial may also be applicable to other stem/progenitor cells and to various types of implants, such as microstructured substrates of orthopedic implants, where the integration into relevant tissues could potentially be improved. Further, with the introduction of microtechnological platforms for cell culture, the pace of stem cell research can be dramatically enhanced.","245 Seiten","https://refubium.fu-berlin.de/handle/fub188/24226||http://dx.doi.org/10.17169/refubium-1998","urn:nbn:de:kobv:188-refubium-24226-7","eng","http://www.fu-berlin.de/sites/refubium/rechtliches/Nutzungsbedingungen","500 Natural sciences and mathematics::570 Life sciences::570 Life sciences","Stem cell||Geometry||Differentiation||signaling pathway","Stem Cell Instruction via Appropriate Geometry and Local Curvature of Microstructured Polymeric Substrates","Dissertation","free","open access","Text","Biologie, Chemie, Pharmazie"