Elucidating Cause-Effect Relationships between Extracellular Matrix Signaling and Mesenchymal Stem Cell Differentiation
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Mesenchymal stem cell (MSC) differentiation is known to be influenced by a range of environmental stimuli. MSC-based bone regeneration strategies would benefit from the identification of scaffold material properties which intrinsically promote osteoblast lineage progression. The aim of this work was to contribute to the understanding of elucidating cause-effect relationships between extracellular matrix (ECM) signaling and osteogenic MSC differentiation using poly(ethylene glycol) diacrylate (PEGDA) hydrogels as a material platform. First, the effect of several ECM proteins associated with bone morphogenesis or bone fracture healing on MSC osteogenesis was investigated. Second, collagen-mimetic proteins (Scl2) were modified in order to incorporate them in a 3D network, and cell adhesion and activation of cell signaling were evaluated, as well. Finally, the influence of integrin α1 and α2 binding on human MSC (hMSC) osteogenesis was investigated toward the goal of deconvoluting the impact of integrin-based interactions on associated cell behavior. In terms of the osteoinductivity of select ECM components, the results showed that both FG and LN enhanced the osteogenic response of encapsulated MSC cells. In addition, the integrin-based interactions supported by these ECM components indicated that integrin α2 and α6 appeared to play an important role in MSC osteogenesis. Regarding Scl2 protein studies, Scl2-1, Scl2-2, and Scl2-3 were functionalized with photocrosslinking sites to enable incorporation into a 3D hydrogel matrix. characterization studies confirmed that the functionalization of the Scl2 proteins did not disrupt triple helix conformation, integrin binding, or cell adhesion. Also, initial cell studies confirmed specific hMSC adhesion to Scl2 proteins and appropriate activation of different MAP kinase pathways. Finally, Scl2 proteins were conjugated into PEGDA hydrogels and their effect on hMSC osteogenesis was evaluated. The results indicated that both PEG-Scl2-2 and PEG-Scl2-3 were osteoinductive, but in different ways. Therefore, to gain insight into the origins of the observed osteogenic responses, the influence of p38 pathway in osteogenesis of hMSC was investigated in order to establish its potential causative relationship with Scl2 proteins. The results of the p38 inhibition studies suggested p38 pathway may regulate osteogenesis in hMSCs. Further research is needed for investigation of detailed mechanism of osteogenesis regulation.
Becerra-Bayona, Silvia M. (2013). Elucidating Cause-Effect Relationships between Extracellular Matrix Signaling and Mesenchymal Stem Cell Differentiation. Doctoral dissertation, Texas A & M University. Available electronically from