Browsing by Subject "translational Research on Oral and Maxillofacial Sciences"

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  • Abushahba, Ahmed (Helsingin yliopisto, 2021)
    Bone tissue engineering (BTE) has shown a great promise in providing the next generation medical bioimplants for treating bone defects. However, BTE faces many obstacles which need to be addressed for promoting translatability. The objective of this thesis work was to explore clinically translatable tissue engineering approaches for the management of craniomaxillofacial bone defects. The role of the employed cells has witnessed a critical turning point towards an increased appreciation of the cellular paracrine effects. This paracrine effect is mediated via secreted proteins and released membrane-bound vesicles called extracellular vesicles (EVs). For advancing our knowledge about the biological roles of EVs, we employed RNA sequencing to provide a comprehensive overview of the expression profiles of small non-coding transcripts carried by the EVs derived from human adipose tissue stromal/stem cells (AT-MSCs) and human pluripotent stem cells (hPSCs). Our findings revealed distinctive small non-coding RNA profiles from hPSCs and AT-MSCs EVs. The regulatory miRNAs of stem cells at cellular level are also present in their EVs, indicating an important regulatory role which is mediated via EVs. Vascularization is the key challenge for BTE applications in large bone defects. The local delivery of growth factors leads to short lived effects. Small molecule chemicals feature alternative cost-effective bioactive agents with better stability. We assessed the ability of two small molecules; DMOG and baicalein, in triggering the proangiogenic secretome of AT-MSCs in vitro. Additionally, other effects, such as proliferation and osteogenic differentiation of AT-MSCs were assessed. DMOG and baicalein efficiently stabilized the hypoxia-inducible factor (HIF-1α) and upregulated proangiogenic cytokines, e.g., vascular endothelial growth factor (VEGF) and platelet derived growth factor-BB (PDGF-BB) of AT-MSCs in normoxic conditions. These effects were further associated with upregulated stemness-related gene expression, slowed proliferation, and reduced osteogenic potential. Chemically-induced hypoxia maintained the stemness and self-renewal properties of AT-MSCs, while enhancing their proangiogenic potential. The in vivo bioreactor (IVB) concept combines the potential of BTE and reconstructive surgery by employing the patient body for prefabricating new prevascularized tissues. Ideally, IVB should minimize the need for exogenous growth factors or cells and harness the native regenerative potential of employed tissues. Using acellular alloplastic bone blocks, we compared muscle-IVB with and without periosteal/pericranial grafts and flaps for prefabricating tissue engineered bone (TEB) flaps. We also assessed their functional outcomes in reconstructing a mandibular defect in an ovine model. The employment of vascularized periosteal flaps did result in more robust vascularization as compared to other IVB techniques. Both the periosteal grafts and periosteal flaps enhanced the performance of the prefabricated TEB flaps after transplantation into a mechanically stimulated bony microenvironment. However, more new bone formation and biomaterial remodeling was associated with the vascularized periosteal flaps.