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MULTI-LAYER AGENT-BASED MODELING FOR BONE TISSUE ENGINEERING
Title
MULTI-LAYER AGENT-BASED MODELING FOR BONE TISSUE ENGINEERING
Creator
Lu, Chenlin
Date
2018, 2018-05
Description
Bone tissue engineering (BTE) has emerged over the past few decades as a potential alternative to the field of conventional bone regenerative...
Show moreBone tissue engineering (BTE) has emerged over the past few decades as a potential alternative to the field of conventional bone regenerative medicine due to the exceedingly high demand of adequate bone grafts. Regeneration of bone tissue in BTE requires synergistic combination of biomaterial scaffolds, growth factors, and osteogenic cells. Scaffolds with well-designed architectures and degradation characteristics, provided with appropriate angiogenic and osteogenic factors are essential for bone tissue regeneration. Taking into account these factors that contribute to bone tissue regeneration process simultaneously and optimizing their characteristics presents a highly difficult task and cannot be addressed with experimentation alone. Computational models combined with experimental methods provide better understanding of the underlying mechanisms of the complex process. The agent-based modeling (ABM) approach is used to develop three-dimensional models of vascularization and bone growth. ABM is a powerful modeling and simulation technique and is naturally suitable for complex biological system as it simulates actions and interactions of individual agents in an attempt to re-create and predict the appearance of complex phenomena. In this work, a multi-layered, agent-based computational model has been proposed to simulate the vascularization and bone tissue regeneration in a porous, biodegradable biomaterial scaffold. This model aims to investigate the interactions between osteogenic cells, signaling molecules, and biomaterial scaffolds in order to enhance scaffold vascularization and bone tissue formation. Our previous works have already investigated the interactions between endothelial cells (ECs) and biodegradable scaffolds, and provided us significant insights into the combined effect of scaffold geometrical properties and degradation dynamics on scaffold vascularization. Furthermore, the controlled release of angiogenic growth factors has been studied tothis work, a multi-layered, agent-based computational model has been proposed to simulate the vascularization and bone tissue regeneration in a porous, biodegradable biomaterial scaffold. This model aims to investigate the interactions between osteogenic cells, signaling molecules, and biomaterial scaffolds in order to enhance scaffold vascularization and bone tissue formation. Our previous works have already investigated the interactions between endothelial cells (ECs) and biodegradable scaffolds, and provided us significant insights into the combined effect of scaffold geometrical properties and degradation dynamics on scaffold vascularization. Furthermore, the controlled release of angiogenic growth factors has been studied to investigate their effects on vascularization process. This work will mainly focus on three aspects: 1) the improvement of scaffold degradation model. 2) the development of vascularized bone regeneration agent-based model in Repast High Performance Computing (Repast HPC). 3) the investigation of in vitro prevascularization strategy to enhance angiogenesis and overall bone regeneration in BTE applications. The developed model integrates all these factors and simulates the regeneration of bone tissue in biodegradable scaffolds over time. Simulation results can be used in combination with experimental data to design optimal scaffold constructs for bone tissue engineering. A multi-layer scaffold model is implemented in the degradation ABM. Scaffold vascularization is enhanced by the multi-layer scaffold strategy without losing the necessary mechanical support of biomaterial scaffolds. A integrated vascularized bone tissue regeneration ABM was developed using Repast HPC platform. The model successfully simulated the scaffold vascularization and coupled osteogenic differentiation in a 3D porous scaffold. The study demonstrated that scaffolds with higher porosity and combined angiogenic and osteogenic GF factor resulted in optimal vascularized bone formation. A diffusion ABM is developed to simulate the growth factor release in the scaffold. Simulation results indicated a good agreement between the diffusion ABM and mathematical model.The prevascularization high performance ABM is developed to simulate the integrated process of in vitro prevascularization followed by in vivo vascularized bone formation and evaluate the potential of prevascularization strategy to enhance overall scaffold vascularization and bone formation. The results demonstrated that prevascularized scaffold increases overall defect vascularization and bone formation upon implantation.
Ph.D. in Chemical and Biological Engineering, May 2018
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INVESTIGATION OF THE EFFICACY OF REACTIVE OXYGEN SPECIES GENERATED BY BOVINE AORTIC ENDOTHELIAL CELLS FOR INITIATING FREE-RADICAL POLYMERIZATION
Title
INVESTIGATION OF THE EFFICACY OF REACTIVE OXYGEN SPECIES GENERATED BY BOVINE AORTIC ENDOTHELIAL CELLS FOR INITIATING FREE-RADICAL POLYMERIZATION
Creator
Lu, Chenlin
Date
2013, 2013-12
Description
Reactive oxygen species are reported to be generated by bovine aortic endothelial cells during ischemia followed by reperfusion. This...
Show moreReactive oxygen species are reported to be generated by bovine aortic endothelial cells during ischemia followed by reperfusion. This biological response, believed to be the cause of post-ischemic reperfusion injury, inspired us to investigate the possibility of coupling it with the initiation of free-radical polymerization to produce polymer hydrogels for cell encapsulation. In this work, the generation of reactive oxygen species during ischemia and reperfusion was examined by fluorescence detection and the feasibility of initiating free-radical polymerization by generated reactive oxygen species was investigated in two sets of experiments. The generation of reactive oxygen species by bovine aortic endothelial cells when subjected to anoxia followed by reoxygenation was investigated in both attached and suspended cells. Both intracellular and extracellular generations of ROS appeared to occur in the experiments of attached cells. Cell viability experiments demonstrated that the generation of ROS was sufficient to cause cell damage and death. The feasibility of initiating free-radical polymerization by reactive oxygen species generated by bovine aortic endothelial cells subjected to anoxia followed by reoxygenation was investigated in two sets of experiments. One set involved the linear polymerization of NVP which allowed us to quantify the extent of polymerization and characterization of the weight conversion of PVP polymer. The other set involved the formation of PEGDA hydrogels which were characterized by imaging and staining methods. To our knowledge this is the first evidence of cell induced polymerization initiated by reactive oxygen species and gelation which can be used for a variety of biomedical applications.
M.S. in Chemical and Biological Engineering, December 2013
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