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A multi-phase structural constitutive model for insights into soft tissue remodeling mechanisms

Wognum, Silvia (2010) A multi-phase structural constitutive model for insights into soft tissue remodeling mechanisms. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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All tissues in the human body continuously grow, remodel, and adapt to changes in their physiological environment, in order to maintain homeostasis or to retain it in case of pathologies. The growth and remodeling (G&R) process results in changes in structure and composition. To elucidate how observed changes in tissue components are related to altered tissue level mechanical behavior, structural constitutive models are required with physiologically relevant model parameters. Specifically what is required is a finite deformation constitutive model describing the tissue mechanical behavior, in combination with the appropriate kinematics for the multiple tissue components, and experimental data of a relevant tissue application. An excellent example is the urinary bladder wall (UBW), which undergoes profound remodeling in response to different pathologies, such as spinal cord injury (SCI). The overall objective of this dissertation was to develop a morphologically-driven, multi-phase constitutive model that would allow for separate investigation of the contribution of individual tissue components to the tissue-level remodeling process. As a first step, a constitutive model was developed of UBW extracellular matrix (ECM). Removing the smooth muscle cells from UBW tissue via decellularization allowed for the separate mechanical and structural investigation of UBW ECM. It was shown that the presence of de novo produced elastin in the UBW ECM post-SCI induced, indirectly, a distinct mechanical behavior with higher compliance, allowing for a higher overall extensibility of the post-SCI UBW and increased bladder storage capacity. The ECM constitutive model was extended and modified to be able to apply it to a multi-component tissue with individual model components existing in different reference states. Parameters were determined from biaxial mechanical data of decellularized and intact UBW tissue using a step-wise fitting approach implemented in MATLAB. As an initial step towards a theoretical G&R framework, a parametric analysis was performed to investigate if observed mechanical changes in post-SCI UBW were due to changes in morphology or intrinsic constituent properties. The developed model has the potential to explain underlying remodeling mechanisms of individual constituents in muscular tissues in several pathologies (e.g. UBW post-SCI), and predict remodeling events in a tissue engineering setting of muscular tissues.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairSacks, Michael Smsacks@pitt.eduMSACKS
Committee MemberRobertson, Anne Mrbertson@pitt.eduRBERTSON
Committee MemberTai, Changfengcftai@pitt.eduCFTAI
Committee MemberDebski, Richard Egenesis1@pitt.eduGENESIS1
Committee MemberAbramowitch, Steven Dsdast9@pitt.eduSDAST9
Date: 30 September 2010
Date Type: Completion
Defense Date: 9 July 2010
Approval Date: 30 September 2010
Submission Date: 16 July 2010
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: constitutive model; contiuum mechanics; remodeling; spinal cord injury; urinary bladder
Other ID:, etd-07162010-163428
Date Deposited: 10 Nov 2011 19:51
Last Modified: 15 Nov 2016 13:46


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