A MULTISCALE APPROACH TO BIOINSTRUCTIVE SYNTHETIC SCAFFOLD DESIGN TO BETTER UNDERSTAND THE TENDON CELL NICHE
Open Access
- Author:
- Banik, Brittany Lynn
- Graduate Program:
- Bioengineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 28, 2017
- Committee Members:
- Justin Lee Brown, Dissertation Advisor/Co-Advisor
Justin Lee Brown, Committee Chair/Co-Chair
Jian Yang, Committee Member
Peter J Butler, Committee Member
Chistopher Niyibizi, Outside Member
Daniel J Hayes, Committee Member - Keywords:
- tendon
tissue engineering
bioinstructive
electrospinning
stem cells
scaffold design
bioreactor - Abstract:
- It is well-known that the dynamic cell niche is composed of numerous physical, mechanical, and biochemical cues that create an instructive microenvironment and facilitate various cellular responses and activities. However, accelerating these cellular responses effectively and completely has been a reoccurring challenge amongst regenerative medicine researchers. Our bodies won’t last forever—organs wear out, parts are damaged, and time and overuse take their toll on tissue functionality. Regenerative medicine is a field that offers innovative solutions to repair, replace, and regenerate tissues. This project focuses specifically on the musculoskeletal field of tendon tissue engineering. Current “solutions” for tendon complications—autografts, allografts, xenografts, and synthetic prostheses—fall short of being completely restorative or therapeutically sound in terms of stability, biomechanics, biological integration, and cellular response. Additionally, there is a limited availability of allografts and autografts, suggesting a need for a better synthetic tendon and ligament graft. This dissertation seeks to utilize a novel scaffold synthesis technique to examine the synergy of scaffold geometry, fiber alignment and diameter, improved interface design, and mechanical stimulation to better understand the tendon cell niche. With the number of people requiring treatment for tendon, ligaments, or joint capsule injuries increasing each year, the poor healing capability of tendons, the significant pain and dysfunction associated with tendon injuries, and revision surgeries required due to failed tendon replacements, an improved graft option is necessary. To begin to address and understand this issue, a hierarchical approach was developed—nano:micro:macro. As such, the following relationships were defined: nano:cell (differentiation promoted by nanofibers), micro:tissue (scaffold architecture and desired anisotropic mechanics), and macro:body (tissue/neotissue formation enhanced by culturing in a bioreactor). The “nano” perspective investigated the utilization of different fiber sizes and alignments to augment or replace Growth Differentiation Factor 7, GDF7 (alias: BMP12). As such, techniques of RT-qPCR and RNA-Sequencing were used to determine if tendon-related genes of interest were positively expressed and, if so, with respect to which architectural feature or growth factor concentration the cells were presented. The “micro” viewpoint gave consideration to a novel design and synthesis of poly(ε-caprolactone) scaffolds that demonstrated mechanical suitability for tendon tissue engineering. Scaffolds of various patterns were stretched to failure in tensile testing. The toe regions and Young’s elastic moduli were determined with the goal to mimic natural tendon mechanics. Lastly, at the “macro” level, a bioreactor was constructed to simulate a more natural cell microenvironment by incorporating physiological, uniaxial, cyclic stretch. The use of a bioreactor provided information on how mechanical stimulation affects scaffold mechanics, collagen content, and tendon-like tissue development. This project provides significant design considerations to improve synthetic tendon replacement options by directing cell growth down the tendon lineage via bioinstructive architecture while maintaining anisotropic mechanical effectiveness.