1. PRELIMINARY STUDY IN CHARACTERIZING TISSUE GROWTH THROUGH RESIDUAL STRAIN Eunice Yi July 2009

2. Introduction  Tissue Engineering  Used to restore and maintain tissue/organ function  The Application  Pediatric Right Ventricular Outflow Tract (RVOT) replacements  The Problem  Body rejecting tissue, growth limitations  The Need  Thorough study of native tissue behavior  AIM  To characterize the pattern of residual strain in porcine pulmonary trunks (PT)

3. The Tissue Pulmonary Trunk Right Ventricle Sinotubular Junction Bifurcation Region Aorta

4. Tissue Preparation  Two rings cut  Sinotubular junction  Bifurcation  Microdots applied Annulus Sinotubular junction MPA Circumference RPA circumference Axial length measurement Bifurcation Ligamentum arteriosum

5. The Tests  Opening Angle/Stretch:  Images taken before and after tissue is cut  Flexural Test:  3-point bending  AC and WC Camera Container with medium Temp control Bending Beam Transverse Bar Tissue Sample

6. NO LOAD 1 st Cut ImageLast Image Taking Images

7. Calculations  ImageJ used to calculate OA and circumferential lengths  Circumferential Stretch  Residual Strain NO LOAD ZERO STRESS

8. OA and Circumferential Stretch Results  Sinotubular junction has greater residual strain than Bifurcation region  Correlation between OA and residual strain Sinus OA (in degrees) Bifurcation OA (in degrees) PAT 10143.961762.0137 PAT 1168.76270.8030 PAT 1285.794712.9927 PAT 1782.882749.2370 Average95.350431.2616 Sinus Bifurcation Sinus EBifurcation ES:B E Ratio PAT 100.90050.9808-0.0945-0.01904.9780 PAT 110.97750.9901-0.0223-0.00992.2581 PAT 120.98430.9921-0.0156-0.00781.9889 PAT 170.95590.9831-0.0431-0.01682.5693 Average0.95460.9865 SEM0.01900.0027 % Error1.99090.2754

9. Explaining the Results Sinus Bifurcation Sinus End Sample Bifurcation End Sample PAT 10PAT 11PAT 12PAT 17AverageSEM% Sinus t avg2.5262.2202.3802.1732.3250.0803.458 Bifurcation t avg1.8682.0801.9732.1662.0220.0653.202

10. Flexural Tests Against Curvature (AC) With Curvature (WC)

11. Flexure Test Results  Comparing against curvature (AC) and with curvature (WC) stiffness for bifurcation and sinus end samples

12. Possible Indication  Similar stiffness values may indicate isotropic properties throughout tissue layers Image: http://www.nature.com/nrm/journal/v8/n11/images/nrm2262-f5.jpg

13. Flexure Test Results  Comparing bifurcation, sinotubular junction, AC, and WC stiffness across all samples

14. Flexural Test Results  Comparing Bifurcation and Sinus End Effective Stiffness  

15. Conclusion and Future Research  Preliminary data is promising and rough trends may be seen  The significance of these trends is difficult to tell  More samples need to be tested  Expand test to see trend of residual strain over different aged samples  Study residual stress

16. Acknowledgements  The national BBSI program (http://bbsi.eeicom.com) is a joint initiative of the NIH-NIBIB and NSF-EEC, and the BBSI @ Pitt is supported by the National Science Foundation under Grant EEC-0234002  Dr. Michael Sacks for this great opportunity  Bahar Fata and Chad Eckert for their guidance and assistance  University of Pittsburgh