Torn tendons and ligaments often require surgical repair to their bony insertions. A large percentage of these repairs have poor outcomes; for example, up to 94% of surgical rotator cuff repairs fail. At the root of these failures is the fundamental challenge of attaching two materials, tendon and bone, with vastly different mechanical properties. The natural tendon-to-bone insertion involves a number of mechanisms that create a strong and tough attachment. Unfortunately, this tissue degrades with age, and is not regenerated in healing. Our overall goal is to develop a multiscale model of the tendon-to-bone insertion that will lead to (1) tissue toughness metrics that can guide clinical decisions for elderly patients, and (2) foundations for future tissue- engineered surgical grafts. Based on our previous work, we hypothesize that toughening and strengthening mechanisms exist across several length scales, and that these are most pronounced in a the compliant region of tissue between tendon and bone that does not regrow in the healing setting. We will characterize the stiffening, strengthening, and toughening mechanisms that contribute to this resilience across scales in natural and pathologic tendon-to-bone insertions as a function of age. The work involves three aims: (1) At the nanoscale, elemental spatial maps will be acquired using transmission electron microscopy electron energy loss spectroscopy to determine mineral and collagen distributions across the insertion. Individual mineralized collagen fibrils will be mechanically tested; we have recently performed such tests on mammalian collagen fibrils. In silico experiments will identify and quantify deformation mechanisms underlying the toughness of mineralized collagen fibrils. (2) At the microscale, synchrotron X-ray diffraction, Raman spectroscopy, and polarized light microscopy will be used to determine the distributions of mineral content and collagen orientation. Mechanics of the tendon-to-bone insertion will be examined with micrometer resolution using a confocal microscope-mounted testing frame. In silico, nonlinear homogenization methods will be used to incorporate mineralized collagen fiber mechanics from Aim 1 into constitutive models of connected networks of mineralized and cross-linked collagen fibers. (3) At the millimeter scale, the 3D inter-digitation geometry of tendon and bone will be determined using phase contrast X-ray computed tomography and the mechanics of the tendon-to-bone insertion will be determined using tissue level tensile tests. In silico experiments combining tendon-to-bone geometry with microscale tissue models will produce hypotheses of mechanisms underlying tendon-to-bone insertion toughness. Mechanical fields will be passed down hierarchical model levels to evaluate collagen fibril response to predicted physiologic and pathologic tendon-to-bone insertion loading. Together, these models and data form the foundation of future tissue engineering efforts and efforts to identify clinically useful metrics of tendon-to-bone tissue health.

Public Health Relevance

Tendon-to-bone integration, required for successful rotator cuff repair and anterior cruciate ligament reconstruction, is rarely achieved in clinical practice (e.g., repairs of massive rotator cuff tears have a 94% failure rate). At the root of these difficulties is the challenge of attaching two vastly different materials: stiff bone and compliant tendon. Our aim is to create multi-scale models of the natural tendon-to-bone insertion in order to guide clinical care decisions and tissue engineering efforts to recapitulate this system at healing insertions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Research Project--Cooperative Agreements (U01)
Project #
5U01EB016422-03
Application #
8913701
Study Section
Special Emphasis Panel (ZEB1-OSR-C (M1))
Program Officer
Peng, Grace
Project Start
2013-08-20
Project End
2018-07-31
Budget Start
2015-08-01
Budget End
2016-07-31
Support Year
3
Fiscal Year
2015
Total Cost
$466,496
Indirect Cost
$98,867
Name
Washington University
Department
Orthopedics
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Babaei, Behzad; Velasquez-Mao, A J; Pryse, Kenneth M et al. (2018) Energy dissipation in quasi-linear viscoelastic tissues, cells, and extracellular matrix. J Mech Behav Biomed Mater 84:198-207
Depalle, Baptiste; Duarte, Andre G; Fiedler, Imke A K et al. (2018) The different distribution of enzymatic collagen cross-links found in adult and children bone result in different mechanical behavior of collagen. Bone 110:107-114
Zhu, Hongyuan; Yang, Xiaoxiao; Genin, Guy M et al. (2018) The relationship between thiol-acrylate photopolymerization kinetics and hydrogel mechanics: An improved model incorporating photobleaching and thiol-Michael addition. J Mech Behav Biomed Mater 88:160-169
Liu, Julia; Das, Debashish; Yang, Fan et al. (2018) Energy dissipation in mammalian collagen fibrils: Cyclic strain-induced damping, toughening, and strengthening. Acta Biomater 80:217-227
Linderman, Stephen W; Golman, Mikhail; Gardner, Thomas R et al. (2018) Enhanced tendon-to-bone repair through adhesive films. Acta Biomater 70:165-176
Shakiba, Delaram; Babaei, Behzad; Saadat, Fatemeh et al. (2017) The fibrous cellular microenvironment, and how cells make sense of a tangled web. Proc Natl Acad Sci U S A 114:5772-5774
Zitnay, Jared L; Li, Yang; Qin, Zhao et al. (2017) Molecular level detection and localization of mechanical damage in collagen enabled by collagen hybridizing peptides. Nat Commun 8:14913
Cheng, Bo; Lin, Min; Huang, Guoyou et al. (2017) Cellular mechanosensing of the biophysical microenvironment: A review of mathematical models of biophysical regulation of cell responses. Phys Life Rev 22-23:88-119
Lipner, Justin; Boyle, John J; Xia, Younan et al. (2017) Toughening of fibrous scaffolds by mobile mineral deposits. Acta Biomater 58:492-501
Babaei, Behzad; Velasquez-Mao, Aaron J; Thomopoulos, Stavros et al. (2017) Discrete quasi-linear viscoelastic damping analysis of connective tissues, and the biomechanics of stretching. J Mech Behav Biomed Mater 69:193-202

Showing the most recent 10 out of 40 publications