Tendon development is the result of multiple regulatory pathways converging to produce and maintain a structure that results in a functional tendon. The overall goal of this application is to define the mechanisms that regulate the sequential events in tendon extracellular matrix assembly. Defining the regulatory pathways essential for normal development, growth and maturation will provide the basis for understanding tendon development. In addition, tendons have a limited capacity for regeneration and developmental paradigms may be applied to promote regenerative healing as well as in the creation of treatment modalities that shift fibrotic repair toward regeneration and restoration of full biomechanical function. Also, this work will provide milestones needed to develop stem cell therapies and evaluate bioengineered scaffolds. Finally, the underlying molecular pathophysiology of connective tissue disorders, e.g., classic Ehlers Danlos Syndrome, a newly defined collagen XII related myopathy, is addressed. This provides a foundation for future translational studies. Our general hypothesis is that tendon matrix assembly is a hierarchal process requiring specific regulatory interactions at each level. This application addresses three key regulatory steps in the development of tendon structure and function: (1) fibril nucleation at the tenocyte surface;(2) stabilization of immature protofibrilsand assembly into fibers;and (3) fibril growth generating mature fibrils. The following hypotheses wil be addressed: (1) Collagens V/XI isoforms regulate tendon fibril assembly involving interactions with collagen I at the tenocyte surface that control the number of protofibrils nucleated, their initial diameter, and influences organization of the developing matrix. (2) Protofibril organizatio and assembly into fibers is mediated through collagens XII and XIV involving coordinate interactions of collagen XIV and collagen XII isoforms. (3) Small leucine-rich proteoglycans (SLRPs) regulate fibril growth during tendon development through synergistic interactions across classes: decorin and biglycan with lumican and fibromodulin.
The specific aims of this application are to:
(Aim 1) elucidate the mechanisms involving collagen V/XI isoforms in the regulation of protofibril nucleation and initial assembly;
(Aim 2) define the coordinate regulatory roles of FACIT collagens XII and XIV in organization of protofibrils during deposition into fibers and fiber assembly;
and (Aim 3) elucidate the mechanisms involving small leucine-rich proteoglycans (SLRPs) in the coordinate regulation of tendon fibril growth and maturation. Existing and newly created mouse models null for a specific matrix molecules will be utilized to analyze the regulation of tendon development using biochemical, immuno-chemical, molecular, morphological and functional approaches. Definition of the regulatory steps in tendon-specific matrix assembly provides a developmental paradigm for understanding of tendon repair versus regeneration, pathobiology, and the manipulation of these processes.

Public Health Relevance

In sports, at work, or due to aging processes, tendon injuries cause significant pain and disability, resulting in enormous healthcare costs, loss of work, and a decrease in the quality of life. The focus of this application is to elucidate the mechanisms regulating tendon extracellular matrix assembly during development, growth and maturation. Tendons have a limited capacity for regeneration and developmental paradigms may be applied to promote regenerative healing and in the creation of treatment modalities that shift fibrotic repair toward regeneration and restoration of full function. Defining the mechanisms required for intercalated growth of fibrils and fibers will provide insight into repair/reintegration at bone-tendon and myotendonous interfaces providing a foundation for design of new therapeutic interventions. In addition, our data will provide milestones needed to develop stem cell therapies and evaluate bioengineered scaffolds. Furthermore, our work provides a foundation for understanding the functional defects observed in musculoskeletal diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR044745-18
Application #
8727253
Study Section
Skeletal Biology Structure and Regeneration Study Section (SBSR)
Program Officer
Tyree, Bernadette
Project Start
1997-09-01
Project End
2017-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
18
Fiscal Year
2014
Total Cost
$329,647
Indirect Cost
$109,147
Name
University of South Florida
Department
Pathology
Type
Schools of Medicine
DUNS #
069687242
City
Tampa
State
FL
Country
United States
Zip Code
33612
Mienaltowski, Michael J; Birk, David E (2014) Mouse models in tendon and ligament research. Adv Exp Med Biol 802:201-30
Mienaltowski, Michael J; Birk, David E (2014) Structure, physiology, and biochemistry of collagens. Adv Exp Med Biol 802:5-29
Mienaltowski, Michael J; Adams, Sheila M; Birk, David E (2014) Tendon proper- and peritenon-derived progenitor cells have unique tenogenic properties. Stem Cell Res Ther 5:86
Zou, Yaqun; Zwolanek, Daniela; Izu, Yayoi et al. (2014) Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice. Hum Mol Genet 23:2339-52
Chiquet, Matthias; Birk, David E; Bönnemann, Carsten G et al. (2014) Collagen XII: Protecting bone and muscle integrity by organizing collagen fibrils. Int J Biochem Cell Biol 53:51-4
Pan, Te-Cheng; Zhang, Rui-Zhu; Arita, Machiko et al. (2014) A mouse model for dominant collagen VI disorders: heterozygous deletion of Col6a3 Exon 16. J Biol Chem 289:10293-307
Smith, Simone M; Zhang, Guiyun; Birk, David E (2014) Collagen V localizes to pericellular sites during tendon collagen fibrillogenesis. Matrix Biol 33:47-53
Pan, Te-Cheng; Zhang, Rui-Zhu; Markova, Dessislava et al. (2013) COL6A3 protein deficiency in mice leads to muscle and tendon defects similar to human collagen VI congenital muscular dystrophy. J Biol Chem 288:14320-31
Mienaltowski, Michael J; Adams, Sheila M; Birk, David E (2013) Regional differences in stem cell/progenitor cell populations from the mouse achilles tendon. Tissue Eng Part A 19:199-210
Chen, Shoujun; Birk, David E (2013) The regulatory roles of small leucine-rich proteoglycans in extracellular matrix assembly. FEBS J 280:2120-37

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