The role of ATP in tendon response to stress

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  • March 22, 2019
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  • Fox, Ann Marie
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
Abstract
  • Tendon cells coordinate activities such as force transmission, cell division, and matrix remodeling to maintain tissue function and integrity. This is especially evident in the response to high mechanical load demands. Signaling to load and the subsequent feedback on gap junction expression and function are likely modulated by ATP, mechanical load, and other mediators. Tenocytes secrete ATP through connexin hemichannels as well as the cystic fibrosis transmembrane regulator channel capable of nucleotide release in tendon cells. The primary goal for this dissertaiton was to define the intersecting pathways of ATP-mediated intercellular signaling in tendons responding to stress. Use of transgenic mice with specific purinoceptor deficits were used to study tenocyte responses to mechanical load. Data supports that stimulation of ATP-activated P2Y2 receptors may amplify a load signal while activation of a P2Y1 purinoreceptor through ADP may dampen a load signal. Wt, P2Y1( -/-), and P2Y2(-/-) cells were subjected to mechanical indentation with a micropipette as well as pharmacological adds to examine select downstream response variations that highlight the interplay between P2Y1 and P2Y2 purinoreceptors. The studies help to unravel the complex and interdependent pathways that regulate responses to load. To investigate the downstream consequences of the altered response communication, mechanical testing of wt and knockout mouse tendons and detailed microscopy studies were performed. This demonstrated the mechanical implications attributable to the omitted ATP and ADP receptors, demonstrating a markedly decreased strength in P2Y1(-/-) tendons. Finally, immunohistochemistry was performed to elucidate the role of connexins in the altered signaling response of purinoreceptor null tenocytes. Images show a both punctate and diffuse cytosolic staining in all cells. However, the degree of cytosolic staining in P2Y2(-/-) cells indicates a potential gap junctional assembly or trafficking problem. Through results of this dissertation, the scientific community will gain a better understanding of the importance of purinoreceptors in the mechanical sensitivity of tendon cells. The information resulting from these experiments may also open doors for pharmaceutical therapy for damaged or deteriorating tendons and will enhance our knowledge of purine receptor interplay that is essential for in vivo maintenance and ex vivo production of tendon tissue.
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  • In Copyright
Advisor
  • Banes, Albert J.
Degree granting institution
  • University of North Carolina at Chapel Hill
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  • Open access
Date uploaded
  • October 19, 2010

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