High-Resolution Magic-Angle Spinning and Nuclear Magnetic Resonance Relaxometry Investigations of Tendon Öffentlichkeit

Abstract

Tendons are an important load-bearing tissue in the musculoskeletal system, with a matrix composition closely associated with its functional status. The extracellular matrix of tendon is composed of collagen fibrils and non-collagenous components consisting of proteoglycans, lipids, and metabolites. Recent work using ultrashort echo time magnetic resonance imaging (UTE-MRI) has reported chemical shifts consistent with proteoglycan and lipid chemical groups. However, there is a lack of prior nuclear magnetic resonance (NMR) studies available to interpret these signals. High-resolution magic-angle spinning (HR-MAS) NMR and NMR relaxometry are used to determine the origin of the chemical shifts and biases in the estimates of relaxation measurements from UTE imaging. This study uses one-dimensional and two-dimensional HR-MAS NMR to characterize tendon matrix composition, providing a clearer interpretation of in vivo UTE-MRI chemical shift signals and their relation to tendon matrix integrity. This study also utilizes NMR relaxometry to explore water dynamics in tendon, allowing for a better interpretation of relaxation signals acquired from UTE-MRI. Five ex vivo samples of both ovine Achilles and rat rotator cuff tendon are obtained. A Bruker Avance III spectrometer at 400 MHz is used to acquire data and MATLAB (MathWorks, USA) and Mestrenova (Mestrelabs, Spain) are used to process and analyze data. Peak assignments are made using prior literature and the HMDB. Analysis of the spectra obtained from HR-MAS NMR shows peaks attributed to biomolecules and residues comprising collagen fibrils and non-collagenous matrix components, allowing for the determination of the origin of chemical shift signals in UTE-MRI. Analysis of the spectra obtained from NMR relaxometry shows two distinct pools of water in tendon that are in chemical exchange, providing a clearer interpretation of relaxation measurements from UTE-MRI. It is concluded that both methods help to better interpret chemical shift and relaxation signals obtained from UTE-MRI of tendon.

Table of Contents

Table of Contents

I. Introduction............................................................................................................................ 3

a. Ultrashort echo time (UTE) imaging................................................................................. 3

b. Objectives of the study ........................................................................................................ 4

c. NMR Spectroscopy .............................................................................................................. 5

d. Tendon structure and function .......................................................................................... 7

e. High-Resolution Magic-Angle Spinning NMR Spectroscopy ...................................... 11

f. 2D NMR Relaxometry....................................................................................................... 12

II. Methods ................................................................................................................................ 14

a. Non-MAS ............................................................................................................................ 14

i. Sample handling............................................................................................................ 14

ii. Experiments .................................................................................................................. 14

b. HR-MAS ............................................................................................................................. 15

i. Sample handling............................................................................................................ 15

ii. Experiments and Data Acquisition ............................................................................... 15

iii. Processing and peak assignments ................................................................................. 17

c. NMR relaxometry.............................................................................................................. 17

i. Sample handling............................................................................................................ 17

ii. Experiment.................................................................................................................... 18

iii. Data acquisition ............................................................................................................ 18

iv. Processing ..................................................................................................................... 19

III. Results .............................................................................................................................. 19

a. Non-MAS spectroscopy..................................................................................................... 19

b. HR-MAS spectroscopy ...................................................................................................... 20

i. Ovine Achilles tendon................................................................................................... 20

ii. Rat rotator cuff tendon .................................................................................................. 23

c. NMR relaxometry .............................................................................................................. 25

IV. Discussion ........................................................................................................................ 29

a. Ovine Achilles tendon ....................................................................................................... 29

b. Rat rotator cuff tendon ..................................................................................................... 31

c. Comparison of ovine Achilles tendon to rat rotator cuff tendon................................. 31

d. NMR relaxometry ......................................................................................................... 33

Conclusion............................................................................................................................ 34

References ........................................................................................................................ 39

VII. Supplemental Figures ...................................................................................................... 44

Supplementary Figure 1. 2D COSY spectrum of ovine Achilles tendon. ........................... 44

Supplementary Figure 2. 2D HSQC spectrum of rat rotator cuff tendons. ....................... 44

Supplementary Figure 3. 2D COSY spectrum of rat rotator cuff tendon.......................... 45

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Nuclear Engineering, Biomedical
Stichwort	Magnetic Resonance Imaging HR-MAS NMR Spectroscopy
Committee Chair / Thesis Advisor	David Reiter, Emory University
Committee Members	Candace Fleischer, Emory University John Heemstra, Emory University

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