Susan Jeno

Date of Award

12-22-1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Jody Rada

Abstract

Characterization of the biochemical structure of cartilage and tendon has been a focus of research in recent decades, but little is known about joint capsules. Classified as dense irregular connective tissue, the extracellular matrix of joint capsules contains water, collagen, and non-collagenous macromolecules including proteoglycans (PGs), and glycoproteins, but specific biochemical composition of human glenohumeral joint capsule has not been elucidated. Structure and function are intimately related, therefore, understanding the structure of the capsule is essential to analysis of its function. The purpose of this research study was to isolate and characterize the PG content and relative proportion of each PG present in different regions of the glenohumeral joint capsule. Eight glenohumeral joint capsules from five donors were used for this study, each being divided into anterior, superior, posterior, and labral regions. The tissue was minced, extracted, and separated by ion- and molecular-sieve chromatography. The PGs were isolated and characterized by dimethylmethlyene blue assay and liquid scintillation counting. PG peak fractions were pooled and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after digestion with specific glycosidases. PG core proteins were identified by Western blot analysis using antisera specific to aggrecan, decorin and biglycan. The relative proportion of PGs in each region was determined by densitometric analysis of the Western blots. Results indicated the labrum contained the largest percentage of aggrecan, but all regions demonstrated the presence of this cartilage-associated PG. Decorin and biglycan were present in all regions of the joint capsule with the relative percentage varying by region. These results indicated that all regions of the glenohumeral joint capsule contain similar types of PGs, but vary in relative proportion of the PGs present. Comparisons of normal and hyperlax samples showed a higher relative percentage of aggrecan in the labrum, anterior, and superior regions of the hyperlax capsules. The relative percentages of decorin and biglycan were greater in anterior and posterior regions of normal capsules and in superior and labral regions of hyperlax tissue. Further research is warranted on the PG content of glenohumeral joint capsules across the life continuum and under different pathological conditions to better understand the structure and function of this essential joint component.

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