Dataset Information

Tendon properties remain altered in a chronic rat rotator cuff model.

ABSTRACT:

Background

Chronic rotator cuff tears are often associated with pain or poor function. In a rat with only a detached supraspinatus tendon, the tendon heals spontaneously which is inconsistent with how tears are believed to heal in humans.

Questions/purposes

We therefore asked whether a combined supraspinatus and infraspinatus detachment in the rat would fail to heal and result in a chronic injury in the supraspinatus tendon.

Methods

We acutely detached the supraspinatus and infraspinatus tendons in a rat model. At 4, 8, and 16 weeks post-detachment, biomechanical testing, collagen organization, and histological grading were evaluated for the detached supraspinatus and infraspinatus tendons and compared to controls.

Results

In the detached supraspinatus tendon, area and percent relaxation were increased at all time points while the modulus and stiffness were similar to those of controls at 4 and 8 weeks. Collagen disorganization increased at late time points while cellularity increased and cells were more rounded in shape. In the detached infraspinatus tendon, area and percent relaxation were also increased at late time points. However, the modulus values initially decreased followed by an increase in both modulus and stiffness at 16 weeks compared to control. In the detached infraspinatus, we also observed a decrease in collagen organization at all time points and increased cellularity and a more rounded cell shape.

Conclusions

Due to the ongoing changes in mechanics, collagen organization and histology in the detached supraspinatus tendon compared to control animals at 16 weeks, this model may be useful for understanding the human chronic tendon tear.

Clinical relevance

This rat rotator cuff chronic model can be used to test hypotheses regarding injury and repair mechanisms that cannot be addressed in human patients or in cadaveric studies.

SUBMITTER: Dourte LM

PROVIDER: S-EPMC2865621 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Publications

Tendon properties remain altered in a chronic rat rotator cuff model.

Dourte LeAnn M LM Perry Stephanie M SM Getz Charles L CL Soslowsky Louis J LJ

Clinical orthopaedics and related research 20100601 6

<h4>Background</h4>Chronic rotator cuff tears are often associated with pain or poor function. In a rat with only a detached supraspinatus tendon, the tendon heals spontaneously which is inconsistent with how tears are believed to heal in humans.<h4>Questions/purposes</h4>We therefore asked whether a combined supraspinatus and infraspinatus detachment in the rat would fail to heal and result in a chronic injury in the supraspinatus tendon.<h4>Methods</h4>We acutely detached the supraspinatus and ...[more]

PMID: 20049569

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Project description:Myosteatosis is the pathological accumulation of lipid that occurs in conjunction with atrophy and fibrosis following skeletal muscle injury or disease. Little is known about the mechanisms by which lipid accumulates in myosteatosis, but many studies have demonstrated the degree of lipid infiltration negatively correlates with muscle function and regeneration. Our goal was to identify biochemical pathways that lead to muscle dysfunction and lipid accumulation in injured rotator cuff muscles, a model that demonstrates severe myosteatosis. Adult rats were subjected to a massive tear to the rotator cuff musculature. After a period of either 0 (healthy control), 10, 30, or 60 days, muscles were prepared for RNA sequencing, shotgun lipidomics, metabolomics, biochemical measures, electron microscopy, and muscle fiber contractility. Following rotator cuff injury, there was a decrease in muscle fiber specific force production that was lowest at 30d. There was a dramatic time dependent increase in triacylglyceride content. Interestingly, genes related to not only triacylglyceride synthesis, but also lipid oxidation were largely downregulated over time. Using bioinformatics techniques, we identified that biochemical pathways related to mitochondrial dysfunction and reactive oxygen species were considerably increased in muscles with myosteatosis. Long chain acyl-carnitines and L-carnitine, precursors to beta-oxidation, were depleted following rotator cuff tear. Electron micrographs showed injured muscles displayed large lipid droplets within mitochondria at early time points, and an accumulation of peripheral segment mitochondria at all time points. Several markers of oxidative stress were elevated following rotator cuff tear. The results from this study suggest that the accumulation of lipid in myosteatosis is not a result of canonical lipid synthesis, but occurs due to decreased lipid oxidation in mitochondria. A failure in lipid utilization by mitochondria would ultimately cause an accumulation of lipid even in the absence of increased synthesis. Further study will identify whether this process is required for the onset of myosteatosis.

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Dataset Information

Tendon properties remain altered in a chronic rat rotator cuff model.

Background

Questions/purposes

Methods

Results

Conclusions

Clinical relevance

Publications

Tendon properties remain altered in a chronic rat rotator cuff model.

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