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Published on: March 22, 2024
Cycle-dependent matrix remodeling gene expression response in fatigue-loaded rat patellar tendons
Hui B Sun1, Nelly Andarawis-Puri, Yonghui Li
1Leni and Peter W. May Department of Orthopaedics, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1188, New York, New York 10029, USA.
Summary
Different fatigue loading cycles impact patellar tendon gene expression. High-cycle loading promotes repair, while low-cycle loading suggests an adaptive hypertrophic response, differing from acute injury.
Area of Science:
- Biomedical Engineering
- Molecular Biology
- Orthopedics
Background:
- Patellar tendon injuries often result from repetitive sub-failure fatigue loading.
- Understanding the molecular response to different loading patterns is crucial for tendon health and injury prevention.
Purpose of the Study:
- To investigate the differential gene expression profiles in patellar tendons subjected to low-cycle (100) versus high-cycle (7,200) fatigue loading.
- To compare these responses with an acute injury model (lacerated tendons).
Main Methods:
- Utilized an established in vivo patellar tendon model.
- Quantified gene expression of matrix remodeling factors (MMPs, TIMPs, collagens) via real-time RT-PCR at 1 and 7 days post-loading.
- Included lacerated tendons as an acute injury control.
Main Results:
- High-cycle loading upregulated TIMP-1, TIMP-2, Col3a1, Col5a1, and MMP-2, while downregulating TIMP-4, MMP-13, and MMP-14, indicating repair/remodeling.
- Low-cycle loading upregulated MMP-2, MMP-3, MMP-13, Col12a1, TIMP-1, TIMP-2, TIMP-3, Col3a1, and Col1a1, suggesting a hypertrophic (adaptive) response.
- Lacerated tendons exhibited an acute wound response with widespread gene upregulation.
Conclusions:
- Distinct molecular responses occur in patellar tendons under different sub-failure fatigue loading conditions.
- High-cycle loading appears to initiate repair, whereas low-cycle loading may drive adaptation, highlighting mechanisms for healthy versus damaging responses.
