The rat as a novel model for chronic rotator cuff injuries

Area of Science:

• Orthopaedics
• Regenerative Medicine
• Animal Models

Background:

• Chronic rotator cuff injuries (CRCIs) pose significant challenges in orthopaedics.
• Existing animal models for CRCIs lack reliability for research.
• Developing effective therapeutic strategies requires a suitable preclinical model.

Purpose of the Study:

• To establish and validate a novel rat model for chronic rotator cuff injuries (CRCIs).
• To characterize the pathological, behavioral, and molecular changes in this new CRCI model.
• To provide a reliable platform for evaluating future therapeutic interventions for rotator cuff repair.

Main Methods:

• Sixty Wistar rats underwent surgery for persistent subacromial impingement, with 30 receiving a 3D-printed PEEK implant (experimental group) and 30 a sham procedure.
• Histological, behavioral, MRI, and gene expression analyses were conducted after 2 and 8 weeks.
• Inflammatory pain-related gene expression (IL-1β, COX-2, TNF-α, NGF) was assessed.

Main Results:

• The experimental group exhibited compensatory gait patterns and developed pathological changes consistent with CRCIs after 8 weeks.
• MRI revealed abnormal supraspinatus tendon-to-bone junctions, tendon contraction, and signal intensity changes.
• Significant nighttime upregulation of IL-1β and COX-2 was observed in the experimental group compared to the sham group.

Conclusions:

• This novel rat model accurately replicates key pathological and molecular features of human chronic rotator cuff injuries.
• The model demonstrates altered gait, distinct histological findings, and specific inflammatory gene expression patterns.
• It offers a cost-effective and reliable preclinical tool for advancing tissue engineering and therapeutic strategies for rotator cuff repair.