How Long Should We Wait to Create the Goutallier Stage 2 Fatty Infiltrations in the Rabbit Shoulder for Repairable Rotator Cuff Tear Model?

Abstract

Background. Significant proportion of rotator cuff tears (RCTs) in clinical field are of a kind of repairable tear wherein the degree of fatty infiltration is of Goutallier stage 1 or stage 2. Therefore, the animal model, showing similar fatty infiltration, seems preferable for researches. The purpose of this study is to find out the proper time frame in which there is Goutallier stage 1 or stage 2 fatty infiltration in the rabbit RCT model for the research of repairable RCT in humans. Methods. Supraspinatus tendon tears were created in forty male New Zealand white rabbits at their right shoulder (n= 8 for each group), and a sham operation on the left shoulder. Rabbits were divided into five groups (2nd, 4th, 6th, 8th, and 12th weeks). Specimens were harvested from the central portion of the supraspinatus muscle for haematoxylin and eosin (H &E) staining, followed by histological and Goutallier grading evaluation. Results are expressed as mean ± standard deviation by Sigma Plot software (version 7.0). Results. At two weeks, mainly lipoblasts were observed around the muscle fibers, and at four weeks these lipoblasts were replaced by mature adipocytes with fatty infiltration amount (2.13 ± 0.35). The degree of muscle atrophy was (1.50 ± 0.53) at four weeks compared to sham group (0.88 ± 0.64) with significant difference (p < 0.05). The inflammatory process appeared as two phases. At two weeks, it was increased with grading value (1.88 ± 0.35). However, in the four-week group, it showed a sharp decrease (0.50 ± 0.53). At six weeks, inflammation reappeared to increase (1.13 ± 0.83). Then, a gradual decline appeared at eight weeks (0.88 ± 0.83) and at 12 weeks (0.50 ± 0.92). Conclusions. At two and four weeks, both fat distribution in rabbit supraspinatus muscles and Goutallier grading scale mostly appeared as grade 2. Therefore, we can consider four weeks to be a suitable period for making a repairable RCT animal model for the human research, considering the early acute tissue reaction at 2 weeks after the tendon tears.

Progression of muscle loss and fat accumulation in a rabbit model of rotator cuff tear

“…Interfascicular fat was significantly increased as early as 1 week after tenotomy, while intrafascicular fat content fluctuated with peaks at 1, 4, and 16 weeks. Interestingly, this pattern is the inverse of inflammatory cell infiltration, which appears to have bimodal peaks at 2 and 6–8 weeks in this model 27 . Overall, inter‐ or intrafascicular fat quantification appears to be more sensitive to early changes than the fat percentage of CSA, which did not reach a statistically significant increase within time point groups until 16 weeks.…”

Engineered Cell Sheets for the Effective Delivery of Adipose-Derived Stem Cells for Tendon-to-Bone Healing

“…Subsequently, animals were allowed free cage activity for 2 weeks to complete the model of a chronic RCT. 1…”

“…Subsequently, animals were allowed free cage activity for 2 weeks to complete the model of a chronic RCT. 1 Repair was performed after 2 weeks; anesthesia and postoperative medications used were the same as those in the previous surgical procedure. The torn supraspinatus tendon and drain were confirmed using the same approach used when inducing the RCT, and the drain was subsequently removed.…”

Engineering Musculoskeletal Grafts for Multi-Tissue Unit Repair: Lessons From Developmental Biology and Wound Healing

“…This similarity in shoulder anatomy makes the rat ideal for modeling rotator cuff diseases such as subacromial impingement, whereby friction between the rotator cuff tendons and the coracoacromial arch during muscular movement leads to pain and reduced range of joint motion. In rabbits, detachment of the rotator cuff tendon(s) resulted in prominent fatty degeneration of skeletal muscle ( Abdou et al, 2019 ), and has been used to simulate chronic rotator cuff tears to study the effect of hypercholesterolemia on skeletal muscle fatty degeneration and bone-to-tendon healing. Indeed, use of such models identified αSMA-positive cells as primary contributors to scar formation ( Moser et al, 2020 ), which may pave the way for identification of new therapeutic targets.…”