Aging Aggravates the Progression of Muscle Degeneration After Rotator Cuff Tears in Mice.

Purpose: The purpose of this study was to evaluate the impact of aging on muscle degeneration after rotator cuff tear (RCT) in mice.

Methods: Young (12-week-old) and aged (50-to-60-week-old) female C57BL/6 mice were used (n = 29 for each group). The rotator cuff was transected, and the proximal humerus was removed to induce degeneration of the rotator cuff muscles.

Retinoic Acid Receptor Agonists Suppress Muscle Fatty Infiltration in Mice.

Background: The infiltration of fat tissue into skeletal muscle, a condition referred to as muscle fatty infiltration or fatty degeneration, is regarded as an irreversible event that significantly compromises the motor function of skeletal muscle.

Purpose: To investigate the effect of retinoic acid receptor (RAR) agonists in suppressing the adipogenic differentiation of fibroadipogenic progenitors (FAPs) in vitro and fatty infiltration after rotator cuff tear in mice.

Study Design: Controlled laboratory study.

Reproducibility of the modified Neer classification defining displacement with respect to the humeral head fragment for proximal humeral fractures.

Background: Although the Neer classification is widely used for the assessment of proximal humeral fractures, its reproducibility has been challenged. The purpose of this study was to evaluate the reproducibility of the conventional Neer classification and a modified classification that defined fracture displacement with respect to the humeral head fragment.

Methods: The fracture patterns in 80 cases of proximal humeral fractures were independently assessed by 6 observers.

Granulocyte-colony stimulating factor enhances load-induced muscle hypertrophy in mice.

Granulocyte-colony stimulating factor (G-CSF) is a cytokine crucially involved in the regulation of granulopoiesis and the mobilization of hematopoietic stem cells from bone marrow. However, emerging data suggest that G-CSF exhibits more diverse functions than initially expected, such as conferring protection against apoptosis to neural cells and stimulating mitogenesis in cardiomyocytes and skeletal muscle stem cells after injury. In the present study, we sought to investigate the potential contribution of G-CSF to the regulation of muscle volume.

Inhibition of PDGFR signaling prevents muscular fatty infiltration after rotator cuff tear in mice.

Fatty infiltration in muscle is often observed in patients with sizable rotator cuff tear (RCT) and is thought to be an irreversible event that significantly compromises muscle plasticity and contraction strength. These changes in the mechanical properties of the affected muscle render surgical repair of RCT highly formidable. Therefore, it is important to learn more about the pathology of fatty infiltration to prevent this undesired condition.

Generation and characterization of a novel shoulder contracture mouse model.

Frozen shoulder is a relatively common disorder that leads to severe pain and stiffness in the shoulder joint. Although this disorder is self-limiting in nature, the symptoms often persist for years, resulting in severe disability. Recent studies using human specimens and animal models have shown distinct changes in the gene expression patterns in frozen shoulder tissue, indicating that novel therapeutic intervention could be achieved by controlling the genes that are potentially involved in the development of frozen shoulder.