Nuclear Lamin A in Rotator Cuff Tear Margin Tenocytes: An Antiapoptotic and Cell Mechanostat Factor.
Abstract BackgroundThe network of intermediate filament proteins underlying the inner nuclear membrane forms the nuclear lamin. A and B-type lamins are the major components of the nuclear lamina. Lamins function in many nuclear activities. The role of lamin-A and transcription factors (NF-kB) as anti-apoptotic is well documented. Recently, lamin-A has also been considered as mechanosensor protein able to maintain nuclear integrity from mechanical insults. We aimed to verify how lamin-A expression varies in healthy cuff cells and in those with different sized tears where various mechanical stresses are present. MethodsForty-three patients with rotator cuff tear (RCT) [23M-20F, mean age (SD): 63.5 (6.1)] were enrolled. Tissue samples excised from the most medial point of tear margins were analyzed for lamin-A expression by immunohistochemistry. Controls were represented by samples obtained by seven healthy supraspinatus tendons excised from patients submitted to reverse shoulder prosthesis implant [3M-4F, mean age (SD): 67.1 (6.3)]. The intensity of staining was graded, and an H-score was assigned. Statistical analysis was performed.ResultsOur study revealed a moderate intensity of lamin-A in the healthy cuff tendons, a higher expression of this protein in the small tears, and a significant decrease of lamin-A with increasing tear size (p<0.0001).ConclusionsOur study emphasizes the importance of early repair of small RCTs since nuclear stability is maintained, and the cellular function is protected by lamin-A overexpression. High re-tear of massive cuff repair could be due to cellular apoptosis and nuclear modifications induced by lamin-A lack.Level of Evidence: III