2017 ISAKOS Biennial Congress ePoster #321

 

Micro-RNA Differential Expression In Rotator Cuff Tendinopathy: An Rna-Sequencing Analysis

Geoffrey D. Abrams, MD, Stanford, CA UNITED STATES
Stanford University/VA Palo Alto, Palo Alto, California, UNITED STATES

FDA Status Not Applicable

Summary

This investigation found 10 differentially expressed miRNA from paired diseased supraspinatus tendon versus control subscapularis tendon.

Abstract

Introduction

Micro-RNAs (miRNA), small non-coding, single-stranded RNAs that regulate post-transcriptional gene expression have been shown to have numerous regulatory functions and remains an attractive target for intervention. There is a little information regarding specific miRNA which are differentially expressed in diseased and normal human tendons. Using RNA-sequencing, this investigation sought to determine the miRNA expression profile within diseased and normal human rotator cuff tendons.

Methods

Institutional Review Board (IRB) approval was obtained. Paired diseased supraspinatus (SS) and control subscapularis (SC) tendon tissue biopsies were taken during arthroscopic shoulder surgery. Inclusion criteria were age 18 years and older with shoulder pain, tendinopathy of the supraspinatus tendon (without full thickness tear) as determined by magnetic resonance imaging (MRI), and no tendinopathy or tearing of the subscapularis on MRI. Exclusion criteria included any prior surgery to the involved shoulder, history of systemic or musculoskeletal inflammatory disease, a diagnosis of diabetes or hypercholesterolemia requiring medication, current smoking habit, receiving a corticosteroid injection to the operative shoulder within three months of surgery, oral anti-inflammatory medication within ten days of surgery, tearing of the supraspinatus greater than two millimeters in any dimension as determined by MRI or arthroscopic visualization, and any visual pathology of the subscapularis during arthroscopy. Samples were placed in formalin and RNAlater, with the later frozen in liquid nitrogen until RNA was extracted. Formalin stored tissue was stained with haematoxylin and eosin and histologic grading under light microscopy was measured using the Bonar scoring system. RNA-sequencing was performed and quantified using the reads per million (RPM) formula. Individual RPMs were averaged among patients to determine total number of miRNAs present while comparisons between patients were performed using a paired Student’s t-test.

Results

Ten paired samples were collected from five male patients (average age 58 years, range 44-65 years). All patients underwent shoulder arthroscopy with debridement and subacromial decompression, with four patients additionally undergoing subpectoral biceps tenodesis and one patient undergoing combined subpectoral bicep tenodesis and arthroscopic distal clavicle resection. The average Bonar score for supraspinatus was 1.6 +/- 0.5 and subscapularis was 0.4 +/- 0.5 (p = 0.03). A total of 633 unique miRNAs were identified in supraspinatus tendon samples, with 346 miRNAs having at least one RPM. For the subscapularis tendon, a total of 718 unique miRNA were identified, with 381 having an average RMP > 1. In the paired analysis, only 10 miRNAs (miR-532, miR-30d, miR-10a, miR-151a, miR-29a, miR-92a, let-7e, miR-99a, miR-126, miR-25) were significantly differentially expressed between supraspinatus and infraspinatus, with a decreased RMP in the diseased state in all but let-7.

Discussion

This investigation found 10 differentially expressed miRNA from paired diseased supraspinatus tendon versus control subscapularis tendon. All miRNAs except let-7 were down-regulated in the disease state. The identified micro-RNA have previously demonstrated roles in collagen expression, MSC differentiation, and molecular inflammation, all of which are key components of tendinopathy. The data presented here can be utilized to further refine the role of particular miRNAs in the development of the disease.