Lightning Podiums: Smorgasboard - Room 802B

Presented by: A. Nakamura

Author(s):

A. Nakamura(1), Y.R. Rampersaud(1,2), S. Nakamura(1), E. Rossomacha(1), J.S. Rockel(1), M. Kapoor(1,3)

(1) University Health Network, Arthritis Program, Toronto, ON, Canada
(2) University Health Network, Spinal Program, Toronto, ON, Canada
(3) University of Toronto, Laboratory Medicine and Pathobiology, Toronto, ON, Canada

Abstract

Purpose: Spine osteoarthritis (facet joint; FJ OA) is among the leading cause of severe low back pain and disability worldwide. The degeneration of facet cartilage is hallmark of FJ OA. However, exact endogenous mechanisms associated with facet cartilage degeneration during FJ OA are unknown. Also, no disease modifying therapies to treat FJ OA exist. We recently screened 2,100 known microRNAs (small non-coding RNAs known to regulate over 60% of all coding genes), and specifically discovered 2 miRNAs, miR-181a-5p & miR-4454, whose expression levels in human facet cartilage dramatically elevate with increased grade of facet cartilage degeneration (Nakamura et al., J Clinical Investigation Insight 2016)1. Our further investigations showed that miR-181a-5p plays an active role in destroying facet cartilage by elevating the inflammatory, catabolic and cell death in vitro and in vivo. This led us to hypothesize that inhibition of miR-181a-5p may be a potential therapeutic target in FJ OA. Therefore, in this study we tested the effect of miR-181-a-5p inhibition (anti-sense inhibitor) on degree of cartilage degeneration in FJ OA animal model in vivo.

Method: Injury (needle puncture)-induced FJ OA model in rats were used for our study as the animal model. Sprague-Dawley rats (n=10/group) were subjected to Injury-induced FJ OA model by the needle puncture through the capsular tissue of FJs. A 26-gauge Hamilton needle passed through the FJ capsular tissue at the 2 spinal levels (L4/5 and L5/6). This model of FJ OA exhibits major OA-like characteristics including proteoglycan loss, chondrocyte cellularity and cartilage degeneration. In-vivo grade miR-181a-5p inhibitor (anti-sense molecule; 5µg/µl ) or control inhibitor (negative scramble control) were injected (n=10 rats) into the two levels of lumbar FJs at 3 and 6 weeks post-injury and histopathological analysis at 12 weeks using Safranin O/ Fast green staining and immunohistochemistry assessment (PARP p-85 and collagen type II cleavage markers) was performed.

Results: Blinded histomorphometric analysis using OARSI scoring revealed that, local treatment with anti-sense miR-181a-5p in-vivo inhibitor resulted in a marked reduction in the severity of FJ OA associated with decreased degree of facet cartilage degeneration, proteoglycan loss and chondrocyte cellularity compared to the treatment with control inhibitor. Immunohistochemical assessment of PARP p-85 and type II collagen cleavage markers (C1/ 2C) further revealed markedly reduced facet chondrocyte cell death and amount of collagen depletion in facet cartilage in miR-181-a-5p inhibitor-treated FJs compared to control inhibitor treated FJs in vivo.

Conclusion: Our preclinical data strongly suggests that local inhibition of miR-181-a-5p may be a potential therapy to halt facet cartilage degeneration during FJ OA. We are currently focusing our studies on identifying the most effective dose, frequency of injections as well as safety profile of this miRNA inhibitor in pre-clinical animal models of FJ OA for their future clinical use. Reference: 1) Nakamura A, et.al. "Identification of microRNA-181a-5p and microRNA-4454 as mediators of facet cartilage degeneration" JCI insight. 2016;1(12):e86820. doi:10.1172/jci.insight.86820.