Is NOD1 Activation Involved in Tendinopathy? Characterization on Clinical Samples and in Vitro Studies of NOD1 Activation on Cultured Tendon Cells
Refereed conference paper presented and published in conference proceedings


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AbstractINTRODUCTION: Tendinopathy is a common and disabling disease, but its aetiopathogenesis is not fully understood. Two case reports of tendinopathy have been documented in relation to Lyme disease (B. burgdorferi) and in both cases, tendinopathy was successfully treated with a course of antibiotics [1, 2]. A number of studies have demonstrated the involvement of Nucleotide Oligomerization Domain (NOD) proteins in Lyme disease [3]. NOD are intracellular proteins which respond to microbial components that enter the cell. The activation of NOD pathways result in the triggering of host defences against the microbes, including expression of pro-inflammatory mediators. It is unknown if NOD activation was involved in tendinopathy cases that did not experience an overt infection. In this study, we propose to investigate the involvement of NOD1 in tendinopathy by 1) detecting its expression in clinical samples of tendinopathy, and 2) determining the effect of NOD1activation on cultured human tendon cells.

METHODS: This study has been approved by the Clinical Research Ethics Committee of the authors’ institution (Ref no.: CRE-2013.479). Ten patellar tendinopathy samples were collected from patients and ten healthy patellar tendon samples were collected from patients undergoing anterior cruciate ligament (ACL) reconstruction surgery. All samples were processed for paraffin embedding and histological sectioning; immunohistochemical (IHC) staining of NOD1 was conducted on consecutive sections in every sample. Cultured tendon progenitor cells were also prepared from healthy tendon samples from patients of ACL reconstruction surgery. After seeding, tendon cells (at passage 5) were incubated with either synthetic NOD1 activator C12-iE-DAP (DAP) at concentrations of 0.1μg/ml and 1μg/ml, or its negative control γ-D-Glu-Lys (Lys) at the same concentrations. An untreated control without DAP or Lys was also included. The cells were harvested at 4 and 24 hours post incubation (n=3), and mRNA was extracted for qPCR to measure the expression levels of NOD1, interleukin-1 beta (IL-1β) and transforming growth factor (TGFβ). A two-way ANOVA was used to detect differences in cell culture study at = 0.05.

RESULTS: Eighty percent of tendinopathy samples were positive for NOD1 and none of the healthy tendons expressed IHC detectable NOD1 in interstitial tenocytes and the difference was statistically significant (Fisher’s exact test, p = 0.000). No change in cell morphology and cell number was observed after treatment with DAP or Lys over a 24 hour time period. At 4 hours, NOD1 mRNA expression was significantly up-regulated in samples treated with DAP as compared to those treated with Lys, without an obvious dose response (Fig. 2A), but no significant differences in IL-1β (Fig. 2B) and TGFβ mRNA expression (Fig. 2C) were noticed at 4 hours. At 24 hours, IL-1β mRNA expression was up-regulated only in the higher dose 1μg/ml, and there were no significant differences in mRNA expression of NOD1 or TGFβ.

DISCUSSION: Increased expression of NOD1 in tendinopathy samples may imply the roles of NOD activation in the pathogenesis. The effects of NOD1 activation on tendon cells were similar to previous reports in other cell types [4]. Further investigation on the relationship of NOD1 activation and tendinopathic changes is necessary. The potential involvement of microbes in tendinopathy may suggest new therapeutic strategies.
Acceptance Date27/03/2015
All Author(s) ListHOPKINS Chelsea, FU Sai Chuen Bruma, CHEUK Yau Chuk, CHAN Kai Ming, ROLF Christer
Name of ConferenceInternational Symposium on Ligaments and Tendons XIV, 2015
Start Date of Conference27/03/2015
End Date of Conference27/03/2015
Place of ConferenceLas Vegas, Nevada
Country/Region of ConferenceUnited States of America
Detailed descriptionorganized by ISLT-XIV committee,
Year2015
Month3
LanguagesEnglish-United Kingdom

Last updated on 2019-14-03 at 14:10