Sensitivity of functional targeted neuropeptide evaluation in testing pregabalin analgesic efficacy in a rat model of osteoarthritis pain

Abstract

The monosodium iodoacetate (MIA)‐induced joint degeneration in rats is the most used animal model to screen analgesic drugs to alleviate osteoarthritis (OA) pain. This study aimed to evaluate the analgesic efficacy of pregabalin (PGB) in an MIA‐induced OA model in rodents by using functional and neuroproteomic pain assessment methods. Treatment group included PGB in curative intent over 9 days compared to gold standard therapy (positive controls) and placebo (negative control). Functional assessments of pain (quantitative sensory testing and operant test) were performed concomitantly with spinal neuropeptides quantification. At day 21 post‐OA induction, PGB in MIA rats reduced tactile allodynia (P = 0.028) and improved the place escape/avoidance behaviour (P = 0.04) compared to values recorded at last time‐point before initiating analgesic therapy. All spinal neuropeptide concentrations, such as substance P, calcitonin gene‐related peptide, bradykinin and somatostatin, came back to normal (non‐affected) rat values, compared to their increase observed in MIA rats receiving the placebo (P < 0.0001). Initiated 13 days after chemical OA induction, repeated medication with PGB provided analgesia according to quantitative sensory testing, operant test and targeted neuropeptides pain assessment methods. This report highlights the interest of using reliable and sensitive methods like targeted neuropeptide quantification to detect the analgesic effects of a test article with concomitant functional assessments of pain when studying OA pain components.

Face and Predictive Validity of MI-RAT (Montreal Induction of Rat Arthritis Testing), a Surgical Model of Osteoarthritis Pain in Rodents Combined with Calibrated Exercise

“…These questions emerged from our own experience with the chemical monosodium iodoacetate (MIA) (2 mg intra-articular injection) in the OA rat model [26,[28][29][30]. Clearly, the functional alterations induced in the MIA OA rat model were fleeting, being maximal D3 post-injection (with a −41.8% average decrease in PWT for N = 34 rats) and reverting to baseline values on D21 (only −7.5% difference).…”

“…After OA induction on D0, 48 female OVX rats were randomly assigned to four equal groups (N = 12) under sedentary or exercise conditions under PA or negative (placebo) control. From D3 to D56, rats in both PA treatment groups received pregabalin (30 mg/kg) combined with carprofen (5 mg/kg) via daily subcutaneous injections [30,77]. Negative control groups included rats receiving a daily subcutaneous injection of vehicle placebo (at an equivalent of 0.9% sterile saline volume of 1 mL/kg).…”

“…Testing was performed during the daylight phase and was undertaken by the same two female observers who were blinded to treatment group allocation. All animals were allowed to acclimate to testing conditions (QST and exercise protocol) according to a validated acclimation protocol based on five days of exposure to the apparatus over two weeks before induction of OA, as previously published [27][28][29][30]. Functional assessments were performed one day before the induction of OA for baseline values (D-1) and on D7, D21, and D56 post-induction of OA pain.…”

“…Euthanasia was performed by decapitation following isoflurane overdose after the last functional evaluation day (D56), after which collection of the whole spinal cord was achieved using a saline flush technique [26][27][28][29][30]. Samples were snap-frozen in cold hexane, stored individually, and kept at −80 • C pending neuropeptidomic analysis.…”

“…Instrument calibration was performed prior to all analyses, and mass accuracy was notably below 1 ppm based on the Thermo Pierce calibration solution and automated instrument protocol. SP, CGRP, BK, SST, Met-ENK, and Leu-ENK peptide quantification was performed using a peak-area ratio of light (unlabeled) and heavy (labeled) isotopes and expressed in fmol/mg of spinal cord homogenate, as previously described [26][27][28][29][30]67].…”