Effect of analgesic therapy on clinical outcome measures in a randomized controlled trial using client-owned dogs with hip osteoarthritis

BACKGROUND: Pain and impaired mobility because of osteoarthritis (OA) is common in dogs and humans. Efficacy studies of analgesic drug treatment of dogs with naturally occurring OA may be challenging, as a caregiver placebo effect is typically evident. However, little is known about effect sizes of common outcome-measures in canine clinical trials evaluating treatment of OA pain. Forty-nine client-owned dogs with hip OA were enrolled in a randomized, double-blinded placebo-controlled prospective trial. After a 1 week baseline period, dogs were randomly assigned to a treatment (ABT-116 – transient receptor potential vanilloid 1 (TRPV1) antagonist, Carprofen – non-steroidal anti-inflammatory drug (NSAID), Tramadol - synthetic opiate, or Placebo) for 2 weeks. Outcome-measures included physical examination parameters, owner questionnaire, activity monitoring, gait analysis, and use of rescue medication. RESULTS: Acute hyperthermia developed after ABT-116 treatment (P < 0.001). Treatment with carprofen (P ≤ 0.01) and tramadol (P ≤ 0.001) led to improved mobility assessed by owner questionnaire. Nighttime activity was increased after ABT-116 treatment (P = 0.01). Kinetic gait analysis did not reveal significant treatment effects. Use of rescue treatment decreased with treatment in the ABT-116 and Carprofen groups (P < 0.001). Questionnaire score and activity count at the end of treatment were correlated with age, clinical severity at trial entry, and outcome measure baseline status (S(R) ≥ ±0.40, P ≤ 0.005). Placebo treatment effects were evident with all variables studied. CONCLUSION: Treatment of hip OA in client-owned dogs is associated with a placebo effect for all variables that are commonly used for efficacy studies of analgesic drugs. This likely reflects caregiver bias or the phenomenon of regression to the mean. In the present study, outcome measures with significant effects also varied between groups, highlighting the value of using multiple outcome measures, as well as an a priori analysis of effect size associated with each measure. Effect size data from the present study could be used to inform design of future trials studying analgesic treatment of canine OA. Our results suggest that analgesic treatment with ABT-116 is not as effective as carprofen or tramadol for treatment of hip arthritis pain in client-owned dogs

Role of Calcitonin Gene-Related Peptide in Bone Repair after Cyclic Fatigue Loading

Calcitonin gene related peptide (CGRP) is a neuropeptide that is abundant in the sensory neurons which innervate bone. The effects of CGRP on isolated bone cells have been widely studied, and CGRP is currently considered to be an osteoanabolic peptide that has effects on both osteoclasts and osteoblasts. However, relatively little is known about the physiological role of CGRP in-vivo in the skeletal responses to bone loading, particularly fatigue loading.We used the rat ulna end-loading model to induce fatigue damage in the ulna unilaterally during cyclic loading. We postulated that CGRP would influence skeletal responses to cyclic fatigue loading. Rats were fatigue loaded and groups of rats were infused systemically with 0.9% saline, CGRP, or the receptor antagonist, CGRP(8-37), for a 10 day study period. Ten days after fatigue loading, bone and serum CGRP concentrations, serum tartrate-resistant acid phosphatase 5b (TRAP5b) concentrations, and fatigue-induced skeletal responses were quantified. We found that cyclic fatigue loading led to increased CGRP concentrations in both loaded and contralateral ulnae. Administration of CGRP(8-37) was associated with increased targeted remodeling in the fatigue-loaded ulna. Administration of CGRP or CGRP(8-37) both increased reparative bone formation over the study period. Plasma concentration of TRAP5b was not significantly influenced by either CGRP or CGRP(8-37) administration.CGRP signaling modulates targeted remodeling of microdamage and reparative new bone formation after bone fatigue, and may be part of a neuronal signaling pathway which has regulatory effects on load-induced repair responses within the skeleton

Functional adaptation in female rats: the role of estrogen signaling.

Sex steroids have direct effects on the skeleton. Estrogen acts on the skeleton via the classical genomic estrogen receptors alpha and beta (ERα and ERβ), a membrane ER, and the non-genomic G-protein coupled estrogen receptor (GPER). GPER is distributed throughout the nervous system, but little is known about its effects on bone. In male rats, adaptation to loading is neuronally regulated, but this has not been studied in females.We used the rat ulna end-loading model to induce an adaptive modeling response in ovariectomized (OVX) female Sprague-Dawley rats. Rats were treated with a placebo, estrogen (17β-estradiol), or G-1, a GPER-specific agonist. Fourteen days after OVX, rats underwent unilateral cyclic loading of the right ulna; half of the rats in each group had brachial plexus anesthesia (BPA) of the loaded limb before loading. Ten days after loading, serum estrogen concentrations, dorsal root ganglion (DRG) gene expression of ERα, ERβ, GPER, CGRPα, TRPV1, TRPV4 and TRPA1, and load-induced skeletal responses were quantified. We hypothesized that estrogen and G-1 treatment would influence skeletal responses to cyclic loading through a neuronal mechanism. We found that estrogen suppresses periosteal bone formation in female rats. This physiological effect is not GPER-mediated. We also found that absolute mechanosensitivity in female rats was decreased, when compared with male rats. Blocking of adaptive bone formation by BPA in Placebo OVX females was reduced.Estrogen acts to decrease periosteal bone formation in female rats in vivo. This effect is not GPER-mediated. Gender differences in absolute bone mechanosensitivity exist in young Sprague-Dawley rats with reduced mechanosensitivity in females, although underlying bone formation rate associated with growth likely influences this observation. In contrast to female and male rats, central neuronal signals had a diminished effect on adaptive bone formation in estrogen-deficient female rats

Reparative bone formation induced by fatigue loading was increased after treatment with CGRP or CGRP_8–37.

<p>Confocal photomicrographs of calcified transverse sections of ulna at 60% of bone length, from proximal to distal <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020386#pone.0020386-Kotha1" target="_blank">[37]</a>. Administration of either CGRP or CGRP_8–37 for 10 days after cyclic fatigue loading of the right ulna increased reparative bone formation in the loaded ulna compared with saline-treated rats. Endosteal bone formation was particularly evident after CGRP_8–37 treatment. Rats treated with CGRP_8–37 also had greater bone formation in the contralateral (left) ulna, which was not loaded, when compared to the left ulna of the saline-treated rats. New bone formation was double labeled with calcein. White arrows indicate periosteal new woven bone formation; pink arrows indicate endosteal new bone. Bar = 250 µm. Cr, cranial; Cd, caudal; Med, medial; Lat, lateral. Saline group, n = 8; CGRP group n = 12; CGRP_8–37 group, n = 12.</p

CGRP or CGRP_8–37 administration did not influence plasma TRAP5b in vivo.

<p>Plasma concentrations of CGRP and TRAP5b, normalized to plasma total protein, 10 days after fatigue loading. (<b>A</b>) Rats in the CGRP group had higher plasma CGRP concentrations when compared to rats in the Saline and CGRP_8–37 groups. No differences were seen between the Saline group and the CGRP_8–37 group. (<b>B</b>) Administration of CGRP or CGRP_8–37 did not have an effect on plasma TRAP5b levels. Error bars represent standard error of the mean. Saline group, n = 8; CGRP group n = 12; CGRP_8–37 group, n = 12.</p

Bone CGRP is increased by mechanical loading.

<p>Cyclic fatigue loading of the right ulna resulted in increased CGRP concentrations in both the fatigue-loaded (right) ulna and the contralateral (left) ulna, when compared to the Baseline group. No differences in CGRP concentrations were seen between the Sham group and the Baseline group. The Fatigue group also had increased CGRP concentrations compared to the Sham group. * −<i>p</i><0.05 versus the relevant baseline control bone. Error bars represent standard error of the mean. Baseline group n = 12; Sham group n = 12; Fatigue group n = 12.</p

Targeted remodeling of bone microdamage.

<p>Photomicrographs of calcified transverse sections of ulna at 60% of bone length, from proximal to distal <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020386#pone.0020386-Kotha1" target="_blank">[37]</a>. Fatigue loading induced microcrack formation and targeted remodeling. (<b>A</b>) Branching microcracks can be appreciated histologically in fatigue-loaded bones. (<b>B</b>) Targeted remodeling resulted in resorption space formation around the areas of microcracking. Bones were bulk-stained with Villanueva bone stain. Black arrows indicate fatigue damage; white asterisks are labeling resorption spaces. Bar = 0.5 mm.</p

Schematic diagram of the rat ulna loading model.

<p>The antebrachium was placed horizontally in loading cups attached to a materials testing machine. The medio-lateral diaphyseal curvature of the rat ulna is accentuated through axial compression, most of which is translated into a bending moment, which is greatest at ∼60% the total bone length measured from the proximal end of the ulna <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020386#pone.0020386-Kotha1" target="_blank">[37]</a>. Ulnae underwent cyclic fatigue loading, initiated at −3,000 µε, with incremental increases in load until fatigue was initiated. Loading was then terminated when 40% loss of stiffness was attained. Reproduced from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020386#pone.0020386-Sample2" target="_blank">[43]</a> with permission from John Wiley & Sons.</p

Multivariate genome-wide association analysis identifies novel and relevant variants associated with anterior cruciate ligament rupture risk in the dog model

Abstract Background Anterior cruciate ligament rupture (ACLR) is a debilitating and potentially life-changing condition in humans, as there is a high prevalence of early-onset osteoarthritis after injury. Identification of high-risk individuals before they become patients is important, as post-treatment lifetime burden of ACLR in the USA ranges from $7.6 to$17.7 billion annually. ACLR is a complex disease with multiple risk factors including genetic predisposition. Naturally occurring ACLR in the dog is an excellent model for human ACLR, as risk factors and disease characteristics in humans and dogs are similar. In a univariate genome-wide association study (GWAS) of 237 Labrador Retrievers, we identified 99 ACLR candidate loci. It is likely that additional variants remain to be identified. Joint analysis of multiple correlated phenotypes is an underutilized technique that increases statistical power, even when only one phenotype is associated with the trait. Proximal tibial morphology has been shown to affect ACLR risk in both humans and dogs. In the present study, tibial plateau angle (TPA) and relative tibial tuberosity width (rTTW) were measured on bilateral radiographs from purebred Labrador Retrievers that were recruited to our initial GWAS. We performed a multivariate genome wide association analysis of ACLR status, TPA, and rTTW. Results Our analysis identified 3 loci with moderate evidence of association that were not previously associated with ACLR. A locus on Chr1 associated with both ACLR and rTTW is located within ROR2, a gene important for cartilage and bone development. A locus on Chr4 associated with both ACLR and TPA resides within DOCK2, a gene that has been shown to promote immune cell migration and invasion in synovitis, an important predictor of ACLR. A third locus on Chr23 associated with only ACLR is located near a long non-coding RNA (lncRNA). LncRNA’s are important for regulation of gene transcription and translation. Conclusions These results did not overlap with our previous GWAS, which is reflective of the different methods used, and supports the need for further work. The results of the present study are highly relevant to ACLR pathogenesis, and identify potential drug targets for medical treatment