Characterization of Fibrodysplasia in the Dog Following Inhibition of Metalloproteinases

Abstract

Musculoskeletal side effects are a widely reported consequence of administration of particular matrix metalloproteinase inhibitors (MMPi) in clinical trials. We describe here histopathological findings during dog studies with a fairly selective MMPi AZM551248, that are consistent with these human clinical changes. They were characterized by a dose-and time-dependent formative connective tissue alteration we have termed "fibrodysplasia." The most sensitive site was the subcuticular connective tissue, although musculoskeletal tissues were also extensively involved. In the subcutis, changes occurred initially around pre-existing blood vessels, but then more diffusely. There was proliferation of cells showing myofibroblast differentiation identified by elevated levels of alpha-smooth muscle actin, fibronectin, and transforming growth factor beta, and the deposition of collagen type III with a lesser quantity of collagen type I. On longer-term administration at lower doses, there was evidence of active fibrodysplasia arising and resolving during the dosing period, resulting in the multifocal deposition of mature collagen. Although there was organ specificity, essentially identical changes occurred at multiple connective tissue sites. We conclude that MMPi-induced fibrodysplasia in animals and, by inference, musculoskeletal side effects in humans are potentially diffuse connective tissue disorders.

The role of microRNAs in the pathogenesis of MMPi-induced skin fibrodysplasia

“…Eleven days administration of AZM551248 was associated with the first histological evidence of FD and also marked the first appearance of elevated TGFβ transcript, consistent with the detection of immuno-reactive TGFβ in activated fibroblasts [9], and in the plasma [15]. Day 11 marked the appearance of cfa-miR-21 as the most highly expressed miRNA.…”

“…The full range of histopathological changes observed in response to MMPi administration have been discussed in detail elsewhere [9]. Briefly, animals receiving vehicle or MMPi for 4 days showed no evidence of fibrodysplastic change.…”

“…The AZM551248 time-course study design and resulting histopathological changes have been reported in detail elsewhere [9,15]. Briefly, 30 female beagle dogs, around 12 months of age were randomly assigned to six experimental groups as described in Table 2.…”

“…Histological assessment reveals several characteristic findings including growth plate thickening, synovial hyperplasia, soft tissue fibroplasias and lymphocyte infiltrates [8]. These features associated with MMPi administration have been collectively termed "fibrodysplasia" [9]. In the canine, the most sensitive site for MMPi- induced fibrodysplasia is the subcuticular connective tissue which is affected from 11 days post-treatment, although other musculoskeletal tissues are extensively involved, as with other species, as administration continues [9].…”

“…This dose has been previously shown to induce subcutaneous FD following 17 days of administration in a pilot study involving two female beagle dogs (data not shown). A detailed histopathological report of the changes associated with FD in this study was published first in 2009 [9] and described a phased onset of FD in the cervical subcutaneous tissue following 11 days administration of AZM551248. More recently, an analysis of the changes in messenger RNA (mRNA) expression and in MMP activity following AZM551248 administration was reported [15].…”