the Gut Microbiome as a Disease Modifier of Heterotopic Ossification

Fibrodysplasia ossificans progressiva (FOP) is a currently untreatable genetic disease in which skeletal muscle repair is redirected to endochondral bone formation (heterotopic ossification, HO) causing pain, muscle destruction, and joint fusion, leading to progressive immobilization and eventually premature death. This project will explore the role of microbiota in inflammation and HO in FOP. Aim 1: Identify the modulatory roles of the gut microbiome in disease progression in FOP mice. Advanced gnotobiotic methods and germ-free FOP mice colonized with defined pro- or anti-inflammatory microbiota. We will also test whether dietary supplementation with probiotic bacteria or compounds that tighten gut barrier integrity will reduce FOP progression. Aim 2: Identify the role of the microbiome in chemokine-dependent polarization and migration of MCYs and macrophages that enhance EHO in FOP. These studies will determine whether the gut microbiome exacerbates EHO in FOP by sensitizing bone marrow MCYs/MΦs to chemokine-induced chemotaxis and increasing the expression of proinflammatory chemokines during flares, which together increase infiltration and inflammatory polarization of MCYs and MΦs. Aim 3: Establish the relationship between gut microbiota, monocyte/macrophage activation, and severity of FOP flares in humans and mice. These studies will determine if the gut microbial community in patients with FOP modulates disease progression by increasing systemic inflammatory tone, thus priming MCY/MΦ activation. Stool samples will be collected from patients with FOP, microbiota analyzed and correlated with FOP disease outcomes. We will also colonize germ-free FOP mice with the microbiome of human FOP patients by fecal transplant in a human microbiome-association (HMA) approach. Finally, we will use a new microfluidic culture system to determine the responses of human iPSC derived M1- and M2-like MΦs from control and FOP patients to defined microbiome antigens.These studies will provide novel mechanistic understanding of how the gut microbiome affects HO and provide a basis for testing how gut microbiome manipulation may augment treatment of FOP and non-genetic HO.