# Primary Cilia Are Required for Efficient BMP Signaling in Traumatic Heterotopic Ossification

## TL;DR

This study shows that primary cilia are essential for BMP signaling in traumatic heterotopic ossification, suggesting they could be a target for treatment.

## Contribution

The study reveals a novel role of primary cilia in traumatic HO development through BMP signaling.

## Key findings

- Disrupted primary cilia function attenuates BMP signaling.
- Deleting Ift88 suppressed pathological BMP signaling and HO formation.
- Ciliation frequency and length were reduced in genetically modified tenocytes.

## Abstract

Background/Objectives: Heterotopic ossification (HO), the aberrant formation of bone within soft tissues, arises either from rare genetic mutations or more commonly from traumatic insults. It is a major cause of morbidity not only in individuals harboring causative mutations, but also in those undergoing musculoskeletal surgery or trauma and in soldiers sustaining blast or burn injuries. Bone morphogenetic protein (BMP) signaling is a central driver of both hereditary and acquired forms of HO. Primary cilia are nonmotile, antenna-like organelles that extend from the cell surface and serve as crucial sensory and signaling hubs by concentrating key pathway components within a confined volume at the ciliary tip. However, their functional role in the pathogenesis of traumatic HO remains poorly understood. Methods: We investigate the role of primary cilia in traumatic HO using a genetically modified mouse model and cellular model. Results: We demonstrate that BMP signaling is attenuated when primary cilia function is disrupted. Both ciliation frequency and ciliary length were reduced in Scleraxis-CreERT2; Intraflagellar transport 88 floxed/floxed (Scx-CreERT2;Ift88fl/fl) tenocytes. Deletion of Ift88 effectively suppressed pathological BMP signaling and inhibited HO formation. Conclusions: These findings establish that functional primary cilia are required for traumatic HO development and highlight ciliary regulation as a potential therapeutic avenue for preventing or mitigating post-traumatic HO.