Irish Scientists Engineer Hybrid Immune Cells to Accelerate Bone Regeneration and Blood Vessel Growth

Scientists develop hybrid macrophages that simultaneously grow bone and blood vessels. A new breakthrough for patients with slow-healing fractures.

By: AXL Media

Published: Apr 29, 2026, 10:24 AM EDT

Source: Information for this report was sourced from EurekAlert!

The Discovery of Dual Action Regenerative Signals

A collaborative team of scientists from Trinity College Dublin and RCSI University of Medicine and Health Sciences has announced the creation of "hybrid" immune cells capable of significantly accelerating bone repair. This advancement focuses on a specialized type of immune cell known as a macrophage, which typically transitions between inflammatory and reconstructive states during the healing process. The breakthrough lies in the hybrid cell’s unique ability to simultaneously stimulate the growth of both new bone tissue and the blood vessels required to nourish it, a dual function that has never been documented before in regenerative medicine.

Decoding the Macrophage Transition Process

Macrophages are essential to the body's natural response to injury, acting as both defenders and coordinators of repair. When a fracture occurs, these cells initially enter an M1 state, rushing to the site to clear dead cells and bone fragments through an inflammatory response. Once the debris is removed, they ideally switch to an M2 state to begin rebuilding the bone structure. According to Professor David Hoey from Trinity’s School of Engineering, the exact mechanism behind this transition has remained a biological puzzle, but the new study clarifies how these cells communicate their status to neighboring tissues through the release of tiny particles called extracellular vesicles.

Harnessing Extracellular Vesicles for Targeted Repair

The research team discovered that the biological signals carried by these extracellular vesicles are entirely dependent on the specific state of the macrophage at the time of release. Their findings revealed that vesicles from M1 macrophages are responsible for kickstarting the formation of new bone, while those from M2 macrophages focus on promoting the growth of new blood vessels. While both processes are necessary for recovery, they typically happen in sequence. By identifying the specific packages of biological signals released by each state, the team established a foundation for creating a more efficient, synchronized healing response.