# Exosomes as Precise Regulators of the Osteoimmune Microenvironment: Engineering Strategies for Bone Regeneration

## TL;DR

This review explores how exosomes can regulate the immune system to promote bone healing and regeneration by modulating the osteoimmune microenvironment.

## Contribution

The paper systematically examines exosome-mediated immune modulation and their potential for precision-based bone regeneration therapies.

## Key findings

- Exosomes can reprogram the immune microenvironment from pro-inflammatory to regenerative states.
- Exosomes deliver functional cargo like miRNAs and proteins to modulate immune cell polarization.
- They show promise in treating complex bone conditions such as osteoporosis and bone defects.

## Abstract

Bone homeostasis is a dynamically orchestrated process that is intricately regulated by the immune system. The emerging field of osteoimmunology has demonstrated that bone homeostasis and repair are governed by a sophisticated crosstalk between immune and skeletal cells, in which immune signals play a critical role in modulating osteogenesis and osteoclastogenesis. Nevertheless, conventional bone repair strategies frequently overlook immune modulation, instead prioritizing structural support or direct osteoinductive effects. Exosomes—endogenous nanovesicles characterized by low immunogenicity and high bioavailability—have emerged as potent mediators within the immune–bone axis. These vesicles mediate intercellular communication by delivering functional cargo, including miRNAs, proteins, and lipids, across biological barriers, thereby enabling precise regulation of inflammatory responses and immune cell polarization. Importantly, exosomes can reprogram the local immune microenvironment from a pro-inflammatory to a regenerative, anti-inflammatory state, thus promoting enhanced bone healing in complex clinical conditions such as osteoporosis and bone defects. This review systematically examines the molecular mechanisms through which exosomes modulate immune responses in bone biology, highlights their pivotal role in reshaping the osteoimmune microenvironment, and discusses their transformative potential in the development of next-generation, precision-based therapeutic approaches for bone regeneration.