Neuro-immune-vascular-stem cell crosstalk in bone/cartilage regeneration: mechanisms, technological advances, and...

Functional regeneration of bone and cartilage remains an urgent clinical challenge in orthopedics, as its repair process involves the synergistic participation of multiple systems and cell types. Traditional studies have mostly focused on the regulatory roles of individual cells or signaling pathways, while recent research has confirmed that bone/cartilage regeneration is governed by a regulatory mechanism centered on the neuro-immune-vascular axis. In this mechanism, mesenchymal stem cells (MSCs), bone marrow mesenchymal stem cells (BMSCs), adipose-derived mesenchymal stem cells (ADSCs), and cartilage progenitor cells (CPCs) serve as key functional cells, interacting sequentially and transcellularly with immune cells and endothelial cells through multiple core signaling pathways. This review systematically summarizes these core signaling pathways, including neurosignal-mediated pathways (CGRP/CRLR, NGF/TrkA, SP/NK1R), immune signal-mediated pathways (IL-4/IL-4R, TGF-β/Smad, TNF-α/NF-κB), endothelial cell-mediated pathways (VEGF/VEGFR, Notch, PDGF/PDGFR), and cross-regulatory pathways (PI3K/Akt, MAPK). These pathways collectively mediate the sequential crosstalk and functional coordination among the four cellular components. Additionally, the review highlights the application achievements of cutting-edge technologies in this field, such as single-cell omics, organoid models, in vivo imaging, new approach methodologies (NAM), microphysiological systems (MPSs), and biosensor-integrated platforms. It thoroughly analyzes the current bottlenecks in network mechanism research and clinical translation, including the spatiotemporal specificity of regulatory targets and the difficulty in simulating complex microenvironments, while proposing breAkthrough directions such as optimizing targeted regulatory strategies, developing intelligent biomaterials, and integrating multi-disciplinary technologies. Notably, the traditional M1/M2 macrophage dichotomy can no longer capture the high heterogeneity of immune cells. Recent single-cell omics studies have identified multiple functionally distinct macrophage subsets in the bone/cartilage regeneration microenvironment. This discovery provides a new perspective for precise immune regulation strategies and also underscores the limitations of the traditional classification framework. Overall, this review aims to establish a systematic framework for understanding the complex regulatory mechanisms of bone/cartilage regeneration and offer theoretical support and research insights for the development of efficient repair strategies.