Fibronectin found to reprogram immune cells and drive tooth regeneration

Dental caries remains the most widespread oral disease on the planet, affecting more than 2.5 billion people with untreated lesions in their permanent teeth. When decay reaches the dental pulp, the standard answer has long been the root canal, a procedure that removes infected tissue but leaves the tooth devitalized, structurally weaker and incapable of forming new dentin. Now a team of researchers in South Korea has uncovered a biological mechanism that could change that calculus entirely. In a study published in Experimental & Molecular Medicine, scientists from Seoul National University and Yonsei University College of Dentistry report that fibronectin, a common structural protein of the extracellular matrix, acts as a molecular switch that reprograms macrophages inside damaged dental pulp from inflammatory fighters into pro-angiogenic builders, ultimately promoting the regeneration of the pulp–dentin complex in a preclinical animal model.

The story begins with the pulp–dentin complex itself, the integrated functional unit that keeps a living tooth alive. Odontoblasts line the periphery of the pulp space and extend processes into the dentinal tubules, serving as sentinels that detect external threats and deposit tertiary dentin as a defensive barrier. Fibroblasts, the most abundant stromal cells in the pulp, produce and maintain the extracellular matrix, while dental pulp stromal cells, or DPSCs, carry remarkable regenerative and immunomodulatory properties, including the ability to differentiate into odontoblast-like cells and contribute to reparative dentin formation. When caries breaches the enamel and advances through dentin, a dynamic network of interdependent relationships emerges among odontoblasts, stromal cells and immune cells, and it is within this network that the Korean team went hunting for the rules of communication.

Macrophages were the obvious suspects. These innate immune cells are the pulp’s frontline defenders, recognizing pathogen-associated molecular patterns through Toll-like receptors and mounting inflammatory responses against bacterial invasion. But macrophages are also indispensable mediators of tissue remodeling, secreting trophic factors such as TGF-beta, VEGF and IGF-1 that regulate the proliferation, migration and differentiation of resident progenitor cells. To see how macrophages behave during actual disease, the researchers examined human dental pulp tissue from healthy teeth and teeth with moderate or severe caries, using immunofluorescence to track CD68-positive macrophages. In healthy pulp, macrophages were sparsely distributed throughout the tissue. As caries progressed, their numbers surged, and they clustered beneath regions of advanced decay near the odontoblast layer.

The most striking observation was physical contact. The proportion of macrophages in intimate contact with Thy-1-positive DPSCs rose from 11.2 percent in healthy teeth to 23.7 percent in moderate caries and 48.7 percent in severe caries, suggesting that these immune–stromal encounters are not incidental but part of an organized defensive response. In vitro, the team co-cultured differentiated human macrophages with primary DPSCs and watched the two cell types lock together, extending lamellipodia and filopodia-like protrusions visible under scanning electron microscopy. Macrophages in direct contact with DPSCs showed markedly increased filamentous actin intensity, particularly at the cell–cell interface, a hallmark of intercellular adhesion mechanisms at work.

What molecule was doing the gluing? The researchers profiled adhesion components by RNA sequencing and tested two hypotheses: direct homophilic binding between matching cell-adhesion molecules, or indirect communication through an extracellular matrix intermediary. The homophilic route failed, as macrophages and DPSCs showed no matching cadherin or ICAM-family expression patterns. The matrix route, however, lit up. DPSCs predominantly expressed fibronectin and type I collagen, while macrophages abundantly expressed the integrin subunits ITGA5 and ITGB1, the canonical receptors for fibronectin. Computational ligand–receptor prediction with CellPhoneDB confirmed statistically significant interactions between fibronectin on DPSCs and multiple integrin receptors on macrophages. Structured illumination microscopy then revealed that integrin alpha-5 clusters on macrophages aligned precisely with fibronectin deposited on the DPSC surface, forming the activated, clustered configuration characteristic of functional adhesion.

The functional proof was decisive. A synthetic RGD peptide that blocks integrin–ligand binding reduced macrophage–DPSC contact in a concentration-dependent manner, while collagenase treatment had no effect. CRISPR-Cas9 knockout of ITGA5 in macrophages slashed both the proportion and the duration of contacts with DPSCs, as live imaging over 48 hours demonstrated. Downstream, phosphorylated focal adhesion kinase rose in macrophages cultured on fibronectin-coated surfaces and climbed even higher in co-culture, implicating the fibronectin–integrin–FAK axis as the signaling conduit between the two cell types.

Then came the transformation. Bulk RNA sequencing of sorted macrophages revealed that co-culture with DPSCs shifted their chemokine repertoire dramatically: pro-inflammatory CCL2 and CCL3 were downregulated, while a suite of ELR-positive CXC chemokines—CXCL2, CXCL3, CXCL5, CXCL6 and CXCL8—known for their angiogenic activity were upregulated, alongside VEGFA. Macrophages seeded on fibronectin-coated plates upregulated these pro-angiogenic factors in a dose-dependent fashion, and silencing FN1 in DPSCs suppressed the effect, confirming fibronectin as the trigger. Flow cytometry showed the macrophages shifting toward an M2-like phenotype, with CD206 rising while CD86 stayed flat. The mechanism ran through NF-kappa-B: p65 accumulated in both cytoplasm and nucleus of co-cultured macrophages, and a live-cell GFP reporter showed that fibronectin-coated surfaces drove NF-kappa-B activity roughly 90 percent higher than LPS treatment, while collagen 1 surfaces did nothing.

The consequences for blood vessels were immediate. Conditioned medium from macrophage–DPSC co-cultures dramatically enhanced tube formation by human umbilical vein endothelial cells, increasing the number of junctions, segments and meshes compared with medium from either cell type alone. Endothelial cells exposed to co-culture medium also showed fewer apoptotic membrane blebs and reduced cleaved caspase-3, indicating improved survival. Blocking CXCR2 or VEGFR signaling with specific inhibitors attenuated both angiogenesis and endothelial survival, pinning the effect on the newly identified chemokine and VEGF pathways. An integrated single-cell RNA sequencing atlas of nearly 20,000 human pulp cells, analyzed with the CellChat framework, independently confirmed the story in real tissue: as caries progressed from healthy to severe, total cell–cell interactions exploded from 278 to 2,470, macrophage–endothelial CXCL signaling strengthened markedly, and macrophages emerged as central hubs of the angiogenic communication network.

The final test was translational. In a canine model of pulp revascularization using immature premolar teeth, the researchers applied fibronectin as a final canal irrigation and on a collagen sponge scaffold, following American Association of Endodontists guidelines in a split-mouth design with 22 roots per group. Eight weeks later, micro-computed tomography showed that fibronectin-treated roots had significantly greater cross-sectional dentin area (3.40 versus 2.39 square millimeters) and far more frequent apical closure (59.1 percent versus 22.7 percent). Histology revealed organized layers of polarized odontoblast-like cells, dentinal tubule-like structures and dentin sialoprotein-positive staining in the treated roots, along with abundant new blood vessels and CD14-positive, CD163-positive M2 macrophages in the stromal region—precisely the cellular signature the in vitro work had predicted. Fibronectin itself was localized along the regenerated odontoblast layer, mirroring its arrangement in healthy human pulp.

The implications reach well beyond the dental chair. Because fibronectin is an endogenous protein with established biocompatibility, it carries minimal risk of adverse reactions compared with exogenous growth factors or synthetic biomaterials, and its angiogenic capabilities suggest potential applications in soft-tissue regeneration, bone-tissue engineering and scaffold-based therapies across regenerative medicine. For the millions of children and adults with immature necrotic teeth—a population for whom conventional root canals arrest root development and increase fracture risk—the prospect of a simple, biologically grounded irrigation solution that coaxes the body’s own immune and stromal cells into rebuilding a living pulp is genuinely tantalizing. The authors caution that species differences in pulp biology, optimization of delivery parameters and long-term follow-up studies all stand between this canine model and human clinical practice. But the core discovery stands: a humble matrix protein, long viewed as passive scaffolding, is in fact an active conductor of the immune–stromal orchestra that turns a damaged, infected pulp environment into a regenerative niche. Teeth, it turns out, may know how to heal themselves—we just needed to learn the language they use to ask for help.

Subject of Research: Fibronectin-mediated macrophage–stromal cell crosstalk driving angiogenesis and regeneration of the dental pulp–dentin complex

Article Title: Fibronectin-guided immune–stromal cell crosstalk promotes angiogenesis in pulp–dentin complex regeneration

Article References: Jeong, S., Park, S. Y., Ku, H., Eom, B. S., Kim, D., & Kim, J. M. (2026). Fibronectin-guided immune–stromal cell crosstalk promotes angiogenesis in pulp–dentin complex regeneration. Experimental & Molecular Medicine. https://doi.org/10.1038/s12276-026-01863-4

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01863-4

Keywords: fibronectin, macrophages, dental pulp stem cells, angiogenesis, dental caries, pulp revascularization, extracellular matrix, integrins, regenerative dentistry, NF-kappa-B, chemokines, tissue regeneration