LAMB3 regulates extracellular matrix stiffness and promotes odontoblast differentiation in dental papilla

Odontoblast differentiation is a key process in tooth development. Although the effect of extracellular matrix (ECM) stiffness on cell differentiation is well established, its role in odontoblast development remains unclear. In this study, we revealed the dental papilla (DP) stiffness gradient along the coronal-apical axis, which corresponded to the expression gradient of mechanosensitive molecules during odontoblast differentiation. Specifically, we found that in DP cell or tissue slice culture in vitro, increasing stiffness of collagen matrix gel promoted DP cell polarity and odontoblast differentiation. Moreover, we screened the expression profile ECM molecules in the tooth germ to identify those that may contribute to the stiffness gradient. We found that laminin subunit β3 (LAMB3), a key ECM component mainly expressed by the dental epithelium, was accumulated around the cusp of DP. In addition, the collagen gel reconstituted with increasing concentration of LAMB3 exhibited increased stiffness. LAMB3-modified collagen gel activated mechanosensitive signaling molecules, promoting the establishment of DP cell polarity and odontoblast differentiation. Finally, we revealed that LAMB3 enhanced collagen gel stiffness by reorganizing the homogeneity of pore size and fibril distribution, as well as increasing fibril connectivity density. Our findings reveal the role of ECM stiffness in tooth development and suggest that LAMB3-modified collagen gel could serve as a promising strategy for dentin regeneration.