Laser Directed Dentin Differentiation of Dental Stem Cells

Objectives: Exciting progress in stem cell biology has opened new vistas in regenerative craniofacial biology. While these advances offer a pool of cells with broad biological potential, the next frontier will probably be our ability to direct differentiation of cells into precise lineages to form tissues and organs for clinical applications. The purpose of this work is to present the mechanistic basis of the ability of low power laser irradiation to direct dentin differentiation of dental stem cells.  

Methods: An infrared laser was used at low power to irradiate human dental stem cells isolated from extracted teeth specimens. Stem cell markers were evaluated using immunoblotting and immunofluorescence while dentin differentiation was assessed with dentin matrix-specific gene expression. A biomaterials-based approach for controlled delivery was used to evaluate in vivo efficacy and the precise molecular pathway of laser directed dentin repair in a rodent pulp capping model. Rat stem cell differentiation and dentin repair was evaluated using high resolution micro-computed tomographic (uCT) imaging, routine and special biochemical stains.       

Results: We had previously presented the ability of LPL to generate specific ROS species that, in turn, could act on a specific amino acid residue on the Latent TGF-β1 resulting in its activation. Human dental stem cells isolated from extracted teeth were subjected to LPL irradiation and resulted in loss of stem cell markers CD44, CD90, CD106, CD117 and Stro-1 while concurrently up-regulating dentin matrix gene expression of ALP, DSP, DMP1 and OPN. A controlled delivery of inhibitors of TGF-β established the critical role of laser-activated TGF-β1 in mediating dental stem cell differentiation and dentin repair in a rat first-molar pulp capping model.

Conclusions: In conclusion, a novel mechanism for LPL activated TGF-β1 is elucidated that could be used as an innovative clinical tool for dentin induction.