In vivo fate of bone marrow mesenchymal stem cells implanted into rat pulpotomized molars

Abstract

In our previous work, we established an in vivo coronal pulp regeneration model in which biodegradable hydrogel-made scaffolds carrying rat bone marrow mesenchymal stem cells (BM-MSCs) were implanted in the coronal pulp chamber of pulpotomized rat maxillary first molars. In this study, we investigated the in vivo fate of LacZ-labeled BM-MSCs in our coronal pulp regeneration model. BM-MSCs were nucleofected with pVectOZ-LacZ plasmid encoding β-galactosidase 1 day before implantation, and the LacZ-transfected BM-MSCs were implanted into the pulpotomized pulp chamber with biodegradable preformed scaffold-hydrogel constructs. Empty vector was used as a control. After 3 and 14 days, the molars were retrieved and subjected to β-galactosidase staining. At 3 days, β-galactosidase-expressing cells with a round profile were located mainly around the scaffold. At 14 days, when the pulp-like tissue had been generated, the majority of β-galactosidase-expressing cells were detected under the newly formed dentin bridge-like structure, where nestin-expressing odontoblast-like cells were arranged. Immunoreactivity for dentin sialoprotein, a marker of mature odontoblasts, was strongly detected under the original dentin. No β-galactosidase staining was observed in the control group. Thus, we demonstrated that BM-MSCs survived for 2 weeks after implantation and colonized within the site of potential cytodifferentiation. Our findings indicated that BM-MSCs could differentiate into cells involved in mineralized tissue formation in the functionally relevant region. Keywords: Lac-Z, Bone marrow mesenchymal stem cells, Dental pulp, Tissue engineering, Differentiation