Delivery of Alkaline Phosphatase Promotes Periodontal Regeneration in Mice

Abstract

Factors regulating the ratio of pyrophosphate (PPi) to phosphate (Pi) modulate biomineralization. Tissue-nonspecific alkaline phosphatase (TNAP) is a key promineralization enzyme that hydrolyzes the potent mineralization inhibitor PPi. The goal of this study was to determine whether TNAP could promote periodontal regeneration in bone sialoprotein knockout mice ( Ibsp−/− mice), which are known to have a periodontal disease phenotype. Delivery of TNAP was accomplished either systemically (through a lentiviral construct expressing a mineral-targeted TNAP-D10 protein) or locally (through addition of recombinant human TNAP to a fenestration defect model). Systemic TNAP-D10 delivered by intramuscular injection at 5 d postnatal (dpn) increased circulating alkaline phosphatase (ALP) levels in Ibsp−/− mice by 5-fold at 30 dpn, with levels returning to normal by 60 dpn when tissues were evaluated by micro–computed tomography and histology. Local delivery of recombinant human TNAP to fenestration defects in 5-wk-old wild type (WT) and Ibsp−/− mice did not alter long-term circulating ALP levels, and tissues were evaluated by micro–computed tomography and histology at postoperative day 45. Systemic and local delivery of TNAP significantly increased alveolar bone volume (20% and 37%, respectively) and cementum thickness (3- and 42-fold) in Ibsp−/− mice, with evidence for periodontal ligament attachment and bone/cementum marker localization. Local delivery significantly increased regenerated cementum and bone in WT mice. Addition of 100-μg/mL bovine intestinal ALP to culture media to increase ALP in vitro increased media Pi concentration, mineralization, and Spp1 and Dmp1 marker gene expression in WT and Ibsp−/− OCCM.30 cementoblasts. Use of phosphonoformic acid, a nonspecific inhibitor of sodium Pi cotransport, indicated that effects of bovine intestinal ALP on mineralization and marker gene expression were in part through Pi transport. These findings show for the first time through multiple in vivo and in vitro approaches that pharmacologic modulation of Pi/PPi metabolism can overcome periodontal breakdown and accomplish regeneration.

Between a rock and a hard place: Regulation of mineralization in the periodontium

“…Similar findings resulted from studies in which TNAP was delivered to Ibsp −/− mice to a fenestration defect (Nagasaki, Nagasaki, Kear, et al, 2021 ). Systemic (lentivirus construct) and local delivery (addition of a recombinant protein) of TNAP substantially increased alveolar bone volume and cementum thickness in Ibsp −/− mice, with greater effects on PDL attachment and improved periodontal structure from local versus systemic application, despite the absence of BSP.…”

“…Its critical functions in periodontal development have led to studies employing TNAP for periodontal repair and regeneration. Systemic and local delivery of TNAP promoted greater periodontal repair in mice lacking BSP, which before treatment displayed severe periodontal breakdown (described in detail in the following sections; Nagasaki et al, 2021 ).…”

Impaired Tertiary Dentin Secretion After Shallow Injury in Tgfbr2-Deficient Dental Pulp Cells Is Rescued by Extended CGRP Signaling

“…The control mandibles were analyzed as described, and their respective segmentation maps were applied. Reconstructed images were analyzed using Analyze 14.0 (AnalyzeDirect, Overland Park, KS), as described previously [69,70]. A region of interest (ROI) was created to encompass the largest region of tertiary dentin found in any of the samples (90 μm total) and this was applied to all injured samples.…”

Impaired Tertiary Dentin Secretion after Shallow Injury in Tgfbr2-Deficient Dental Pulp Cells Is Rescued by Extended CGRP Signaling

“…The control mandibles were analyzed as described, and their respective segmentation maps were applied. Reconstructed images were analyzed using Analyze 14.0 (AnalyzeDirect, Overland Park, KS, USA), as described previously [105,106]. A region of interest (ROI) was created to encompass the largest region of tertiary dentin found in any of the samples (90 µm total), and this was applied to all injured samples.…”