Biosynthetic polyphosphate enhances osteogenesis of human periodontal ligament stem cells and promotes periodontal bone regeneration in a murine periodontal bone defect model

Introduction Periodontal bone regeneration remains a significant challenge in clinical dentistry due to the complex structure of periodontal tissues and their limited intrinsic regenerative capacity. Innovative biomaterial-based strategies are therefore required. Polyphosphates (Poly(P)) have shown promising regenerative potential; however, conventional chemical synthesis methods are limited by high costs and product impurity concerns. Methods We established an eco-friendly biosynthetic strategy using a genetically engineered environmental bacterium overexpressing polyphosphate kinase (PPK1) to produce high-purity polyphosphates (Bio-Poly P) from wastewater-derived phosphate sources. Structural characterization was performed to confirm physicochemical properties. The effects of Bio-Poly P on human periodontal ligament stem cells (hPDLSCs) were assessed by CCK8 assays, qRT-PCR, alkaline phosphatase (ALP) activity, and Alizarin Red staining. In vivo osteogenic potential was evaluated using a murine periodontal bone defect model with micro-CT analysis after 4 weeks of implantation. Results In vitro , Bio-Poly P at 1.25 and 2.5 mg/ml did not reduce hPDLSC proliferation at 24, 48, and 72 h, whereas higher concentrations (≥5 mg/ml) significantly inhibited proliferation (P < 0.0001). At day 7, Bio-Poly P at 0.25, 1.25, and 2.5 mg/ml significantly upregulated COL1A1 expression (P < 0.0001), while only 1.25 mg/ml enhanced OCN (P < 0.0001) and OPN (P < 0.01). No effect was observed on RUNX2 at this time point. By day 14, all three concentrations significantly increased the expression of RUNX2, OCN, OPN , and COL1A1 . Enhanced ALP activity and calcium deposition were confirmed by biochemical assays and Alizarin Red staining, with the 1.25 mg/ml group showing the greatest mineralization. In vivo , Bio-Poly P significantly improved bone mineral density, bone volume/tissue volume ratio, and trabecular thickness compared with untreated defects, with regenerative outcomes comparable to the clinical control Bio-Oss® (P > 0.05). Discussion This study demonstrates that Bio-Poly P possesses favorable biosafety and osteoinductive properties, effectively enhancing osteogenic differentiation of hPDLSCs in vitro and promoting periodontal bone regeneration in vivo . By leveraging a cost-effective and sustainable biosynthetic production method, Bio-Poly P represents a promising alternative to chemically synthesized polyphosphates for clinical periodontal regeneration.