Periodontal Ligament Transplantation With Gold Nanoparticles Prevents Orthodontic Root Resorption

Objectives: To investigate whether a novel biomimetic periodontal ligament transplantation can prevent orthodontically induced inflammatory root resorption (OIIRR) in a rat model of orthodontic tooth movement (OTM).
Methods: Human PDLSCs were isolated from extracted teeth and characterized as mesenchymal stem cells. Simultaneously, gold nanocomplexes (AuNCs) were synthesized using gold nanoparticles complexed with Poly-L-lysine and hydrobromide rhodamine B isothiocyanate. In vitro, the effects of AuNCs on the viability and osteogenic differentiation capacity of PDLSCs were tested by cytotoxicity assay, ALP and ARS staining, RT-qPCR, and immunofluorescence staining, respectively. The AuNC-treated hPDLSCs were encapsulated in a type-I collagen hydrogel scaffold to mimic their native physiological niche and were then transplanted into a rat model of OTM. Thirty-five twelve-week-old male Wistar rats were included in this study and divided into 6 groups: (1) no OTM, (2) OTM, (3) Sham injection + OTM, (4) AuNCs injection + OTM, (5) PDLSCs + OTM, (6) AuNCs-induced PDLSCs + OTM. OIIRR was evaluated longitudinally, before and 31 days after OTM with micro-CT, based on a rigid voxel-based registration. Immunohistochemisty was additionally performed at 31 days.
Results: In vitro, 0.1 mg/mL 40nm AuNCs were easily taken up by primary hPDLSCs with limited cytotoxicity and promoted osteogenic differentiation of hPDLSCs effectively, as shown by upregulation of ALP, COL1, OSTERX and RUNX2 expression. In vivo, micro-CT showed that OIIRR was significantly prevented in Group 6 (AuNCs-induced PDLSCs), compared to Groups 2, 3, 4 and 5 (p＜0.05). There was no significant difference in OIIRR between Groups 1 and 6 (p=0.81). Increased immunoreactivity of p62 and LC3 suggests that the underlying mechanism can be linked to the autophagy-induced osteogenesis triggered by the AuNC-hPDLSC transplantation.
Conclusions: Injection of with collagen-1 embedded AuNC-treated hPDLSCs prevented OIIRR. This study presents an innovative AuNCs-based strategy for stem cell therapy in orthodontics.