Nicotine is a risk factor for dental caries: An in vivo study

Background/purpose: Streptococcus mutans is an important pathogen in the development of dental caries. Many studies have focused on the relationship between nicotine and S. mutans in vitro. The aim of this study was to investigate the effect of nicotine on the growth of S. mutans and its cariogenic potential in vivo. Materials and methods: Sixteen male Specific-pathogen-free Wistar rats were divided into 2 groups (nicotine-treated and nicotine-untreated group) and infected with S. mutans. The S. mutans suspension was treated with 1 mg/mL nicotine in the nicotine-treated group. The Keyes method was used to evaluate sulcal caries of rats, and dental plaque on molar teeth was observed by scanning electron microscopy (SEM). Results: Incidence of sulcal caries was higher in nicotine-treated group compared to nicotine-untreated group (42.7 ± 1.7 vs 37.3 ± 4.9, P = 0.009). Severity of caries increased with nicotine treatment. The slightly dentinal caries scores and moderate dentinal caries scores were higher in the presence of nicotine (P < 0.001). Increased number of S. mutans cells attached to dental surface was observed under SEM in the nicotine-treated group. Conclusion: Nicotine would promote the attachment of S. mutans to dental surface, and further increase the incidence and severity of dental caries. Therefore, nicotine might be a risk factor for smoking-induced caries. Keywords: Dental caries, Streptococcus mutans, Nicotine, Rat

Injectable and Photocurable Gene Scaffold Facilitates Efficient Repair of Spinal Cord Injury

RNA interference-based gene therapy has led to a strategy for spinal cord injury (SCI) therapy. However, there have been high requirements regarding the optimal gene delivery vector for siRNA-based SCI gene therapy. Here, we developed an injectable and photocurable lipid nanoparticle GelMA (PLNG) hydrogel scaffold for controlled dual siRNA delivery at the SCI wound site. The prepared PLNG scaffold could efficiently protect and retain the bioactivity of the siRNA nanocomplex. It facilitated sustainable siRNA release along with degradation in 7 days. After loading dual siRNA targeting phosphatase and tensin homologue (PTEN) and macrophage migration inhibitory factor (MIF) simultaneously, the locally administered siRNAs/PLNG scaffold efficiently improved the Basso mouse scale (BMS) score and recovered ankle joint movement and plantar stepping after treatment with only three doses. We further proved that the siRNAs/PLNG scaffold successfully regulated the activities of neurons, microglia, and macrophages, thus promoting neuron axon regeneration and remyelination. The protein array results suggested that the siRNAs/PLNG scaffold could increase the expression of growth factors and decrease the expression of inflammatory factors to regulate neuroinflammation in SCI and create a neural repair environment. Our results suggested that the PLNG scaffold siRNA delivery system is a potential candidate for siRNA-based SCI therapy