ABSTRACT
@#Tissue engineering provides a new possibility for pulp regeneration. As one of the three elements of tissue engineering, scaffolds have attracted increasing attention. Because the root canal system is limited by the unique anatomical structure of the long and narrow lumen, the preformed scaffold cannot be completely covered with the whole root canal space, although it is convenient to apply, so the injectable scaffold may be an ideal choice for pulp tissue engineering. Hydrogels are hydrophilic polymer networks with physical properties similar to soft tissues. They can provide a porous hydrophilic microenvironment, which facilitates the diffusion of oxygen and nutrients. In recent years, researchers have used injectable hydrogels with different mechanical properties and/or loaded biologically active ingredients as scaffolds to promote revascularization and the regeneration of pulp. The results show that natural polymer hydrogels, synthetic polymer hydrogels, and composite hydrogels combining natural and synthetic polymers all have excellent biocompatibility. The types and mechanical properties of hydrogels and the addition of bioactive ingredients can influence the behavior of stem cells, and gelatin-based hydrogels and fibrin-based hydrogels can also achieve rapid vascularization, which creates the conditions for the formation of pulp-like tissues. Among them, photocrosslinked methacrylated gelatin/hyaluronic acid hydrogels, two/multicomponent hydrogels combined with chitosan with antibacterial and temperature-sensitive properties and new self-assembled peptides have become major research topics in recent years due to their excellent properties. To develop suitable hydrogel scaffolds and promote their application in pulp regeneration, this article reviews the research progress in the types, preparation, and application of injectable hydrogels used for dental pulp regeneration.
ABSTRACT
BACKGROUND: Previous studies have found that polygonatum sibiricum polysaccharide (PSP) exhibits anti-osteoporosis effect, but its therapeutic effect in ovariectomized osteoporotic rats and the molecular mechanisms are poorly understood. OBJECTIVE: To investigate the effect of administration of PSP on the bone microstructure, bone mineral density as well as osteoblast- and osteoclast-related gene expression in rats. METHODS: Twenty-five infertile female Sprague-Dawley rats aged 3 months were randomly allotted into five groups (n=5 per group): sham operation (same volume normal saline), model, zoledronate (0.2 mg/kg?d), high-dose PSP (800 mg/kg?d) and medium-dose PSP (400 mg/kg?d) groups. All rats were subjected to ovariectomy except sham operation group. The administration was intragastrically given every 2 days beginning at 7 days after modeling and lasted 12 weeks. Then, the rats were sacrificed, and the uterus was weighed. The bilateral tibias were removed, one side for histomorphometric analysis by micro-CT, and the other one for RNA detection by qualified PCR. RESULTS AND CONCLUSION: Compared with the sham operation group, the rat body mass in the model group was significantly increased and the weight of uterus was significantly decreased (P < 0.05). Compared with the model group, zoledronate and high-dose PSP could significantly alleviate the excessive increase in body mass (P < 0.05). The bone mineral density in the model group was decreased by 63% compared with the sham operation group (P < 0.01), Compared with the model group, after 12-week high-dose PSP and zoledronate administration, the bone mineral density was increased by 44% and 38%, respectively (P < 0.01); the trabecular bone volume fraction and trabecular number rose significantly(P<0.05),while the trabecular separation decreased significantly(P<0.05).In vivo,PSP could significantly promote the expression levels of osteoblast-related genes (alkaline phosphatase, RUNX2, Col1a1 and osteocalcin), and significantly inhibit the expression levels of osteoblast-related genes (ACP5 and CTSK) (P < 0.05). These results imply that high-dose PSP can reduce bone loss and decrease of bone mineral density, improve the destruction of bone microstructure, as well as promote osteoblast-related genes but inhibit osteoclast-related gene mRNA expression in the ovariectomized rats.