Dentin Phosphophoryn-Derived Peptide Promotes Odontoblast Differentiation In Vitro and Dentin Regeneration In Vivo

The purpose of the present study was to investigate the effect of a peptide (i.e., SESDNNSSSRGDASYNSDES) derived from dentin phosphophoryn (DPP) with arginine-glycine-aspartic acid (RGD) motifs on odontoblast differentiation in vitro and to compare it with calcium hydroxide—a material used conventionally for vital pulp therapy—in terms of reparative dentin formation and pulp inflammation in vivo. Alkaline phosphatase activity assay and alizarin red S staining were performed to evaluate odontoblast-differentiation in cell culturing experiments. To observe the reparative dentin formation and pulp inflammation animal experiment was performed and examined by histological methods. The difference between the experimental group and the control group was analyzed statistically using a one-way ANOVA test. The results revealed that the DPP-derived RGD-containing peptide triggered odontoblast differentiation and mineralization in vitro. In rats undergoing direct pulp capping, the DPP-derived RGD-containing peptide was found to induce intensively formed reparative dentin with high compactness at week 4. On histological and morphometrical examinations, a smaller degree of pulpitis was observed in the specimens treated with the peptide than in those treated with calcium hydroxide. This study suggests that the DPP-derived RGD-containing peptide is a biocompatible, biodegradable and bioactive material for dentin regeneration.     

Changes of the nerve fibers innervating the minor salivary glands in Sjögren syndrome

INTRODUCTION: A large number of nerve fibres containing different neuropeptides/transmitters are also found in the salivary glands. The number and the distribution of nerve fibres is altered in many diseases, including in Sj?gren's syndrome. AIM: Therefore in the present study the distribution and precise localisation of the nerve fibres containing the frequently observed neuropeptides were studied in the minor salivary glands. METHODS: Vasoactive intestinal polypeptide, neuropeptide Y, substance P, calcitonin gene-related peptide, somatostatin, nitric oxide synthase and tyrosine beta-hydroxylase antibodies were used as primary antisera, and then by the aid of avidin-biotin-peroxidase complex method the immunoreactive fibers in human labial glands (control and with Sj?gren's syndrome) and in minor glands of the root of the rat's tongue were detected. RESULTS: Large number of vasoactive intestinal polypeptide and nitric oxide synthase immunoreactive nerve fibres were seen around the acini. The neuropeptide Y and tyrosine beta-hydroxylase positive nerve fibres were mainly found around the blood vessels. Some of the IR fibers were also found around the excretory ducts. In the biopsy of patients with Sj?gren's syndrome, the acini were destroyed and only few excretory ducts were seen. The number of the nerve fibres was significantly decreased and many degenerated fibres were also observed among the acini. The electron-microscopic examinations showed that the immunoreactive nerve fibres were in close association to the secretory cells, to the smooth muscle cells of blood vessels and to the immunocells. The synaptic gap between the nerve fibres and the target cells were 40-200 nm. CONCLUSIONS: On the bases of the distribution of the different transmitters containing nerve fibres and their relationship to effector cells, the authors suppose that these transmitters control the function of the gland and regulate the blood flow. The close association to immunocells and decreasing the nerve fibres in Sj?gren's syndrome imply that they may have also a role in the neuroimmunologic processes.     

Plasticity of the different neuropeptide-containing nerve fibres in the tongue of the diabetic rat

Common oral complications of diabetes mellitus are xerostomia, impairment of taste, atrophic lesions of the tongue, leukoplakia, lichen oris planus, and tumours, which might be the consequence of chronic inflammation and changes in innervation. In this work, we examined the density of different neuropeptide-containing nerve fibres immunohisto- and immunocytochemically in the root of the control and diabetic rat's tongue. Quantitative analysis showed that the number of immunoreactive (IR) nerve fibres was decreased after 1 week of the streptozotocin treatment, which was prevented by immediate insulin treatment. However, after 4 weeks duration of diabetes, the number of all investigated IR nerve fibres increased significantly (p<0.05), which was further enhanced by the delayed insulin treatment. The numbers of substance P (SP) and vasoactive intestinal polypeptide IR perikarya were also increased by insulin treatment. The electron-microscopic investigations showed that some of the nerve terminals from diabetic animals were found in degeneration. After 4 weeks duration of diabetes, the number of inflammatory cells as well as the mast cell/nerve fibre contacts was also increased. The immunocells also showed IR for SP and neuropeptide Y in the diabetic rats. The insulin treatment decreased both the number and the immunoreactivity of these cells. The increased synthesis and/or regeneration of neuropeptide-containing nerves might indicate the plasticity of nerve fibres in diabetes mellitus, which might happen as a consequence of the changes in the level of neurotrophic factors released by increased number of inflammatory cells or as an effect of insulin.     

Morphological evidence of sensory neurons in the root of the rat tongue

In our previous studies, a large number of substance P (SP)-immunoreactive (IR) nerve fibers were detected in the rat tongue and their number increased after inflammation, suggesting that these fibers might be involved in the axon reflex. Therefore, in this study, we have examined the different neuropeptide-containing nerve elements by light, electron, and confocal laser microscopy. SP, vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) IR varicose fibers were numerous compared with other ones. Small groups of ganglia with perikarya IR for SP, VIP, NPY, galanin, and somatostatin were observed. The SP-IR nerve cell bodies were mainly located in the tunica propria just below the epithelial lining. Double-labeling immunohistochemistry showed that the intrinsic SP-IR neurons did not colocalize VIP. The SP containing nerve terminals were observed in and below the epithelium as well as in very close contact to or making real synapses with other neurons in the intralingual ganglion. Our data confirmed the possibility of intrinsic sensory neurons, which might be the afferent branch of the intralingual reflex arch, while the VIP- and NPY-IR neurons located in the salivary glands, around the blood vessels, and in the muscle layer might constitute the efferent site of this reflex.