Raquitismo hipofosfatêmico familiar : estudo sobre peptídeos salivares e estrutura mineral dentária

Abstract

X-linked hypophosphatemic rickets (XLHR) is the most common cause of heritable rickets, with an incidence of 1:20,000 live births, representing more than 80% of familial hypophosphatemic rickets. Saliva is the most easily available and accessible body fluid, which makes it one of the most sought after tools in diagnostic pathology. In this context, this thesis, constituted by 4 articles aimed to: (1) describe the main systemic manifestations, oral findings and dental management in 3 generations of an affected family; (2) analyze the mineralization pattern of enamel and dentin in patients affected by XLHR using micro-CT, and to associate enamel and dentin mineralization in primary and permanent teeth with tooth position, gender and presence/absence of this disease; (3) evaluate the peptide profile in the saliva of patients with X-linked hypophosphatemic rickets using high performance liquid chromatography; and (4) characterize salivary proteins in this condition using unidimensional electrophoresis. On study 1, oral exams, laboratorial and histologic evaluations, cone-beam computed tomographies, panoramic and periapical radiographs were performed to properly institute the most adequate treatment strategy. On study 2, teeth were collected from 5 individuals from the same family. Gender, age, tooth position (anterior/posterior) and tooth type (deciduous/permanent) were recorded for each patient. Following collection, teeth were placed in 0.1% thymol solution until Micro-CT scan. Projection images were reconstructed and analyzed. On study 3, unstimulated whole and stimulated parotid saliva were obtained from 8 individuals with (AFF) and 8 healthy individuals, both genders, without (CON) x-linked hypophosphatemic rickets aged from 8 to 66 years. Supernatants were analyzed by high performance liquid chromatography, and the salivary flow rate (ml/min) was calculated. Each major peak in the HPLC chromatogram of each sample was characterized. On study 4, unstimulated whole and stimulated parotid saliva were also obtained, being total protein concentration determined by the Bicinchoninic Acid Protein (BCA) method. Proteins were characterized according to their molecular weights within the unidimensional electrophoresis. The study 1 showed the importance of the knowledge of clinical signs and symptoms of XLHR for the correct diagnosis of this disease, and for the establishment of preventive and comprehensive dental care. On article 2, teeth of all affected patients presented dentin with a different mineralization pattern compared to the teeth of the healthy individual with dentin defects observed next to the pulp chambers. On the third article, whole and parotid salivary flows were significantly different (p = 0.001), being flow of whole saliva higher (0.518 ± 0.282 mL/min) than parotid saliva (0.124 ± 0.086 mL/min). Whole salivary flow rate was higher in the AFF group (0.698 ± 0.229) than in the CON group (0.339 ± 0.210 mL/min) (p = 0.006). Twenty-eight peaks were found in whole and 21 peaks in parotid saliva. Whole saliva of the CON group presented lower number of peaks than AFF group. In parotid saliva, peaks 17 and 28 (retention times: 24 and 39 min) were found exclusively in the AFF group, and peak 13 (retention time: 19 min) exclusively in the CON. Article 4 showed difference concerning to total protein concentration between whole and parotid saliva (p < 0.001), being higher concentration found in whole saliva (102.603 ± 42.336 µg/mL) than in parotid saliva (0.699 ± 0.438 µg/mL). Bands with 102 kDa, 48 kDa and 24 kDa presented higher intensity in whole saliva of CON group (p = 0.015, p = 0.043 and p = 0.022). In conclusion, XLHR patients presented specific characteristics in dentin mineralization and salivary proteins and peptides, which can lead to differentiate these patients from healthy individuals, improving the diagnostic field.