Evolución del germen dental trasplantado heterotópicamente en la dermis: un estudio histológico en la rata

En este estudio hemos analizado la potencialidad de desarrollo del germen dental en fase de corona. Para ello, los gérmenes dentales de rata recién nacida fueron trasplantados en las bolsas dérmicas de la oreja de ratas isogénicas. Siete y catorce días después del trasplante, se desarrollaron las estructuras morfológicas dentales típicas, con ameloblastos y odontoblastos bien diferenciados. Ulteriormente, los procesos de reacción inflamatoria del tejido huésped con infiltración celular abocaron a la desaparición de los tejidos dentales. Desde el primer momento de nuestro análisis, los trasplantes desarrollaron una dentina anómala u osteoide cuyo tamaño fue paulatinamente incrementando con el tiempo, llegando a sustituir al resto de los tejidos dentales. Esta dentina osteoide, fruto tanto de la transformación de los odontoblastos del trasplante en células de alta actividad secretora como de la inducción que el germen dental ejerce en el tejido huésped circundante; y a diferencia de la observada en estudios previos, mostró diversos grados de polimerización fibrilar, lo que nos induce a sugerir que nuestro modelo puede ser un buen medio de estudiar los mecanismos de reacción en la formación de tejidos reactivos a la lesión dental.The main goal of this study was the analysis of the developmental potentiality of tooth germ from late bell stage on, after its heterotopic placement within the skin. Teeth germs of newborn rats were grafted within a skin pouch of the ear of adult rats. Seven to fourteen days after grafting, dental germs developed normal dental structures in which ameloblasts and odontoblasts were well differentiated. Twenty to forty-one days after graft, the inflammatory host reaction destroyed the dental developed tissues by cell infiltration. The dentin of the grafts was of osteoid characteristics, and its size increased dependinng on grafting time until the complete substitution of all dental tissues. This atypical dentin showed several degrees of polymerisation from collagen fibres smooth dentin devoid near the graft a to fibres rich dentin far from the dental germ. Present results suggest that this type of dental graft could be a valuable model to study the self-development of dental tissues and the reactive mechanisms taking place after dental injuries

The role of LRAPs regeneration/repair of periondontal tissue: study of cementoblasts culture

BV UNIFESP: Teses e dissertaçõe

Apoptosis during alveolar bone resorption and dental eruption in rats

Durante os movimentos eruptivos dos germes dentais em desenvolvimento, o osso alveolar sofre uma continua, rapida e intensa reabsorcao. Tem sido sugerido que a reabsorcao e mediada por citocinas produzidas pelo reticulo estrelado e pelo foliculo dental. Uma vez que e conhecido que algumas citocinas promovem a apoptose das celulas osseas em geral, parece que a apoptose pode estar envolvida na sequencia de eventos que leva a reabsorcao do osso alveolar. Por isso examinamos o osso alveolar de ratos jovens com o proposito de detectar apoptose. Fragmentos de osso alveolar fixados em Bouin para morfologia e em formaldeido para o metodo do TUNEL para deteccao de apoptose, foram processados para microscopia de luz. Para microscopia eletronica, especimes fixados em mistura de glutaraldeido-formaldeido foram processados pelos metodos convencionais. Os resultados mostraram estruturas arredondadas/ovoides TUNEL positivas na superficie ossea e dentro de lacunas osteociticas. Estas estruturas - tambem coradas pela hematoxilina - foram interpretadas, respectivamente, como osteoblastos/celulas de revestimento osseo e osteocitos sofrendo apoptose. Osteoclastos tambem exibiram corpos apoptoticos TUNEL positivos dentro de grandes vacuolos; contudo os nucleos dos osteoclastos foram encontrados sempre TUNEL negativos. Cortes ultrafinos revelaram imagens tipicas de apoptose - corpos arredondados/ovoides com uma densa cromatina em forma de meia-lua - na superficie ossea, correspondendo a osteoblastos/celulas de revestimento osseo em apoptose. Osteocitos tambem mostraram imagens compativeis com apoptose. Grandes vacuolos dos osteoclastos frequentemente continham material celular fragmentado. Parece razoavel sugerir, a partir dos nossos resultados e da literatura existente, que citocinas do reticulo estrelado/foliculo dental pode de fato deflagrar a apoptose dos osteocitosBV UNIFESP: Teses e dissertaçõe

The role of parathyroid hormone-related protein in the regulation of osteoclastogenesis by cementoblasts

Background: Parathyroid hormone-related protein (PTHrP) promotes osteoclastogenesis by inhibiting expression of osteoprotegerin (OPG), a decoy receptor for the receptor activator of nuclear factor kappa B (RANK), and by enhancing production of RANK ligand (RANKL) by osteoblasts. However, little is known regarding the role of PTHrP in regulating cementoblast-mediated osteoclastogenesis.Methods: This study determined the impact of PTHrP on osteoclastogenesis using: 1) OCCM-30 (immortalized murine cemento-blasts), 2) RAW 264.7 cells (murine myeloid cells), or 3) OCCM-30 plus RAW 264.7 cells. Cells were treated with PTHrP (1-34), RANKL, or PTHrP and RANKL combined. Enzyme-linked immuno-sorbent assays (ELISAs) for OPG and RANKL were performed on media and cell lysates, and tartrate-resistant acid phosphatase (TRAP) and mRNA detection for the osteoclast associated receptor (OSCAR) were performed.Results: the highest numbers of TRAP-positive cells and cells expressing OSCAR were found in the RAW cell group treated with either RANKL alone or RANKL and PTHrP. TRAP-positive cells were fewer when OCCM cells were co-cultured with RAW, but the greatest numbers were still with both PTHrP and RANKL. OPG levels were highest from OCCM cells and PTHrP decreased these levels. in contrast, RANKL levels were low in OCCM cell lysates and PTHrP increased RANKL. in vivo studies also revealed high osteoclastic activity surrounding developing teeth in mice administered PTH.Conclusions: These results demonstrate that PTHrP influences the balance of OPG and RANKL production by cementoblasts, and further indicate that this effect, in the context of surrounding cells, might have a significant impact on osteoclastogenesis, root resorption, and tooth eruption.Univ Michigan, Sch Dent, Dept Periodont Prevent Geriatr, Ann Arbor, MI 48109 USAUniversidade Federal de São Paulo, Sch Med, Dept Morphol, São Paulo, BrazilUniv Washington, Sch Dent, Dept Periodont, Seattle, WA 98195 USAUniv Michigan, Sch Med, Dept Pathol, Ann Arbor, MI 48109 USAUniversidade Federal de São Paulo, Sch Med, Dept Morphol, São Paulo, BrazilWeb of Scienc