|Tipo di tesi||Tesi di dottorato di ricerca|
|Titolo||Modificazioni strutturali e del cell-signalling osteocitario nella rigenerazione ossea in risposta al trattamento con Teriparatide|
|Titolo in inglese||Bone texture modifications and osteocyte cell-signaling changes occurring during bone regeneration in response to treatment with Teriparatide|
|Settore scientifico disciplinare||BIO/16 - ANATOMIA UMANA|
|Corso di studi||Scuola di D.R. in MEDICINA MOLECOLARE E RIGENERATIVA|
|Data inizio appello||2016-04-05|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
Lo scopo della presente tesi di dottorato è stato quello di analizzare gli aspetti strutturali ossei le modificazioni del cell-signalling osteocitario durante la riparazione di lesioni scheletriche indotte (in vivo) e in un modello cellulare immortalizzato (in vitro) a seguito del trattamento con Teriparatide (farmaco osteo-protettore).
The purpose of this thesis is to analyze the structural bone tissue modifications and the alteration of osteocyte cell-signaling during the repair of experimentally induced bone lesions (in vivo) and in an immortalized cell model (in vitro) under the treatment of the osteo-protective drug Teriparatide. Teriparatide is the active fragment (1-34) of the endogenous human parathyroid hormone (PTH). The physiological effect of PTH is to induce hypercalcemia: this effect is partially achieved by increasing both the calcium intestinal absorption and the renal tubular reabsorption; however, under non-physiological conditions the hypercalcemia is mainly resulted by the increase of bone resorption. Many studies showed that chronic administration of high doses of PTH results in decreased bone mass while intermittent exposure to PTH activates osteoblast bone deposition. In particular, it has been shown that intermittent exposure to PTH increases bone density by stimulating osteogenesis; whereas continued exposure to the same hormone causes strong bone reabsorption. Most of the structural studies published so far about the effect of Teriparatide focused their attention on the amount of newly-deposed bone without investigating the quality of the newly-formed bone tissue; moreover most of the papers enhance the attention to the osteoblast’s cellular and molecular involvement during the process of bone repair, ignoring the pivotal role that the osteocytes play in the bone environment by means of the modulation of their signaling. In many previous published papers it has been shown that osteocytes are the main actors of the communication among bone cells, in particular they are in close contacts with osteoblasts through cytoplasmic extensions and specialized gap-junctions, indicative of their guide role. Bone regeneration retraces the sequence of events occurring in membranous ossification: after a preliminary formation of fibrous tissue and the successive vascular proliferation, two different types of osteogenesis follow: firstly the process of Static Osteogenesis (SO), which produces preliminary bony trabeculae with woven texture, under factors/cytokines of vascular origin, and after that the process of Dynamic Osteogenesis (DO) starts, in which osteoblasts, driven by osteocytes, produce a more ordered (mainly lamellar) and more mechanical valid bone. At the present state of knowledge there are no scientific references focused on the functional relationships among osteocytes and osteoblasts during the bone repair process. This doctoral work focused at first on the morphological analysis of qualitative repair of lesions experimentally induced in diaphysis of rats femurs and then on the study of the osteocyte cell-signaling, both in response to the treatment with Teriparatide in order to deepen the knowledge of morphological and molecular events that occur in bone regeneration, with particular attention to the osteocyte signaling. The results obtained showed that intermittent administration of Teriparatide in the animal model anticipates the beginning of Dynamic Osteogenesis, which is characterized by the production of a more resistant bone. The molecular biology data were performed on an osteocyte immortalized cellular model (MLO-Y4) treated with the drug at different time points. Microarray analysis showed different expression of genes involved in osteocyte signaling compared with the control condition. These results lead us to perform new and more focused analysis of proteomics and to use a new bone cell line (IDG-SW3). This cell line is capable of going through a complete differentiation from pre-osteoblast to late osteocyte, allowing us to better understand the signaling modifications that may occur during the treatment with Teriparatide.