Local release of DMP1 and its impact on bone repair in osteoporotic rats

• Grant number: 24/19648-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: May 01, 2025
• End date: February 29, 2028
• Field of knowledge: Health Sciences - Dentistry
• Principal Investigator: Roberta Okamoto
• Grantee: Laura Vidoto Paludetto
• Host Institution: Faculdade de Odontologia (FOA). Universidade Estadual Paulista (UNESP). Campus de Araçatuba. Araçatuba , SP, Brazil

Abstract

ABSTRACTThe increasing longevity of the population has led to an increase in the prevalence of metabolicdiseases, including osteoporosis, while at the same time increasing the demand for oralrehabilitation with osseointegrated implants. However, the patient's systemic condition is one ofthe factors that interferes with the process of osseointegration and bone reconstruction, andosteoporosis is one of the conditions that can compromise this process. Considered a public healthproblem in post-menopausal women due to a decrease in oestrogen production, osteoporosis ischaracterized by a decrease in bone mass and an imbalance in bone metabolism, which cancompromise the success of rehabilitations with osseointegrated implants. In this context, thefunctionalization of implants and biomaterials with bioactive molecules is a strategy that canimprove bone repair in patients with compromised bone tissue. Therefore, this study aims toinvestigate the impact of local release of the DMP1 protein on peri-implant bone repair and criticalcalvarial defects in osteoporotic rats. The hypothesis is that DMP1, a non-collagenous proteinresponsible for initiating the enucleation of hydroxyapatite in calcified tissues and capable ofstimulating osteoblastic differentiation, will have positive effects on bone repair compromised byosteoporosis. To this end, 104 rats will be divided into 5 experimental groups: Calvaria + Clot(CC): group in which critical calvarial defects will be made in the animals and filled only withblood clot; Calvaria + Gelfoam ® (CG): group in which critical calvarial defects will be made inthe animals and filled with Gelfoam ®; Calvaria + Gelfoam ® + DMP1 (CGD): group in whichcritical calvarial defects will be made in the animals followed by their filling with Gelfoam ®functionalized with DMP1; Tibia + Implant (TI): group in which titanium implants withoutfunctionalization will be installed in the animals' tibials and Tibia + Implant + DMP1 (TID): groupin which titanium implants functionalized with DMP1 will be installed in the animals' tibials. Onday 0, the animals in all the experimental groups (CC, CG, CGD, TI and TID) will undergo bilateralovariectomy. On day 90, after the induction of osteoporosis, the animals in the calvaria groups(CC, CG and CGD) will be subjected to the making and filling of critical calvaria defects, accordingto the experimental group, while the animals in the tibia groups (TI and TID) will be subjected tothe installation of functionalized or non-functionalized implants in their tibias. In order to analyzebone repair, a multidisciplinary approach will be used so that biomechanical, structural, cellularand molecular responses can be characterized. Thus, after 14 and 28 days (days 104 and 118,respectively), the animals in all the experimental groups (CC, CG, CGD, TI and TID) will beeuthanized. The samples from the animals euthanized 14 days after surgery will be subjected toRT-PCR (ALP, iBSP, OCN, RUNX2, via Wnt, OPG, RANKL, TRAP, VEGF and CD31),histological, immunohistochemical (ALP, OPN, OCN, RUNX2, via Wnt, OPG, RANKL, TRAP,VEGF and CD31), birefringence and, in the TI and TID groups, biomechanical (counter-torque)analyses. Samples from animals euthanized 28 days after surgery were analyzed by RT-PCR (ALP,iBSP, OCN, RUNX2, Wnt pathway, OPG, RANKL, TRAP, VEGF and CD31), microtomography(BV.TV, Tb.Th, Tb.N, Tb.Sp, Po.tot and I. S), confocal microscopy (daily mineral apposition,active mineralization surface and bone dynamics), histology, immunohistochemistry (ALP, OPN,OCN, RUNX2, Wnt pathway, OPG, RANKL, TRAP, VEGF and CD31), birefringence and, in theTI and TID groups, biomechanics - counter-torque. The quantitative data will be subjected to thehomoscedasticity test to select the appropriate statistical test (parametric or non-parametric) with a significance level of 5% (p¿0.05).