Influência do treinamento de força associado ou não ao raloxifeno sobre o perfil transcricional e microestrutural ósseo de ratas Wistar naturalmente envelhecidas / Influence of strength training associated or not with raloxifene on transcriptional and microstructural bone profile of naturally aged female Wistar rats

A ocorrência de doenças crônicas e degenerativas é significativamente maior nos organismos durante o envelhecimento, dentre elas, a osteoporose, que resulta em aumento no número de fraturas. As fraturas são as consequências mais dramáticas da osteoporose, sendo que do colo do fêmur é a mais severa, com maior incidência de morbidades e mortalidade. A menor concentração plasmática de estrogênio nas mulheres menopausadas, exerce ação primordial no desenvolvimento desta doença. Desta maneira, o objetivo deste estudo foi estudar a prevenção da osteoporose em decorrência do envelhecimento reprodutivo feminino, especificamente no período de periestropausa, utilizando treinamento de força (TF), raloxifeno (Ral) ou combinação de TF e Ral. Durante 120 dias, ratas Wistar no período do envelhecimento (18 a 21 meses) realizaram TF em escada três vezes por semana, receberam Ral (1mg/Kg/dia) por gavagem, ou realizaram TF associado ao tratamento com Ral. Microarquitetura óssea cortical e trabecular, densidade mineral óssea areal (DMOa), força óssea, imunoistoquímica (OCN, TRAP e SOST) e superfície de osteoclastos do colo do fêmur foram avaliadas, além de PCR (Runx2, Sp7, Alp, Bsp, Ocn, Rank, Rankl, Opg, Trap e Ctsk) e Western Blot (p-ERα e TRAP) do tecido ósseo de todo o fêmur. Os resultados demonstram que os tratamentos modularam o ciclo de remodelamento ósseo de maneiras diferentes: TF estimulou RNAm de marcadores osteoblásticos e osteoclásticos, enquanto Ral diminuiu marcadores osteoclásticos e TF associado a Ral aumentou marcadores osteoblásticos e diminuiu osteoclásticos. Ambos tratamentos resultaram em melhora da microarquitetura trabecular do colo do fêmur de ratas na periestropausa, todavia, apenas o TF foi capaz de melhorar além da microarquitetura trabecular, a cortical e força óssea. Desta maneira, sugerimos que a realização de TF, utilização de Ral ou a associação de TF e Ral durante a periestropausa são intervenções válidas na prevenção de osteoporose em decorrência do envelhecimento reprodutivo feminino, porém os efeitos do TF parecem ser superiores. Levando em consideração que a carga mecânica gerada pelo TF age também em tecidos não esqueléticos, concluímos que TF pode ser intervenção sistêmica para osteoporose. Esses resultados adicionam novas informações à literatura sobre terapêuticas preventivas para osteoporose e fornecem informações relevantes para estudos pré-clínicos(AU)

The association of aging with osteoporosis results in an increased number of fractures. In these fractures, the femoral neck is involved in 75% of affected women and is one of the most dramatic possible consequences. The aim of this study was to prevent female osteoporosis using strength training (ST), raloxifene (Ral) or a combination of ST plus Ral during the natural female aging process, specifically in the periestropause period. For 120 total days, aging female Wistar rats at 18-21 months of age performed ST on three times per week, and Ral was administered daily by gavage (1mg/kg/day). Bone microarchitecture, areal bone mineral density (aBMD), bone strength of the femoral neck, immunohistochemistry, western blotting (p-ERα and TRAP) and RT-PCR were assessed. We found that the treatments modulate the bone remodeling cycle in different ways. Both ST and Ral treatment resulted in improved bone microarchitecture in the femoral neck of rats in late periestropause. However, only ST improved cortical microarchitecture and bone strength in the femoral neck. In addition, ST stimulated mRNA levels of osteoclastic and osteoblastic markers, while Ral decreased mRNA levels of osteoclastic markers. The combined ST plus Ral therapy increased osteoblastic markers and decreased osteoclast markers. In this way, we suggest that SF, the use of Ral or the association of ST and Ral during periestropause are valid interventions in the prevention of osteoporosis due to female reproductive aging, but the effects of ST seem to be superior, taking into account that the mechanical load generated by ST also acts on nonskeletal tissues, we conclude that ST can be a systemic intervention for osteoporosis. These results add new information to the literature on preventive therapies for osteoporosis and provide relevant information for preclinical studies(AU)

Aging impairs osteoblast differentiation of mesenchymal stem cells grown on titanium by favoring adipogenesis

ABSTRACT Aging negatively affects bone/titanium implant interactions. Our hypothesis is that the unbalance between osteogenesis and adipogenesis induced by aging may be involved in this phenomenon. Objective We investigated the osteoblast and adipocyte differentiation of mesenchymal stem cells (MSCs) from young and aged rats cultured on Ti. Material and Methods Bone marrow MSCs derived from 1-month and 21-month rats were cultured on Ti discs under osteogenic conditions for periods of up to 21 days and osteoblast and adipocyte markers were evaluated. Results Cell proliferation, alkaline phosphatase (ALP) activity, extracellular matrix mineralization and gene expression of RUNX2, osterix, ALP, bone sialoprotein, osteopontin, and osteocalcin were reduced in cultures of 21-month rats compared with 1-month rats grown on Ti. Gene expression of PPAR-γ , adipocyte protein 2, and resistin and lipid accumulation were increased in cultures of 21-month rats compared with 1-month rats grown on the same conditions. Conclusions These results indicate that the lower osteogenic potential of MSCs derived from aged rats compared with young rats goes along with the higher adipogenic potential in cultures grown on Ti surface. This unbalance between osteoblast and adipocyte differentiation should be considered in dental implant therapy to the elderly population.