Exerccio 9- introdues

Contextualization

Gap

State-of-the-Art

importance of the study

purpose of the paper

Radiation Physics and Chemistry, Fator de Impacto 1.189, Fator Qualis B3

Enhanced release of bone morphogenetic proteins from demineralized bone matrix by

gamma irradiation

Volume 111, June 2015, Pages 6266. doi:10.1016/j.radphyschem.2015.02.012

Nak-Yun Sung, Jong-il Choi

1.Introduction

Demineralized bone matrix (DBM) is used extensively for bone implants. Its porous structure is

suitable for bone growth, and its matrix proteins like collagen provide an osteoconductive

support matrix (Gebhart and Lane, 1991 ). Many studies have demonstrated the clinical

potential of DBM implants in the treatment of bone defects (Piattelli et al., 1996; Trevisiol et

al., 2007; Urist, 1965). One of the major challenges with the used of DBM products is ensuring

sterility. Although DBM is exposed to concentrated acid and chloroform during the preparation

process, subsequent handling or incorporation into a composite can lead to contamination. A

safe sterilization method is required to prevent disease transmission and graft contamination.

Gamma irradiation is an effective method for the terminal sterilization of medical devices, as

irradiation does not leave any harmful residues and can be applied to the final product with a

relatively short processing time (Glowacki, 2005). Therefore, some tissue banks employ

gamma irradiation from 60cobalt to kill bacteria, spores, and viruses at a dose ranging from 15

to 25 kGy. However, this method is not utilized by all tissue banks, and some physicians choose

not to use bone implants treated with irradiation because of the documented possibility that

DBM products become less efficacious following gamma irradiation (Anderson et al., 1992;

Currey et al., 1997; Fideler et al., 1995; Gibbons et al., 1991 ; Noyes et al., 1984; Rasmussen et

al., 1994; Salehpour et al., 1995). Several studies have reported the effect of gamma

irradiation on osteoinductive activities of DBM, but osteoinductive testing methods varied

among studies; therefore, the results were inconsistent. The purpose of this study was to

compare the osteoinductive activity assayed between gamma-irradiated and non-irradiated

DBMs in vitro, and bone morphogenetic proteins (BMPs) of DBM were also isolated to

investigate the effect of gamma irradiation

Basic & Clinical Pharmacology & Toxicology Online, Fator de Impacto 2.294, Fator Qualis B2

Effect of risedronate on osteoblast differentiation, expression of receptor activator of NF-B ligand and apoptosis in mesenchymal stem cells

Basic Clin Pharmacol Toxicol. 2011 Aug;109(2):78-84. doi: 10.1111/j.1742- 7843.2011.00685.x.

Fujita H, Kurokawa K, Ogino T, Ono M, Yamamoto M, Oka T, Nakanishi T, Kobayashi N, Tanaka

N, Ogawa T, Suzaki E, Utsumi K, Sasaki J.

Bisphosphonates (BPs) are potent antiresorptive agents and have become the first choice for

the treatment of osteoporosis, metastatic bone disease, Paget s disease and other bone

diseases [1]. BP is a class of non-hydrolysable analogues of pyrophosphate that preferentially

binds to bone hydroxyapatite. BPs can be divided into two groups. One is a non-nitrogen-

containing BP group such as clodronate and the other is a nitrogen-containing BP group such

as risedronate (RIS) alendronate, pamidronate and zoledronate (ZOL). Nitrogen-containing BPs

inhibit farnesyl pyrophosphate (FPP) synthase of the mevalonate pathway, preventing

posttranslational prenylation of GTP-binding proteins, and this inhibition results in dysfunction

and apoptosis of osteoclasts [2,3]. Cell-permeable isoprenoid geranylgeraniol (GGOH) bypasses

FPP synthase and replenishes the cells with a substrate for protein geranylgeranylation, while

GGOH addition blocked the nitrogen-containing BP-induced apoptosis of osteoclasts [4]. ZOL

also directly promoted the proliferation and differentiation of human osteoblast-like cells in

vitro [5]. However, a recent report showed that BPs suppress osteoblast activity independently

of bone resorption in vivo [6]. In addition, an increase in osteoclast numbers and deep

osteoclastic pits have been demonstrated in BP-related osteonecrosis of the jaw, a serious side

effect of nitrogen-containing BP, in patients treated with high-dose BPs [711]. Thus, the

physiological effects of BPs in the regulation of bone metabolism remain unclear. MSCs and

osteoblas precursors can also be targets of BPs. BPs may have indirect effects on bone

resorption mediated by the RANKL of cells from the osteoblast lineage. However, the effects of

BPs on the osteoblast differentiation and RANKL in MSCs are not fully elucidated In this study,

we tested the hypothesis that RIS suppressed osteoblast differentiation and RANKL expression

in MSC. We also investigated whether RIS induced MSC apoptosis and its mechanisms,

particularly focusing on the caspase activation and isoprenoid depletion

Chemical Research in Toxicology, Fator de Impacto 3.667, Fator Qualis A2

Aberrant Cytokinesis and Cell Fusion Result in Multinucleation in HepG2 Cells Exposed to

Silica Nanoparticles

Chem Res Toxicol. 2015 Mar 16;28(3):490-500. doi: 10.1021/tx500473h

Yu Y, Duan J, Geng W, Li Q, Jiang L, Li Y, Yu Y, Sun Z.

Silica nanoparticles (SiNPs) are materials intentionally produced, manufactured, or engineered.

It is among the most utilized nanomaterials in nanotechnology products.1 SiNPs are

industrially used in cosmetics, dentistry, and food ingredients, and in biomedical fields such as

gene therapy, medical imaging, and drug delivery.2,3 It has been reported that about 20% of

toothpastes contain SiNPs.4 Recently, the silica based diagnostic nanoparticles in the form of

C-dots (Cornell dots) were approved by Food and Drug Administration (FDA) for stage I

human clinical trials.5 The high-volume production of SiNPs and their widespread use might

lead to significant environmental, occupational, and consumer exposure. Growing concerns

about the safety of SiNPs were raised. International Agency for Research on Cancer (IARC) had

classified amorphous silica in group 3 (inadequate evidence for carcinogenicity).6 The

Organization of Economic Cooperation and Development (OECD) also listed the SiNPs in the

priority of nanomaterials requiring urgent evaluation.

Various environmental and toxicological studies have been conducted to investigate the toxic

potential of the SiNPs. Most of these studies were described in recent review articles.7,8

Simultaneously, we have also evaluated the safety of SiNPs both in vivo and in vitro.9 11

SiNPs were able to penetrate cells and enter the cell nucleus, binding to macromolecules

including protein and DNA.12,13 It could affect nuclear integrity by forming intranuclear

protein aggregates that can cause inhibition of replication and transcription.13 Previously, we

have demonstrated that the SiNPs could induce DNA damage cell cycle arrest and

multinucleation in HUVECs, L-02, and HepG2 cells,1416 suggesng certain genotoxicity of the

SiNPs. The existing results of genotoxicity studies were consistent with the fact that the SiNPs

were genotoxic.17,18 The genotoxic effects of multinucleation, micronuclei, and chromosomal

aberrations contributed to genetic instability and even tumor initiation.19,20 Titanium dioxide

nanoparticles have been demonstrated to induce multinucleation, chromosomal instability,

and cell transformation in vitro,21 further leading to DNA damage and genetic instability in

vivo in mice.22 A recent carcinogenicity study reported that SiNPs could induce 9.4% tumor

incidence in the lungs of female Wistar rats after intratracheal instillation.2

Multinucleated cells are eukaryotic cells that have two or more nuclei within one cytoplasm.

They can be divided into syncytium and plasmodium.24 The syncytium is generated by cell

fusion and naturally occurs in specialized cells, such as osteoclasts and skeletal muscle

cells.25,26 The plasmodium could result from abnormal cytokinesis,27 spindle assembly check-

point (SAC) defects,28 or acytokinetic cell division.29 It can be observed in hepatocytes and

some tumor cells. Moreover, the defective DNA repair mechanisms could also cause DNA

damage-induced multinucleation.30 Multinucleated cells induced by SiNPs was first observed

in our previous study,15 and the same case was also reported in other nanoparticles.31 33

Although the multinucleation effects occurred after different nanoparticles exposure, the

underlying mechanism of multinucleated cells formation is still unclear. Therefore, it is

necessary to investigate the possible ways and potential biological consequences of

multinucleated cells resulted from SiNP exposure. The present study was a continuous

mechanistic research of the formation of multinucleated cells in HepG2 cells exposed to the

SiNPs. Cellular internalization and multinucleation were first investigated. Time-lapse confocal

imaging was performed to determine whether the multinucleated cells resulted from cell

fusion or abnormal cell division. In a cell mitosis study, the cell cycle and chromosomal

passenger complex (CPC) were evaluated. For further mechanism study, cell cycle control

proteins in G1/S and G2/M checkpoints along with the MAPK/ERK1/2 signaling pathway were

determined.