Functionally relevant genetic variants of glutathione S-transferase GSTM5 in cynomolgus and rhesus macaques.

Glutathione S-transferase (GST) is a family of enzymes important for conjugation with glutathione of endogenous and exogenous compounds. Human GSTM1 null allele is associated with toxicity and cancers. Cynomolgus and rhesus macaques have molecular and enzymatic similarities of GSTs to humans; however, genetic variants have not been investigated. In macaques, instead of pseudogenized GSTM1, GSTM5 is a predominant GSTM isoform. In this study, re-sequencing of GSTM5 in 64 cynomolgus and 31 rhesus macaques found 6 non-synonymous variants, and 1 variant (IVS5 + 1) causing exon skip. Of these 7 variants, 3 and 1 were found only in Indochinese and Indonesian cynomolgus macaques, respectively. Cynomolgus GSTM5-mediated styrene 7,8-oxide and trans-stilbene oxide conjugation activities correlated with GSTM protein levels immunochemically quantified in cynomolgus liver samples. Using recombinant GSTM5 proteins, 4 of the 6 non-synonymous variants including E29Q, L96R, M166V and S201N showed substantially lower metabolic activities. Moreover, a homozygote for E29Q and heterozygotes for S201N or IVS5 + 1 showed significantly lower conjugation activities in liver cytosolic fractions as compared with wild-type animals. Therefore, the present results suggest that inter-animal variability of GST-dependent drug metabolism is at least partly accounted for by GSTM5 variants in cynomolgus and rhesus macaques as pre-clinical animal models.

The use of porous beta-tricalcium phosphate blocks with platelet-rich plasma as an onlay bone graft biomaterial.

BACKGROUND: An experimental study of rabbit calvaria evaluated the suitability of porous beta-tricalcium phosphate (beta-TCP) block as a biomaterial for onlay bone grafting and determined whether the addition of platelet-rich plasma (PRP) can accelerate bone formation inside the pores of the beta-TCP block. METHODS: In eight rabbits, the calvarium was exposed, and the marrow was penetrated. The beta-TCP blocks were made of Ca3(CO4)3 (porosity, 75%; diameter, 8 mm; thickness, 5 mm). For the experimental group, the blocks were treated with PRP; for the control group, the blocks were treated with venous blood only. Each block was placed in the bone, attached with a titanium screw, and covered with a cutaneous flap. The animals were sacrificed after 3 months, and the tissue ingrowth into the blocks was euthanized. RESULTS: Histologic and histomorphometric measurements demonstrated that there was no inflammatory infiltration around the blocks in either group. New bone formation inside the blocks originated from the parent bone in both groups. The mineralized bone generated tended to climb along the inner walls of the block. In addition, mineralized bone formation was noted around the titanium screw. Furthermore, there was no significant difference between the experimental and control groups in the relative amounts of newly generated tissue and mineralized bone generated in the blocks. CONCLUSION: Porous beta-TCP block is a promising biomaterial for clinical situations requiring bone augmentation; however, the addition of PRP did not induce significantly more new bone formation.