Biomechanical properties of bones from rats treated with sevelamer [Biomehanička svojstva kostiju štakora tretiranih sevelamerom]

Drača, Nataša and Tikvica, Ana and Eljuga, Domagoj and Semenski, Damir and Brnčić, Mladen and Vukičević, Slobodan (2011) Biomechanical properties of bones from rats treated with sevelamer [Biomehanička svojstva kostiju štakora tretiranih sevelamerom]. Collegium Antropologicum, 35 (2). pp. 557-563. ISSN 0350-6134

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Abstract

Sevelamer hydrochloride is used for ten years in patients on dialysis as a phosphate binder. We have previously shown that oral application of sevelamer prevents the bone loss and increases the bone volume in ovariectomized rats. In this study we further analysed the biomechanical properties of bones from rats treated with sevelamer utilizing a threepoint bending test to determine the mechanical properties of the cortical bone of the mid-shaft femur, while the indentation test was used to determine the mechanical properties of cancellous bone in the marrow cavity of the distal femoral metaphysis. Parameters analyzed included: maximum load (F(u)), stiffness (S), energy absorbed (W), toughness (T) and ultimate strength (sigma). The intrinsic properties, stress, elastic modulus and toughness were determined from measured maximum load, strains, stiffness, energy absorbed, outer and inner diameters, and calculated bone cross-sectional moment of inertia. Sevelamer was given to rats for 25 weeks with a content of 3% of sevelamer in a standard diet, starting immediately following ovariectomy (OVX). Animals were divided to the following groups: (1) Sham; (2) Sham + sevelamer 3%; (3) OVX; (4) OVX + sevelamer 3%. Our results showed that sevelamer particularly influenced the rat trabecular bone by increasing the maximum load for 26.2%, energy absorbed for 24.2% and the ultimate strength for 26.2% in sham animals treated with sevelamer 3%, as compared to sham rats. Sevelamer 3% in OVX rats also increased the maximum load for 71.4%, stiffness for 70.7%, energy absorbed for 55.9% and the ultimate strength for 71.3% as compared to OVX controls. In the three bending test sevelamer had a very little effect on preventing loss of bone strenght in the cortical bone. These results collectively suggest that sevelamer improves bone biomechanical properties, mainly affecting trabecular bone quality in both normal and ovariectomized rats.

Abstract in Croatian

Sevelamer hidroklorid koristi se već 10 godina u pacijenata na dijalizi kao fosfatni vezač. Naša prethodna istraživanja pokazala su da oralna primjena sevelamera sprečava gubitak koštane mase i povećava koštani volumen u ovarijektomiranih štakora(1). U ovom ispitivanju analizirali smo biomehaničke karakteristike kostiju štakora tretiranih sevelamerom pomoću »threepoint bending» testa kako bi se odredila biomehanička svojstva kortikalne kosti središnjeg dijela femura, dok se za mehaničke karakteristike trabekularne kosti distalne femoralne metafize koristio test indentacije. Analizirani parametru su bili: maksimalno opterećenje (F(u)), rigidnost (S), apsorbirana energija (W), čvrstoća (T) i maksimalna jakost (sigma). Endogene karakteristike, stres, elastični modul i čvrstoća kostiju dobivene su pomoću izmjerenog maksimalnog opterećenja, rigidnosti, apsorbirane energije, vanjskih i unutarnjih dijametara kosti te izračunatog inercijskog momenta koštanog presjeka. Štakori su dobivali sevelamer 25 tjedana sa standardnom prehranom, počevši odmah nakon ovarijektomije (OVX). Životinje su podijeljene u slijedeće grupe : (1) Sham (lažno operirane životinje); (2) Sham + sevelamer 3%; (3) OVX; (4) OVX + sevelamer 3%. Naši rezultati su pokazali da je sevelamer osobito utjecao na trabekularnu kost povećavajući maksimalno opterećenje za 26,2%, apsorbiranu energiju za 24,2% i maksimalnu jakost za 26,2% u životinja koje su dobivale 3% sevelamera u usporedbi sa životinjama koje su dobivale standardnu prehranu. Sevelamer 3% u ovarijektomiranim štakorima je također povećao maksimalno opterećenje za 71,4%, rigidnost za 70,7%, apsorbiranu energiju za 55,9% i maksimalnu jakost za 71,3% u usporedbi sa OVX kontrolama. U »threepoint bending« testu sevelamer je imao mali utjecaj na sprečavanje gubitka jakosti kortikalne kosti. Ovi rezultati pokazuju da sevelamer poboljšava biomehanička svojstva kosti, prvenstveno djelujući na trabekularnu kost u normalnih i ovarijektomiranih štakora.

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