BONE CHANGES IN MUCOPOLYSACCHARIDOSIS VI IN CATS AND THE EFFECTS OF BONE-MARROW TRANSPLANTATION - MECHANICAL TESTING OF LONG BONES

Mucopolysaccharidosis VI (MPS VI) is a genetic lysosomal storage disea se in which a defect in aryl sulfatase B leads to accumulation of the glycosaminoglycan dermatan sulfate and abnormalities in the developmen t of cartilage and bone, A feline model of this disease was used to ev aluate the efficacy of bone marrow transplant (BMT) therapy, Long bone s from MPS VI cats (N = 6) and MPS VI + BMT cats (N = 7) were compared with control cats (N = 11) and control + BMT cats (N = 5) in mechanic al tests, Dissected femurs and tibias were subjected to three-point be nding and a subgroup of tibias were tested with the mechanical respons e tissue analyzer (MRTA) in which vibration is used to measure tissue impedance, Cats with MPS VI had markedly decreased stiffness and stren gth in both bones (p < 0.01). There was no significant difference in t he MPS VI + BMT group, In the tibias, there was also decreased stiffne ss and strength in the control + BMT group as compared to controls (p < 0.05). However, when cross-sectional area was used to normalize for bone size there was good correlation with strength in both femurs (r = 0.907, p < 0.01) and tibias (r = 0.915, p < 0.1), and there were no s ignificant differences between groups in the modulus of elasticity, In the tibias, in which stiffness was measured by MRTA, there was signif icant correlation with three-point bending stiffness, These results in dicate that, in cats with MPS VI, the decreases in stiffness and stren gth of long bones can be largely accounted for by the decrease in bone size (osteopenia) that is present.