Effect of MPC-11 myeloma and MPC-11 + IL-1 receptor antagonist treatment on mouse bone properties

This study examines the effects of an IL-6-producing murine multiple myeloma cell line on trabecular and cortical mouse bone, and evaluates the efficacy of interleukin-1 receptor antagonist (IL-1ra) in mitigating bone destruction. Six-week-old BALB/c mice were assigned to two groups: normal controls and myeloma animals (5 x 10(7) MPC-11 cells on day 0). Myeloma animals were further assigned to three unique groups: MPC-11 only; MPC-11 treated with hyaluronic acid (HA); and MPC-11 + IL-1ra/HA (100 mg/kg). Disease development was assessed at 14 and 21 days via spleen, liver, and proximal tibia histology; histomorphometry at the femoral middiaphysis; and long bone composition and mechanical testing. Histologic analysis revealed marked myeloma infiltration into organs and bone marrow and gross bone resorption of the proximal tibia. IL-1ra tended to decrease bone resorption at the proximal tibia; however, it had no effect on quantitatively measured bone parameters. Whole femur and tibia, and tibial epiphysis, percent mineralization was decreased (3.0%, 2.9%, and 6.3%, respectively) in all MPC-11 groups. The presence of myeloma did not affect long bone stiffness, strength, or length over the 3 week study. The percent of the femoral endosteal perimeter showing excessive resorption ( approximately 60%) in the MPC-11 groups increased significantly after 21 days. MPC-11 cell presence caused no change in bone formation or morphology. Normal growth mechanisms were not impacted, as the bones lengthened and increased in size and mass despite the presence of myeloma. IL-1 does not appear to be a primary factor in in vivo bone destruction caused by the MPC-11 cell line. These findings reveal the stochastic nature of bone lesions in multiple myeloma and suggest that IL-1 is not a cytokine critical to this disease pathology.