Relationship between abnormal osteoblasts and cellular immunity in multiple myeloma

Bone destruction and abnormal immunity always occur in patients with multiple myeloma (MM), which manifested by impaired osteoblasts and immune system. In this study, we investigated the quantity and function of osteoblasts by co-culture, the status of cellular immunity by flow cytometry, and the relationship between them in MM patients. The results showed that the numbers and function of osteoblasts in MM patients were lower than those in normal controls. Bortezomib could increase the numbers, calcium depositions and the expression of Bone morphogenetic protein–2 (BMP-2) mRNA of osteoblasts from MM patients in vitro. The status of cellular immunity in MM patients was abnormal, including decreased ratio of CD4⁺/CD8⁺, DC1/DC2 and Th1/Th2, and increased ratio of regulatory T cells. The ratio of CD4⁺/CD8⁺(r = 0.685) and CD4⁺CD25⁺/CD3⁺T(r = 0.568) were positively correlated with the quantity of osteoblasts (both P < 0.05). The serum interleukin-7(IL-7) level of MM patients was higher than that of normal controls (2.07 ± 0.71 vs. 1.62 ± 0.15 ng/L, P < 0.05), and was negatively correlated with the quantity of osteoblasts (r = -0.682, P < 0.01). Our data indicated that the proliferation and osteogenic potential of osteoblasts in MM patients were decreased which could be recovered by bortezomib in vitro. The down-regulation of cellular immunity was correlated with the quantity of osteoblasts.