CYTOKINE RELEASE FROM MARROW MONONUCLEAR-CELLS IS NEGATIVELY CORRELATED TO CORTICAL ELASTICITY IN NON-OSTEOPOROTIC POSTMENOPAUSAL WOMEN

Activation of bone remodeling is likely to be under the control of mec hanical factors acting, in part, through soluble local factors. We the refore investigated a relationship between cytokine production by marr ow cells and bone elasticity. We studied 36 non-osteoporotic postmenop ausal women undergoing hip arthroplasty for hip arthrosis (mean age. 6 8 +/- 8 years; lumbar BMD Z-score: +0.54 +/- 0.33 SD). Adherent marrow mononuclear cells were cultured for 48 hours with autologous plasma, and supernatants were harvested for PGE2, IL-1, TNF-alpha, and IL-6 me asurements. Femoral neck cortical bones were removed during surgery fo r cortical histomorphometric evaluation and determination of elasticit y indices (C-33) using ultrasonic transmission method. In this nonoste oporotic population, femoral neck longitudinal elasticity indices were inversely correlated to both cortical thickness (r = -0.58, P < 0.01) and cortical porosity (r = -0.33, P < 0.01). The longitudinal elastic ity indices were also negatively correlated to basal IL-1 and TNF-alph a release by adherent mononuclear marrow cells (r = -0.59, P < 0.01; r = -0.60, P < 0.01, respectively). However, no relationship was found between the three cytokines tested and either cortical thickness or po rosity. These data show a link between cortical biomechanical properti es and local factors involved in bone remodeling. We suggest that incr eased bone elasticity decreases transmission of strain, which in turn decreases cytokine release from marrow cells. However, whether cytokin es influence bone elasticity or vice versa remains to be demonstrated.