Bone Marrow Adipocytes Abnormalities In AML During Complete Remission And The Study On The Forming Mechanisms

Objectives: We retrospectively study the bone marrow biopsies of AML patients during complete remission and normal controls by quantitatively analyzing the morphological characteristics of bone marrow adipocytes and explore the correlation between the abnormal adipocytes and the prognosis of AML. Furthermore, we investigate the formation mechanism of abnormal adipocytes in AML during complete remission(CR), which may provide a novel insight into the early intervention and treatment of leukemia.Methods:(1)As a defined marker of adipocytes, FABP4 was stained by immunohistochemistry in the paraffin-embedded bone marrow biopsies of AML patients during CR and normal controls. The volume, number and size of bone marrow adipocytes were quantitatively analyzed in 63 AML patients during complete remission and 63 normal controls based on a self-developed grid-computing method. Meanwhile, the correlation between the abnormal adipocytes and prognosis of AML was assessed by ROC curve and Kaplan-Meier survival analysis.(2)Bone marrow mesenchymal stem cells(MSCs) were isolated and induced into adipocytes in vitro. The MSC-derived adipocytes and mononuclear cells(MNCs) isolated from bone marrow were treated with cytarabine(Ara-C) and the supernatant and cells were collected to investigate their effects on the functions of adipocytes derived from bone marrow MSCs.(3) The effects of Ara-C on the functions of bone marrow MNCs were studied at gene and protein levels. Effective cytokines in supernatant were screened out to initially explore the formation mechanism of abnormal adipocytes in AML patients during CR.Results:(1) The volume of bone marrow adipocytes and single adipocyte area duringremission were(18.0%±12.0%) and(1485.4±555.9)μ m2 respectively, which were significantly higher than those in normal controls((27.4%±10.5%)and(1920.4±374.5)μ m2 respectively)(P<0.05). Besides, there was no correlation between the volume and single adipocyte area of bone marrow in the patients with AML during complete remission and their age, sex and BMI(P>0.05);(2) The correlation analysis between the volume of bone marrow adipocytes and RFS in AML during remission revealed that the area under the curve(AUC)was 0.629 and higher rate of relapse and shorter relapse-free survival in patients with the volume of adipocyte more than 21.5%(P<0.05); OS analysis revealed that the AUC was 0.636 and higher mortality and shorter overall survival in patients with the volume of adipocyte more than 22.5%(P<0.05); The correlation analysis between single adipocyte area of bone marrow and RFS in AML during remission revealed that the AUC was 0.515 and the cut-off value was 986.5μ m2, but there was no significant difference in the RFS between the groups with single adipocyte area more than 986.5μ m2 and less than 986.5μ m2(P>0.05); OS analysis revealed that the AUC was 0.523 and the cut-off value was 1236.5μ m2, but there was also no significant difference in overall survival between the groups with single adipocyte area more than 1236.5μ m2 and less than 1236.5μ m2(P>0.05).(3) There was no significant difference in the morphology, surface marker, adipogenic capability and osteogenic capability of bone marrow MSCs between the patients with AML during complete remission and normal controls(P>0.05).The supernatant of bone marrow MNCs after chemotherapy significantly inhibited MSC adipogenesis(P<0.05), while the supernatant of adipocytes after chemotherapy had no significant effect on the adipogenic capability of MSC(P>0.05).(4) The m RNA expression levels of leptin, GH, and CTGF of bone marrow MNCs increased significantly after 6 hours chemotherapy, while there was no significant change in the m RNA expression levels of resistin, LRP16 and S100A16. However, only the expression of CTGF significantly increased compared with that before chemotherapy at protein level.Conclusions:(1) Bone marrow adipocytes in AML during CR are abnormal and associated with relapse-free survival and overall survival. Therefore, adipocytes in AML during CR may act as an important indicating factor for poor prognosis, which may provide new ideas for early intervention and treatment of AML.(2) The supernatant of bone marrow MNCs after chemotherapy inhibit the adipogenic differentiation of bone marrow MSC. The mechanism may be that bone marrow mononuclear cells release cytokines CTGF induced by chemotherapy to inhibit the adipogenic differentiation, which resulting that bone marrow adipocytes stay at early stage with less volume and number as well as smaller single adipocyte area.