Muraoka K, Ishii E, Tsuji K, Yamamoto S, Yamaguchi H, Hara T, Koga H, Nakahata T, Miyazaki S
Division of Paediatrics, Saga Prefectural Hospital Koseikan, Japan.
Br J Haematol. 1997 Feb;96(2):287-92. doi: 10.1046/j.1365-2141.1997.d01-2028.x.
Congenital amegakaryocytic thrombocytopenia (CAMT) is an uncommon disorder in newborns and infants, characterized by isolated thrombocytopenia and megakaryocytopenia in the first year without physical anomalies. The defect of thrombopoiesis is not well understood. Recently, thrombopoietin (TPO), the ligand for the c-mpl receptor, was cloned. Accumulating evidence from in vitro and in vivo studies indicate that TPO plays a key role in the regulation of megakaryocytopoiesis. In this study we examined the effect of TPO on megakaryocyte colony formation from a patient with CAMT using a plasma-containing methylcellulose clonal culture. The in vitro results demonstrated a defective response to TPO in megakaryocyte colony formation from bone marrow mononuclear cells (MNC) of the patient. although interleukin-3 (IL-3) but not stem cell factor (SCF) induced only a small number of megakaryocyte colonies. These findings indicated that thrombocytopenia in CAMT could not be corrected by administration of TPO in vitro. Additionally, clonal cultures containing SCF, IL-3, IL-6 and erythropoietin showed decreased numbers of erythroid and myelocytic progenitors in the bone marrow of the patient. The serum TPO level measured by enzyme-linked immunosorbent assay was significantly higher than that in healthy controls. By PCR, marrow MNC from healthy children and from a patient with essential thrombocytosis expressed c-mpl mRNA, whereas no c-mpl mRNA was detected in marrow MNC from the patient with CAMT. There was no difference in the CD34 expression and c-kit mRNA between the CAMT patient and healthy children. The results of this study suggest that the pathophysiology in CAMT may be a defective response to TPO in haemopoietic cells through impaired expression of c-mpl mRNA.
先天性无巨核细胞性血小板减少症（CAMT）是新生儿和婴儿中一种罕见的疾病，其特征为出生后第一年出现孤立性血小板减少和巨核细胞减少，且无身体异常。血小板生成缺陷的原因尚不清楚。最近，血小板生成素（TPO），即c-mpl受体的配体，已被克隆。来自体外和体内研究的越来越多的证据表明，TPO在巨核细胞生成的调节中起关键作用。在本研究中，我们使用含血浆的甲基纤维素克隆培养法，检测了TPO对一名CAMT患者巨核细胞集落形成的影响。体外研究结果显示，该患者骨髓单个核细胞（MNC）的巨核细胞集落形成对TPO的反应存在缺陷。虽然白细胞介素-3（IL-3）而非干细胞因子（SCF）仅诱导产生少量巨核细胞集落。这些发现表明，体外给予TPO无法纠正CAMT中的血小板减少。此外，含有SCF、IL-3、IL-6和促红细胞生成素的克隆培养显示，该患者骨髓中的红系和髓系祖细胞数量减少。通过酶联免疫吸附测定法测得的血清TPO水平显著高于健康对照。通过PCR检测，健康儿童和原发性血小板增多症患者的骨髓MNC表达c-mpl mRNA，而CAMT患者的骨髓MNC中未检测到c-mpl mRNA。CAMT患者与健康儿童之间的CD34表达和c-kit mRNA无差异。本研究结果提示，CAMT的病理生理学机制可能是造血细胞对TPO的反应缺陷，这是由于c-mpl mRNA表达受损所致。
