Sola-Visner Martha C, Christensen Robert D, Hutson Alan D, Rimsza Lisa M
Department of Pediatrics, University of Florida, Gainesville, FL 32611, USA.
Pediatr Res. 2007 Apr;61(4):479-84. doi: 10.1203/pdr.0b013e3180332c18.
Thrombocytopenia is frequent among sick neonates, but little is known about its underlying mechanisms. It is known, however, that neonatal megakaryocytes are smaller and of lower ploidy than their adult counterparts and that smaller megakaryocytes produce fewer platelets than larger, more polyploid, megakaryocytes. We hypothesized that neonatal megakaryocytes would not increase their size in response to thrombocytopenia, thus limiting the ability of neonates to mount a response. To test this, we obtained marrow specimens from thrombocytopenic and nonthrombocytopenic neonates and adults. Megakaryocytes were immunohistochemically stained, quantified using an eyepiece reticle, and measured using an image analysis system with incorporated electronic micrometer. We found that, after adjusting for differences in cellularity, neonates and adults had similar megakaryocyte concentrations. When samples from the same sources were compared (tibial clot and vertebral body sections in neonates, iliac crest biopsies in adults), there were also no differences in megakaryocyte concentration between thrombocytopenic and nonthrombocytopenic subjects. The megakaryocyte diameter, however, was greater in adults than in neonates (19.4 +/- 3.0 versus 15.3 +/- 1.7 microm, p<0.0001). Thrombocytopenic adults also had a higher proportion of large megakaryocytes than nonthrombocytopenic adults (p<0.001). This was not observed among thrombocytopenic neonates, suggesting a developmental limitation in their ability to increase megakaryocyte size.
血小板减少症在患病新生儿中很常见，但其潜在机制却鲜为人知。然而，已知新生儿巨核细胞比成人巨核细胞更小且多倍体程度更低，并且较小的巨核细胞产生的血小板比更大、多倍体程度更高的巨核细胞少。我们推测新生儿巨核细胞不会因血小板减少而增大其大小，从而限制了新生儿做出反应的能力。为了验证这一点，我们从血小板减少和非血小板减少的新生儿及成人身上获取了骨髓标本。巨核细胞经免疫组织化学染色，使用目镜测微尺进行定量，并使用带有电子测微计的图像分析系统进行测量。我们发现，在调整细胞密度差异后，新生儿和成人的巨核细胞浓度相似。当比较来自相同来源的样本时（新生儿中的胫骨血块和椎体切片，成人中的髂嵴活检）,血小板减少和非血小板减少的受试者之间的巨核细胞浓度也没有差异。然而，成人巨核细胞的直径大于新生儿（19.4±3.0对15.3±1.7微米, p<0.0001）。血小板减少的成人中大型巨核细胞的比例也高于非血小板减少的成人（p<0.001）。在血小板减少的新生儿中未观察到这种情况，这表明他们在增大巨核细胞大小的能力方面存在发育限制。
