Differences between newborn and adult mice in their response to immune thrombocytopenia.
BACKGROUND
Sick neonates frequently develop severe thrombocytopenia.


OBJECTIVE
In order to test the ability of fetal mice to increase their megakaryocyte size and ploidy in response to thrombocytopenia, we injected an antiplatelet antibody (MWReg30) into pregnant mice daily for 7 days, and into nonpregnant adult mice to serve as controls. After that time, platelet counts were obtained and megakaryocytes in the bone marrow, liver, and spleen were stained with anti-von Willebrand factor antibody, individually measured, and quantified.


RESULTS
Our study demonstrated that megakaryocytopoiesis in newborn mice shares many features of human fetal/neonatal megakaryocytopoiesis, including the small size of megakaryocytes. In response to thrombocytopenia, adult mice increased megakaryocyte volume and concentration, primarily in the spleen. Newborn mice, in contrast, increased the megakaryocyte concentration in the spleen, but exhibited no increase in megakaryocyte volume in any of the organs studied. In fact, the megakaryocyte mass was significantly lower in the bone marrow of thrombocytopenic neonates than in age-matched controls.


CONCLUSIONS
We concluded that fetuses have a limited ability to increase their megakaryocyte mass in response to consumptive thrombocytopenia, compared to adult mice. These observations provide further evidence for the existence of biological differences between fetal/neonatal and adult megakaryocytopoiesis.
Department of Pediatrics, University of Florida, Gainesville, FL, USA.
Zhongbo
Z
Hu
William B
WB
Slayton
Lisa M
LM
Rimsza
Matthew
M
Bailey
Hannes
H
Sallmon
Martha C
MC
Sola-Visner
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000009:adverse effects; D001792:Blood Platelets / Q000166:cytology / Q000276:immunology*; D001853:Bone Marrow / Q000276:immunology; D048429:Cell Size; D005260:Female; D008099:Liver / Q000166:cytology / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D011247:Pregnancy; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013921:Thrombocytopenia / Q000276:immunology* / Q000473:pathology; D034061:Thrombopoiesis / Q000276:immunology*; D014841:von Willebrand Factor / Q000032:analysis / Q000276:immunology
D000906:Antibodies; C029417:Von Willebrand antigen; D014841:von Willebrand Factor