ABSTRACT
El estudio de la megacariopoyesis humana se ha visto obstaculizado por la relativa escasez de megacariocitos en la médula ósea (0,05-0,2 % de las células medulares), lo que ha llevado a la optimización de protocolos de expansión in vitro a partir de precursores de diversos orígenes (cordón umbilical, médula ósea y sangre periférica con o sin movilización previa). Los cultivos celulares a partir de precursores han permitido la producción y el estudio tanto de megacariocitos así como de proplaquetas y plaquetas Sin embargo, la producción in vitro óptima de megacariocitos que culminen todos los estadios de diferenciación es un reto aún no resuelto. En este trabajo reportamos los hallazgos concernientes a la determinación de las condiciones y concentraciones de trombopoyetina para lograr una óptima relación entre la cantidad de trombopoyetina empleada y el porcentaje y grado de diferenciación megacariocítica en muestras obtenidas de cinco donantes alogénicos aceptados para trasplante de médula ósea.
The study of human megakaryocytopoiesis has been hampered by the relative scarcity of megakaryocytes in bone marrow (0.05-0.2 % of medullary cells), which has led to the optimization of protocols of in vitro expansion of precursors from diverse sources (umbilical cord, bone marrow and peripheral blood with or without previous mobilization). Cell cultures from different precursors have allowed the production and study of megakaryocytes as well as proplatelets and platelets. However, the in vitro production of megakaryocytes that culminate all stages of differentiation is a challenge that has not yet been resolved. In this work we report the findings related to the determination of thrombopoietin treatment conditions and concentrations to achieve an optimal relationship between the amount of thrombopoietin and the percentage and degree of megakaryocytic differentiation in five allogeneic donors that were accepted for bone marrow transplantation.
O estudo da megacariopoiese humana tem sido dificultado pela relativa escassez de megacariócitos na medula óssea (0,05-0,2 % das células medulares), o que levou à otimização dos protocolos de expansão in vitro a partir de precursores de diversas origens (cordão umbilical, medula óssea e sangue periférico com ou sem mobilização prévia). Culturas de células a partir de precursores permitiram a produção e o estudo tanto de megacariócitos e de proplaquetas e plaquetas. No entanto, a produção ótima in vitro de megacariócitos que culminam em todas as fases de diferenciação é um desafio ainda não resolvido. Neste trabalho, relatamos as descobertas relativas à determinação das condições e concentrações de trombopoietina para obter uma relação ótima entre a quantidade de trombopoietina usada e a taxa e o grau de diferenciação megacariocítica em amostras obtidas de cinco doadores alogênicos aceitos para transplante de medula óssea.
Subject(s)
Humans , Thrombopoietin/analysis , Megakaryocytes/cytology , Antigens, CD34/analysis , Cells, Cultured/cytology , Leukapheresis , Platelet Membrane Glycoprotein IIb/analysis , Integrin beta3/analysis , Culture Techniques/methodsABSTRACT
Liver tissuses obtained from 5 human fetuses between 11 weeks and 23 weeks of gestation during the high activity of hepatic hemopoiesis were observed with transmission electron microscope using continuous series of thin sections. The objective of present study was to evaluate ultrastructures of megakaryopoietic cells, the migration of extravascular megakaryocyte into the sinusoidal lumen and the relevence between a migrated megakaryocyte and a Kupffer cell. Immature megakaryocytes were usually observed between growing hepatic laminae and within hepatic sinusoids. A megakaryoblast contained numerous polyribosomes, rather large mitochondria, short tubular elements of rough endoplasmic reticulum and small granules. Moreover, demarcation tubules and a few small specific granules were observed in immature megakaryocytes. The nucleus was mononuclear but frequently indented. With maturation, the nuclei were multilobulated. In the cytoplasm, in contrast to the decrease in polyribosomes and rough endoplasmic reticulum, the numerous specific granules and well -developed demarcation membrane system were predominant. Thereafter cytoplasmic zonation was observed clearly in maturing and mature megakaryocytes. Some megakaryocytes passed through the sinusoidal lining epithelium and into the hepatic sinusoids. The cell to cell interaction was often found as adhesion between migrated megakaryocyte and Kupffer cell, and erythroblasts within megakaryocyte (emperipolesis). These results suggest that intravascular megakaryopoiesis in addition to extravascular megakaryopoiesis occurs to produce platelet during the human fetal liver.
Subject(s)
Humans , Pregnancy , Blood Platelets , Cell Communication , Cytoplasm , Emperipolesis , Endoplasmic Reticulum, Rough , Epithelium , Erythroblasts , Fetus , Liver , Megakaryocyte Progenitor Cells , Megakaryocytes , Membranes , Mitochondria , Polyribosomes , ThrombopoiesisABSTRACT
Cyclic thrombocytopenia is a rare disorder with cyclic change of the platelet counts. Although the pathogenesis of the disorder has not been clarified, recent reports suggest that periodic destruction and/or ineffective production of platelets may be important causes of the disease. We report a 24-year-old female with the episodes of severe thrombocytopenia (minimum platelet count 2x109/L) followed by normal or higher platelet counts (maximum platelet count 877x109/L). The period of platelet count fluctuation was about 20-40 days. Morphological examination of bone marrow showed the cyclic disappearance of mature and immature megakaryocytes. These findings indicate that the cause of platelet fluctuation is periodic failure of megakaryocytopoiesis.