Isolation and Characterization of Normal Human Megakaryocytes

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Abstract
Summary Human megakaryocytes have been isolated from marrow obtained from ribs removed at thoracotomy. All but one of the patients had normal pre‐operative platelet and leucocyte counts. Megakaryocytes averaged 0·37% of all cells in marrow cell suspensions from nine consecutive subjects. A 283‐fold purification (to 10·3%) was achieved by a density gradient centrifugation followed by two successive velocity sedimentations at unit gravity. The net yield, 12 800 megakaryocytes per specimen, was sufficient for many kinds of morphological study. Bright‐field, phase contrast, and electron microscopy were used to characterize the younger and smaller megakaryocytes. Ploidy analyses were carried out on 100–235 megakaryocytes per specimen; 8N was the predominant ploidy class in isolated megakaryocyte populations from three individuals. The mean megakaryocyte diameter was 24 μm in three other specimens and the range was 10–48 μm. This data had a normal distribution and overlapped minimally with the size range of all other marrow cells. The presence of a distinct size threshold (at 11·5 μm) implied that size alone may be a sufficient objective criterion for identification of human megakaryocytes.