Megakaryocytopoiesis and apoptosis in patients with myelodysplastic syndromes

Excessive naked megakaryocyte nuclei in myelodysplastic syndrome mimicking idiopathic thrombocytopenic purpura: a complicated pre- and post-transplantation course

A boy 3 years 7 months old with thrombocytopenia and history of intracranial hemorrhage who underwent bone marrow transplantation is presented. He was refractory to steroids, immunoglobulin G, vincristine, azathioprine, cyclosporine A, interleukin-11, chemotherapy, and splenectomy. Idiopathic thrombocytopenic purpura was excluded by light /electron microscopic and flow cytometric findings; the diagnosis of refractory cytopenia, a subgroup of pediatric myelodysplastic syndrome, was made. Naked megakaryocyte nuclei were 55.38 +/- 28.2% vs. 31.67 +/- 23.22% of all megakaryocytes in the patient and the control group of 9 patients with idiopathic thrombocytopenic purpura, respectively (p = .016). The posttransplatation course was complicated by delayed platelet engraftment, bronchiolitis obliterans associated with pneumocystis carinii pneumonia, which resolved completely.

Differentiation and hematopoietic-support of clonal cells in myelodysplastic syndromes

Studies were performed to obtain evidence of the differentiating and hematopoietic potential of marrow clone-original cells in patients with myelodysplastic syndromes (MDS). First, results of correlation analysis between bone marrow clonal cells and blast percentages for a total of 60 MDS showed that almost all cases had higher clonal (mean 50.1%) than blast proportion (mean 7.0%) (p < 0.001). In contrast, in 16 AML patients, mean clone/blasts disparity was nearly zero. Secondly, the amount of clone-original individual cells were defined in mature hematopoietic cells, mean 47.9% in segmented granulocytes, 47.1% in orthochromatic normoblasts and 37.8% in mature megakaryocytes. In addition, FISH examination showed approximately similar proportions of clonal cells in peripheral blood and marrow for all 22 tested cases (mean 39.1% in blood vs 49.8% in marrow). Moreover, the neutrophils in MDS peripheral blood oxidized dihydrorhodamine123 (DHR) nearly the same as neutrophils in a normal donor's circulation, while obviously poor function was observed in neutrophils from AML blood. Of note, research on clonality had an unexpected outcome as most of the typical morphological dysplastic cells possessed normal karyotypes. These findings lead to the proposal that the biological features of MDS clones are distinctive from those of AML clones.

Comparative study on cancer cell apoptosis between gastric and intestinal-type human gastric carcinoma

Apoptosis of cancer cells between the gastric and intestinal-type human gastric carcinoma were compared in terms of the expression of oncogene MDM2 and CD68, the histological types, the infiltration depth, and lymph node metastasis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay was employed to stain apoptotic cells. Histochemical method(AB-PAS) was applied to stain mucus that is neutral or acidic in nature. Immunohistochemical method (SABC) was used to detect expression of MDM2 and CD6. The results showed that the mean apoptosis index (AI) of total 48 cases was 8.60+/-2.60. AI in the 30 intestinal type cases was significantly higher than that in the 18 gastric type cases (t=4.67, P<0.01). In the 30 intestinal type cases, the spontaneous apoptosis index of MDM2 negative cases was significantly higher than that of the positive cases (t=7.16, P<0.01). And in the 18 gastric type cases, the same result was found. (t=11.39, P<0.01). The MDM2 positive ratio in gastric type cases was higher than that in intestinal type cases (chi2=4.68, P<0.05). There is no significant difference in AI between cases of lymph node metastasis and non-metastasis cases in intestinal type cases (t=0.26, P>0.05). But in the gastric type cases, a significant difference existed (t=5.87, P<0.01). A significant difference in lymph node metastasis ratio was found between the two gastric carcinoma types (chi2=4.48, P<0.05). The CD68 expression ratio in the 30 intestinal type cases was much lower than that in the 18 gastric type cases (t=4.29, P<0.01). AI of 25 MDM2-positive cases was much lower than that of the 23 MDM2-negative cases (t=7.80, P<0.01). CD68 positive ratio in the 25 MDM2-negative cases was much lower than that in the 23 negative cases. The difference was statistically significant (t=10.90, P<0.01). Except for few cells scattering within the cancer nest, most CD68 positive cells infiltrated in the interstitium around the cancer tissue. In the high-AI cases, CD68-positive cells increased. And the CD68-positive cells decreased in low-AI cases (r=0.96, P<0.01). Logistic regression analysis suggested that among the control variables, only AI was a statistically significant factor in the regression model (chi2=9.64, P<0.01). We concluded that (1) the spontaneous apoptosis index in gastric-type cases of gastric carcinoma was significantly lower than that in intestinal type cases; (2) AI in the two types was influenced by the expression of MDM2 and lymph node metastasis, but no visible connection was found between AI and the infiltration depth or histological types; (3) in the intestinal type cases, AI and the CD68-positive cells increased in MDM2-negative cases.

Megakaryocytic dysfunction in myelodysplastic syndromes and idiopathic thrombocytopenic purpura is in part due to different forms of cell death

Platelet production requires compartmentalized caspase activation within megakaryocytes. This eventually results in platelet release in conjunction with apoptosis of the remaining megakaryocyte. Recent studies have indicated that in low-risk myelodysplastic syndromes (MDS) and idiopathic thrombocytopenic purpura (ITP), premature cell death of megakaryocytes may contribute to thrombocytopenia. Different cell death patterns have been identified in megakaryocytes in these disorders. Growing evidence suggests that, besides apoptosis, necrosis and autophagic cell death, may also be programmed. Therefore, programmed cell death (PCD) can be classified in apoptosis, a caspase-dependent process, apoptosis-like, autophagic and necrosis-like PCD, which are predominantly caspase-independent processes. In MDS, megakaryocytes show features of necrosis-like PCD, whereas ITP megakaryocytes demonstrate predominantly characteristics of apoptosis-like PCD (para-apoptosis). Triggers for these death pathways are largely unknown. In MDS, the interaction of Fas/Fas-ligand might be of importance, whereas in ITP antiplatelet autoantibodies recognizing common antigens on megakaryocytes and platelets might be involved. These findings illustrate that cellular death pathways in megakaryocytes are recruited in both physiological and pathological settings, and that different forms of cell death can occur in the same cell depending on the stimulus and the cellular context. Elucidation of the underlying mechanisms might lead to novel therapeutic interventions.