[A contribution to a study of apoptosis of hematopoietic stem cells CD34+ by flow cytometry before and after cryopreservation]

Apoptosis represents a particular form of programmed cell death which appears in all the damaged cells and potentially hazardous. It plays a crucial role in the development of multicellular organisms by assuring and maintaining the cellular homeostasis. Thus, apoptosis intervenes not only in the normal process of organisms' development but also in immune defence and in cancerous cells detection. Indeed, any blockage in the program of the apoptotic machinery would be responsible of some neurodegenerative and auto-immune diseases and could play a crucial role in different steps of carcinogenesis. Some researchers were very interested in studying apoptosis in hematopoietic stem cells CD34+ which could be intended to be reinfused to patients suffering from malignant diseases. They have noted that kinetic study of apoptosis of the hematopoietic stem cells CD34+ after the process of cryoconservation is also necessary. Such study permits to quantify the real and exact number of the viable hematopoietic stem cells CD34+ and therefore to eliminate such risk which would be associated with the reinfusion of apoptotic cells to patients. In this paper, we describe our contribution to hematopoietic stem cells CD34+ study by flow cytometry before and after cryopreservation by using annexin V as a specific probe allowing detection of phosphatidyl serine, one of the major features of apoptosis. But, we have noted a pronounced induction of apoptosis in peripheral mobilized blood compared to cytapheresis (after cryopreservation: 29.79% of apoptotic HSC CD34+ in peripheral mobilized blood but only 11.67% apoptotic HSC CD34+ in cytapheresis). Besides, we have noticed that hematopoietic stem cells CD34+ have had a statute of viability better than other mononuclear cells. These results put in value the reliability, the simplicity and the efficiency of flow cytometry for the analysis of apoptosis in hematopoietic stem cells CD34+ by following the intensity of fluorescence of annexin V.