Institute of Hematology and Blood Transfusion, Prague, Czech Republic Erythroid and granulocytic precursors represent convenient models to study both natural and induced apoptotic process with and without preceding terminal maturation because their maturation stages are well known and defined. Terminal maturation of erythroblasts preceding the programmed cell death is accompanied by the chromatin condensation, transformation of nucleoli to micronucleoli and formation of HERDS (nuclear heterogeneous ectopic ribonucleoprotein derived structures: see, Biggiogera et al., 1999). Pathological erythroblasts in refractory anemia of myelodysplastic syndrome entering to premature apoptosis exhibited structural abnormalities of micronucleoli as well as their premature loss and HERDS. In cultured leukemic granulocytic precursors (HL-60 cells), the apoptotic process without previous terminal maturation induced by photodynamic treatment (see Smetana et al., 2000) was characterized by chromatin condensation, reduction of AgNORs, fibrillar centers and surrounding dense fibrillar components without reduction of the nucleolar size. Thus presented observations indicated that in pathological erythroblasts the apoptotic process was preceded by terminal maturation in which the transformation of nucleoli to micronucleoli with structural abnormalities, loss of nucleoli together with characteristic chromatin condensation and HERDS reflected the irreversible pre-apoptotic state. Such state, however, was absent after induction of the apoptotic process in HL-60 cells by photodynamic treatment.
The present study was supported by the Grant NC/7603/3 of the Inner Grant Agency of the Ministry of Health of the Czech Republic
References:
Biggiogera et al., Histochem. Cell Biol. 112, 473, 1999
Smetana et al., J. Photochem. Photobiol. B: Biol. 59, 80, 2000
