APOPTOSIS DURING HUMAN
FETAL KIDNEY
DEVELOPMENT
Kidney
morphogenesis is a complex and stepwise process. The formation of mature kidney
in mammals is preceded by two primitive embryonic kidneys known as pronephros
and mesonephros. Metanephros develops as a result of reciprocal inductive
interactions between two primordial mesodermal derivates: ureteric bud, an
epithelial outgrowth of the Wolffian duct, and metanephric blastema, a group of
mesenchymal cells. The ureteric bud induces the metanephric mesenchyme to
differentiate and form nephrons, whilst the metanephric mesenchyme induces the
ureteric bud to grow and branch to form collecting ducts. The nephron goes
through four developmental stages, which are described as: 1) vesicle, 2)
comma-shaped and S-shaped stages, 3) developing capillary loop, and finally 4)
maturing glomerulus. Apoptosis (programmed cell death) is a predominant form of
physiological cell death, by which organism eliminate unwanted or damaged cells.
It is the major component of normal development and disease. Apoptosis is the
result of series of biochemical processes happening in certain order in a dying
cell, among which the most important is activation of enzyme families called
caspases which influence different cell components. Apoptosis is characterized
by membrane blebbing, shrinkage of the cell, nuclear fragmentation and chromatin
condensation. Organelles are preserved almost intact. Cell surface molecules
change. A variety of physiological and pathological stimuli can initiate
apoptosis. They act via receptor mechanisms, through biochemical agents, or
cause DNA and cell membrane damage. Apoptosis is an important component of fetal
development. It is thought that apoptosis is the one of the main regulatory
events involved in kidney morphogenesis, considering that among great number of
developed cells, only a few of them are involved in the developing program by
escaping apoptosis. In any period during kidney development about 3 to 5%of
cells are apoptotic. Thorough elucidation of the regulators controlling
apoptotic pathways during development may contribute to the development of
therapeutic agents that can prevent onset of developmental abnormalities of the
kidney. Acta Medica Medianae 2005; 44(1): 69-72.
Key words: apoptosis, development, kidney