Role of apoptosis and proliferation in differentiation of human retina,regio olfactoria and regio respiratoria

Apoptosis and proliferation are very important processes during central nervous system development. In our study we concentrated on human fetus retina, regio respiratoria and olfactoria. The aims of our work were to evaluate a proliferative activity proved by PCNA and KI-67 gene expressions, to measure an expression of anti-apoptotic gene bcl-2, and finally to compare levels of apoptosis and proliferation in the areas investigated. Altogether we studied 29 fetuses between the 5th to 13th week of gestation (WG). Parallel sections were elaborated by using standard methods of immunohistochemistry for the detection of proteins PCNA, Bcl-2 and Ki-67. Apoptotic cells were detected by two methods: TUNEL (for the detection of DNA fragmentation) and Apostain (for evidence of ssDNA). The results of semiquantitative evaluation show that expressions of proteins PCNA and KI-67 begins after the 6th WG, from the 8th to 13th WG they are very high in all investigated areas. Occurrence of apoptotic cells in regio respiratoria is sporadic between the 5th to 9th WG, while later it is widely spread. Apoptosis in regio olfactoria appears after the 9th WG and it is also very extensive. In the retina we found a higher frequency of apoptotic cells only in the 11th to 13th WG. The results of both methods for detection of apoptosis were concordant. Anti-apoptotic gene bcl-2 was detectable in all examined areas, but it followed no orderly pattern. We conclude, that the expression of apoptosis increases with the age from the 7th to 13th WG, and that both apoptosis and proliferation participate in the morphogenesis of fetuses between the 5th to 13th WG.