Changes in transcription pattern lead to a marked decrease in COX, CS and SQR activity after the developmental point of the 22(nd) gestational week.

Tissue differentiation and proliferation throughout fetal development interconnect with changes in the oxidative phosphorylation system (OXPHOS) on the cellular level. Reevaluation of the expression data revealed a significant increase in COX4 and MTATP6 liver transcription levels after the 22(nd) gestational week (GW) which inspired us to characterize its functional impact. Specific activities of cytochrome c oxidase (COX), citrate synthase (CS), succinate-coenzyme Q reductase (SQR) and mtDNA determined by spectrophotometry and RT-PCR were studied in a set of 25 liver and 18 skeletal muscle samples at 13(th) to 29(th) GW. Additionally, liver hematopoiesis (LH) was surveyed by light microscopy. The mtDNA content positively correlated with the gestational age only in the liver. The activities of COX, CS and SQR in both liver and muscle isolated mitochondria significantly decreased after the 22(nd) GW in comparison with earlier GW. A continuous decline of LH, not correlating with the documented OXPHOS-specific activities, was observed from the 14(th) to the 24(th) GW indicating their exclusive reflection of liver tissue processes. Two apparently contradictory processes of increasing mtDNA transcription and decreasing OXPHOS-specific activities seem to be indispensable for rapid postnatal adaptation to high energy demands. The inadequate capacity of mitochondrial energy production may be an important factor in the mortality of children born before the critical developmental point of the 22(nd) GW.

Analysis of expression profiles of genes involved in F(o)F(1)-ATP synthase biogenesis during perinatal development in rat liver and skeletal muscle.

During the process of intra-uterine mammalian fetal development, the oxygen supply in growing fetus is low. A rapid switch from glycolysis-based metabolism to oxidative phosphorylation (OXPHOS) must proceed during early postnatal adaptation to extra-uterine conditions. Mitochondrial biogenesis and mammalian mitochondrial F(o)F(1)-ATP synthase assembly (complex V, EC 3.6.3.14, ATPase) are complex processes regulated by multiple transcription regulators and assembly factors. Using RNA expression analysis of rat liver and skeletal tissue (Rattus norvegicus, Berkenhout, 1769), we describe the expression profiles of 20 genes involved in mitochondrial maturation and ATP synthase biogenesis in detail between the 16th and 22nd day of gestation and the first 4 days of life. We observed that the most important expression shift occurred in the liver between the 20th and 22nd day of gestation, indicating that the fetus prepares for birth about two days before parturition. The detailed mechanism regulating the perinatal adaptation process is not yet known. Deeper insights in perinatal physiological development will help to assess mitochondrial dysfunction in the broader context of cell metabolism in preterm newborns or neonates with poor adaptation to extra-uterine life.

Placental tissue as model for pilot study focused on RNA analysis from human foetal tissue.

Early neonatal adaptation to extrauterine life is i.a. dependent on effective mitochondrial biogenesis during foetal development. Understanding of mitochondrial biogenesis is limited, because only scarce data are available from prenatal studies including RNA analyses in human foetal tissues. Aims of the study were focused on the factors affecting RNA quality in human placental tissue (HPT) including temperature, time period before HPT freezing and the Apgar score. In addition, optimal reference genes for mRNA quantification by real-time PCR in HPT were studied. Samples of HPT were obtained after the birth of 20 term neonates. Seven HPT were used for the time-course study of RNA degradation in two different temperatures (0 °C and 24 °C). Various instruments NanoDrop (NanoDrop Technologies), Experion (Bio-Rad Laboratories), Agilent 2100 Bioanalyzer (Agilent Technologies) were used for analysis of RNA integrity, purity and yield. Identification of suitable reference genes was achieved by analysing six candidate genes (ATP5O, SDHA, TBP, HPRT, PMBS, ATP6) for their expression stability (GeNorm application). The results showed that the HPT samples for RNA analyses must be frozen immediately after birth in -80 °C or stored at 0 °C maximally for 1 hour. The reference genes ATP50 and SDHA were the most stable for mRNA quantification in HPT. Human placenta represents easily obtainable source of foetal tissue for studies concerning mitochondrial biogenesis. We demonstrated that the critical limit for optimal storage and handling of HPT are the temperature and the time period before freezing of the samples.