Neonatal cardiomyocyte ploidy reveals critical windows of heart development.

BACKGROUND: The aim of our study was to find out, whether cardiomyocyte genome duplication participates in developmental programming of adult hypertension and impaired heart aerobic capacity, and if it does, whether ploidy-related programming is reversible and what are the timeframes of the most critical window. For this propose we studied the effect of the well-known factors of programming, including growth retardation, infection, and cardiac overload on the level of neonatal cardiomyocyte ploidy, protein content and shape. METHODS: Using the model of rat cryptosporidial gastroenteritis, we shifted the time point of infection day by day through the neonatal period and traced the immediate and postponed effects of disease on isolated cardiomyocyte ploidy, phenotype, and protein content. RESULTS: We found that gastroenteritis caused cardiac atrophy and a burst-like premature genome accumulation, elongation, narrowing and protein loss in the cardiomyocytes. These changes resulted in sharp increase of DNA content at the expense of contractile proteins. We also revealed clear indications of critical window of heart development during the peak of cardiomyocyte transition from proliferation to hypertrophy. After the rehabilitation, the atrophy of heart and cardiomyocyte remodelling showed a conspicuous restoration, whereas the hyperpolyploidization did not regress. An irreversible manner of excessive genome duplication and its well-known ability to alter gene expression confirm our suggestion that it is implicated in the ontogenetic programming of heart development. CONCLUSION: We provided the first evidence that developmental programming can operate through cardiomyocyte genome duplication and that the critical window coincides with cell transition from proliferation to hypertrophy. Our data help determine the timing of critical window for human heart and would allow successful prevention of human cardiac abnormalities even before they become tangible.

Impact of neonatal cryptosporidial gastroenteritis on epigenetic programming of rat hepatocytes.

Inflammation, malnutrition and growth retardation during critical time-windows of development play a powerful role in ontogenetic programming of the life-long risk to many adult diseases (including metabolic syndrome, obesity and diabetes). Cellular mechanisms and the accurate timing and duration of critical periods for the liver remain obscure. To resolve this problem, we developed a postnatal suckling-weanling rat model of mild, moderate, and acute gastroenteritis challenged by a protozoan parasitic spread throughout the whole world, namely Cryptosporidium parvum. The physiological state of the liver was evaluated by hepatocyte ploidy and protein content that were measured by cytophotometry and image analysis on isolated cells. Hepatocyte ploidy is known to irreversibly increase after stress and is associated with the decrease in liver physiological capacity. Hepatocyte hypertrophy reflects cell functional loading. From our results, cryptosporidiosis is able to provoke a burst in premature hepatocyte polyploidization and hypertrophy (in proportion to parasitic load), and thus plays an important role in epigenetic programming of hepatocyte structure and function. We revealed two sensitive periods in liver growth. The first period (the less sensitive) covers the time before the establishment of homoiothermy, i.e. 6-9 days after birth. The second period (the more sensitive) covers the time of weaning when the change of type of nutrition and the peak of hepatocyte polyploidization and differentiation occurs. Thus, our data provide direct evidence that phenomenon of ontogenetic programming is reflected at the cellular level.

Parasitophorous vacuole: morphofunctional diversity in different coccidian genera (a short insight into the problem).

We present a short insight into the problem of parasitophorous vacuole (PV) formation as a most peculiar kind of cell vacuolization occurring in the course of intracellular development of coccidian pathogens of the genera Eimeria, Isospora, Toxoplasma, Sarcocystis, Cryptosporidium, Epieimeria, and Karyolysus. The review focuses on the morpho-functional diversity of PVs in these parasites. By the present time, the PVs containing different parasite genera and species have been examined to different extent. The membrane of the PV (PVM) obviously derives from the host cell plasmalemma. But soon after parasite penetration, the morphofunctional organization and biochemical composition of the PVM drastically changes: its proteins are selectively excluded and those of the parasite are incorporated. As the result, the PV becomes not fusigenic for lysosomes or any other vacuoles or vesicles, because host cell surface markers necessary for membrane fusion are eliminated from the PVM during parasite invasion. The pattern of the PVs is parasite specific and demonstrates a broad diversity within the same genera and species and even at different stages of the endogenous development. The PV is far from being an indifferent membrane vesicle containing the parasite. Instead, it represents a dynamic system that reflects the innermost events of host-parasite relationships, thus promoting the accomplishing of the parasite life cycle, which, in its turn, is a necessary prerequisite of the parasite eventual survival as a species.