Browsing by Subject "maturation"

There is a great demand of cultured human hepatocytes for hepatotoxicity studies, drug testing, disease modelling and liver transplantation purposes. The current gold standard, primary human hepatocytes (PHHs), suffer from poor availability and high variability. Furthermore, PHHs are short-lived in in vitro cultures. Pluripotent stem cell (PSC)-derived hepatocyte-like cells (HLCs) have emerged as potential substitutes for PHHs in in vitro studies. PSCs are widely available, and additionally allow studies of hepatogenesis and open possibilities for personalized medicine. However, obtaining HLCs with mature hepatocyte functions in vitro has turned out to be challenging, and the differentiated cells have remained immature compared to PHHs. In vivo, hepatic differentiation and maturation of PSCs is guided by cues from the environment. Mimicking the 3D cellular environment in vitro has already shown encouraging results, but today, HLCs are still awaiting to fulfil their promise as a new gold standard. The aim of this study was first to select a new working human PSC line for in vitro hepatic differentiation and maturation. Hepatic differentiation and maturation of the selected cell line, embryonic stem cell line ESI-017, was next studied in five different 3D culture conditions (spheroids in suspension culture, four different hydrogels: Matrigel, collagen type I, mixture of Matrigel and collagen type I and alginate) with the aim to find the most favourable culture condition for later studies. For this, the PSCs were first differentiated to definitive endoderm cells and then to hepatoblasts in 2D cultures, on Matrigel- and laminin-521-coated plates, respectively. The PSC-derived hepatoblasts were then transferred for 16 days to the different 3D culture conditions for hepatic maturation. Of the conditions, suspension culture and mixture of Matrigel and collagen type I -hydrogel were estimated most promising and were selected for further studies. Hepatic maturation of the PSC-derived HLCs was estimated by analysing protein and mRNA expression levels of key marker genes, such as CYP3A4, AAT, MRP2, HNF4A, ALB, AFP, CK-8/18 and CK-19 by immunofluorescence staining and qPCR, respectively, and by cell morphology. Based on cell morphology and noticeable level of CYP3A4 expression, suspension culture shows most potential of the studied conditions in hepatic maturation of PSC-derived hepatoblasts. However, given that expression level of many other hepatocyte marker genes in these HLCs remained low compared to PHHs or human fetal liver samples, it is evident that adjustments to protocol and culturing conditions are still needed.

In teleost fish, various egg traits play a crucial role in the development, growth, and survival of the offspring and thus affect maternal reproductive success. Atlantic salmon (Salmo salar) is a species where age at maturity, an important life-history trait influencing reproductive success, is under environmental and genetic control. In this study, I assessed how genetics of the vgll3 genotype and the dietary energy content affect egg traits and female maturation rate. The fish used in this study were lab-bred, three-year- old female Atlantic salmon with different vgll3 genotypes fed on one of two diets differing in energy content. The eggs traits included in the study were egg size, lipid, and protein content. Female maturation rate was not affected by the energy level of the diet or the vgll3 genotype. Egg size expressed as egg dry weight differed between females in the two feed treatments. These differences may be attributed to the increased lipid content of the eggs due to the higher fat content of the maternal diet. Females receiving high energy feed had a significantly higher egg lipid content compared to the low energy feed treatment. Females homozygous for the vgll3 allele associated with early maturity had a significantly lower egg lipid content in comparison to the females homozygous for the vgll3 late maturity allele indicating a potential reproductive fitness cost associated with early maturity. No effect of diet or vgll3 was found in egg protein content. This study provides the first evidence of vgll3 not only affecting Atlantic salmon age at maturity, as found in previous studies, but also egg lipids through maternal provisioning of nutrients.

Cardiovascular diseases are the most common causes of mortality worldwide. More adequate human-based models would be needed for the purposes of disease modeling and drug development. One of the most promising fields of in vitro modeling is the use of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). A central problem of hPSC-CMs is their immature or fetal-like phenotype compared to adult human cardiomyocytes regarding many structural, functional, and metabolic properties. The development of metabolic properties is considered to be a central driver of cardiomyocyte maturation. One practicable way to promote the metabolic maturation of hPSC-CMs in vitro is the use of various biochemical cues in the cell culturing media. The topic of this study was the metabolic maturation of hPSC-CMs. The research questions were: What biochemical cues have been suggested to be involved in the hPSC-CM maturation in vitro? What signaling pathways connected to the biochemical cues have been explored in the context of the maturation of hPSC-CM? What experimental results have been achieved on the effects of the biochemical cues and the involvement of the signaling pathways? The study was conducted as a systematic review with the database Scopus (Elsevier). The final set of materials consisted of 46 original research articles published in peer-reviewed journals in English in the years 2013–2022. Out of the materials, 11 articles (24%) were characteristically longitudinal studies. They indicated that the pathways leading to metabolic changes such as PPARs (peroxisome proliferator-activated receptors) and PGC-1α (peroxisome proliferator-activated receptor γ coactivator 1α) are activated already in early stages. In 12 articles (26%), pharmacological agents were used to target the metabolic pathways, and in 8 articles (17%) techniques affecting the gene expression were utilized. The most recent studies involved ever more frequently combinations of different techniques. Considering the use of biochemical cues, the trend has been to favor fatty acids, thyroid hormone and dexamethasone over glucose, insulin and insulin-like growth factor. Some cues such as retinoic acid and neuregulin 1 have been tested only in single experiments. In addition to the nuclear receptor mediated pathways, the energy sensors AMPK (AMP-activated protein kinase) and mTOR (mechanistic target of rapamycin), the oxygen sensor HIF-1α (hypoxia-inducible factor 1α), and the microRNAs turned out to be central.

Sleep spindles are thalamocortical oscillations that occupy the sigma band with trait-like inter-individual variability. Sleep spindles associate with reasoning abilities according to several studies, but some discrepancy exists in the strength and even direction of the associations. This may, to some extent, be due to methodological differences. The stage of brain maturation also affects spindle manifestation. In this community-based study, associations between spindle characteristics and reasoning abilities are examined in an understudied age group, adolescents. An all-night polysomnography was conducted at homes of 178 adolescents (104 girls). Working memory, visuospatial reasoning and verbal reasoning were measured in the same evening. An automatic algorithm was used to detect slow (10–13 Hz) and fast (13–16 Hz) spindles in frontal and central scalp derivations in NREM 2 sleep stage. The associations between spindle variables (density and intensity) and the cognitive test scores were analyzed with linear regression. Genders apart, the analyses were conducted first on the whole group and then separately on the Above Median (AM) and Below Median (BM) intelligence subgroups. In the analyses with all subjects, higher central fast density associated with better verbal reasoning in girls. When examining the subgroups separately, this association was not perceived in the AM group but appeared prominently in the BM group girls. No other associations were found between the spindle variables and the cognitive test scores. A positive spindle-intelligence relation is an established finding in females, but more commonly the association is typified by fluid/visuospatial reasoning and frontal brain areas. In the present study, young age may have related to the accentuated relative significance of more caudal brain regions and verbal intelligence in relation to spindles. The ongoing neural maturation and the heterogeneity of the sample may have contributed to the nature of the findings. More adolescent studies are needed to gain understanding of the matter.