The cultivation of human embryonic liver cells

Advanced bioengineering of male germ stem cells to preserve fertility

In modern life, several factors such as genetics, exposure to toxins, and aging have resulted in significant levels of male infertility, estimated to be approximately 18% worldwide. In response, substantial progress has been made to improve in vitro fertilization treatments (e.g. microsurgical testicular sperm extraction (m-TESE), intra-cytoplasmic sperm injection (ICSI), and round spermatid injection (ROSI)). Mimicking the structure of testicular natural extracellular matrices (ECM) outside of the body is one clear route toward complete in vitro spermatogenesis and male fertility preservation. Here, a new wave of technological innovations is underway applying regenerative medicine strategies to cell-tissue culture on natural or synthetic scaffolds supplemented with bioactive factors. The emergence of advanced bioengineered systems suggests new hope for male fertility preservation through development of functional male germ cells. To date, few studies aimed at in vitro spermatogenesis have resulted in relevant numbers of mature gametes. However, a substantial body of knowledge on conditions that are required to maintain and mature male germ cells in vitro is now in place. This review focuses on advanced bioengineering methods such as microfluidic systems, bio-fabricated scaffolds, and 3D organ culture applied to the germline for fertility preservation through in vitro spermatogenesis.

Modulation of human fetal hepatocyte survival and differentiation by interactions with a rat liver epithelial cell line

Fetal human hepatocytes were isolated by collagenase digestion of liver fragments and cultured either alone or mixed with rat liver epithelial cells. Whereas they did not survive more than 2-3 weeks and showed rapid morphologic and functional alterations in conventional culture, fetal hepatocytes survived and retained or reverted to a globular morphology for several weeks and showed active albumin secretion for at least 13 days when cultured with rat liver cells. Increased levels of secreted albumin correlated with deposition of an insoluble extracellular material containing fibronectin and type III collagen located principally between the two cell types and around parenchymal cells. These observations show that fetal human hepatocytes are able to interact in vitro with another epithelial liver cell type obtained from a divergent species and that these cell-cell interactions influence both hepatocyte survival and expression of albumin.

Changes in some chromatin and cytoplasmic enzymes of perinatal rat hepatocytes during culture

Hepatocytes prepared from rats at various perinatal stages were cultured in selective medium that does not allow fibroblastic cell growth. Cell population remained homogeneous during the culture. Hepatocytes undergo divisions for a period, which varies according to the stage of development of the rat. Light and electron microscope observations showed the presence of numerous cytoplasmic organelles; moreover, hydrocortisone-induced structures similar to bile canaliculi. Chromatin protein kinase decreased rapidly during culture except in samples prepared from 17-day fetuses in which it remained unchanged for 2 days and decreased to a lesser extent afterwards. Chromatin nonhistone proteins were incubated with (gamma-32P) ATP and the phosphorylation pattern analyzed on polyacrylamide gels. Many radioactive peaks were observed in chromatin proteins from 17-day fetuses; they were much lower in proteins than 19-day fetuses. The phosphorylation pattern was analyzed in hepatocytes after 2 days of culture. Many radioactive peaks were observed with proteins from hepatocytes taken from 17-day fetuses; no radioactivity was observed in proteins from 19-day fetuses. This is in contrast with the absence of radioactive peaks in chromatin proteins from adult rat hepatocytes. In cytoplasm, aldolase and pyruvate kinase specific activities varied according to the age of the rat. They strongly decreased during culture except in hepatocytes and 15- and 17-day fetuses, in which they remained stable for a least 5 days. The stability of chromatin and cytoplasmic enzymes in hepatocytes from 17-day fetuses could result from their ability to be regulated by hormones that are secreted at this stage of development.

Isolation and growth of adult human epidermal keratinocytes in cell culture

Human epidermal keratinocytes may be isolated in high yield from 0.1 mm keratotome sections of adult skin by short-term trypsin release. When plated on a collagen-coated plastic surface or on a collagen gel, keratinocytes attach with high efficiencies (greater than 70%) and form confluent, stratified cultures. Cell populations of predominantly basal cells produce proliferative primary cell cultures while populations of basal cells and malpighian cells result in nonproliferative primary cultures. Both nonproliferative and proliferative primary cultures may be subcultured on collagen gels following dispersion by trypsin and EDTA. Methotrexate strongly inhibits proliferative keratinocytes at low concentrations (0.1 microgram/ml) but has no cytotoxic effect on non-proliferative cells. L-serine and dexamethasone increase the multiplication rate of both primary and subcultured human keratinocytes.

Parenchymal cells from adult rat liver in nonproliferating monolayer culture. I. Functional studies

Parenchymal cells from adult rat liver have been established in primary monolayer culture. Donor animals are subjected to a partial hepatectomy and, 4 days later, cells are prepared by collagenase perfusion of the regenerated liver. The hepatic parenchymal cells, separated from nonparenchymal material and suspended in serum-free medium, are placed in plastic tissue culture dishes, where they form a monolayer within 24 h. The monolayer cells exhibit minimal mitotic activity and demonstrate several major metabolic functions characteristic of liver in vivo; these include albumin synthesis and secretion, gluconeogenesis from 3-carbon precursors, responsiveness to insulin and glucagon, glycogen synthesis, and activity of two microsomal enzymes. These functions are present in the monolayer cells for several days at activities similar to those observed in the liver in vivo. The findings indicate that hepatic parenchymal cells in this monolayer system are viable and behave in many respects like normal adult rat liver.

Production of albumin and other serum proteins by clonal cultures of normal human liver

Clonal cell strains have been isolated from normal human liver. These cells, while resembling fibroblasts morphologically, function as hepatocytes, as shown by their ability to synthesize and secrete an antigen identical to human serum albumin. Human diploid and aneuploid cell lines from nonliver sources do not exhibit this property. The spectrum of serum proteins synthesized varied from clone to clone and cell line to cell line.

Morphology and function of cells of human embryonic liver in monolayer culture

A system for culturing human fetal liver cells in monolayers is described and the effects of various conditions of growth on the morphology and function of the cultured cells are presented. The addition of 10% calf serum or 1% human serum to the growth medium accelerated the proliferation of the liver cells, with subsequent loss of characteristic morphology and specific functional activity. In the absence of serum, the cultured liver cells retained their morphology and their function for at least 4 wk, as evidenced by secretion of serum albumin and storage of glycogen and iron.

The circumfusion system for multipurposeculture chambers. II. The protracted maintenance of differentiation of fetal and newborn mouse liver in vitro

The circumfusion system is a complex in vitro pumping unit incorporating 12 multipurpose culture chambers through which a serum-supplemented fluid nutrient is recirculated at a rate of 4.5 ml/min per chamber. This system was used to study the differentiative responses of fetal and newborn mouse liver explants placed in the serum-free environment formed between the sheets of unperforated cellophane and cover glasses of the chambers. Hepatocytes (parenchymal cells) were discernible in 3-5 days. They retained many of their features of differentiation in the circumfusion system for more than 120 days of cultivation. The living morphological characteristics of the hepatocytes were studied by phase-contrast microscopy (direct viewing and time-lapse cinemicrography) and by special cytochemical staining. Electron micrographs were made of both fresh liver specimens and the cultured cells. Comparisons of the cultured parenchymal cells with their in vivo progenitors showed a remarkable preservation of their differentiated state.