Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo in 1993 as a first generation internet teaching tool consolidating human embryology teaching for first year medical students.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human.

The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Molecular switch turns on self-renewal after liver damage

The liver is one of the few organs in our body that can regenerate itself, but how it occurs is a biological mystery. New research has identified a protein complex that acts as a molecular switch turning on a self-regeneration program in the liver.

The protein complex fine tunes liver metabolism, allowing
it to run efficiently in parallel with tissue damage repair.

The new knowledge from BRIC, University of Copenhagen and the Finsen Laboratory, Rigshospitalet, challenges the current focus on stem cells and may point towards future simplification of treatments used for repairing tissue damage.

"Our new data challenge the predominant 'stem cell-mania' as the results reveal important molecular mechanisms that enable ordinary liver cells to divide and repair tissue damage. This may point to ways of using ordinary liver cells for therapeutic purposes, as these cells may be easier to use than stem cells," says Head of Clinic and Professor Bo Porse who has lead the investigation.

Protein complex turn on self-renewal genes
When the specialised cell types of our body are formed from stem cells during development, they generally lose the ability to divide and make new cells. Tissue renewal is therefore a job for the stem cells present in our body.

One exception is the specialised cells of the liver called hepatocytes. They are responsible for the metabolic functions of the liver, but can at the same time produce new liver cells. How that is possible is a bit of a mystery.

"Our results show how a protein complex is changed upon damage to the liver, making it function as a 'switch' turning on a self-renewal program in the hepatocytes. The protein complex literally turns on selected genes that enable division of the hepatocytes, while maintaining their metabolic functions," says postdoc Janus Schou Jakobsen, who has lead the experimental part of the investigation.

The extraordinary ability of the liver cells to divide almost
indefinitely resembles the ability of stem cells to self-renew
and this finding challenges the current focus on
stem cells and stem cell therapy.

Self-renewal programs in non-stem cells
The new results from Bo Porse’s research group are consistent with new studies of self-renewal in the group of white blood cells called macrophages.

"We see a clear overlap in the molecular mechanisms
controlling self-renewal in hepatocytes and macrophages
and this could indicate the existence of a more general
self-renewal program used by specialised cell types.

If this is the case, it can really change the current
perception that only stem cells are responsible for
renewal of our tissues."

Janus Schou Jakobsen
leader of the experiment

The study addresses basic research questions, but if it can be shown that one can turn on and off specific sets of genes, making many types of specialised cells divide, it can have great impact on future regenerative treatments. It is very likely easier to make a specialised cell copy itself, than to extract the very scarce stem cells and accurately reprogram them to the specialised cell type of need.

"Currently, so-called cancer stem cells receive much attention - these are single cancer cells that are difficult to kill. They have taken over stem cell programs enabling them to divide uncontrolled and to reform an entire tumour. It is likely that cancer cells can also hijack the self-renewal programs we have identified in liver cells. Increased knowledge on these self-renewal programs may therefore lead to a new understanding of cancer cell biology and open up for new treatment strategies," says Bo Porse.

The next step for the researchers is to dig deeper into a
molecular understanding of how self-renewal systems
can be turned on and off in specialised cell types.

Original paper: The results have been published as advance online publication by the journal Genome Research and the final version will appear late March/early April. Jakobsen et al: Temporal mapping of CEBPA and CEBPB binding during liver regeneration reveals dynamic occupancy and specific regulatory codes for homeostatic and cell cycle gene batteries.

Research support: The research has been supported by the Novo Nordisk Foundation and the Danish Cancer Society.

Original article: http://news.ku.dk/all_news/2013/2013.3/self-repair_of_liver_damage/