Dynamics of hepatocyte proliferation in regenerating fetal rat liver

Evolution of Regeneration in Animals: A Tangled Story

The evolution of regenerative capacity in multicellular animals represents one of the most complex and intriguing problems in biology. How could such a seemingly advantageous trait as self-repair become consistently attenuated by the evolution? This review article examines the concept of the origin and nature of regeneration, its connection with the processes of embryonic development and asexual reproduction, as well as with the mechanisms of tissue homeostasis. The article presents a variety of classical and modern hypotheses explaining different trends in the evolution of regenerative capacity which is not always beneficial for the individual and notably for the species. Mechanistically, these trends are driven by the evolution of signaling pathways and progressive restriction of differentiation plasticity with concomitant advances in adaptive immunity. Examples of phylogenetically enhanced regenerative capacity are considered as well, with appropriate evolutionary reasoning for the enhancement and discussion of its molecular mechanisms.

Therapeutic Potential of Umbilical Cord Stem Cells for Liver Regeneration

The liver is a vital organ for life and the only internal organ that is capable of natural regeneration. Although the liver has high regeneration capacity, excessive hepatocyte death can lead to liver failure. Various factors can lead to liver damage including drug abuse, some natural products, alcohol, hepatitis, and autoimmunity. Some models for studying liver injury are APAP-based model, Fas ligand (FasL), D-galactosamine/endotoxin (Gal/ET), Concanavalin A, and carbon tetrachloride-based models. The regeneration of the liver can be carried out using umbilical cord blood stem cells which have various advantages over other stem cell types used in liver transplantation. UCB-derived stem cells lack tumorigenicity, have karyotype stability and high immunomodulatory, low risk of graft versus host disease (GVHD), low risk of transmitting somatic mutations or viral infections, and low immunogenicity. They are readily available and their collection is safe and painless. This review focuses on recent development and modern trends in the use of umbilical cord stem cells for the regeneration of liver fibrosis.

Role of Progenitor Cells in Liver Regeneration after Subtotal Resection

In the liver of rats subjected to subtotal liver resection (80% organ weight), the expression of sox9 gene and SOX9 protein content increased and cells with hepatocyte morphology expressing SOX9 appeared; the proportion of cells expressing cytokeratin-19 also increased. Based on these data, we cannot completely exclude the involvement of resident progenitor cells and hepatocyte reprogramming in liver regeneration after subtotal resection, however, the contribution of these processes seems to be insignificant. The leading mechanism of liver mass recovery after subtotal resection is proliferation of hepatocytes.

Hemopoietic cell proliferation and death in the regenerating fetal rat liver

The proliferation and death of hemopoietic cells in the regenerating liver of 17-day outbred albino rat fetuses were studied during 2 days after resection of 20% of the organ. The mitotic index of hemopoietic cells in the resected liver increased significantly 24 h after the operation in comparison with the control fetuses. No increase in the counts of apoptotic hemopoietic cells was detected in the regenerating liver. Hence, resection of 20% of the liver in rat fetuses stimulated the proliferation of hemopoietic cells and did not stimulate their apoptosis.