Abstract
Tissue regeneration is a complex and highly orchestrated process leading to the reconstitution of damaged tissue and recovery of its function. Haematopoietic tissue has extensive regenerative potential which is attributed to the presence of haematopoietic stem cells.
This paper briefly discusses the current understanding of haematopoietic stem cells and their participation in steady-state haematopoiesis. It also gives an overview of the three phases of embryonic and foetal haematopoiesis preceding the establishment of steady-state adult haematopoiesis.
The paper presents the main conclusions drawn from our analysis of intensively regenerating bone marrow following severe damage by ionizing radiation. The research revealed a fundamental role that the developmentally advanced myeloid progenitor cells play in bone marrow regeneration, which occurs during the virtual absence of stem cells and multipotent progenitors.
The regeneration induced by progenitors explains why the strong regenerative power of this tissue cannot be transplanted to other subjects with damaged haematopoiesis. A comparison of the rapidly expanding regenerating bone marrow with the expanding foetal liver haematopoiesis showed significant differences between them.
However, there is a similarity between intensively regenerating haematopoiesis and embryonic definitive haematopoiesis occurring prior to the emergence of haematopoietic stem cells.