Pluripotent stem cells do not completely maintain normal human steady-state haemopoiesis

Area of Science:

• Hematology
• Cell Biology
• Stem Cell Research

Background:

• Established theory posits continuous replacement of recognizable bone marrow cells from precursor sources.
• Direct evidence for steady-state influx from pluripotent stem cells (PSCs) into recognizable bone marrow compartments is lacking.
• Pluripotent stem cells (PSCs) in various species resemble atypical lymphocytes.

Purpose of the Study:

• To investigate the contribution of pluripotent stem cells (PSCs) to the recognizable bone marrow cell pool in humans.
• To assess the metabolic activity and cell cycle kinetics of human bone marrow cells, including potential PSCs.

Main Methods:

• Quantitative 14C-autoradiography used to measure DNA and protein synthesis rates in individual human bone marrow cells.
• Analysis of the relationship between protein synthesis rate and cell cycle progression across different proliferative compartments.
• Characterization of lymphoid cells, presumed to contain PSCs, within the human bone marrow.

Main Results:

• A positive correlation was observed between protein synthesis rate and cell cycle progression in all proliferative compartments.
• Lymphoid cells (potential PSCs) exhibited low metabolic rates, indicating slow growth and long cell cycle times.
• The low frequency (<2%) and metabolic characteristics of potential PSCs in human bone marrow do not support continuous supply to blast cells.

Conclusions:

• Pluripotent stem cells (PSCs) are unlikely to be the continuous source for recognizable bone marrow blast cells under steady-state conditions.
• Self-maintenance within the pool of recognizable normal bone marrow blast cells is suggested as a more plausible mechanism.