Backgrond: Hematopoietic Stem Cells (HSCs), which have the ability to differentiate into various types of blood cell lines,
are usually separate from the bone marrow. But these cells are also present in a small amount in the peripheral blood,
and their amounts increase in blood following the injection of G-CSF. However, the mechanism involved in moving HSCs
under the influence of G-CSF is unknown. The aim of the present study was to investigate the role of circadian rhythms and
nervous system in HSCs mobilization. Despite the abandant information on the effect of 24-hour rhythms in physiological
processes in the body, there is no evidence of the role of circadian rhythms and its relation to the nervous system receiving
environmental information and neurotransmitters in HSCs mobilization.
Materials and methods: An experimental study was performed on 15 healthy bone marrow donors. Samples from
peripheral blood were taken at 9 o’clock in the morning and 9 o’clock at night before the injection of G-CSF as control
group, and at 9 o’clock in the morning and 9 o’clock at night on the fourth day of the G-CSF injection. The total counts of
leukocytes and CD34 + stem cells were performed on the samples using flow cytometry. Plasma levels of adrenaline and
noradrenaline were measured using ELISA method running Paired T test.
Results: In the present study, it was found that total cell count, stem cell count (CD34 +)(p value: 0.03), and plasma levels
of adrenaline (p value: 0.04) and noradrenaline (p value: 0.01) in the morning increased over night. Additionally, after
receiving the G-CSF, adrenalin and norepinephrine levels are higher in the early hours after the onset of lighting compared
with the night, and CD34 + cells count was higher in the morning compared with that in the evening similar to control
samples.
Discussion: Although numerous factors are involved in the etiology of azoospermia, clinical tests and genetic counseling
plays an important role in early detection of disease that helps to retrieve sperm production and fertility to the patient in
many cases.
Conclusion: Given that the number of stem cells and total WBC count in the morning were more than those at nights, in
general, following the injection of G-CSF, the number of stem cells circulating with the same pattern shows a multiplier
increase, it is suggested that the phenomenon of mobilization, like other biological processes of the body, is affected
by circadian rhythms. Therefore, increased secretion of adrenaline and noradrenaline in the morning and the effect on
ß2-adrenergic receptors in the bone marrow space resulted in increased mobilization and, during the day, reducing the
secretion of these neurotransmitters leads to the opposite process and reduces mobilization in the final hours of the day
and at night. In fact, G-CSF, along with other functional mechanisms for increasing the mobilization of stem cells to
the peripheral blood, uses this natural remedy for the body. These findings can be effective in enhancing approaches to
improving mobilization with the help of the nervous system.

Keywords: Mobilization, Adrenaline, Noradrenaline, circadian Rhythms, Granulocyte-colony Stimulating Factors(G-CSF)

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