Ex-vivo exposure to a small molecule, enhances migration and homing of murine Hematopoietic and stem and progenitor cells

Acute Radiation Syndrome (ARS) or sickness occurs after a whole-body exposure to a high dose of ionising radiation over a short time frame. This type of acute exposure is often associated with accidental exposure as in the case of atomic bomb survivors, nuclear radiation accident victims and sometimes planned exposure like radiation therapy patients. Based on the differences in the cellular sensitivity to Ionising radiation, ARS is broadly divided into hematopoietic (Bone marrow syndrome), gastrointestinal, and neurovascular syndrome. Thus, the amount of radiation dose absorbed by the body, determines the severity of symptoms and the type of ARS. Additionally, ARS manifest in 4 stages, namley Prodromal, Latent, Manifest illness, Recovery or death stage. Hematopoietic stem and progenitor cells (HSPCs) are the key regulators of hematopoiesis which give rise to different, mature and committed lineages. Exposure to acute dose of 2.5-5 Gy whole-body radiation results in the loss of HSPCs leading to the inability of the system to generate differentiated lineages which ultimately cause hematopoietic form of acute radiation syndrome (hs-ARS). Lymphocytes, granulocytes and platelets are the first to decline and are considered most radiosensitive. The prodromal stage occurs within a few hours and lasts upto 2 days. Hallmark symptoms involve nausea and vomiting, followed by a latent stage where no visible symptoms appear and the patient shows clinical improvement and may feel well, although the bone marrow cells are dying simultaneously. This stage lasts for 1-6 weeks. This is followed by the Manifest illness stage where the symptoms reappear. The circulating blood cells drop for several weeks. The primary cause of death is infection and haemorrhage (as the platelet number declines, the body losses the clotting ability). Finally arrives the recovery or death stage and depending upon the dose absorbed and  radiation induced damage, at low doses, the surviving bone marrow cells may repopulate and lead to full recovery. On the other hand if the dose is high, it may lead to death.