Effect of a hyperthermic treatment on the pluripotent haemopoietic stem cell in normal and anaemic mice

Abstract

Up to now, the hyperthermic sensitivity of pluripotent haemopoietic stem cells is unknown, and the few existing data from reports in the literature are conflicting. There are two main drawbacks in the set-up of those studies: (1) only CFU-S day 9 results were presented, whereas it is questionable if this assay gives a true reflection of the pluripotent stem cell, and (2) no attention has been paid to heat effects on the seeding efficiency, i.e. the amount of stem cells which will lodge in the spleen. The present study focused on the procedural differences and compared the results of a hyperthermic treatment (60 min, 42°C) on the stem cells, assayed with the CFU-S day 9 and the CFU-S day 12 method, using the following three stem cell suspensions, all differing in their proliferative activity: bone marrow from normal mice and bone marrow and spleen cells from anaemic mice. Furthermore, we investigated the seeding efficiency before and after heat treatment. Resting stem cells, assayed with the CFU-S day 12 method, turned out to be resistant to hyperthermia as compared with the active cycling stem cells, while with the CFU-S day 9 assay the stem showed the same thermosensitivity in the two bone marrow suspensions. The active cycling stem cells do not significantly differ in thermosensitivity, in CFU-S day 9 and day 12 assays, although there is a difference between bone marrow and spleen. Hyperthermia appears to influence the seeding efficiency for spleen CFU-S; an increase of 1ċ73 was observed. The difference in heat sensitivity between the resting and the active cycling stem cells, assayed with both in vivo methods, however, cannot be explained by a change in seeding efficiency only. Comparing the amount of cycling cells in the three stem cell suspensions and their thermosensitivity leads to the conclusion that the differences in heat sensitivity might be fully explained by the cycling status of the stem cell.

Key Words:

• hyperthermia
• haemopoietic stem cells
• CFU-S
• cycle state