Monday, July 27, 2015

A possible technique to accumulate stem cells

During the period  (1961-1969) I was a cell biologist doing cancer research in the Department of Cancer Research at the University of Saskatchewan  in Saskatoon and later at the Winnipeg Clinic Research Institute Laboratory which I set up  in 1965  following an invitation from Dr. P. Thorlakson. During this time I became proficient in the techniques of tissue culture, cellular autoradiography and DNA cytophotometry. Using these techniques I detailed a method for the analysis of stages of the cell cycle, viz.  Cells in G1, S (DNA synthesis), M, G2, and Go stages-  I considered such an analysis essential for oncologists employing chemotherapy and/or radiology and various other methods for treating patients with cancer. In 1967 I was one of 12 scientists invited by the Horner drug company to participate in a Cancer Symposium held in Montreal on the occasion of Canada's centennial .  ( See my publication in CMAJ : Hrushovetz, S.B. Analysis of stages of the cell cycle of normal and malignant tissue and its importance in cancer chemotherapy ). 
Using these techniques- Cells which have 2C amounts of DNA (2C refers to the amount of DNA found in a non dividing cells) belong to the G1 stage ; cells which are actively synthesizing  DNA (in the S stage) and  detected with cellular autoradiography following pulse labelling  with tritiated thymidine), G2 cells - are the non labelled cells which  have double or 4C amounts on DNA- i.e. they have completed their DNA synthesis but still have not undergone the process of mitosis or cell division, while   the cells undergoing this  process of cell division are in the M stage.
On reviewing you will note that my technique was somewhat different from data published at that time by other biologists  in that I added colchicine. Colchicine is a natural alkaloid which destroys the mitotic spindle. Of interest  many doctors  currently still use colchicine for the treatment of some  gout. This mitotic spindle is essential for the chromosomes to line up on the metaphase plate to move to the poles of the dividing cell. Once the chromosomes reach the poles, a membrane forms across the equatorial plate, completing  the formation of 2 daughter cells. Since for most cells this process of duplicating its DNA and undergoing cell division is usually accomplished in a 24 hour period it was felt that  after exposure to colchicine for 24 hours any cells which were not labelled were  cells which had 2C amounts of DNA. They are believed to be the cells which performed the functions of that tissue and/or organ. Biologists designate such cells  as the Go population.
 Recently- some 50 years later it occurred to me that maybe these Go stage cells could also be considered to be the  stem cells? 
It would be interesting to find out. If this hypothesis is  proven correct,  then colchicine pretreatment could become a rapid method for harvesting stem cells.

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