Impact of controlled-rate freezing interruption on cell viability

by Alexey Bersenev on July 16, 2014 · 1 comment

in clinical lab, cord blood

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If you process cells for clinical use, you probably perform cryopreservation in the device, called controlled-rate freezer (CRF). This is the most frequent and routine procedure in cord blood banking. CRF uses liquid nitrogen (LN) to cool cells in controlled manner. The whole procedure takes usually 40-60 min and finished by freezing cells at -80C. However, sometimes such freezing procedure could be interrupted by errors (the most frequent cause – not enough LN or pressure in the tank, connected to CRF). The authors of new study, published in Transfusion, asked “How such interruptions in different time points of CRF procedure will impact cord blood cell viability”?

Interestingly, cord blood cell viability was not affected in any time point of interruption CRF if cells were transferred into mechanical -80C freezer for ~18 hours and then to LN for long-term storage (it was ~51-57% for CD45+ cells and 89-92% for CD34+ cells). However, if cord blood products were transferred in LN directly, viability of CD34+ was significantly lower at +4C (78%) and CD45+ cells at +4C, -10C, -20C (~32%) of CRF interruption points. Colony-forming ability was affected greater than CD34+ viability at +4C to -30C interruption points. The study tested cord blood products, cryopreserved with 10% DMSO.

Some conclusions from this important study:

  1. If you have CRF interruption, don’t panic! Transfer cells to -80C mechanical freezer and next morning to LN freezer. Check viability and potency (CFU for cord blood) in retention vials.
  2. You can safely transfer your cells directly to LN freezer if CRF was interrupted after reaching -40C temperature point.
  3. Always check potency of cells in case of CRF interruption, since it could not correlate with viability.
  4. Viability of different cell populations (CD34+ vs. CD45+) could differ significantly in case of CRF interruption.
  5. CRF interruptions could be tested by cell manufacturing team as part of freezing procedure validation.
  6. The results of this study could be implemented in “disaster plan” of cryopreservation departments of cord blood banks.

{ 1 comment… read it below or add one }

Rodrigo Arancibia July 22, 2014 at 11:14 am

Great info! and nicely put


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