Do cells remain viable during longterm low temperature storage?

obesityDevelopment of regenerative and reproductive medicine, increase of the level of insurance culture and a more conscious attitude of modern people to their health led to the high popularity of biobanks worldwide.

Biobanks are medical institutions that are engaged in long-term storage and cryopreservation of biological material under conditions of the ultra-low temperatures. Frozen cells and tissues in the future may be used for the treatment or rehabilitation. Cord blood banks, banks of reproductive cells and tissues (sperm, ovarian tissue, embryos, eggs, etc.), banks of peripheral blood, bone marrow, etc are the most popular ones among biobanks.

Theoretically, from the point of scientific view, biological tissue in liquid nitrogen at −196 C can be stored indefinitely, but modern pragmatic person, the client of biobank, often wants to get more specific answers to the questions: «How long can frozen cells be stored without loss of viability? Has anyone conducted such research? Are there any documented evidences for the viability of thawed biomaterial after prolonged cryo-storage?»

First cryobanks of cord blood began to be created in the 90s of 20th century in the United States, and during this period the American scientists, along with donor or private (owned by customers) samples of umbilical cord blood preserved a certain number of reference samples that at certain intervals were thawed, cell viability and their suitability for clinical use were assessed.

Thus, according to the famous American scientist, patriarch of cord blood banking H.Broxmeyer, cord blood cryo-storage for 24 years does not have a negative impact on the quality indices of stem cells (2013).

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Important evidence of the viability of frozen biological material was obtained by reproductologists. So, today in the world at least 25 children were born to women, who were retransplanted own frozen ovarian tissue. Also in the history of in vitro fertilization there is evidence that about 2 000 children were born from pregnancies from frozen eggs and more than 300 000 children — from pregnancies from frozen sperm.

In 2010, in the US state of Virginia a child from the embryo, which was stored in a frozen state during 20 years was born. And in 2014, a new scientific sensation occurred in Japan, where a healthy baby was born from an egg frozen 13 years ago.

Thus, the results of biological studies and world clinical experience concerning frozen biomaterial after prolonged low temperature storage suggests that the correct cryopreservation and cryo-storage allow to use frozen cells and tissues, even after many years quite successfully.

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However, procedure of freezing and proper conditions of cryo-storage have huge impact on the quality indices of the stored cells and tissues. That is why, Association of cryobanks of cord blood and other human tissues and cells recommends that when choosing a biobank special attention should be paid at the qualification of personnel of the selected institution, their level of professional recognition among national and foreign cryobiologists, as well as experience and reputation of the cryobank.

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