Abstract 20 Long-Term Follow-Up of Cryopreserved Umbilical Cord Tissue as a Source of Mesenchymal Stem Cells

INTRODUCTION: Mesenchymal stem cells (MSCs) can differentiate into various cell types and exhibit immunomodulatory and paracrine effects. The cryopreservation of umbilical cord tissue as a viable source of MSCs has great potential for the field of regenerative medicine. We previously demonstrated that it is feasible to cryopreserve umbilical cord tissue cut into small fragments measuring 2 to 5 mm in length and obtain viable cells by thawing them between 30 and 60 days after freezing. OBJECTIVES: We aim to assess the condition of previously frozen samples for periods exceeding one year and analyze the data obtained from the cryopreservation of new samples. METHODS: A total of 834 new samples were frozen with our protocol for umbilical cord tissue cryopreservation. These Samples were thawed after obtaining microbiological contamination results of each sample. Additionally, a group of 100 samples that have been kept frozen for at least one year were selected to be thawed to assess the viability of the tissue frozen for extended periods of time. All cultures were maintained and the days to reach confluence were registered. RESULTS: The microbial analysis of the group of 834 new samples showed similar microbial profile and risk factors to those previously reported by us, with higher contamination frequencies associated with vaginal delivery and samples obtained by less experienced personnel in the operating room. Moreover, similar to our previous reports, the most frequent microorganism detected in contaminated samples were Staphylococcus sp, Escherichia Coli, Enterococcus sp and Streptocuccus sp. The group of 100 samples that were kept frozen for a minimum period of one year were thawed to assess if we could obtain viable cells from them. All cell cultures obtained from the thawed tissue were successful, reaching confluence between days 18 and 23, which is consistent with our previously observed timings. DISCUSSION: New cryopreserved tissue samples, and samples frozen for more than one year had viable cells that can be expanded as a source of MSCs. Microbial profile of those samples showed association with sample collection conditions at the operating room indicating that proper training of the personnel is the key to reduce contamination rates.