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Background Aims: In 2016, specifications for both pre-cryopreserved and post-thawed cord blood were defined in the sixth edition of NetCord Foundation for the Accreditation of Cellular Therapy (FACT) Standards for Cord Blood Banks. However, for several experts, harmonization regarding flow cytometry analysis performed on post-thawed samples is still a concern. A multicenter study led by Héma-Québec aimed to provide scientific data to support the cord blood accreditation bodies such as NetCord FACT in the revision of standards., Methods: Twelve cord blood units were processed for plasma and red cell reduction following standard operating procedures. Cord blood unit aliquots were shipped to eight participating centers under cryogenic conditions for analysis before and after standardization of protocol. Repeatability of stem cell count, measured pre- and post-intervention with the centers, was estimated using multilevel linear regression models with a heterogeneous compound symmetry correlation structure among repeated measures., Results: Excellent inter-center repeatability was reported by each participant regarding the viable CD34+ cells concentration, and a successful improvement effect of protocol standardization was also observed. However, we observed that better control over the critical parameters of the protocol did not have a significant effect on improving homogeneity in the enumeration of CD45+ cells., Conclusions: The current practice in cord blood selection should now also consider relying on post-thaw CD34+ concentration, providing that all cord blood banks or outsourcing laboratories in charge of the analysis of post-thaw CB samples take into account the consensual recommendations provided in this work and adhere to a good-quality management system., Competing Interests: Declaration of Competing Interest The authors have no commercial, proprietary, or financial interest in the products or companies described in this article., (Copyright © 2019 International Society for Cell and Gene Therapy. All rights reserved.)

Background Aims: The human mesenchymal stromal cell (hMSC), a type of adult stem cell with a fibroblast-like appearance, has the potential to differentiate along the mesenchymal lineage and also along other cell lineages. These abilities make hMSC a promising candidate for use in regenerative medicine. As the hMSC represents a very rare population in vivo, in vitro expansion is necessary for any clinical use. hMSC characterization is commonly carried out through the expression of specific markers and by the capability of differentiating toward at least adipo-, osteo- and chondrocytic lineages. Commitment processes also result in significant changes in the ultrastructure in order to acquire new functional abilities; however, few studies have dealt with the ultrastructural characteristics of hMSC according to the time of incubation and type of media., Methods: The immunophenotype, functional characteristics and ultrastructural features of bone marrow (BM) hMSC cultured in two different media were investigated. The media chosen were Iscove's modified Dulbecco's medium (IMDM) and the Dulbecco's modified Eagle medium (DMEM). The latter has been recommended recently by two international transplantation and cytotherapy societies, the International Society of Cellular Therapy (ISCT) and European Group for Blood and Bone Marrow Transplantation (EBMT), for hMSC expansion for clinical applications., Results and Conclusions: The present results indicate that culture conditions greatly influence hMSC ultrastructural features, proliferation, growth and differentiation. In particular, our findings demonstrate that DMEM preserves the hMSC stem features better. Furthermore, the results obtained in IMDM suggest that a small size does not always correlate with conditions of cell immaturity and a greater proliferative potential.

Background Aims: Bone marrow (BM) is the most used source of hemopoietic stem cells (HSC) and mesenchymal stromal cells (MSC) in both hematologic settings and regenerative medicine. We compared the feasibility and reproducibility of two gravity separation techniques, with or without the use of a density gradient, in terms of both hematopoietic and mesenchymal human BM progenitors., Methods: A total of 16 BM samples was processed to obtain mononuclear cells (MNC) and buffy coats (BC). The efficiency of the two procedures was evaluated by recovery of white blood cells (WBC), MNC and CD34(+) cells, clonogenic assays, red blood cell (RBC) depletion, cell viability, expression of embryonic transcriptional regulators and MSC assessment., Results: The two procedures yielded a comparable recovery of HSC. Non-density gradient separation (NDGS) of BM resulted in four times higher MSC recovery and higher expression of embryonic stem cell markers (Nanog and Sox2) compared with density-gradient separation (DGS). MSC derived from both procedures was comparable in terms of phenotype, differentiation and proliferation potential., Conclusions: NDGS is less time consuming, provides a better MSC enrichment and appears to be a suitable cell preparation method for clinical applications.

Background: Mesenchymal stem cells (MSC) are multipotent progenitors retaining the capability to undergo multilineage differentiation, mostly towards all the mesodermal cellular lineages. MSC growing under standard conditions are composed of two main subpopulations with a characteristic distribution in the morphologic flow cytometric scatter: RS (recycling stem) cells (small, agranular) and m (mature) MSC (large, moderately granular cells)., Methods: MSC obtained from BM of healthy donors and expanded in culture were characterized by evaluating both the expression of conventional markers and differentiation potential. We used CFSE, a lipophilic dye that is taken up by cell membranes, to investigate separately the proliferative activity of RS cells and mMSC subsets., Results: With flow cytometric analysis, RS cells and mMSC showed nearly the same immunophenotypic pattern, even if a significantly smaller percentage of RS cells expressed some of the classic mesenchymal Ag. The RS cell fraction was confirmed to have a higher proliferative potential and such a feature was particularly evident under certain culture conditions., Discussion: CFSE has been shown as a reliable method for studying the proliferative activity of MSC subpopulations identified by flow cytometric analysis. The acquisition parameter strategy is crucial for the accuracy of the analysis.