Experimental murine models are an essential tool in the field of bone marrow (BM) transplantation research. Therefore, numerous mice are required to obtain a sufficient number of BM cells, which is in contrast with the Reduction principle of the 3R principles. The selection of the cell source and the isolation protocol are therefore critical in obtaining a sufficient yield of cells for experiments. Nowadays, the vertebrae are already used as an extra source of BM cells to enrich the number of isolated cells from the long bones and ilia (LBI), when needed. Yet, little is known if BM cells from LBI and vertebrae share the same characteristics and can be pooled together for further analysis. Therefore, in this study, we aimed to compare the quantity and characteristics of haematopoietic and stromal cell lines in the BM from the LBI and vertebrae. To count haematopoietic and mesenchymal stem/stromal progenitors, colony-forming unit assays were performed. To determine the expansion capacity of mesenchymal stem/stromal cells (MSCs), cultivation of MSCs and measurement of the expression of surface markers by flow cytometry was performed. The characterisation and enumeration of immune cell populations was also performed by flow cytometry. Here, we show that the vertebrae are a comparable source of BM cells to the LBI regarding the analysed parameters.

Background The association of the ABO blood group with COVID‐19 disease has been confirmed by several studies, with the blood group A patients being more susceptible and prone to a more severe clinical course of the disease. Additionally, several authors also addressed the association of ABO‐types and the levels of anti‐SARS‐CoV‐2 antibodies in convalescents, mostly supporting a theory that the non‐O blood group convalescents present with higher levels of anti‐SARS‐CoV‐2 antibodies. Study Design and Methods Since previous findings were based on small convalescent cohorts, we quantified the anti‐SARS‐CoV‐2 antibody levels in a total of 3187 convalescent plasma donors with three commercial serological and one standard neutralizing antibody test. The majority of donors had undergone a mild form of the disease and the median time of sampling was 66 days after diagnosis. Results None of the antibody quantitation results showed any significant association with the ABO blood group types. The same result was evident in the subgroup of vaccinated individuals (n = 370) and the subgroups when stratified according to post‐COVID‐19 periods (0–60, 60–120, and 120–180 days). Conclusion In conclusion, we found no evidence to confirm that the ABO blood group types influence the level of SARS‐CoV‐2 antibody response in COVID‐19 convalescent plasma donors.

The aging of multicellular organisms is a complex process, which is a result of various mutually complementary causes. One of these causes is the aging of stem cells. The biological function of stem cells is the replacement of cells that are lost due to illness, injury or normal fluctuations in the maintenance of tissue homeostasis. Molecular mechanisms involved in stem cell aging are similar to those involved in the aging of somatic cells. They include DNA damage and mutations, cell senescence, stem cell exhaustion, telomere shortening, epigenetic changes (alterations of histones and DNA and the consequent dysregulation of gene expression), changes in microRNAs, changes in metabolism, nutrient sensing, decline in mitochondrial integrity and biogenesis, alterations in microenvironment, accumulation of paracrine factors, and loss of cell polarity and proteostasis. Stem cells have developed special mechanisms that compensate for age-related accumulations of errors and they manage to maintain their stemness for a long time, however, they are able to keep cells in a good condition only for a limited period. This article describes the various mechanisms of stem cell aging and their consequences.

By extrapolating our murine data, and data from some previous studies to a human non-conditioned autologous CD34 HSPC transplantation setting, we conclude that approximately 44 million CD34 HSPCs would be needed to achieve 20% donor chimerism in a 70-kg human, which could serve as a starting point for the future use of HSCPs in gene and cell therapy.

The removal of leukocytes from blood components helps to prevent or reduce some adverse reactions that occur after blood transfusions. The implementation of the leukodepletion process in the preparation of blood units requires quality control, consisting of a reliable cell counting method to determine residual leukocytes in blood components. The most widely used methodology is a flow cytometric bead-based counting method. To avoid the need for commercial counting beads, we evaluated a volumetric counting method of leukocyte enumeration. A total of 160 specimens of leukodepleted plasma, red cell and platelet units, as well as 58 samples of commercially available controls containing different concentration levels of leukocytes, were included in the study. The conventional quality control method using the bead-based counting method performed with the FACSCalibur flow cytometer was compared to the bead-based counting method and the volumetric counting method performed with the MACSQuant 10 flow cytometer. Our results show that the MACSQuant bead-based method, as well as the volumetric MACSQuant method, meet the sensitivity requirements of residual leukocyte enumeration when compared to the gold standard, bead-based FACSCalibur method. We conclude that the volumetric method can be a substitute for the bead-based counting of residual leukocytes in a variety of blood components.