Background. Human cardiac-derived progenitor cells (hCPCs) have shown promise in treating heart failure (HF) in adults. The purpose of this study was to describe derivation of hCPCs from pediatric patients with end-stage HF. Methods. At surgery, discarded right atrial tissues (hAA) were obtained from HF patients (n = 25; hAA-CHF). Minced tissues were suspended in complete (serum-containing) DMEM. Cells were selected for their tissue migration and expression of stem cell factor receptor (hc-kit). Characterization of hc-kitpositive cells included immunohistochemical screening with a panel of monoclonal antibodies. Results. Cells, including phase-bright cells identified as hc-kitpositive, spontaneously emigrated from hAA-CHF in suspended explant cultures (SEC) after Day 7. When cocultured with tissue, emigrated hc-kitpositive cells proliferated, first as loosely attached clones and later as multicellular clusters. At Day 21~5% of cells were hc-kitpositive. Between Days 14 and 28 hc-kitpositive cells exhibited mesodermal commitment (GATA-4positive and NKX2.5positive); then after Day 28 cardiac lineages (flk-1positive, smooth muscle actinpositive, troponin-Ipositive, and myosin light chainpositive). Conclusions. C-kitpositive hCPCs can be derived from atrial tissue of pediatric patients with end-stage HF. SEC is a novel culture method for derivation of migratory hc-kitpositive cells that favors clinical translation by reducing the need for exogenously added factors to expand hCPCs in vitro.

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Background While studies have shown that antibody detection may be delayed if an antibody identification (ABID) is not performed every 3 days, little data exist on the potential major risk of an acute hemolytic transfusion reaction (aHTR). Study Design and Methods At our institution, if no change in the screen, or a positive crossmatch, ABIDs are performed every 30 days. Between January 1, 2015 and May 31, 2019, all new antibodies detected within 28 days of a prior transfusion were identified. Testing results and patient charts were reviewed for evidence of hemolysis. The $211 patient charge was used to determine the cost for ABIDs performed during the studied time period. Results For 36 patients, a new clinically significant alloantibody was detected within 28 days of an antigen‐positive transfusion. Only one of these patients had a history of prior alloimmunization and put at possible risk due to the ABID policy. For this patient, while there was less than the expected increment to an antigen‐positive unit, there was no clinical or laboratory evidence of an aHTR. During this same time, 6095 ABIDs were performed, at a cost of approximately $1.29 million, and 72,665 red cell transfusions occurred. Conclusion With an ABID every 30 days, only one patient, over 4.5 years, was put at potential risk for hemolysis from one transfusion (0.001% of the total units transfused during the time period). While antibody detection may be delayed, performing ABIDs every 30 days saves money and medical laboratory scientist time and should be balanced against potential patient harm.

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