Healthy donors
In the study, a total of 45 healthy adult individuals who routinely received BM examination as allo-HSCT donors from July 1, 2020 to March 1, 2021 at Peking University Institute of Hematology were enrolled. Donors aged <30 years, 30-45 years, and >45 years were divided into the young, middle-aged and old groups respectively, with 15 donors per group. The donor characteristics, including age, sex, and routine peripheral blood parameters were evaluated among young, middle-aged and old donors.
Peking University People’s Hospital Ethics Committee consented the study. Moreover, all subjects signed informed consent before enrollment, in conformity to the Declaration of Helsinki.
Characterization of BM ECs
BM mononuclear cells (BMMNCs) were isolated with Ficoll-Paque solution (HaoYang, Tianjin, China). The following multicolour flow cytometry panel were applied to quantify ECs in BM: anti-CD34-PE/Cy7, anti-CD309-PE, and anti-CD133-APC (BD Biosciences, CA, USA). ECs were identified as CD34+CD309+CD133+, and the relative EC frequency was expressed as a fraction of BMMNCs[23-27]. Samples were collected on a BD LSRFortessa flow cytometer and the compensation adjustion as well as data analysis were accomplished via a BD LSRFortessa software.