CD61 expression in LT-HSCs. (A) Number of reports used in the aging signature, reporting differential expression of genes of the integrin family. (B) CD61 messenger RNA (mRNA) expression measured by reverse transcription PCR in LT-HSCs, short-term HSCs (ST-HSCs), and MPP isolated from young (2-4 months old) and aged (>22 months old) mice. (C) Protein level of CD61 on LT-HSCs from young (2-4 months old), middle-aged (10-12 months old) and aged (>22 months old) mice measured by flow cytometry. (D) Protein level of CD61 on LT-HSCs, ST-HSCs, and MPPs from young, middle-aged, and aged mice measured by flow cytometry. MPP, multipotent progenitor.