Altered features of HSPCs and BM niche elements in TDT patients. (A) Cell cycle analysis was performed by using Ki67 and 7-AAD staining of CD34⁺CD38⁻ primitive HSPCs from healthy donors (HD; n = 3) or TDT patients (n = 5). (B) Gene expression profile analysis was performed on CD34⁺ cells purified from the BM of TDT patients. Functional annotation by Partek software showed that genes could be grouped into a limited number of biological categories. Statistically significant (P < .05) GO categories are reported. In particular, most probe sets upregulated in TDT cells were enriched in response to stress and cell response to DNA damage and oxidative stress. One-way ANOVA was performed. (C-D) Representative images and quantitative IHC evaluation of collagen I deposition and JAG1 in the BM stromal niche of patients with TDT and control biopsies from healthy BM samples and patients affected by secondary polycythemia (Sec. Polycyt.). Original magnification ×400; inset ×630. Normal BM, n = 2; Sec. Polycyt., n = 2; TDT, n = 2. IHC on human BM sections by staining with anti-collagen-I and anti-JAG1 antibodies were performed. *P < .05. ES, enrichment score.