Dynamics of clonal hematopoiesis and cellular responses to stress-induced toxicity in autologous stem cell transplantation.

Autologous stem cell transplantation (ASCT) involves harvesting hematopoietic stem and progenitor cells (HSPCs) prior to chemotherapy and subsequent repopulation of the bone marrow. This process imposes a bottleneck, providing a framework to dissect the unresolved short- and long-term clonal dynamics during hematopoietic reconstitution. By integrating bulk error-corrected targeted sequencing of clonal hematopoiesis (CH)-associated genes with mitochondrial single-cell Assay for Transposase-Accessible Chromatin sequencing (mtscATAC-seq), we characterized mutational trajectories in frequently altered hematological genes and traced clonal evolution through somatic mitochondrial DNA variants, revealing post-transplant cellular heterogeneity and clonal architecture. Among 60 patients (multiple myeloma, n = 51; non-Hodgkin lymphoma, n = 6; Hodgkin lymphoma, n = 3), CH-associated mutations were identified in 53% pre-ASCT, predominantly involving DNMT3A. A transient increase in mutation counts and gene diversity occurred 10-25 days post-ASCT, with a gradual clonal expansion two years post-transplantation. Tandem ASCT amplified clonal complexity, with a twofold increase in mutation count and gene-level diversity, while preserving clonal trajectories across both transplant courses. Mitochondrial single-cell profiling in longitudinal samples of 3 patients showed patient-specific immune reconstitution and clonal dynamics, with balanced multilineage output from graft HSPCs. Collectively, our findings provide a firsthand comprehensive view of ASCT-induced clonal dynamics and immune reconstitution, paving the way for targeted gene-specific post-transplant monitoring.