Allogeneic Peripheral Blood Stem Cell Transplant: Correlation of Donor Factors with Yield, Engraftment, Chimerism, and Outcome: Retrospective Review of a Single Institute During a 3-Year Period

Lineage-specific early complete donor chimerism and risk of relapse after allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia

Recipient–donor chimerism is routinely analyzed after allogeneic hematopoietic stem cell transplantation (HSCT) to monitor engraftment and graft rejection. For malignancies, chimerism can also be used to screen for disease relapse post-HSCT but methodology and interpretation of results are not standardized and likely depend on underlying diagnosis. We have implemented highly sensitive and accurate methodologies for chimerism analysis for the purpose of improving relapse prediction. Here, we report an exploratory retrospective analysis of clinical routine chimerism results from all 154 HSCTs for acute myeloid leukemia (AML) performed at our center during the years 2015–2020 with the aim of suggesting a clinically useful threshold at which risk of relapse is high. Relapse was not reliably predicted based on single elevated chimerism values obtained before time of overt relapse. However, early complete donor chimerism, here defined as recipient DNA < 0.2% in CD33⁺ cells in any blood or bone marrow sample taken during the first 60 days after HSCT, correlated inversely with relapse during the observation time (log-rank test P = 0.033). We propose that achievement of complete chimerism determined early after HSCT using sensitive methods can be used for risk-stratification of AML patients.

Stem cells: Haemobiology and clinical data summarising: A critical review

Stem cells (SC) are the unique and "key-cells" in the human body "working" as a source of producing a large number (proliferation) of mature (differentiation) cells inside different tissues ("cytopoiesis") - while at the same time maintaining the ability to "reproduce" themselves (self-renewal). These events are balanced by interactive signals from the extracellular matrix, as well as microenvironment provided by stromal cells. On the other hand, SC plasticity (so-called "inter-systemic plasticity") is the ability of the most "primitive" (immature) adult SCs to switch to novel identities. The phrase SC plasticity also involves phenotypic potential of these cells, broader than spectrum of phenotypes of differentiated cells in their original tissues. Recent increasing clinical use of cell-mediated therapeutic approaches has resulted in enlarged needs for both, higher quantity of SCs and improved operating procedures during extracorporeal manipulations. The aim of harvesting procedures is to obtain the best SC yield and viability. The goal of optimised cryopreservation is to minimise cellular thermal damages during freeze/thaw process (cryoinjury). Despite the fact that different SC collection, purification and cryopreservation protocols are already in routine use - a lot of problems related to the optimal SC extracorporeal manipulations are still unresolved. The objective of this paper is to provide an integral review of early haemobiological and cryobiological research in the unlimited "SC-field" with emphasis on their entities, recent cell-concepts, extracorporeal manipulative and "graft-engineering" systems. Their therapeutic relevance and efficacy in "conventional" SC transplants or regenerative medicine will be briefly summarised. Finally, in this paper original results will not be pointed out - related to neither SC transplants nor regenerative medicine - but a light will be shed on some of them.