The effect of bone marrow graft composition on pediatric bone marrow transplantation outcomes

Effects of CD34+ cell dose on engraftment and long-term outcomes after allogeneic bone marrow transplantation

BACKGROUND

The number of CD34+ cells in the graft is generally associated with time to engraftment and survival in transplantation using cord blood or allogeneic peripheral blood stem cells. However, the significance of abundant CD34+ in bone marrow transplantation (BMT) remained unclear.

METHODS

We retrospectively reviewed 207 consecutive adult patients who underwent their first BMT at Jichi Medical University between January 2009 and June 2021.

RESULTS

The median nucleated cell count (NCC) and CD34+ cell dose were 2.17 × 108/kg (range .56-8.52) and 1.75 × 106/kg (.21-5.84), respectively. Compared with 104 patients in the low CD34+ group (below the median), 103 patients in the high CD34+ group (above the median) showed faster engraftment at day +28 in terms of neutrophil (84.6% vs. 94.2%; p =  .001), reticulocyte (51.5% vs. 79.6%; p < .001), and platelet (39.4% vs. 72.8%; p < .001). There were no significant differences in overall survival, relapse, nonrelapse mortality, acute or chronic graft-versus-host disease, or infectious complications between the two groups in univariate and multivariate analyses. Low or high NCC had no significant effect on overall survival, nonrelapse mortality, cumulative incidence of relapse and graft-versus-host disease, either. While a positive correlation was observed between NCC and the CD34+ cell dose, a high CD34+ cell dose was associated with rapid hematopoietic recovery, even in patients with NCC below the median.

CONCLUSION

Measurement of CD34+ cell dose in addition to NCC was useful for predicting hematopoietic recovery, but seemed to have little influence on the long-term outcome in BMT.

Advances in preclinical hematopoietic stem cell models and possible implications for improving therapeutic transplantation

Hematopoietic stem cell transplantation (HSCT) is a treatment for many malignant, congenital, and acquired hematologic diseases. Some outstanding challenges in the HSCT field include the paucity of immunologically‐matched donors, our inability to effectively expand hematopoeitic stem cells (HSCs) ex vivo, and the high infection risk during engraftment. Scientists are striving to develop protocols to generate, expand, and maintain HSCs ex vivo, however these are not yet ready for clinical application. Given these problems, advancing our understanding of HSC specification, regulation, and differentiation in preclinical models is essential to improve the therapeutic utility of HSCT. In this review, we link biomedical researchers and transplantation clinicians by discussing the potential therapeutic implications of recent fundamental HSC research in model organisms. We consider deficiencies in current HSCT practice, such as problems achieving adequate cell dose for successful and rapid engraftment, immense inflammatory cascade activation after myeloablation, and graft‐vs‐host disease. Furthermore, we discuss recent advances in the field of HSC biology and transplantation made in preclinical models of zebrafish, mouse, and nonhuman primates that could inform emerging practice for clinical application.

Infusion of Hematopoietic Stem Cell Products Using Pump Mechanism: An Approach Worth Consideration?

Hematopoietic stem cell transplantation using progenitor cells is a potentially curative treatment option for patients with high-risk malignancies and nonmalignant hematologic, immunologic, and genetic conditions. There is a need for evidence regarding safe practices and controlled infusion processes. Syringe and intravenous infusion pumps are not commonly used to deliver hematopoietic stem cell products (HPCs) due to a paradigm of thought that suggests that the pressure from the pump might damage the HPCs. Here, we describe a retrospective analysis of 114 patients who received HPC infusions using either a syringe or intravenous pump, providing support for this method along with successful engraftment data. This method may be a viable option to obtain reliable and consistent infusion rates, especially in pediatrics. To the best of our knowledge, this is the only study to date demonstrating safely using syringe and intravenous pump mechanisms in the setting of autologous and allogeneic pediatric stem cell transplantation.