autologous blood and marrow transplantation - Blog Science ...

Minimal Therapy Models of Transplantation
F.M. Stewart, S. Zhong, PJ. Quesenberry
Classic transplantation models involve lethal myeloablation, a setting in which
a few or very large numbers of infused marrow stem cells will give 100% donor
cells after transplantation. Using a BALB/c male/female marrow transplant model
that detects male DNA in host tissues by Southern blot or fluorescent in-situ
hybridization (FISH), we have shown that high levels of male BALB/c marrow
chimerism can be established in untreated female BALB/c hosts, albeit by infusing
relatively high levels of cells. We have shown that exposure to doses of irradiation
that cause minimal myeloablation (50-100 cGy) leads to very high levels of donor
chimeras, such that relatively small numbers of marrow cells can give donor
chimerism in the 40-100% range. Our studies of radiation sensitivity of long-term
engrafting cells have shown that 100 cGy, while not myelotoxic, is stem cell toxic,
and imply that the final host:donor ratios are determined by competition between
host and donor stem cells. In this minimal myeloablation model, we further
delineated the basic characteristics of engraftment from marrow infused at different
time intervals after 100 cGy whole-body irradiation and engraftment of 100 cGy of
marrow cells irradiated in vivo. The results show that infusing cells at longer time
intervals after 100 cGy still results in high levels of engraftment, suggesting a
failure of renewal of host stem cells at the time intervals evaluated. We also have
evaluated secondary engraftment after minimal ablation and the effects of 5-FU
and hydrea on engraftment in these models. Finally, we have begun work in an
allogeneic model (B6.SJL donor/Balb/c recipient) using donor spleen cell infusions
and anti-CD40 ligand followed by low-dose irradiation (100 cGy) as minimal
preparative treatment. Transplanted mice were killed at 6 weeks posttransplant, and
engraftment was determined by measuring the percentage of donor cells in marrow,
spleen, and thymus using fluorescent antibody staining with FITC-CD45.1. The
results of these studies will be presented. Ultimately, these studies should provide
nontoxic approaches for improved stem cell engraftment in clinical gene therapy,
or stem cell expansion strategies, and should form a base for the development of an
approach to nontoxically create allochimeras for therapy of hemoglobinopathies or
for cellular immune therapy of cancer.
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