Background: Despite advancements in comprehension of molecular mechanisms governing bone marrow (BM) homing of hematopoietic stem cells, cord blood transplant (CBT) suffers from a slow rate of hematopoietic recovery. Intrabone (i.b.) injection has been proposed as a method able to improve speed of BM engraftment with respect to conventional i.v. protocols. However, the mechanisms underlying this benefit are largely unknown.
Aim: To verify whether i.b.-CBT determines a local engraftment able to predict the reconstitution of recipient hematopoiesis.
Design and methods: Twenty-one patients with hematologic malignancies received i.b. injection into both iliac crests of 3.2 ± 0.68 ∗ 107/kg cord blood cells. One month following i.b.-CBT, PET-CT imaging was performed. Maximal standardized uptake values (SUVs) were assessed in BM of both iliac crests and in all lumbar vertebrae.
Results: Maximal SUV within iliac crests was higher than in lumbar vertebrae (4.1 ± 1.7 versus 3.2 ± 0.7, resp., P = 0.01). However, metabolic activity in these two different BM districts was significantly correlated (r = 0.7, P < 0.001). Moreover, FDG uptake values within the injection site closely predicted platelet recovery 100 days after i.b.-CBT (r = 0.72, P < 0.01).
Conclusions: The metabolic activity of injected BM predicts the subsequent rate of hematopoietic recovery after i.b.-CBT, suggesting a pivotal role of the local engraftment in the reconstitution of recipient hematopoiesis.