Intra-bone marrow injection of bone marrow and cord blood cells: An alternative way of transplantation associated with a higher seeding efficiency

Intravenous (IV) injection is currently the normal method for transplanting hematopoietic cells. However, the problem of seeding efficiency and homing is relevant especially when a limited number of stem cells is available. Intra-bone marrow (IBM) injection of bone marrow cells (BMCs) may overcome this problem.Irradiated (750 cGy) C57BL/6J mice were transplanted with 1 × 10 ⁵ BMCs harvested from transgenic mice expressing an enhanced version of the green fluorescent protein (EGFP ⁺) via IBM or with 1 × 10 ⁶ EGFP ⁺ BMCs via IV. Irradiated (320 cGy) NOD/SCID mice were transplanted with 1 × 10 ⁶ human cord blood (CB) cells via IBM or with 1 × 10 ⁷ human CB cells via IV.In C57BL/6J mice after 90 days, the fraction of EGFP ⁺ cells harvested was 37% and 53% in IV-treated and IBM-treated (contralateral tibia and femur in the IBM) mice, respectively: the expansion folds were 114 and 1760, respectively. In NOD/SCID mice, the percentages of CD45 ⁺ cells and CD45 ⁺/CD34 ⁺ cells were, at 30 days, 3.3% and 0.3% in IV-treated mice, and 4.4% and 1.1% in IBM-treated mice. At 60 days, the percentages of CD45 ⁺ cells and CD45 ⁺/CD34 ⁺ cells were 2.1% and 0.3% in IV-treated mice and 1.4% and 0.4% in IBM-treated mice. At day 90 the percentages of CD45 ⁺ cells and CD45 ⁺/CD34 ⁺ cells were 3% and 0.3% in IV-treated mice and 2.3% and 0.4% in IBM-treated mice.Our data demonstrate that IBM transplantation is associated with a seeding efficiency 15 times greater than IV transplantation. IBM transplantation may improve the results of transplant and may be useful in several settings: 1) when a limited number of hematopoietic progenitors are available; and 2) in experiments aiming to place in the bone marrow stem cells of other lineages (CNS, muscle, etc.).