Earlier hematopoietic reconstitution by mouse cord blood transplantation combined with bone marrow c-kit(+) hematopoietic progenitor cells / 中国实验血液学杂志

ABSTRACT

This study was purposed to investigate the accelerating effect of newborn mouse cord blood transplantation combined with hematopoietic progenitor cells of bone marrow (BM) on the early hematopoietic reconstitution after transplantation, and the long-term chimerism of cord blood-derived cells, so as to develop a combined transplantation method for accelerating the early hematopoietic reconstitution. The lin(-)sca-1(-)c-kit(+) (c-kit(+)) cells and lin(-)sca-1(+) (sca-1(+)) cells in the bone marrow of BDF1 mice were isolated by MACS method. Biological characteristics in vitro of isolated fractions were observed and compared by semisolid colony culture combined with Giemsa staining. After transplantation of cord blood (CB) alone, or together with graded numbers of either c-kit(+) or sca-1(+) cells isolated from BDF1 mice (CD45.1) bone marrow into lethally irradiated CD45.2 congenic BDF1 mice, numbers of WBC and platelet were measured within 22 days of post-transplantation. The proportion of chimerism on granulocyte, T and B cell was dynamically measured by flow cytometry within 60 weeks of post-transplantation. The results showed that the number of colony from BM c-kit(+) cells cultured in semi-solid agar medium was significantly smaller than that from BM sca-1(+) population, which showed low proliferative potential in vitro and morphological characteristics of medium- or large-sized blast-like cells. The co transplantation of CB and BM c-kit(+) cells or sca-1(+) cells at the dosages of 1 × 10(4) or 2.5 × 10(4) or 5 × 10(4) to recipient mice leads to the quantity of WBC and platelets increased to 1 × 10(9)/L and 1 × 10(12)/L at day 12, whereas the injection of CB alone resulted at day 17. When mice were transplanted with CB together with BM c-kit(+)cells, and the CB-donor type cells in the peripheral blood increased progressively, while congenic donor BM-derived stem cells decreased gradually. After cotransplantation with CB and BM c-kit(+) cells for 60 weeks, a frequency of complete chimerism in CB-derived cells was continually maintained in granulates (96.68 ± 2.68)% and B lymphocytes (92.55 ± 3.04)%, while T lymphocytes (67.96 ± 7.91)% were dominantly derived from CB. On the other hand, congenic bone marrow or residual-derived cells were the dominant population, and the ratio of CB-derived cells in the peripheral blood was less than 10% (6.19 ± 7.62)% after cotransplantation with CB and sca-1(+)cells for 60 weeks. It is concluded that the cotransplantation of CB and BM congenic c-kit(+) cells is able to accelerate early hematopoietic reconstitution of recipient mice due to congenic marrow cells. Complete or main chimerism of cord blood is formed in long-term multilineage reconstitution of granulocytes, B cells and T lymphocytes.