Human allogeneic stem cell maintenance and differentiation in a long- term multilineage SCID-hu graft

Abstract

The ability to determine the functional capacity of putative human hematopoietic stem cell (HSC) populations requires in vivo assays in which long-term multilineage differentiation can be assessed. We hypothesized that if human fetal bone was transplanted adjacent to a fetal thymus fragment in severe combined immunodeficient (SCID) mice, a conjoint organ might form in which HSC in the human bone marrow (BM) would mimic human multilineage differentiation into progenitor cells, B cells, and myeloid cells; undergo self-renewal; and migrate to and differentiate into T cells within the thymic microenvironment. To test this possibility, SCID mice were transplanted subcutaneously with HLA class I mismatched fetal bone, thymus, and spleen fragments (SCID-hu BTS). We found that the BM of SCID-hu BTS grafts maintained B cells, myeloid cells, CD34+ cells for at least 36 weeks posttransplant. Assayable hematopoietic progenitors colony-forming units-granulocyte- macrophage were present in 100% (66/66) of grafts over a period of 28 weeks. Cells with a HSC phenotype (CD34+Thy-1+Lin-) were maintained for 20 weeks in SCID-hu BTS grafts. These CD34+Thy-1+Lin- cells had potent secondary multilineage reconstituting potential when isolated and injected into a secondary HLA mismatched SCID-hu bone assay and analyzed 8 weeks later. In addition, early progenitors within the BM of SCID-hu BTS grafts were capable of migrating to the human thymus and undergoing differentiation through immature CD4+CD8+ double-positive T cells and produce mature T cells with a CD4+CD8- or CD8+CD4- phenotype that could be detected for at least 36 weeks. Phenotypically defined human fetal liver (FL) and umbilical cord blood (UCB) hematopoietic stem cell populations were injected into irradiated SCID-hu BTS grafts to assess their multilineage repopulating capacity and to assess the ability of the BTS system to provide an environment where multiple lineages might differentiate from a common stem cell pool. Injection of irradiated grafts with FL HSC or UCB HSC cells resulted in donor- derived B cells, myeloid cells, immature and mature T cells, and CD34+ cells in individual grafts when analyzed 8 weeks postreconstitution, further showing the multipotential nature of these stem cell populations. In addition, a strong correlation was observed between maintenance of host graft-derived CD8+ cells and failure of donor stem cell engraftment.(ABSTRACT TRUNCATED AT 400 WORDS)

SCID Mouse Models of Human Stem Cell Engraftment

“…Investigators have used SCID-hu mice as model systems for the study of human stem cell phenotype and differentiation [42][43][44][45][46][47][48][49][50][51][52], human gene therapy protocols [53][54][55], human T-cell differentiation [56], and homing of human myeloma cells to the bone marrow [57]. SCID-hu mice, in combination with cotransplanted thymic fragments, have been used to investigate the primitive hemopoietic stem cell that populates the T-cell lineage [42,58], for studies of human T-cell function [59,60], and for infection of human T cells and thymus with HIV [61,62]. Although an important experimental system, human fetal tissues are not readily available and impose a number of ethical concerns and constraints that limit their widespread use among laboratories.…”

Sustained proliferation, multi‐lineage differentiation and maintenance of primitive human haemopoietic cells in NOD/SCID mice transplanted with human cord blood

“…Thus, multi-lineage haemopoiesis has been successfully established by in utero transplantation of fetal lambs (Zanjani et al, 1994) and dogs (Omori et al, 1996), by direct injection of human fetal tissues (e.g. bone or fetal liver) previously implanted into mice with the severe combined immunodeficiency (SCID) mutation (the so-called SCID-hu mouse model) (McCune et al, 1988;Kyoizumi et al, 1992;Fraser et al, 1995), and by simple intravenous injection of various types of myeloablated immunodeficient mice (e.g. SCID mice, BEIGE-NUDE-Xid mice [bnx mice], and nonobese-diabetic-SCID [NOD/SCID] mice) (Kamel-Reid & Dick, 1988;Lapidot et al, 1992;Nolta et al, 1994;Lowry et al, 1996;Pflumio et al, 1996;Larochelle et al, 1996;Cashman et al, 1997).…”

Delineation of the human hematolymphoid system: potential applications of defined cell populations in cellular therapy

“…long-term repopulating potential of CD34+Thy-U cells was confirmed by the presence of CD19+ B cells and CD33* myeloid cells as well as by the maintenance of CD34+ progenitor cells in the fetal human bone graft which could he retransplanted and shown to engraft in secondary hosts ( Fig. IB) (44). The T-lymphoid potential of the CD34"^Thy-1 * cell population has been demonstrated in the SCID-hu thymus assay (16,45).…”