ES-Cell Derived Hematopoietic Cells Induce Transplantation Tolerance

Background: Bone marrow cells induce stable mixed chimerism under appropriate conditioning of the host, mediating the induction of transplantation tolerance. However, their strong immunogenicity precludes routine use in clinical transplantation due to the need for harsh preconditioning and the requirement for toxic immunosuppression to prevent rejection and graft-versus-host disease. Alternatively, embryonic stem (ES) cells have emerged as a potential source of less immunogenic hematopoietic progenitor cells (HPCs). Up till now, however, it has been difficult to generate stable hematopoietic cells from ES cells. Methodology/Principal Findings: Here, we derived CD45 + HPCs from HOXB4-transduced ES cells and showed that they poorly express MHC antigens. This property allowed their long-term engraftment in sublethally irradiated recipients across MHC barriers without the need for immunosuppressive agents. Although donor cells declined in peripheral blood over 2 months, low level chimerism was maintained in the bone marrow of these mice over 100 days. More importantly, chimeric animals were protected from rejection of donor-type cardiac allografts. Conclusions: Our data show, for the first time, the efficacy of ES-derived CD45 + HPCs to engraft in allogenic recipient

Low antigenicity of hematopoietic progenitor cells derived from human ES cells

Eun-Mi Kim1, Nicholas Zavazava1,21Department of Internal Medicine, University of Iowa and Veterans Affairs Medical Center, Iowa City, Iowa, USA; 2Immunology Graduate Program, University of Iowa, Iowa City, Iowa, USAAbstract: Human embryonic stem (hES) cells are essential for improved understanding of diseases and our ability to probe new therapies for use in humans. Currently, bone marrow cells and cord blood cells are used for transplantation into patients with hematopoietic malignancies, immunodeficiencies and in some cases for the treatment of autoimmune diseases. However, due to the high immunogenicity of these hematopoietic cells, toxic regimens of drugs are required for preconditioning and prevention of rejection. Here, we investigated the efficiency of deriving hematopoietic progenitor cells (HPCs) from the hES cell line H13, after co-culturing with the murine stromal cell line OP9. We show that HPCs derived from the H13 ES cells poorly express major histocompatibility complex (MHC) class I and no detectable class II antigens (HLA-DR). These characteristics make hES cell-derived hematopoietic cells (HPCs) ideal candidates for transplantation across MHC barriers under minimal immunosuppression.Keywords: human embryonic stem cells, H13, hematopoiesis, OP9 stromal cells, immunogenicit

ES-derived HOXB4-expressing HPCs induce immunological tolerance to donor type cardiac allografts.

<p>A) Treatment protocol: MRL recipient mice were transplanted HPCs 14 days prior to transplantation of cardiac allografts which was performed between days 0 and 7. Cardiac function and survival were monitored by daily abdominal palpations. B) Graft survival: Chimeric MRL recipient mice tolerated donor type cardiac allografts, but not Balb/c third party allografts. Non-chimeric MRL mice acutely rejected allografts within 13 days. Syngeneic grafts were additionally used as controls.</p

Tolerance induction is accompanied by the presence of CD4FoxP3⁺ T cells in the tolerated allografts but not in the syngeneic control grafts.

<p>A) & B) Frozen sections of tolerated cardiac allografts were stained for CD4 on day 40 post-transplantation using a peroxidase-conjugated antibody (A). A section from an acutely rejected graft was used as control (B). Positively stained cells are stained brown. C)–H) To determine whether any of the CD4⁺ T cells were Tregs, frozen sections were co-stained for CD4 (FITC) and FoxP3 (PE). In the tolerant allograft, FoxP3⁺ cells (C) and CD4⁺ (D) cells were detected, which overlapped when merged (E) suggesting that the CD4⁺ cells expressed FoxP3. In contrast, none of the syngeneic or rejected allografts showed any FoxP3-expressing cells, as reflected by the merged stains of both FoxP3 and CD4 stains in F and G, respectively. (Magnification for C–E: ×600; magnification for F and G: ×200.)H) Lastly, splenic CD4⁺ T cells from these tolerant animals were used as responder cells in an ELISPOT assay that measured IL-2 production. Controls were animals pre-sensitized with two separate IP injections of donor splenocytes and non-transplanted control animals. The sensitized animals showed a higher number of IL-2 spots against the donor splenocytes, as expected. However, the control non-sensitized and tolerant animals showed equal numbers of spots, suggesting that indeed the tolerant animals had no activated alloreactive T cells. All three groups of animals responded equally to third-party Balb/c splenocytes.</p

HPC-induced mixed chimerism preserves organ architecture post-transplantation.

<p>Transplanted syngeneic and allogenic animals were sacrificed at either 40 or 100 days post-transplantation and the histology of the grafts studied after H & E staining. These grafts showed preservation of the muscle architecture and lack of mononuclear cell infiltration in the syngeneic and tolerant grafts, but massive tissue destruction in the acutely rejected control grafts.</p

Tracking embryonic hematopoietic stem cells to the bone marrow: nanoparticle options to evaluate transplantation efficiency

Abstract Background As the prevalence of therapeutic approaches involving transplanted cells increases, so does the need to noninvasively track the cells to determine their homing patterns. Of particular interest is the fate of transplanted embryonic stem cell-derived hematopoietic progenitor cells (HPCs) used to restore the bone marrow pool following sublethal myeloablative irradiation. The early homing patterns of cell engraftment are not well understood at this time. Until now, longitudinal studies were hindered by the necessity to sacrifice several mice at various time points of study, with samples of the population of lymphoid compartments subsequently analyzed by flow cytometry or fluorescence microscopy. Thus, long-term study and serial analysis of the transplanted cells within the same animal was cumbersome, making difficult an accurate documentation of engraftment, functionality, and cell reconstitution patterns. Methods Here, we devised a noninvasive, nontoxic modality for tracking early HPC homing patterns in the same mice longitudinally over a period of 9 days using mesoporous silica nanoparticles (MSNs) and magnetic resonance imaging. Results This approach of potential translational importance helps to demonstrate efficient uptake of MSNs by the HPCs as well as retention of MSN labeling in vivo as the cells were traced through various organs, such as the spleen, bone marrow, and kidney. Altogether, early detection of the whereabouts and engraftment of transplanted stem cells may be important to the overall outcome. To accomplish this, there is a need for the development of new noninvasive tools. Conclusions Our data suggest that multifunctional MSNs can label viably blood-borne HPCs and may help document the distribution and homing in the host followed by successful reconstitution