Sebastian Brenner

Migration of hematopoietic stem cells: Application to stem cell transplantation

Previous and current research

Cell migration, homing and engraftment

Regulated movement of stem cells is critical for organ development, for homeostasis and tissue regeneration. Directed cell migration is regulated in part by the chemokine receptor CXCR4. Our laboratory studies the migration of hematopoietic and mesenchymal stem cells with regard to CXCR4 expression and investigates their homing and engraftment potential in NOD/SCID mice. Migration of leukemic stem cells also plays a critical role for relapse and disease outcome in leukemia. The FLT3-ITD (fms like tyrosin kinase 3 - internal tandem duplication) mutation is a poor prognostic factor in acute myeloid leukemia. To elucidate the interaction of FLT3-ITD and CXCR4, we study the role of FLT3-ITD in the migration of leukemic stem cells.
In order to screen for new migration relevant factors, we developed a phenotypic selection assay that enables the enrichment of non-migrating murine hematopoietic progenitor cells after transduction with a genome wide retroviral shRNA library. shRNA retrieval from non-migrating cell clones resulted in a candidate list of migration relevant genes that will be characterized using molecular and phenotypic analyses to identify their cellular regulatory mechanisms during migration.
CD34+ hematopoietic cells are heterogeneous and consist of lineage restricted committed progenitors and a small subset of stem cells. Ex vivo cultivation of hematopoietic stem cells (HSC) leads to a progressive loss of long-term repopulating cells. Understanding the composition of the HSC compartment during ex vivo culture is critical for clinical applications, where HSC are genetically engineered. Our laboratory has characterized the CD34+ population upon initiation of cell proliferation ex vivo and has found that selection of late dividing cells is an excellent means to enrich NOD/SCID long-term repopulating cells from ex vivo cultured CD34+ cells. Furthermore, the potent population of late dividing cells was shown to retain the stem cell marker CD133 that is progressively lost in proliferating cells. These findings will allow to further confine the hematopoietic stem cell compartment and might be the basis for new ex vivo protocols for gene therapy that selectively targets long-term repopulating cells.

Gene therapy for chronic granulomatous disease (CGD)

Gene therapy is the functional correction of a genetic defect by insertion of a normal and active copy of the responsible gene into patients’ cells to cure a disease. Chronic granulomatous disease (CGD) is an inherited immunodeficiency, caused by a defect in the multi-enzyme NADPH-oxidase complex. Affected phagocytes are unable to generate reactive oxygen metabolites and are thus severely impaired in killing certain opportunistic bacteria leading to life threatening infections. Our lab has long-standing expertise in retroviral vector development. In the past, we have demonstrated efficient correction of human CGD cells in vitro and in the NOD/SCID mouse model using lentiviral- and gammaretroviral vectors. We are currently performing a large animal study, where we analyse the efficiency of a new retroviral vector expressing the therapeutic transgene for CGD as well as the selection gene ΔMGMT.

Future prospects and goals

Identification and characterisation of genes involved in cell migration

Improvement of hematopoietic stem cell homing

Retroviral gene therapy for patients with chronic granulomatous disease

About

1999-2003: Postdoctoral-training at the Laboratory of Host Defenses, National Institutes of Health, USA since 2003: Group leader at the Department of Pediatrics, TU Dresden since 2006: Board certified Pediatrician

Selected publications

Ryser MF, Ugarte F, Thieme S, Gentsch M, Bornhäuser M, Roesen-Wolff A, Brenner S.: mRNA transfection of a CXCR4-GFP fusion protein - generated by a simple three step PCR protocol - results in efficient migration of primary mesenchymal stem cells. Tissue Engineering, in print.

Brenner S, Ryser MF, Whiting-Theobald NL, Gentsch M, Linton GF, Malech HL.: The late dividing population of gamma-retroviral vector transduced human mobilized peripheral blood progenitor cells contributes most to gene-marked cell engraftment in nonobese diabetic/severe combined immunodeficient mice.  Stem Cells. 2007 Jul;25(7):1807-13.

Brenner S, Ryser MF, Choi U, Whiting-Theobald N, Kuhlisch E, Linton G, Kang E, Lehmann R, Rosen-Wolff A, Rudikoff AG, Farese AM, MacVittie TJ, Roesler J, Horwitz ME, Malech HL.: Polyclonal long-term MFGS-gp91phox marking in rhesus macaques after non-myeloablative transplantation with transduced autologous peripheral blood progenitor cells. Mol Ther. 2006 Aug;14(2):202-11.

Brenner S, Whiting-Theobald N, Kawai T, Linton GF, Rudikoff AG, Choi U, Ryser MF, Murphy PM, Sechler JM, Malech HL.: CXCR4-transgene expression significantly improves marrow engraftment of cultured hematopoietic stem cells. Stem Cells. 2004;22(7):1128-33.

Brenner S, Whiting-Theobald NL, Linton GF, Holmes KL, Anderson-Cohen M, Kelly PF, Vanin EF, Pilon AM, Bodine DM, Horwitz ME, Malech HL.: Concentrated RD114-pseudotyped MFGS-gp91phox vector achieves high levels of functional correction of the chronic granulomatous disease oxidase defect in NOD/SCID/beta -microglobulin-/- repopulating mobilized human peripheral blood CD34+ cells. Blood. 2003 Oct 15;102(8):2789-97.

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