Cellular therapies

Project leader: Carlijn Voermans PhD

Projects in this research line are focused on the development of new approaches that can facilitate hematopoietic stem cell transplantation or new cellular therapies.

Hematopoiesis

Bone marrow microenvironment

For long our research has been directed on the interaction between hematopoietic cells and the bone marrow microenvironment (BME). Mesenchymal stromal cells (MSCs), form the major constituent of the BME. Although MSCs are successfully applied for cellular therapy the mechanism underlying the homing and migration of these cells are poorly understood. Furthermore we are investigating the role of extracellular matrix proteins and adhesive receptors which are differentially expressed in regenerating hematopoietic cells.

Megakaryocytopoiesis

Thrombocytopenia is the most frequent clinical problem in autologous stem cell- and cord blood transplantation. We are therefore investigating megakaryocytopoiesis, in order to develop in vitro protocols for expanding megakaryocytes or even to produce platelets. At present our research is focused on the role of the megakaryocytic specific transcription factor MEIS1. 

New cellular therapies

Since our department is housing the certified Laboratory for Stem Cell Transplantation (link naar de website van het SCL) we are collaborator for academic partners to develop cellular products. At present we are involved in a project on dendritic cell therapy. Since 1990 we are working on technique development for Minimal residual disease detection of malignant disease in bone marrow, peripheral blood and stem cell grafts.

Recent results

Bone marrow microenvironment

Mesenchymal stromal cells are widely used for cellular therapy. However, high cell numbers are needed for therapy since the homing ability of these cells to the tissues of interest is low. More insight in the trafficking of these cells is therefore of utmost importance. Cell cycle is a process that has been demonstrated to be involved in homing of HSC. We now observed that the migratory MSC fraction contained significantly less cells in S- and G2/M-phase as compared to the non-migrating MSC. By microarray analysis genes that are differentially expressed between migrating and non-migrating MSC were identified, including NR4A1, NR4A2, CYR61, SMAD7, AXIN1, ID3 and HIST1H2AK. The largest group of upregulated genes in the migrating MSC subpopulation are involved in (or related to) the G-protein coupled receptor protein signalling pathway. SDF-exposure induced large differences compared to cultured MSC, and the data was enriched for genes involved in the (regulation of) cell cycle, response to wound healing and regulation of cell differentiation. These results indicate that besides promoting MSC migration, SDF may also induce other (paracrine) functions which MSC may have in the injured niche.

Carlijn Voermans has demonstrated during her stay at the Reya-lab in the USA that the ECM protein βig-h3 is strongly upregulated in regenerating mouse HSC. Ectopic expression of βig-h3 causes an accelerated differentiation of HSCs and rapid exhaustion of murine, primitive progenitors in vivo as well as in vitro. We now demonstrate that human CD34+ cells adhere to Big-h3 and that overexpression of Big-H3 accelerates differentiation of these cells towards megakaryocytes.

Megakaryocytopoiesis

We have shown that MEIS1 is uniquely restricted to MKs and platelets. In primary haematopoietic progenitor (CD34+) cells two splice variants of MEIS were identified, which were differentially expressed in the different stem cell sources. During megakaryocytic differentiation both MEIS1 transcripts were upregulated. Downregulation of MEIS1 using lentiviral short-hairpin RNAs (shRNA) in DAMI and primary cells resulted in reduced proliferation. This effect was caused both by cell cycle arrest and by increased apoptosis. Comparative transciptional profiling showed a total of 255 and 273 up- and down-regulated genes, respectively upon MEIS1-knock down. Consistent with the role of MEIS1 in MK differentiation, down-regulated genes were significantly enriched with functional categories such as response to wounding, hemostasis, and coagulation. Among these genes are several regulators of platelet volume, recently identified in genome wide association studies.

Cellular neovascularization therapy

We have previously shown that Endothelial colony forming cells (CFU-EC) are monocytic cells. CD4+ T-cells facilitated the monocytic colony formation, by the secretion of (a) soluble factor(s) upon CD3-MHC-classII interaction. Last year we showed that monocytes activated by this T cell factor(s) showed an increased revascularizing potential in the ischemic hind limb model in nude mice.

Also blood outgrowth endothelial cells (BOEC) are candidate for vascular cell therapy. It had been suggested that cord blood derived BOECs are superior. However, we showed that the phenotype and functional characteristics of BOECs isolated from cord blood and peripheral blood were almost equal. A slightly more angiogenic phenotype favors CB-BOEC, but addition of VEGF to PB-BOEC induces equal proliferation and tube formation.