Engraftment Outcomes after HPC Co-Culture with Mesenchymal Stromal Cells and Osteoblasts

Influential factors for optimizing and strengthening mesenchymal stem cells and hematopoietic stem cells co-culture

Mesenchymal stem cells (MSCs) and Hematopoietic stem cells (HSCs) are two types of bone marrow stem cells that can proliferate and differentiate into different cell lineages. HSCs interact with MSCs under protective conditions, called niche. Numerous studies have indicated supportive effects of MSCs on HSCs proliferation and differentiation. Furthermore, HSCs have many clinical applications and could treat different hematologic and non-hematologic diseases. For this purpose, there is a need to perform in vitro studies to optimize their expansion. Therefore, various methods including co-culture with MSCs are used to address the limitations of HSCs culture. Some parameters that might be effective for improving the MSC/ HSC co-culture systems. Manipulating culture condition to enhance MSC paracrine activity, scaffolds, hypoxia, culture medium additives, and the use of various MSC sources, have been examined in different studies. In this article, we investigated the potential factors for optimizing HSCs/ MSCs co-culture. It might be helpful to apply a suitable approach for providing high-quality HSCs and improving their therapeutic applications.

Endothelium-targeted human Delta-like 1 enhances the regeneration and homing of human cord blood stem and progenitor cells

Background

Umbilical cord blood (UCB) is becoming an alternative cell source for hematopoietic stem cell transplantation (HSCT). However, umbilical cord blood transplantation (UCBT) has been severely limited by low and finite numbers of hematopoietic stem cells and their delayed engraftment. New strategies are needed to improve ex vivo expansion efficiency and in vivo haematopoietic recovery.

Methods

We produced an endothelium-targeted soluble Notch ligand, the Delta-Serrate-Lag-2 (DSL) domain of human Delta-like 1 fused with a RGD motif (hD1R), and tested the effects of this protein on human umbilical cord blood hematopoietic stem and progenitor cell (UCB-HSPC) ex vivo and in vivo.

Results

hD1R-mediated ex vivo expansion system was able to significantly increase the absolute number of UCB-HSPCs. The hD1R-expanded cells had the enhanced homing and maintained long-term hematopoietic stem cell repopulation capacity in the bone marrow of immunodeficient nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice. Moreover, systemic administration of hD1R promoted the in vivo regeneration of donor cells in recipient mice and accelerated hematopoietic recovery, particularly in settings wherein the HSPCs dose was limiting.

Conclusions

Our results indicated that hD1R might be applied in improving hematopoietic recovery and HSC engraftment in human UCBT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0761-0) contains supplementary material, which is available to authorized users.

Phenotypic, Morphological and Adhesive Differences of Human Hematopoietic Progenitor Cells Cultured on Murine versus Human Mesenchymal Stromal Cells

Xenogenic transplantation models have been developed to study human hematopoiesis in immunocompromised murine recipients. They still have limitations and therefore it is important to delineate all players within the bone marrow that could account for species-specific differences. Here, we evaluated the proliferative capacity, morphological and physical characteristics of human CD34⁺ hematopoietic stem and progenitor cells (HSPCs) after co-culture on murine or human bone marrow-derived mesenchymal stromal cells (MSCs). After seven days, human CD34⁺CD133^– HSPCs expanded to similar extents on both feeder layers while cellular subsets comprising primitive CD34⁺CD133⁺ and CD133⁺CD34^– phenotypes are reduced fivefold on murine MSCs. The number of migrating HSPCs was also reduced on murine cells suggesting that MSC adhesion influences cellular polarization of HSPC. We used atomic force microscopy-based single-cell force spectroscopy to quantify their adhesive interactions. We found threefold higher detachment forces of human HSPCs from murine MSCs compared to human ones. This difference is related to the N-cadherin expression level on murine MSCs since its knockdown abolished their differential adhesion properties with human HSPCs. Our observations highlight phenotypic, morphological and adhesive differences of human HSPCs when cultured on murine or human MSCs, which raise some caution in data interpretation when xenogenic transplantation models are used.