Substrate-mediated nanoparticle/gene delivery to MSC spheroids and their applications in peripheral nerve regeneration

Hematopoietic and mesenchymal stem cells: polymeric nanoparticle uptake and lineage differentiation

The combination of stem cell therapy and nanoparticles promises to enhance the effect of cellular therapies by using nanocarriers as drug delivery devices to guide the further differentiation or homing of stem cells. The impact of nanoparticles on primary cell types remains much more elusive as most groups study the nanoparticle-cell interaction in malignant cell lines. Here, we report on the influence of polymeric nanoparticles on human hematopoietic stem cells (hHSCs) and mesenchymal stem cells (hMSCs). In this study we systematically investigated the influence of polymeric nanoparticles on the cell functionality and differentiation capacity of hHSCs and hMSCs to obtain a deeper knowledge of the interaction of stem cells and nanoparticles. As model systems of nanoparticles, two sets of either bioinert (polystyrene without carboxylic groups on the surface) or biodegradable (PLLA without magnetite) particles were analyzed. Flow cytometry and microscopy analysis showed high uptake rates and no toxicity for all four tested particles in hMSCs and hHSCs. During the differentiation process, the payload of particles per cell decreased. The PLLA-Fe particle showed a significant increase in the IL-8 release in hMSCs but not in hHSCs. We assume that this is due to an increase of free intracellular iron ions but obviously also depends on the cell type. For hHSCs and hMSCs, lineage differentiation into erythrocytes, granulocytes, and megakaryocytes or adipocytes, osteocytes and chondrocytes, was not influenced by the particles when analyzed with lineage specific cluster of differentiation markers. On the other hand qPCR analysis showed significant changes in the expression of some (but not all) investigated lineage markers for both primary cell types.

Enhanced Autophagy of Adipose-Derived Stem Cells Grown on Chitosan Substrates

Autophagy is an important protein quality control mechanism for cells under stress conditions to promote cell survival. Modulation of autophagy on biomaterial substrates is rarely reported. In this study, the autophagy of adipose-derived stem cells (ADSCs) cultured on chitosan (CS) substrates was examined. Compared to the traditional monolayer culture, ADSCs cultured on CS substrates showed spheroid formation as well as a prolonged upregulation of autophagosomal marker-microtubule-associated protein 1 light chain 3 (LC3) II protein expression. In addition, the green fluorescent protein tagged-LC3 (GFP-LC3) expressing ADSCs also revealed more GFP-LC3 puncta on CS substrates. The enhanced autophagy on CS substrates was associated with Ca(2+), while ethylene glycol tetraacetic acid (EGTA), a Ca(2+) chelator, repressed the autophagy in a dose-dependent manner. Moreover, ADSC spheroids on CS substrates demonstrated a higher survival rate and autophagy response upon H2O2 treatment. The upstream components of autophagy signal pathway-UNC51-like kinase 1 (Ulk1), autophagy-related protein 13 (Atg13), and autophagy/beclin-1 regulator 1 (Ambra1) genes were more highly expressed in ADSC spheroids before and after adding H2O2 than those in the conventional culture. EGTA also decreased the cell viability and autophagy-associated gene expression for ADSC spheroids on CS substrates after H2O2 treatment. Therefore, we suggest that three-dimensional (3D) cell culture on CS may confer ADSCs the ability to increase the autophagic flux in response to stimulations in a Ca(2+)-dependent manner.