Regulation of Hematopoietic Stem Cell Behavior by the Nanostructured Presentation of Extracellular Matrix Components

Abstract

Hematopoietic stem cells (HSCs) are maintained in stem cell niches, which regulate stem cell fate. Extracellular matrix (ECM) molecules, which are an essential part of these niches, can actively modulate cell functions. However, only little is known on the impact of ECM ligands on HSCs in a biomimetic environment defined on the nanometer-scale level. Here, we show that human hematopoietic stem and progenitor cell (HSPC) adhesion depends on the type of ligand, i.e., the type of ECM molecule, and the lateral, nanometer-scaled distance between the ligands (while the ligand type influenced the dependency on the latter). For small fibronectin (FN)–derived peptide ligands such as RGD and LDV the critical adhesive interligand distance for HSPCs was below 45 nm. FN-derived (FN type III 7–10) and osteopontin-derived protein domains also supported cell adhesion at greater distances. We found that the expression of the ECM protein thrombospondin-2 (THBS2) in HSPCs depends on the presence of the ligand type and its nanostructured presentation. Functionally, THBS2 proved to mediate adhesion of HSPCs. In conclusion, the present study shows that HSPCs are sensitive to the nanostructure of their microenvironment and that they are able to actively modulate their environment by secreting ECM factors.

Nanoscale Ligand Spacing Influences Receptor Triggering in T Cells and NK Cells

“…This self-assembly-based technique has proved its value in determining spatial effects on signaling in a variety of cellular systems 22, 46–49 , founded on the ability to readily pattern large substrate areas with feature sizes as small as ~10 nm. Nanopattern formation is based on forming two-dimensional close-packed layers of block copolymer micelles whose cores are loaded with gold (III) chloride.…”

Biophysical regulation of hematopoietic stem cells

“…a threshold value: at distances smaller than this value HSPCs are able to adhere, whereas at larger distances no adhesion occurs) is dependent on (i) cell type, (ii) the receptor that is targeted in the cell membrane and (iii) the presented ligand. 57 For example, for the small ligand cRGD that is recognized by the integrin alpha5beta1 receptor of HSPCs the critical distance is ∼40 nm, whereas for a fibronectin protein domain (that also contains the RGD sequence and targets the same receptor in the membrane) the value lies between 85 nm and 110 nm. Explanations for the observed discrepancy between HSC adhesion to cRGD and the fibronectin domain are two-fold: (i) the fibronectin protein domain is larger and more flexible than the small cRGD peptide.…”

“…The increased binding stability should facilitate cell adhesion at lower ligand concentrations (in other words, binding at greater lateral distances between functionalized nanoparticles is possible). In addition to influencing HSC † adhesion, nanopatterning also affects other cell functions such as gene expression, 57 lipid raft clustering (which is assumed to be a prerequisite for successful signal transduction via transmembrane receptors), and receptor distribution in the cell. 55 Little is known about the impact of nanotopographymeaning all sorts of nanoscale topological surface featureson HSCs.…”

The role of novel and known extracellular matrix and adhesion molecules in the homeostatic and regenerative bone marrow microenvironment

“…125 Similarly, presentation of ECM molecules in nanostructure patterns with variable interligand spacing modulated HSPC adhesion, although colony forming capacities were not affected. 128 These studies illustrate that matrix density and the presentation of specific adhesive ligands contribute to the HSPC niche in the BM. The evaluation of semisolid hydrogels and other artificial BM niches with or without the addition of cellular and molecular factors will reveal insight in HSPC niche requirements.…”