Cell adhesion and cell proliferation and cell differentiation on cultured cells
Answers
Answer:
The present report is an extension of our preceding publication in Biomaterials (2013) entitled “Effect of RGD nanospacing on differentiation of stem cells.” Cell-adhesive peptide arginine-glycine-aspartate (RGD) was nanopatterned on a non-fouling poly(ethylene glycol) (PEG) hydrogel, and mesenchymal stem cells (MSCs) derived from rat bone marrow were cultured on the patterned surfaces at nanospacings from 37 to 124 nm. Cell adhesion parameters such as spreading areas varied with RGD nanospacings significantly. The differences were well observed at both the first and eighth days, which confirmed the persistence of this nanospacing effect on our nanopatterns. The proliferation rate also varied with the nanospacings. Osteogenic and adipogenic inductions were undertaken, and a significant influence of RGD nanospacing on stem cell differentiation was found. The effect on differentiation cannot be simply interpreted by differences in cell adhesion and proliferation. We further calculated the fractions of single, coupled, and multiple cells on those nanopatterns, and ruled out the possibility that the extent of cell-cell contact determined the different differentiation fractions. Accordingly, we reinforced the idea that RGD nanospacing might directly influence stem cell differentiation.
Keywords: stem cell, nanopattern, cell differentiation, cell adhesion, cell proliferation, RGD, PEG hydrogel
Introduction
Stem cells play a vital role in organogenesis.1,2 In tissue engineering and regenerative medicine, stem cells are usually loaded into biomaterials instead of being used alone.3–8 Ideally, biomaterials should, to a certain extent, mimic the extracellular matrix (ECM) to promote cell adhesion, proliferation, and differentiation.9–13 Hence, interactions between cells and materials become a key fundamental topic.14–16 One of the core peptide sequences in ECM proteins is arginine-glycine-aspartate (RGD), which can be specifically bound to integrin, a receptor across the membrane.17 The RGD motif has been usefully employed in cell research and biomaterial modification.18–21
Considering that the size of integrin is about 8 to 12 nm,22 patterns with RGD peptides grafted onto nanodots of about 10 nm diameter are important when investigating the effect of spatial distribution of RGD ligands on cell behavior.23 An ideal RGD nanopattern should be based upon a perfect non-fouling background. A hydrogel of poly(ethylene glycol) (PEG) affords such a background, and a transfer lithography technique has been proposed to generate gold patterns on PEG hydrogels.24,25 After grafting RGD-thiol ligands onto gold domains embedded in the PEG hydrogel, RGD patterns on a non-fouling background were obtained.
Although cell adhesion and migration on RGD nanopatterns have been extensively investigated,23,25 the behaviors of stem cells on those patterns have not yet been reported until 2013. Our group examined osteogenic and adipogenic differentiations of mesenchymal stem cells (MSCs) derived from the bone marrow of rats and found an underlying nanospacing effect.26 The present report is an extension of our preceding publication.26 A schematic presentation of this study is given in Figure 1. Novelty is claimed as follows: (1) besides cell differentiation, adhesion of stem cells will be analyzed, and besides average values, the distributions of spreading area, circularity, and aspect ratio of cells on nanopatterns of varied nanospacings will be reported; (2) proliferation rates of stem cells on RGD nanopatterns will be examined; (3) we will compile statistics about single, coupled, and multiple cells on nanopatterns, to check whether or not cell-cell contact on nanopatterns of varied nanospacings can account for the origins of the nanospacing effect on stem cell differentiation.
Answer:
▪︎ Cell proliferation is the process that results in an increase of the number of cells, and is defined by the balance between cell divisions and cell loss through cell death or differentiation. Cell proliferation is increased in tumours.
▪︎Cell adhesion is the process by which cells form contacts with each other or with their substratum through specialized protein complexes. Intercellular adhesion can be mediated by adherens junctions, tight junctions and desmosomes, whereas cells can interact with extracellular matrix molecules through focal adhesions.
▪︎Cellular differentiation is the process in which a cell changes from one cell type to another. Usually, the cell changes to a more specialized type. Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.
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