Directing hMSCs fate through geometrical cues and mimetics peptides.

The native microenvironment of mesenchymal stem cells (hMSCs)-the extracellular matrix (ECM), is a complex and heterogenous environment structured at different scales. The present study aims at mimicking the hierarchical microorganization of proteins or growth factors within the ECM using the photolithography technique. Polyethylene terephthalate substrates were used as a model material to geometrically defined regions of RGD + BMP-2 or RDG + OGP mimetic peptides. These ECM-derived ligands are under research for regulation of mesenchymal stem cells osteogenic differentiation in a synergic manner. The hMSCs osteogenic differentiation was significantly affected by the spatial distribution of dually grafted peptides on surfaces, and hMSCs cells reacted differently according to the shape and size of peptide micropatterns. Our study demonstrates the presence of a strong interplay between peptide geometric cues and stem cell differentiation toward the osteoblastic lineage. These tethered surfaces provide valuable tools to investigate stem cell fate mechanisms regulated by multiple ECM cues, thereby contributing to the design of new biomaterials and improving hMSCs differentiation cues.

Fusion-mediated chromosomal instability promotes aneuploidy patterns that resemble human tumors.

Oncogenesis is considered to result from chromosomal instability, in addition to oncogene and tumor-suppressor alterations. Intermediate to aneuploidy and chromosomal instability, genome doubling is a frequent event in tumor development but the mechanisms driving tetraploidization and its impact remain unexplored. Cell fusion, one of the pathways to tetraploidy, is a physiological process involved in mesenchymal cell differentiation. Besides simple genome doubling, cell fusion results in the merging of two different genomes that can be destabilized upon proliferation. By testing whether cell fusion is involved in mesenchymal oncogenesis, we provide evidence that it induces genomic instability and mediates tumor initiation. After a latency period, the tumor emerges with the cells most suited for its development. Furthermore, hybrid tumor genomes were stabilized after this selection process and were very close to those of human pleomorphic mesenchymal tumors. Thus genome restructuring triggered by cell fusion may account for the chromosomal instability involved in oncogenesis.

Controlled Nanoscale Topographies for Osteogenic Differentiation of Mesenchymal Stem Cells.

Nanotopography with length scales of the order of extracellular matrix elements offers the possibility of regulating cell behavior. Investigation of the impact of nanotopography on cell response has been limited by the inability to precisely control geometries, especially at high spatial resolutions and across practically large areas. In this paper, we demonstrate well-controlled and periodic nanopillar arrays of silicon and investigate their impact on osteogenic differentiation of human mesenchymal stem cells (hMSCs). Silicon nanopillar arrays with critical dimensions in the range of 40-200 nm, exhibiting standard deviations below 15% across full wafers, were realized using the self-assembly of block copolymer colloids. Immunofluorescence and quantitative polymerase chain reaction measurements reveal clear dependence of osteogenic differentiation of hMSCs on the diameter and periodicity of the arrays. Further, the differentiation of hMSCs was found to be dependent on the age of the donor. While osteoblastic differentiation was found to be promoted by the pillars with larger diameters and heights independent of donor age, they were found to be different for different spacings. Pillar arrays with smaller pitch promoted differentiation from a young donor, while a larger spacing promoted those of an old donor. These findings can contribute for the development of personalized treatments of bone diseases, namely, novel implant nanostructuring depending on patient age.

Single or Mixed Tethered Peptides To Promote hMSC Differentiation toward Osteoblastic Lineage.

The commitment and differentiation of human mesenchymal stem cells (hMSCs) are guided by bioactive molecules within the extracellular matrix. Among the various approaches to design biomaterials, the functionalization of biomaterial surfaces with peptides from the sequence of proteins from the extracellular matrix is quite common. The purpose of this functionalization is to recruit hMSCs and promote their differentiation into the appropriate lineage. The aim of this work was to investigate the influence of RGD and FHRRIKA peptides and peptide sequences taken from bone morphogenic protein (BMP-2) and histone H4 (osteogenic growth peptide; OGP) either tethered alone or as a mixture on the surface of a model material and to also examine the level of hMSC osteogenic commitment without using a differentiation medium. Grafting of the different peptides was assessed by X-ray photoelectron spectroscopy (XPS), while their surface density was quantified by fluorescence microscopy, and their surface properties were assessed by atomic force microscopy (AFM) and contact angle (CA). The osteogenic commitment of hMSCs cultured on the different surfaces was characterized by immunohistochemistry using Runx-2 as an earlier osteogenic marker and OPN, a late osteogenic marker, and by RT-qPCR through the expression of ColI-a1, Runx-2, and ALP. Biological results show that the osteogenic commitment of the hMSCs was increased on surfaces tethered with a mixture of peptides. Results indicate that tethered peptides in the range of pmol mm-2 were indeed effective in inducing a cellular response after 2 weeks of cell culture without using an osteogenic media. These findings contribute to the research efforts to design biomimetic materials able to induce a response in human stem cells through tethered bioactive molecules for bone tissue engineering.