Bone transplantation is one of the most widely performed clinical procedures. Consequently, bone regeneration using mesenchymal stem cells and tissue engineering strategies is one of the most widely researched fields in regenerative medicine. Recent scientific consensus indicates that a biomimetic approach is required to achieve proper regeneration of any tissue. Exosomes are nanovesicles secreted by cells that act as messengers that influence cell fate. Although exosomal function has been studied with respect to cancer and immunology, the role of exosomes as inducers of stem cell differentiation has not been explored.
Researchers from the University of Illinois at Chicago hypothesized that exosomes can be used as biomimetic tools for regenerative medicine. In this study they have explored the use of cell-generated exosomes as tools to induce lineage specific differentiation of stem cells. Their results indicate that proosteogenic exosomes isolated from cell cultures can induce lineage specific differentiation of naïve MSCs in vitro and in vivo. Additionally, exosomes can also bind to matrix proteins such as type I collagen and fibronectin enabling them to be tethered to biomaterials. Overall, the results from this study show the potential of cell derived exosomes in bone regenerative medicine and opens up new avenues for future research.
Generation and endocytosis of exosomes
(a) a representative TEM image showing the presence of exosomes in our purified samples. Scale bar represents 100 nm. The white arrows in the image point to exosomes. The grids were stained with phosphotungstic acid and hence the background is black. (b) Representative confocal micrograph showing the presence of endocytosed exosomes. White arrows point to the endocytosed exosomes. (c) Confocal micrograph showing the absence of exosomes or nonspecific presence of labeling dye. The scale bar in the confocal micrographs represents 20 μm.