Abstract

Secreted MSC therapeutic is an exosome

Sai Kiang Lim, Research Director, A*STAR Institute of Medical Biology

Mesenchymal stem cell (MSC) is presently the most prominent stem cell candidate in regenerative medicine, and is being tested against an increasingly wide spectrum of disease indications. It use was initially rationalized on its multi-lineage differentiation potential. However, this rationale is being challenged by recent observations in animal and clinical studies where functional improvements did not correlate with the degree of engraftment and differentiation of MSCs at the sites of injury. Instead many recent clinical trials were rationalized on the secretion. My lab had through systemic fractionation of the secretion demonstrated that the active agent in the secretion was a secreted extracellular vesicle known as exosome. Exosome is a bi-lipid membrane vesicle that is generated through an endosomal pathway. It carries proteins and RNAs. The proteins are localized at the membrane and luminally. Therefore, exosome can act on target cells extracellularly through its membrane proteins or intracellularly when it is internalized by cells either through endocytosis or membrane fusion. In this presentation, I will discuss some of the biochemical activities of exosomes and their contribution to the therapeutic efficacy of MSC exosomes.