Cell-derived microparticles (MPs) are vesicles, 0.1 to 1 micron in size, budding from cellular plasma membrane under stress or activation. MPs are important in cell-cell communication by transferring cargo, such as RNAs, proteins, and lipids, from parent to target cells. We focus on megakaryocytic (Mk) MPs (MkMPs), which are the most abundant MPs in circulating blood. Megakaryocytes (Mks) derive from human hematopoietic stem and progenitor cells (HSPCs). MkMPs target HSPCs to program them into generating Mks leading to platelet generation without addition of thrombopoietin. The recognition is specific for HSPCs and the outcomes specific for Mk and platelet generation. Uptake of MkMPs by HSPCs is though both endocytosis and membrane fusion. Using various inhibitors, we found that macropinocytosis and lipid rafts play an important role in the uptake of MkMPs by HSPCs. MkMPs target and enter HSPCs in the uropod part of HSPCs, through specific receptor recognition. In order to pursue therapeutic applications of MkMPs, we transfused human MkMPs in a simple murine model with and without induced thrombocytopenia to show that they induce de novo platelet biogenesis in the mice. We argue then for using MkMPs in lieu of platelet transfusions, especially because MkMPs can be kept frozen without loss of function. To explore their use in gene therapy, we show that loading them with plasmid DNA or miRNAs leads to efficient, functional delivery to HSPCs. Furthermore, taking advantage of the ability of Mk membranes to recognize specifically HSPCs, we use these membranes to cloak synthetic nanoparticles for cargo delivery to HSPCs.
Eleftherios (Terry) Papoutsakis is the Unidel Eugene DuPont Professor in the Dept. of Chem. & Biomolecular Engineering & the Dept. of Biological Sciences at the University of Delaware. Papoutsakis’ group is active and has made important contributions in the areas of clostridia genetics and metabolic engineering with emphasis recently in syntrophic co-cultures and synthetic methylotrophy; animal-cell biotechnology; & stem-cell bioengineering with emphasis on hematopoietic engineering and the use of extracellular vesicles.
Dr. Papoutsakis has been recognized by numerous awards, including election to National Academy of Engineering (USA) in 2018, the 2017 American Chemical Society (ACS) E. V. Murphree Award in Industrial and Engineering Chemistry, the 2013 DIC Wang for Excellence in Biochemical Engineering, SBE/AIChE (Soc. Biological Eng.; Amer. Institute of Chem. Engineers), the 2012 James E. Bailey Award, SBE/AIChE; election as Fellow of ACS (2011), the 2010 Metabolic Engineering Award, the 2005 Amgen Biochemical Engineering Award, the 2004 Merck Cell Culture Engineering Award & the 2003 Alpha Chi Sigma AIChE Award. He received his BS/MS in Chemical Engineering from the National Technical University of Athens; MS/PhD in Chemical Engineering from Purdue University. He has supervised over 60 PhD, 30 MS, 31 postdoctoral and 65 undergraduate research students, funded by over $37 million in grants from NIH, NSF, DOE, ARPA-E, ONR, ARO & EPA.