Human umbilical cord perivascular cells: A novel source of the organophosphate antidote butyrylcholinesterase

Abstract Human butyrylcholinesterase (BChE) is a well-characterized bioscavenger with significant potential as a prophylactic or post-exposure treatment for organophosphate poisoning. Despite substantial efforts, BChE has proven technically challenging to produce in recombinant systems. Recombinant BChE tends to be insufficiently or incorrectly glycosylated, and consequently exhibits a truncated half-life, compromised activity, or is immunogenic. Thus, expired human plasma remains the only reliable source of the benchmark BChE tetramer, but production is costly and time intensive and presents possible blood-borne disease hazards. Here we report a human BChE production platform that produces functionally active, tetrameric BChE enzyme, without the addition of external factors such as polyproline peptides or chemical or gene modification required by other systems. Human umbilical cord perivascular cells (HUCPVCs) are a rich population of mesenchymal stromal cells (MSCs) derived from Wharton's jelly. We show that HUCPVCs naturally and stably secrete BChE during culture in xeno- and serum-free media, and can be gene-modified to increase BChE output. However, BChE secretion from HUCPVCs is limited by innate feedback mechanisms that can be interrupted by addition of miR 186 oligonucleotide mimics or by competitive inhibition of muscarinic cholinergic signalling receptors by addition of atropine. By contrast, adult bone marrow-derived mesenchymal stromal cells neither secrete measurable levels of BChE naturally, nor after gene modification. Further work is required to fully characterize and disable the intrinsic ceiling of HUCPVC-mediated BChE secretion to achieve commercially relevant enzyme output. However, HUCPVCs present a unique opportunity to produce both native and strategically engineered recombinant BChE enzyme in a human platform with the innate capacity to secrete the benchmark human plasma form.