Treatment of Radiation-Induced Xerostomia with INF-g Pre-Licensed Mesenchymal Stromal Cells (MSCs)

Abstract

<h3>Purpose/Objective(s)</h3> There is a <b>critical need</b> for a treatment that will safely and effectively alleviate radiation-induced xerostomia (RIX). Head and neck radiation results in hyposalivation and altered sialochemistry which patients experience as xerostomia. We preformed preclinical and a pilot clinical study to determine if IFN-ɣ stimulated marrow-derived mesenchymal stromal cells (MSC(M)) from HNC patients could function as a source of autologous cells for the treatment of RIX. <h3>Materials/Methods</h3> Bone marrow aspirates from HNC patients previously treated with chemoradiation were obtained (IRB #2019-0497, NCT 04007081). MSC(M)s were isolated from bone marrow, expanded in culture, surface marker expression confirmed via flow cytometry, stimulated with IFN-ɣ, and cryopreserved. Thawed MSC(M)s were profiled to evaluate their functionality after cryorecovery. Cells were tested for their ability to stimulate salivary production in a murine model of RIX by injecting 1 × 10⁶ cells into the submandibular gland (SMG) one week after delivery of a 15 Gy dose of radiation. Efficacy was evaluated by histology and saliva production. <h3>Results</h3> MSC(M)s from six patients were expanded to >20 × 10⁶ cells (median 15.5, range of 8-20 days). Post-thaw cultures demonstrated robust growth, with a median doubling time of 3.1 days. Cultured cells showed an MSC(M) phenotype, positive for CD73, CD90, and CD105 and negative for CD14, CD20, CD34, or CD45. IFN-ɣ stimulated MSC(M)s had immunomodulatory potential based on increased expression of IDO, ICAM-1, PD-L1, MHC I and MHC II expression compared with non-stimulated MSC(M)s (391%, 263%, 114%, 70% and 196% percent increase respectively). In a murine model of RIX, delivery of a single 15 Gy dose to the SMG resulted in decreased saliva production, structural changes evidenced by decreased acinar size, increased fibrosis, and immune cell infiltration. Injection of MSC(M)s to the SMG following radiation resulted in improved saliva production, a reduction in fibrosis, and an increase in the size and density of acini within the tissue compared to control. <h3>Conclusion</h3> These data strongly support the feasibility of a first-in-human clinical trial of autologous IFN-ɣ stimulated MSC(M)s to treat RIX and the potential of using human-derived MSC(M)s in future murine studies of RIX.