Optimizing Stem Cell Niche For Post-Irradiation Regeneration.

Abstract Radiotherapy involves unavoidable co-irradiation of the normal tissue, often resulting in side effects that limit the dose to the tumor and/or reduce quality of life of cancer survivors. The response of normal tissues to irradiation is mainly determined by the survival and regenerative potential of the tissue stem cells, and modulated by inflammatory processes, vasculature damage, altered neuronal innervation and fibrosis. Indeed, transplantation of tissue specific stem cells has been shown to restores tissue homeostasis and prevent late radiation effects. However, the radiation-induced senescence, fibrosis, and chronic inflammation may chance the stem cell niche engender an unfavorable environment for the regenerative potential of the tissue’s stem cells. Here changes in the salivary gland stem cell niche will be discussed using irradiated murine submandibular salivary gland tissue and derived organoids. Recently, we have developed methods to culture murine and patient specific tissue resembling salivary gland organoids (SGO). SGO contain all the glandular lineages, are able to extensively self-renew and up on transplantation rescue salivary gland function, allowing the study of radiation responses. The role of stemness factors, senescence and inflammatory processes in stem cell self-renewal and differentiation and post-irradiation regeneration will be discussed. Using SGO formation efficiency (OFE) as a measure of regenerative potential it is shown that stem cell potency after in vivo irradiation, is time dependent reduced. Interestingly, the conditioned medium of irradiated SGO reduced the OFE of unirradiated SGO. The potential role of radiation-induced senescence-associated secretory phenotype, hippo-signaling and inflammation through activation of cytosolic DNA sensing pathways on stem cells function will be addressed. Radiation-induced environmental changes in the stem cells niche have a severe impact on stem cell function. Modulation of these effect may enhance regenerative potential of surviving stem cells and improve engraftment and regeneration after stem cell transplantation. Supported by the Dutch Cancer Society (KWF, grant No. 10650 and 12092) and The Netherlands Organisation for Health Research and Development (ZonMw, Grant nrs. 11.600.1023 and 40-43600-98-14003). Citation Format: Rob P. Coppes. Optimizing stem cell niche for post-irradiation regeneration [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr IA-020.