Assessment of the role and antioxidative and antiapoptotic effects of delta-opioid peptide d-ala2-leu5-enkephalin on the viability of hematopoietic stem cells

Mammadova A., Assessment of the Role and Antioxidative and Antiapoptotic Effects of Delta-opioid Peptide D-Ala2-Leu5-Enkephalin on the viability of Hematopoietic Stem Cells, Hacettepe University Graduate School of Health Sciences Stem Cell Program Master Thesis, Ankara, 2019. Hematopoietic Stem Cells (HSCs) are adult stem cells with the capacity for self-renewal and differentiation into all blood cell lineages. When HSCs are used for transplantation or gene therapy purposes, they can be exposed to short term cell culture and/or freezing procedures. However, the viability and function of HSCs may be negatively affected by oxidative and endoplasmic reticulum stress induced by these processes. There is a need for the development of novel short term HSC expansion protocols that are highly effective, non-toxic and protect cell viability. Therefore, in the framework of this thesis, the role of Delta Opioid Receptor (DOR) activating synthetic peptid D-Ala2-Leu5-Enkephalı̇n (DADLE) on in vitro expansion, oxidative stress, ER stress and hypothermic storage of HSCs was assessed. Umbilical Cord Blood CD34+ HSCs were exposed to oxidative stress induced by H2O2 and ER stress induced by Tunicamycin (TM) and Thapsigargin (TG). Cell proliferation was assessed using WST-1; cell cycle analysis were done using BrdU; apoptosis was measured with Annexin-V/Propidium Iodide and the formation of Reactive Oxygen Species were assessed using H2DCFDA. RT-qPCR was used to investigate the effect of these stress conditions on gene expression of HSCs. Although DADLE was able to protect HSCs in vitro from oxidative stress and ER stress inducing molecules, DADLE was not able to protect HSCs from hypothermia-induced apoptosis. In this study, the effects of DADLE on HSCs were determined for the first time. Alone or in combination with other anti-oxidants or ER stress protective agents, DADLE might be helpful in the development of novel protocols for the ex vivo expansion of HSCs for clinical use, by promoting their survival through enhanced viability and by supporting their long-term maintenance and/or stemness. Key Words: DADLE, Hematopoietic Stem Cells (HSCs), Oxidative Stress, ER Stress, Hypothermia.