טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLiat David
SubjectEstablishing a Model of Erythrophagocytosis with in vivo
Generated Senescent Erythrocytes
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Assistant Professor Meyron Holtz Esther
Full Thesis textFull thesis text - English Version


Abstract

Erythrophagocytosis (EPC) is a normal part of the systemic iron cycle that eliminates 2-3 million senescent red blood cells (sRBCs) every second. In some diseases, such as diabetes mellitus, the RBC life span is shortened and EPC rates are elevated. Also, lowered chemotaxis activity of macrophages (MPs) was observed in thalassemics while EPC rates were elevated. These findings indicate a close relationship between EPC and MP activation status. After EPC the MP is facing a great metabolic stress in the form of toxic materials such as heme and free iron that is released after breaking down of the RBC. Therefore, questions that are asked regarding EPC are whether there is an immunologic/inflammatory response of MPs after EPC, what the factors that mediate this response are and how does this response affect immune homeostasis and iron recycling. Since the mechanism by which MPs recognize sRBCs is still controversial and poorly understood, and articles published so far initiated EPC by manipulating the RBC in a way that will induce EPC, we developed a hypertransfusion model for generating in vivo aged RBCs that will be used for analysis of MPs that have recognized and phagocytosed RBCs in response to the whole range of physiologic senescence signals. Three different hypertransfusion protocols were evaluated. RBCs from hypertransfused mice showed aging signs similar to normally aged RBCs, such as lower esterase activity, elevated phosphatidylserine on the outer leaflet of the membrane and lower oxidative stress. A model of in vitro EPC was established successfully by exposing MPs to RBC-populations enriched for senescent cells. We also have indication that these RBCs are phagocytosed more in vivo in spleens of hypertransfused mice compared to control. This hypertransfusion model can be a successful tool for future studies on the MP immune response to EPC.