Developmental potential of the murine embryonic stem cells transplanted into the healthy rat brain--novel insights into tumorigenesis.
Although engraftment of undifferentiated pluripotent embryonic stem cells (ESCs) into the injured central nervous system (CNS) may lead to targeted cell replacement of lost/damaged cells, sustained proliferative activity combined with uncontrolled differentiation of implanted cells presents a risk of tumor formation. As tumorigenic potential is thought to be associated with pluripotency of embryonic stem cells, pre-differentiation may circumvent this problem. Recently, it has been demonstrated that tumorigenesis occurs despite pre-differentiation if the neural precursor cells are implanted into the brain of a homologous animal (e.g., mouse to mouse). However, xenotransplantation (e.g., mouse to rat) without pre-differentiation, lead to the development of healthy neuronal cells, in absence of tumor formation, suggesting that tumor-suppressive effects of host tissue on engrafted ESCs may play a role in transplant tumorigenesis. We critically investigated tumorigenesis and possible mechanisms of anticipated tumor-suppressive effect under conditions analogous to previously published studies. Xenotransplantation of D-3 murine ESCs into uninjured adult rat brains lacking any preliminary inflammatory potential was found to lead to tumor formation in 5 out of 8 of animals within 2 weeks postimplantation. Tumor-suppressive effects, reflected by Erdo et. al could possibly be ascribed to immunomodulatory activity of macrophages scavenging the tumorigenic fraction of the implanted cells. The importance of number of engrafted cells, implantation site and immunosuppressive effects are discussed as possible variables determining tumorigenic outcome after ESC transplantation.
Molcanyi
Marek
M
Clinic of Neurosurgery, University of Cologne, Germany.
Riess
Peter
P
Haj-Yasein
Nadia Nabil
NN
Bentz
Kristine
K
Loehr
Mario
M
Kuchta
Johannes
J
Zivcak
Jozef
J
Stenzel
Werner
W
Miletic
Hrvoje
H
Hescheler
Jurgen
J
Neugebauer
Edmund
E
Hampl
Jurgen Anton
JA
Ernestus
Ralf-Ingo
RI
Schafer
Ute
U
D000818:Animals; D001921:Brain / Q000473:pathology*; D001932:Brain Neoplasms / Q000209:etiology / Q000473:pathology*; D002454:Cell Differentiation; D053595:Embryonic Stem Cells / Q000166:cytology / Q000637:transplantation*; D008297:Male; D051379:Mice; D010587:Phagocytosis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014183:Transplantation, Heterologous