Influence of local environment on the differentiation of neural stem cells engrafted onto the injured spinal cord.
OBJECTIVE
In vitro, neural stem cells (NSCs) proliferate as undifferentiated spheroids and differentiate into neurons, astrocytes and oligodendrocytes. These features make NSCs suitable for spinal cord (SC) reconstruction. However, in vivo experiments have demonstrated that in the injured SC transplanted NSCs either remain undifferentiated or differentiate into the astrocytic phenotype. The microenvironment of the injured SC is believed to play a crucial role in driving the differentiation of the engrafted NSCs. Here, we tested the hypothesis that inflammatory cytokines (ICs) may be involved in the restricted differentiation of NSCs after grafting onto the injured SC.


METHODS
As the first step, we used immunohistochemistry to analyse the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and interferon (IFN)-gamma in the normal SC of mice and following traumatic injury. Then, we investigated whether a combination of TNF-alpha, IL-1beta and IFN-gamma may affect the phenotype of murine NSCs in vitro.


RESULTS
We found that TNF-alpha, IL-1beta and IFN-gamma, which are absent in the normal SC, are all expressed in the injured SC and the expression of these cytokines follows a timely tuned fashion with IFN-gamma being detectable as long as 4 weeks after injury. In culture, exposure of proliferating NSCs to a combination of TNF-alpha, IL-1beta and IFN-gamma was per se sufficient to induce the astrocytic differentiation of these cells even in the absence of serum.


CONCLUSIONS
In the traumatically injured SC, differentiation of engrafted NSCs is restricted towards the astrocytic lineage because of the inflammatory environment. ICs are likely to play a major role in differentiation of NSCs in the in vivo conditions.
Ricci-Vitiani
Lucia
L
Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.
Casalbore
Patrizia
P
Petrucci
Giovanna
G
Lauretti
Liverana
L
Montano
Nicola
N
Larocca
Luigi Maria
LM
Falchetti
Maria Laura
ML
Lombardi
Dario Giuseppe
DG
Gerevini
Valeria Di Giorgio
VD
Cenciarelli
Carlo
C
D'Alessandris
Quintino Giorgio
QG
Fernandez
Eduardo
E
De Maria
Ruggero
R
Maira
Giulio
G
Peschle
Cesare
C
Parati
Eugenio
E
Pallini
Roberto
R
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D016207:Cytokines / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000637:transplantation*; D013119:Spinal Cord Injuries / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D033581:Stem Cell Transplantation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D016207:Cytokines; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma