The therapeutic effect of glial progenitor transplantation in diseases of dysmyelination is currently attributed to the formation of new myelin. Using magnetic resonance imaging (MRI), we show that the therapeutic outcome in dysmyelinated shiverer mice is dependent on the extent of cell migration but not presence of mature and compact myelin. Human or mouse glial restricted progenitors (GRPs) were transplanted into rag2−/− shiverer mouse neonates and followed for over one year. Mouse GRPs produced mature myelin as detected with multi-parametric MRI, but showed limited migration without extended animal lifespan. In sharp contrast, human GRPs migrated extensively and significantly increased animal survival, but production of mature myelin did not occur until 46 weeks post-grafting. We conclude that human GRPs can extend the survival of transplanted shiverer mice prior to production of mature myelin, while mouse GRPs fail to extend animal survival despite early presence of mature myelin. This paradox suggests that transplanted GRPs provide therapeutic benefits through biological processes other than mature myelin capable to facilitate rapid conduction, challenging the current dogma of the role of myelin in the function of the central nervous system.

The discovery that somatic cells can be induced into a pluripotent state by the expression of reprogramming factors has enormous potential for therapeutics and human disease modeling. With regard to aging and rejuvenation, the reprogramming process resets an aged, somatic cell to a more youthful state, elongating telomeres, rearranging the mitochondrial network, reducing oxidative stress, restoring pluripotency, and making numerous other alterations. The extent to which induced pluripotent stem cell (iPSC)s mime embryonic stem cells is controversial, however, as iPSCs have been shown to harbor an epigenetic memory characteristic of their tissue of origin which may impact their differentiation potential. Furthermore, there are contentious data regarding the extent to which telomeres are elongated, telomerase activity is reconstituted, and mitochondria are reorganized in iPSCs. Although several groups have reported that reprogramming efficiency declines with age and is inhibited by genes upregulated with age, others have successfully generated iPSCs from senescent and centenarian cells. Mixed findings have also been published regarding whether somatic cells generated from iPSCs are subject to premature senescence. Defects such as these would hinder the clinical application of iPSCs, and as such, more comprehensive testing of iPSCs and their potential aging signature should be conducted.

Isolation and propagation of neural stem cells derived from human brain tissue uniquely enables the study of human neurogenesis in vitro. In addition, ex vivo-expanded human neural stem/precursor cells (NPCs) may offer novel therapeutic strategies. We investigated the effects of extracellular nucleotides on the proliferation and differentiation of human mesencephalic neural stem/precursor cells (hmNPCs). When combined with the mitogens epidermal growth factor and fibroblast growth factor 2, UTP (1 lM) boosted proliferation of hmNPCs as shown by increased expression of the proliferation marker proliferating cell nuclear antigen (330%). UTPinduced proliferation was abrogated by the preferential P2Y receptor blocker pyridoxal phosphate-6-azophenyl-2¢,4¢-disulphonic acid (PPADS). UTP also stimulated dopaminergic differentiation. Treatment with UTP (100 lM) increased the number of tyrosine hydroxylase (TH)-positive cells and TH protein by 267 and 319% respectively. UTP-stimulated dopaminergic differentiation of hmNPCs was blocked by the P2 receptor antagonists suramin (10 lM) and PPADS (100 lM). In addition, UDP (1 lM) enhanced TH protein expression by 194%. During differentiation, treatment with UTP stimulated the extracellular signal-regulated kinase (ERK) pathway. Both ERK1/2 phosphorylation and dopaminergic differentiation were inhibited by U0126, a selective ERK kinase inhibitor, as well as by suramin. When other P2 receptor agonists (ATP, ADP and adenosine 5¢-O-(2-thiophosphate) (ADPbS); all 100 lM) were applied, both proliferation and dopaminergic differentiation of NPCs were compromised. We conclude that uracil nucleotides exert specific P2 receptor-mediated effects on midbrain-derived human NPCs, and may be used to enhance both proliferation and dopaminergic differentiation. Keywords: extracellular signal-regulated kinase 1/2 pathway, neural stem/precursor cells, P2 receptors, tyrosine hydroxylase, UTP. Neural stem/precursor cells (NPCs) serve as a model of brain development, providing promise for currently incurable brain diseases and injuries. Based on their unique capacity to migrate throughout the brain and to target invading tumour cells, transplantation of NPCs offers a new

Background Pediatric low-grade glioma (pLGG) is the most common childhood brain tumor. Many patients with unresectable or recurrent/refractory tumors have significant lifelong disability. The majority of pLGG have mutations increasing the activity of the Ras/mitogen-activated protein kinase (MAPK) pathway. Activation of mammalian target of rapamycin (mTOR) is also a hallmark of pLGG. We therefore hypothesized that the dual target of rapamycin complexes 1 and 2 (TORC1/2) kinase inhibitor TAK228 would synergize with the mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor trametinib in pLGG. Methods We tested TAK228 and trametinib in patient-derived pLGG cell lines harboring drivers of pLGG including BRAFV600E and neurofibromatosis type 1 loss. We measured cell proliferation, pathway inhibition, cell death, and senescence. Synergy was analyzed via MTS assay using the Chou–Talalay method. In vivo, we tested for overall survival and pathway inhibition and performed immunohistochemistry for proliferation and vascularization. We performed a scratch assay and measured angiogenesis protein activation in human umbilical vein endothelial cells (HUVECs). Results TAK228 synergized with trametinib in pLGG at clinically relevant doses in all tested cell lines, suppressing proliferation, inducing apoptosis, and causing senescence in a cell line–dependent manner. Combination treatment increased median survival by 70% and reduced tumor volume compared with monotreatment and control cohorts. Vascularization of tumors decreased as measured by CD31 and CD34. Combination treatment blocked activation of focal adhesion kinase (FAK) and sarcoma proto-oncogene non-receptor tyrosine kinase (SRC) in HUVEC cells and reduced HUVEC migration compared with each drug alone. Conclusions The combination of TAK228 and trametinib synergized to suppress the growth of pLGG. These agents synergized to reduce tumor vascularity and endothelial cell growth and migration by blocking activation of FAK and SRC.

Orthotopic xenotransplantation studies represent the final stage in preclinical cancer research and could facilitate the implementation of precision medicine. To date, these xenografts have been tested in immunodeficient animals, but complete elimination of the adaptive immunity is a significant drawback. We present a method of efficient human glioblastoma (GBM) cell engraftment in adult mice with intact immune systems, mediated by a transient blockade of T-cell co-stimulation. Compared to transplants grown in immunodeficient hosts, the resulting tumors more accurately resemble the clinical pathophysiology of patient GBMs, which are characterized by blood-brain-barrier leakage and strong neo-vascularization. We expect our method to have great utility for studying human tumor cell biology, particularly in the field of cancer immunotherapy and in studies on microenvironmental interactions. Given the straightforward approach, the method may also be applicable to other tumor types and additional model organisms.