Knockdown of NAT12/NAA30 reduces tumorigenic features of glioblastoma-initiating cells.

BACKGROUND: Glioblastoma (GBM) is the most common primary brain malignancy and confers a dismal prognosis. GBMs harbor glioblastoma-initiating cells (GICs) that drive tumorigenesis and contribute to therapeutic resistance and tumor recurrence. Consequently, there is a strong rationale to target this cell population in order to develop new molecular therapies against GBM. Accumulating evidence indicates that Nα-terminal acetyltransferases (NATs), that are dysregulated in numerous human cancers, can serve as therapeutic targets. METHODS: Microarrays were used to study the expression of several NATs including NAT12/NAA30 in clinical samples and stem cell cultures. The expression of NAT12/NAA30 was analyzed using qPCR, immunolabeling and western blot. We conducted shRNA-mediated knockdown of NAT12/NAA30 gene in GICs and studied the effects on cell viability, sphere-formation and hypoxia sensitivity. Intracranial transplantation to SCID mice enabled us to investigate the effects of NAT12/NAA30 depletion in vivo. Using microarrays we identified genes and biochemical pathways whose expression was altered upon NAT12/NAA30 down-regulation. RESULTS: While decreased expression of the distal 3'UTR of NAT12/NAA30 was generally observed in GICs and GBMs, this gene was strongly up-regulated at the protein level in GBM and GICs. The increased protein levels were not caused by increased levels of the steady state mRNA but rather by other mechanisms. Also, shorter 3'UTR of NAT12/NAA30 correlated with poor survival in glioma patients. As well, we observed previously not described nuclear localization of this typically cytoplasmic protein. When compared to non-silencing controls, cells featuring NAT12/NAA30 knockdown exhibited reduced cell viability, sphere-forming ability, and mitochondrial hypoxia tolerance. Intracranial transplantation showed that knockdown of NAT12/NAA30 resulted in prolonged animal survival. Microarray analysis of the knockdown cultures showed reduced levels of HIF1α and altered expression of several other genes involved in the hypoxia response. Furthermore, NAT12/NAA30 knockdown correlated with expressional dysregulation of genes involved in the p53 pathway, ribosomal assembly and cell proliferation. Western blot analysis revealed reduction of HIF1α, phospho-MTOR(Ser2448) and higher levels of p53 and GFAP in these cultures. CONCLUSION: NAT12/NAA30 plays an important role in growth and survival of GICs possibly by regulating hypoxia response (HIF1α), levels of p-MTOR (Ser2448) and the p53 pathway.

Targeting PBK/TOPK decreases growth and survival of glioma initiating cells in vitro and attenuates tumor growth in vivo.

BACKGROUND: Glioblastomas are invasive therapy resistant brain tumors with extremely poor prognosis. The Glioma initiating cell (GIC) population contributes to therapeutic resistance and tumor recurrence. Targeting GIC-associated gene candidates could significantly impact GBM tumorigenicity. Here, we investigate a protein kinase, PBK/TOPK as a candidate for regulating growth, survival and in vivo tumorigenicity of GICs. METHODS: PBK is highly upregulated in GICs and GBM tissues as shown by RNA and protein analyses. We knocked down PBK using shRNA vectors and inhibited the function of PBK protein with a pharmacological PBK inhibitor, HITOPK-032. We assessed viability, tumorsphere formation and apoptosis in three patient derived GIC cultures. RESULTS: Gene knockdown of PBK led to decreased viability and sphere formation and in one culture an increase in apoptosis. Treatment of cells with inhibitor HITOPK-032 (5 µM and 10 µM) almost completely abolished growth and elicited a large increase in apoptosis in all three cultures. HI-TOPK-032 treatment (5 mg/kg and 10 mg/kg bodyweight) in vivo resulted in diminished growth of experimentally induced subcutaneous GBM tumors in mice. We also carried out multi-culture assays of cell survival to investigate the relative effects on GICs compared with the normal neural stem cells (NSCs) and their differentiated counterparts. Normal NSCs seemed to withstand treatment slightly better than the GICs. CONCLUSION: Our study of identification and functional validation of PBK suggests that this candidate can be a promising molecular target for GBM treatment.

Comparison of glioma stem cells to neural stem cells from the adult human brain identifies dysregulated Wnt- signaling and a fingerprint associated with clinical outcome.

Glioblastoma is the most common brain tumor. Median survival in unselected patients is <10 months. The tumor harbors stem-like cells that self-renew and propagate upon serial transplantation in mice, although the clinical relevance of these cells has not been well documented. We have performed the first genome-wide analysis that directly relates the gene expression profile of nine enriched populations of glioblastoma stem cells (GSCs) to five identically isolated and cultivated populations of stem cells from the normal adult human brain. Although the two cell types share common stem- and lineage-related markers, GSCs show a more heterogeneous gene expression. We identified a number of pathways that are dysregulated in GSCs. A subset of these pathways has previously been identified in leukemic stem cells, suggesting that cancer stem cells of different origin may have common features. Genes upregulated in GSCs were also highly expressed in embryonic and induced pluripotent stem cells. We found that canonical Wnt-signaling plays an important role in GSCs, but not in adult human neural stem cells. As well we identified a 30-gene signature highly overexpressed in GSCs. The expression of these signature genes correlates with clinical outcome and demonstrates the clinical relevance of GSCs.

Timing of de novo mutagenesis--a twin study of sodium-channel mutations.

De novo mutations are a cause of sporadic disease, but little is known about the developmental timing of such mutations. We studied concordant and discordant monozygous twins with de novo mutations in the sodium channel α1 subunit gene (SCN1A) causing Dravet's syndrome, a severe epileptic encephalopathy. On the basis of our findings and the literature on mosaic cases, we conclude that de novo mutations in SCN1A may occur at any time, from the premorula stage of the embryo (causing disease in the subject) to adulthood (with mutations in the germ-line cells of parents causing disease in offspring).

RhoA regulation of cardiomyocyte differentiation.

Earlier findings from our laboratory implicated RhoA in heart developmental processes. To investigate factors that potentially regulate RhoA expression, RhoA gene organisation and promoter activity were analysed. Comparative analysis indicated strict conservation of both gene organisation and coding sequence of the chick, mouse, and human RhoA genes. Bioinformatics analysis of the derived promoter region of mouse RhoA identified putative consensus sequence binding sites for several transcription factors involved in heart formation and organogenesis generally. Using luciferase reporter assays, RhoA promoter activity was shown to increase in mouse-derived P19CL6 cells that were induced to differentiate into cardiomyocytes. Overexpression of a dominant negative mutant of mouse RhoA (mRhoAN19) blocked this cardiomyocyte differentiation of P19CL6 cells and led to the accumulation of the cardiac transcription factors SRF and GATA4 and the early cardiac marker cardiac α -actin. Taken together, these findings indicate a fundamental role for RhoA in the differentiation of cardiomyocytes.

A comparative study of the structural organization of spheres derived from the adult human subventricular zone and glioblastoma biopsies.

Sphere forming assays have been useful to enrich for stem like cells in a range of tumors. The robustness of this system contrasts the difficulties in defining a stem cell population based on cell surface markers. We have undertaken a study to describe the cellular and organizational composition of tumorspheres, directly comparing these to neurospheres derived from the adult human subventricular zone (SVZ). Primary cell cultures from brain tumors were found to contain variable fractions of cells positive for tumor stem cell markers (CD133 (2-93%)/SSEA1 (3-15%)/CXCR4 (1-72%)). All cultures produced tumors upon xenografting. Tumorspheres contained a heterogeneous population of cells, but were structurally organized with stem cell markers present at the core of spheres, with markers of more mature glial progenitors and astrocytes at more peripheral location. Ultrastructural studies showed that tumorspheres contained a higher fraction of electron dense cells in the core than the periphery (36% and 19%, respectively). Neurospheres also contained a heterogeneous cell population, but did not have an organization similar to tumorspheres. Although tumorspheres clearly display irregular and neoplastic cells, they establish an organized structure with an outward gradient of differentiation. We suggest that this organization is central in maintaining the tumor stem cell pool.

Aqp 9 and brain tumour stem cells.

Several studies have implicated the aquaporins (aqp) 1, 4, and 9 in the pathogenesis of malignant brain tumours, suggesting that they contribute to motility, invasiveness, and oedema formation and facilitate metabolism in tumour cells under hypoxic conditions. We have studied the expression of aqp1, 4, and 9 in biopsies from glioblastomas, isolated tumour stem cells grown in a tumoursphere assay and analyzed the progenitor and differentiated cells from these cultures. We have compared these to the situation in normal rat brain, its stem cells, and differentiated cells derived thereof. In short, qPCR in tumour tissue showed presence of aqp1, 4, and 9. In the tumour progenitor population, aqp9 was markedly more highly expressed, whilst in tumour-derived differentiated cells, aqp4 was downregulated. However, immunostaining did not reveal increased protein expression of aqp9 in the tumourspheres containing progenitor cells; in contrast, its expression (both mRNA and protein) was high in differentiated cultures. We, therefore, propose that aquaporin 9 may have a central role in the tumorigenesis of glioblastoma.

Could cells from your nose fix your heart? Transplantation of olfactory stem cells in a rat model of cardiac infarction.

This study examines the hypothesis that multipotent olfactory mucosal stem cells could provide a basis for the development of autologous cell transplant therapy for the treatment of heart attack. In humans, these cells are easily obtained by simple biopsy. Neural stem cells from the olfactory mucosa are multipotent, with the capacity to differentiate into developmental fates other than neurons and glia, with evidence of cardiomyocyte differentiation in vitro and after transplantation into the chick embryo. Olfactory stem cells were grown from rat olfactory mucosa. These cells are propagated as neurosphere cultures, similar to other neural stem cells. Olfactory neurospheres were grown in vitro, dissociated into single cell suspensions, and transplanted into the infarcted hearts of congeneic rats. Transplanted cells were genetically engineered to express green fluorescent protein (GFP) in order to allow them to be identified after transplantation. Functional assessment was attempted using echocardiography in three groups of rats: control, unoperated; infarct only; infarcted and transplanted. Transplantation of neurosphere-derived cells from adult rat olfactory mucosa appeared to restore heart rate with other trends towards improvement in other measures of ventricular function indicated. Importantly, donor-derived cells engrafted in the transplanted cardiac ventricle and expressed cardiac contractile proteins.

Olfactory mucosa is a potential source for autologous stem cell therapy for Parkinson's disease.

Parkinson's disease is a complex disorder characterized by degeneration of dopaminergic neurons in the substantia nigra in the brain. Stem cell transplantation is aimed at replacing dopaminergic neurons because the most successful drug therapies affect these neurons and their synaptic targets. We show here that neural progenitors can be grown from the olfactory organ of humans, including those with Parkinson's disease. These neural progenitors proliferated and generated dopaminergic cells in vitro. They also generated dopaminergic cells when transplanted into the brain and reduced the behavioral asymmetry induced by ablation of the dopaminergic neurons in the rat model of Parkinson's disease. Our results indicate that Parkinson's patients could provide their own source of neuronal progenitors for cell transplantation therapies and for direct investigation of the biology and treatments of Parkinson's disease. Disclosure of potential conflicts of interest is found at the end of this article.

Identification and characterization of a new source of adult human neural progenitors.

Adult neural progenitor cells (aNPCs) are a potential source for cell based therapy for neurodegenerative diseases and traumatic brain injuries. These cells have been traditionally isolated from hippocampus, subventricular zone and white matter. However, there is still a need for an easily accessible source with better yield to counter the limitations of small surgical samples of previously characterized aNPCs. Here we show that ultrasonic aspirate (UA) samples currently considered as 'biological waste after surgery,' offer a good source for aNPCs. Furthermore, we show that culture conditions dictated the phenotype of cells across patients. The neurosphere-enriched cells were more similar to freshly isolated brain cells, while cells expanded adherently in serum conditions were similar to mesenchymal stem cells. However, cells expanded in these adherent conditions expressed some NPC and glial markers in addition to active canonical Wnt signaling. This suggests a mesenchymal-neuroectodermal hybrid nature of these cells. Finally, we show that UA-NPCs are comparable to those from neurogenic regions. Our findings suggest that UA samples can be used as a source for fresh and in vitro propagated aNPCs that could have various clinical applications.

Brain tissue banking for stem cells for our future.

In our lab we study neurogenesis and the development of brain tumors. We work towards treatment strategies for glioblastoma and towards using autologous neural stem cells for tissue regeneration strategies for brain damage and neurodegenerative disorders. It has been our policy to try to establish living cell cultures from all human biopsy material that we obtain. We hypothesized that small pieces of brain tissue could be cryopreserved and that live neural stem cells could be recovered at a later time. DMSO has been shown to possess a remarkable ability to diffuse through cell membranes and pass into cell interiors. Its chemical properties prevent the formation of damaging ice crystals thus allowing cell storage at or below -180 C. We report here a protocol for successful freezing of small pieces of tissue derived from human brain and human brain tumours. Virtually all specimens could be successfully revived. Assays of phenotype and behaviour show that the cell cultures derived were equivalent to those cultures previously derived from fresh tissue.

Ultrasonic Surgical Aspirate is a Reliable Source For Culturing Glioblastoma Stem Cells.

Glioma stem cells (GSCs) are thought to be the source of tumor growth and therapy resistance. To understand the biology of GSCs, and target these tumors therapeutically, we need robust strategies for in vitro expansion of primary GSCs. To date, tumor core biopsies have been the main established source of GSCs. Since these samples are used for diagnostic purposes, the available tissue for cell culture and therapeutic targeting can be limited. In addition, a core biopsy is usually taken from one part of the tumor, thus would be unlikely to represent intra-tumor heterogeneity. To overcome these problems, tissue fragments from all over the tumor can be collected using an ultrasonic aspirator during surgery, thus assembling a "global tumor biopsy". Usually, this ultrasonic aspirate (UA) sample is considered as biological waste after operations. Here, we show that UA samples offer a large and reliable source of live cells. Similar to core biopsies, UA samples enriched for GSCs that differentiated into neural lineages, showed inter-individual variation of GSC markers, and induced tumors. Molecular profiling showed that UA samples cover tumor heterogeneity better than core biopsies. These results suggest that UA samples can be used to establish large scale cultures for therapeutic applications.

Combined expressional analysis, bioinformatics and targeted proteomics identify new potential therapeutic targets in glioblastoma stem cells.

Glioblastoma (GBM) is both the most common and the most lethal primary brain tumor. It is thought that GBM stem cells (GSCs) are critically important in resistance to therapy. Therefore, there is a strong rationale to target these cells in order to develop new molecular therapies.To identify molecular targets in GSCs, we compared gene expression in GSCs to that in neural stem cells (NSCs) from the adult human brain, using microarrays. Bioinformatic filtering identified 20 genes (PBK/TOPK, CENPA, KIF15, DEPDC1, CDC6, DLG7/DLGAP5/HURP, KIF18A, EZH2, HMMR/RHAMM/CD168, NOL4, MPP6, MDM1, RAPGEF4, RHBDD1, FNDC3B, FILIP1L, MCC, ATXN7L4/ATXN7L1, P2RY5/LPAR6 and FAM118A) that were consistently expressed in GSC cultures and consistently not expressed in NSC cultures. The expression of these genes was confirmed in clinical samples (TCGA and REMBRANDT). The first nine genes were highly co-expressed in all GBM subtypes and were part of the same protein-protein interaction network. Furthermore, their combined up-regulation correlated negatively with patient survival in the mesenchymal GBM subtype. Using targeted proteomics and the COGNOSCENTE database we linked these genes to GBM signalling pathways.Nine genes: PBK, CENPA, KIF15, DEPDC1, CDC6, DLG7, KIF18A, EZH2 and HMMR should be further explored as targets for treatment of GBM.

Focal adhesion dynamics are altered in schizophrenia.

BACKGROUND: Evidence from genetic association studies implicate genes involved in neural migration associated with schizophrenia risk. Neural stem/progenitor cell cultures (neurosphere-derived cells) from olfactory mucosa of schizophrenia patients have significantly dysregulated expression of genes in focal adhesion kinase (FAK) signaling, a key pathway regulating cell adhesion and migration. The aim of this study was to investigate whether olfactory neurosphere-derived cells from schizophrenia patients have altered cell adhesion, cell motility, and focal adhesion dynamics. METHODS: Olfactory neurosphere-derived cells from nine male schizophrenia patients and nine male healthy control subjects were used. Cells were assayed for cell adhesion and cell motility and analyzed for integrins and FAK proteins. Focal adhesions were counted and measured in fixed cells, and time-lapse imaging was used to assess cell motility and focal adhesion dynamics. RESULTS: Patient-derived cells were less adhesive and more motile than cells derived from healthy control subjects, and their motility was reduced to control cell levels by integrin-blocking antibodies and by inhibition of FAK. Vinculin-stained focal adhesion complexes were significantly smaller and fewer in patient cells. Time-lapse imaging of cells expressing FAK tagged with green fluorescent protein revealed that the disassembly of focal adhesions was significantly faster in patient cells. CONCLUSIONS: The evidence for altered motility and focal adhesion dynamics in patient-derived cells is consistent with dysregulated gene expression in the FAK signaling pathway in these cells. Alterations in cell adhesion dynamics and cell motility could bias the trajectory of brain development in schizophrenia.

Expansion of multipotent stem cells from the adult human brain.

The discovery of stem cells in the adult human brain has revealed new possible scenarios for treatment of the sick or injured brain. Both clinical use of and preclinical research on human adult neural stem cells have, however, been seriously hampered by the fact that it has been impossible to passage these cells more than a very few times and with little expansion of cell numbers. Having explored a number of alternative culturing conditions we here present an efficient method for the establishment and propagation of human brain stem cells from whatever brain tissue samples we have tried. We describe virtually unlimited expansion of an authentic stem cell phenotype. Pluripotency proteins Sox2 and Oct4 are expressed without artificial induction. For the first time multipotency of adult human brain-derived stem cells is demonstrated beyond tissue boundaries. We characterize these cells in detail in vitro including microarray and proteomic approaches. Whilst clarification of these cells' behavior is ongoing, results so far portend well for the future repair of tissues by transplantation of an adult patient's own-derived stem cells.

Characterization of olfactory stem cells.

There is worldwide enthusiasm for the prospect of some kind of cellular transplant therapy for repair of failing organs. The olfactory mucosa of a patient's nose is easily biopsied to provide a ready source of multipotent cells. In this article we address practical issues pertinent to using olfactory neural stem cells for tissue repair. These cells are emerging as potentially most significant candidates for human tissue repair strategies. Previously we have shown that stem cells from olfactory mucosa are multipotent. As well, we have recently published three potential clinical applications. Their expression of dopaminergic markers in vitro and in a Parkinson's rat transplant model has been demonstrated. Their conversion to chondrogenic phenotype in vitro and in vivo has also been described, as has their transplant into a rat model of cardiac infarction. Here we examine in detail the biology of the olfactory neural stem cell using the rat as our animal model cell source. We establish its presence by examining self-renewal capacity and for phenotypic acquisition in inductive circumstances. We determine its frequency within the cell population and show that our culture system selects for this putative stem cell. Our studies demonstrate that adult olfactory stem cells, when transplanted into an environmental niche different from that of their origin, are able to demonstrate multipotency by acquiring the phenotype of the resident cells. We investigate how immediate the instruction need be. We test the hypothesis that olfactory neurospheres contain stem cells whose capacity for differentiation is triggered by signals of the immediate environmental niche. Significantly, of importance to any tissue regeneration endeavor, stem cell numbers were shown to be enriched by our culture methods. This was confirmed whether measured by sphere-forming capacity or differentiation response rate.

Predifferentiated brain-derived adult human progenitor cells migrate toward ischemia after transplantation to the adult rat brain.

BACKGROUND: The adult human brain contains neural stem/progenitor cells (AHNPCs) that can survive transplantation into the adult rat brain, migrate toward a lesion, and display limited neuronal differentiation in vivo. OBJECTIVE: To investigate the effect of manipulating AHNPCs before grafting by predifferentiation, ie, initiating neuronal differentiation before transplantation, and to determine whether this cell priming would affect their ability to migrate in vivo. METHODS: AHNPCs were prepared from temporal lobe resections for epilepsy. Seven days after global brain ischemia, predifferentiated AHNPCs (exposed to basic fibroblast growth factor, heparin, and laminin) were transplanted to the left hippocampus. Four and 10 weeks after transplantation, brain sections were analyzed by immunohistochemistry. RESULTS: Transplanted primed cells expressed committed neuronal markers at a much earlier stage compared with nonprimed AHNPCs and were found colabeled with human markers within the damaged CA1 region 4 weeks after grafting. Furthermore, predifferentiated AHNPCs migrated preferentially into an ischemic lesion, similar to their undifferentiated counterparts. The chemoattractant effect from the expression of stromal cell-derived factor-1α (SDF-1α) in ischemic CA1 on AHNPCs expressing CXC chemokine receptor 4 (CXCR4) may explain this preference in migration in vivo. CONCLUSION: The plasticity of neural progenitors derived from the adult human brain may be greater than previously assumed in that manipulation before grafting may influence the phenotypes seen in vivo. The SDF-1α-CXCR4 axis is involved in the targeted migration toward an ischemic lesion in the adult rat brain, similar to previous reports on endogenous progenitors in rats and grafted fetal human neural progenitors.

Brain tumor stem cells maintain overall phenotype and tumorigenicity after in vitro culturing in serum-free conditions.

Traditional in vitro culturing of tumor cells has been shown to induce changes so that cultures no longer represent the tumor of origin. Serum-free culturing conditions are used in a variety of cancers to propagate stem-like cells in vitro. Limited reports, however, exist on the effects of such propagation. We have compared cells from brain tumor biopsies cultivated under serum-free conditions at passages 2 and 10 to describe the effects of in vitro culturing. We were able to establish cell lines from 7 of 10 biopsies from patients with glioblastoma. The cell lines adapted to conditions and had 2.2 times increased population doubling rate at later passages. Karyotyping and comparative genomic hybridization analysis revealed that all examined cell lines had cytogenetic aberrations commonly found in glioblastomas, and there were only minor differences between tumor and early and late passages in the same culture. Whole-transcriptome analysis shows that tumors had interindividual differences. Changes in the overall expression patterns through passaging were modest, with a significant change in only 14 genes; the variation among cultures was, however, reduced through passages. The ability to differentiate differed among tumors but was maintained throughout passaging. The cells initiated tumors upon transplantation to immunodeficient mice with differing phenotypes, but a given cell culture maintained tumor phenotype after serial cultivation. The cultures established maintained individual characteristics specific to culture identity. Thus, each cell culture reflects an image of the tumor--or a personalized model--from which it was derived and remains representative after moderate expansion.

Disease-specific, neurosphere-derived cells as models for brain disorders.

There is a pressing need for patient-derived cell models of brain diseases that are relevant and robust enough to produce the large quantities of cells required for molecular and functional analyses. We describe here a new cell model based on patient-derived cells from the human olfactory mucosa, the organ of smell, which regenerates throughout life from neural stem cells. Olfactory mucosa biopsies were obtained from healthy controls and patients with either schizophrenia, a neurodevelopmental psychiatric disorder, or Parkinson's disease, a neurodegenerative disease. Biopsies were dissociated and grown as neurospheres in defined medium. Neurosphere-derived cell lines were grown in serum-containing medium as adherent monolayers and stored frozen. By comparing 42 patient and control cell lines we demonstrated significant disease-specific alterations in gene expression, protein expression and cell function, including dysregulated neurodevelopmental pathways in schizophrenia and dysregulated mitochondrial function, oxidative stress and xenobiotic metabolism in Parkinson's disease. The study has identified new candidate genes and cell pathways for future investigation. Fibroblasts from schizophrenia patients did not show these differences. Olfactory neurosphere-derived cells have many advantages over embryonic stem cells and induced pluripotent stem cells as models for brain diseases. They do not require genetic reprogramming and they can be obtained from adults with complex genetic diseases. They will be useful for understanding disease aetiology, for diagnostics and for drug discovery.

Olfactory stem cells can be induced to express chondrogenic phenotype in a rat intervertebral disc injury model.

BACKGROUND: In humans, lower back pain is one of the most common causes of morbidity. Many studies implicate degeneration of intervertebral discs as the cause. In the normal intervertebral disc, the nucleus pulposus exerts a hydrostatic pressure against the constraining annulus fibrosus, which allows the disc to maintain flexibility between adjacent vertebrae, while absorbing necessary compressive forces. The nucleus pulposus performs this role because of its hydrophilic gel-like structure. The extracellular matrix of the nucleus pulposus is up to 80% hydrated, as a result of large amounts of the aggregating proteoglycan, chondroitin sulfate proteoglycan (CSPG). This proteoglycan is enmeshed in a randomly orientated network of fine collagen Type II (CT2) fibers. STUDY DESIGN AND PURPOSE: A useful adult tissue-derived stem cell is that from the olfactory mucosa, the organ of smell. These cells, accessible in humans from nasal biopsies, are multipotent and are able to make many cell types from all germ layers. They are easily grown in vitro and can be expanded to large numbers and stored frozen. These qualities indicate the potential for autologous transplantation for disc repair. In this article, using a rat model, we explore the hypothesis that olfactory stem cells can differentiate into a nucleus pulposus chondrocyte phenotype in vitro, as well as in vivo after transplantation into the injured intervertebral disc. PATIENT SAMPLE: Female rats (14 weeks) were anesthetized with xylazine/ketamine. The abdominal wall was shaved and injected with local anesthetic (lidocaine) before incision. The ventral part of the lumbar spine, including two intervertebral discs, was exposed. Disc degeneration was then induced in the two exposed discs by needle aspiration of the nucleus pulposus. The prominent spina iliaca posterior superior was used as an anatomical landmark for identification of the first disc. Two weeks later, one injured intervertebral disc was exposed in a second, similar, surgery and 20,000 olfactory neurosphere-derived cells were transplanted with a 25-G needle. OUTCOME MEASURES: In vitro induction of nucleus pulposus chondrocyte phenotype is measured by the percentage of cells expressing CT2 and CSPG. In vivo, a successful outcome is evidence of engraftment of donor-derived cells and their expression of CT2 and CSPG. METHODS: In this article, we tested two hypotheses: the first that progenitor cells within olfactory neurospheres could be induced to express markers distinctive of the nucleus pulposus when placed in vitro in a coculture experiment. The second hypothesis tested the same induction in genetically labeled transplanted cells within damaged vertebral discs in vivo. The two markers measured are those held by current literature to engender the necessary cushioning characteristics of nucleus pulposus, CT2 and CSPG. RESULTS: Our experiments demonstrated virtually 100% induction of these two markers in vitro. Also, this induction was achieved in donor-derived cells after delivery to the nucleus pulposus region of animals whose discs had previously been lesioned 2 weeks before transplant. CONCLUSIONS: These results provide a rationale for moving toward more extensive larger animal studies for assessment of regeneration before human trials where relief of symptoms can be more easily assessed.