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.

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.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0432-z) contains supplementary material, which is available to authorized users.

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.

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.

Abstract B186: Knockdown of a chromatid segregation mediator gene impairs tumor growth in glioblastoma multiforme

Glioblastoma Multiforme (GBM) is the most common primary brain malignancy and despite multimodal therapy including surgery, irradiation and chemotherapy median survival remains 12–15 months. Increasing body of evidence from our and other groups is confirming the existence of a stem-like cell population within these tumors believed to confer tumor growth, invasiveness, and therapy resistance. Adult human neural stem cells (aHNSCs) are suggested to be the cells of origin for the glioblastoma stem-like cells (GSCs).

To identify new molecular targets we performed a micro-array analysis on the transcriptome of 33000 genes identifying differentially expressed genes in 5 aHNSC and 9 GSC cultures. Amongst the genes highly up-regulated in GBM, several were involved in cell division and the regulation of cell cycle. For further analysis, we chose the Chromatid Segreration Mediator (CSM), a centromere specific gene important for appropriate chromatid segregation during mitosis. This candidate gene was strongly expressed in GSCs but was almost undetectable in aHNSCs. Abundance of the CSM protein may lead to aneupleudy, which is a common feature of GBMs.

The high levels of CSM mRNA were confirmed by analyzing 16 GSC cultures with micro-array and qPCR. CSM was also over-expressed on protein level, and was found to be highly immunopositive in glioblastoma biopsies compared to the normal human brain. In silico analysis, using Rembrandt, identifies CSM-gene over-expression as a negative prognostic indicator in glioma patients.

In order to study the functional role of this gene in GBM, we used lentiviral-based knock-down (KD) technology to obtain specific down regulation of the gene. We transduced different shRNA constructs in 2 GBM cultures and achieved KD-efficieny of 55–65%.

Growth of tumors was measured by proliferation assay and the relative number of sphere-forming cells (widely known as GSCs) was quantified with a sphere-formation assay.

In our KD-cultures we observed a moderate reduction of proliferation (25%). Interestingly, the sphere forming capacity was dramatically reduced by 60–70%, indicating a significant decrease in number of GSCs. Cell-cycle analysis revealed that it was 30–40% less cells in G2/M-phase and 15–20% more cells in G0/G1-phase in the KD compared to non-silencing control.

We find our results very promising and suggest that Chromatid Segregation Mediator gene might have potential as a novel therapeutic target for GBM management.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B186.

Abstract B202: Identification of new molecular targets in glioblastoma

Glioblastoma multiformae (GBM) is the most common primary brain tumor and one of the most malignant human cancers (median survival 14 months from diagnosis despite combined surgery/irradiation/chemotherapy). Evidence from our and other groups indicates that glioblastoma stem-like cells (GSCs) contained within these tumors are critically important in GBM initiation, progression, and resistance to therapy. To identify new targets for glioblastoma treatment, we have systematically compared gene expression in nine primary GBM cell cultures to that in five primary neural stem cell cultures from the adult human brain (ahNSCs), using microarrays. Rigorous bioinformatic filtering identified 20 genes whose RNA expression levels were very high in primary GSC cultures but were undetectable in ahNSCs. The identified genes are involved in cell-cycle/division, epigenetic regulation, signaling and down-regulation of tumor-suppressors. Several of the candidate genes are implicated in cancer (breast, ovary and colon), while others have no known associations to cancer or have unknown functions.

A total of nine new GBM primary cultures were further analyzed by real-time polymerase chain reaction (qPCR), Western blot and Immunohistochemistry on tissue sections and cell cultures. qPCR confirmed the increased expression of 17 of the candidate genes. These results were in good accordance with the information provided by public data bases (Rembrant, TCGA). Western blot performed on 17 candidates showed increased protein levels in 9 cases thus demarcating these as best candidates for molecular targeting. The rest of the proteins featured aberrant isoforms, probably due to alternate splicing, modifications, cleavage or degradation. Further bioinformatics analysis identified a subset of 5 candidates that are particularly highly up-regulated in GBM when compared to low-grade gliomas.

To explore the functional importance of the potential target genes we established lentiviral-based shRNA delivery and started to test the potential of gene knock-downs (KDs) to inhibit growth of tumor cells. Our preliminary results look very promising. Three different lentiviral vectors, designed to silence a candidate gene encoding a tumor-suppressor binding protein kinase, were tested in three different primary GBM cultures and achieved a KD efficiency of 60–70%. We used proliferation essays to describe the growth speed of GBMs. To estimate relative numbers of sphere-forming cells (widely referred to as cancer stem cells) we performed sphere-forming assays (SFAs). The KD of the protein kinase gene resulted both in dramatic reduction of growth speed (50–70%) and in the number of sphere-forming cells (50–70%). In addition, the volume of the spheres was reduced to 50%. Cell cycle analysis revealed that there was doubling of the number of KD cells arrested in G2/M phase compared to non-silencing controls. There was also an increase (20–65%) in the proportion of apoptotic cells in 2 out of 3 GBM KD cultures.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B202.

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.

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.

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).

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.

Exploring atypical locations of mammalian neural stem cells: the human filum terminale

Neurogenesis is a multifactorial event determined by local environmental cues, inherent cellular program as well as cellular milieu and may not necessarily be restricted to the SVZ and SGZ. NSCs have been isolated from or neurogenesis has been demonstrated in traditionally non neurogenic regions. This more permissive view of neurogenesis, however, is not widely accepted due to concerns regarding the methodologies used. Furthermore, it is compounded by the fact that the basal levels of increased neurogenesis in such regions has not been completely confirmed and thus precludes a paradigm shift. Were this non limited view of neurogenesis to be generally accepted after thorough investigation, it would open new avenues for regenerative medicine and stem cell therapy.

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.

Isolation of human multipotent neural progenitors from adult filum terminale

Stem cells have been isolated from several CNS regions, including the spinal cord. However, the terminal end of the spinal cord, filum terminale, has been referred to as a fibrovascular tag without neurogenic potential and of no clinical significance. Recently, we were fortunate to acquire some samples of this tissue. We show for the first time that progenitor cells exhibiting the hallmarks of stem cells can be isolated from adult human filum terminale (FTNPs). More specifically, FTNPs self-renew and proliferate to form neurospheres, and exhibit tripotent differentiation into neurons, astrocytes, and oligodendrocytes. Equally important, FTNPs develop the electrophysiological profile of neurons and glia. Whole-cell patch-clamp recordings show beta-III-tubulin(+) neurons exhibiting overshooting action potentials, displaying both the fast inactivating TTX-sensitive sodium current as well as 4-AP and TEA sensitive potassium currents. To assess potency in vivo, FTNPs were transplanted into the posterior periventricular region of control or ischemic rat brains. Despite a vigorous immune response against the xenograft, FTNPs survived and were found not only in the graft area but had also migrated to the lesioned CA1 region. Notwithstanding the immune response, FTNPs differentiated into astrocytes, but no neuronal differentiation was observed in the transplant milieu tested. However, neuronal differentiation in vivo cannot be ruled out and assessment of the conditions necessary to promote neurogenesis in vivo requires more research. Significantly, no tumor formation or aberrant cell morphology was seen in or adjacent to the graft area. Thus, filum terminale provides a novel source of adult human neural progenitor cells that develop into functional neurons with possible clinical applications.

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.

Multipotent stem cells from adult olfactory mucosa

Multipotent stem cells are thought to be responsible for the generation of new neurons in the adult brain. Neurogenesis also occurs in an accessible part of the nervous system, the olfactory mucosa. We show here that cells from human olfactory mucosa generate neurospheres that are multipotent in vitro and when transplanted into the chicken embryo. Cloned neurosphere cells show this multipotency. Multipotency was evident without prior culture in vitro: cells dissociated from adult rat olfactory mucosa generate leukocytes when transplanted into bone marrow-irradiated hosts, and cells dissociated from adult mouse olfactory epithelium generated numerous cell types when transplanted into the chicken embryo. It is unlikely that these results can be attributed to hematopoietic precursor contamination or cell fusion. These results demonstrate the existence of a multipotent stem-like cell in the olfactory mucosa useful for autologous transplantation therapies and for cellular studies of disease.

Neurogenesis in adult human

This report describes neurogenesis in the adult human olfactory epithelium in vitro. Olfactory epithelium was collected at autopsy and by biopsy, and grown in serum-free medium. Basic fibroblast growth factor induced the differentiation of bipolar cells which were immunopositive for several neuronal proteins but not glial proteins. [3H]thymidine autoradiography confirmed that these neurones were born in vitro. The results demonstrate that the adult human olfactory epithelium retains the capacity for neurogenesis and neuronal differentiation, at least until the age of 72 years. It is now possible to examine neurones and neurogenesis in biopsies from patients with disorders that may involve a neurodevelopmental or neurodegenerative aetiology such as schizophrenia, bipolar disorder and Alzheimer's disease.

Developmental variations in the interactions of pyruvate kinase and glyceraldehyde-3-phosphate dehydrogenase with subcellular structure in cavian tissues

The activities and interactions with cellular structure of glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase have been studied in the major tissues of the guinea pig during development. The extent of activity variation in these tissues is described along with the putative physiological determinants of these alterations in activity. As to binding, overall the present data provide a firm indication that the extent of enzyme-structure interactions is appreciable at all ontogenic stages, and when viewed in conjunction with other parallel studies on other enzymes and other animals, serve to confirm the broad biological significance of enzyme-structure associations in the compartmentation of glycolysis. The existence and significance of genetic and epigenetic modifications of these enzymes during development is also discussed.

Ontogenic activities and interactions of the lactate dehydrogenase isozymes with cellular structure in the guinea pig

The LDH activities and isozyme distributions associated with soluble and particulate fractions of five major tissues have been followed during the development of the guinea pig. Evidence has been provided for an appreciable degree of interaction between LDH and cellular structure in all these tissues (liver, kidney, skeletal muscle, brain and heart) at all stages of development, but particularly in the early foetal stages. These data have been discussed in relation to the nature and extent of this binding and the correlations with the metabolic emphases in these tissue situations during development.

Ontogenic characteristics of cavian aldolase

In order to extend the available information on the ontogenic significance of the interactions between aldolase and cellular structure, the nature and extent of these associations have been studied in the tissues of the guinea pig during development, along with analyses of the isozyme status in the bound and soluble compartments. In all tissues investigated, a significant degree of binding was evident, along with a considerable variation in the degree of association of aldolase with structure during development. Binding was particularly extensive in the early foetal stages and, in general, binding preference was directed towards A-type activity over the B- and C-type of enzyme. The significance of these ontogenic phenomena have been discussed in relation to the variations in phenotype of individual tissues during maturation and the metabolic correlations of this biphasic micro-organization.