susan barnett - Academia.edu (original) (raw)
Papers by susan barnett
Molecular and Cellular Biology, 1996
Introduction of simian virus 40 T antigen into rodent fibroblasts gives rise to cells that can pr... more Introduction of simian virus 40 T antigen into rodent fibroblasts gives rise to cells that can proliferate indefinitely but are dependent upon it for maintenance of their growth once the normal mitotic life span has elapsed. Inactivation of T antigen in these immortalized cells causes rapid and irreversible cessation of growth. To determine whether this growth arrest is associated with entry into senescence, we have undertaken a genetic and biological analysis of conditionally immortal (tsa) cell lines derived by immortalizing rat embryo fibroblasts with the thermolabile tsA58 T antigen. This analysis has identified the following parallels between the tsa cells after inactivation of T antigen and senescent rat embryo fibroblasts: (i) growth arrest is irreversible; (ii) it occurs in G1 as well as G2; (iii) the G1 block can be partially overcome by stimulation with 20% fetal calf serum, but the G2 block cannot be overcome; (iv) 20% fetal calf serum induces c-fos, but c-myc is unaltere...
The Neuroscientist, 2012
Astrocytes are the most abundant cell type in the adult central nervous system (CNS), and their f... more Astrocytes are the most abundant cell type in the adult central nervous system (CNS), and their functional diversity in response to injury is now being appreciated. Astrocytes have long been considered the main player in the inhibition of CNS repair via the formation of the gliotic scar, but now it is accepted that astrocyte can play an important role in CNS repair and remyelination. Interest in the relationship between astrocytes and myelination focused initially on attempts to understand how the development of plaques of astroglial scar tissue in multiple sclerosis was related to the failure of these lesions to remyelinate. It is now considered that this is an end stage pathological response to injury, and that normally astrocytes play important roles in supporting the development and maintenance of CNS myelin. This review will focus on how this new understanding may be exploited to develop new strategies to enhance remyelination in multiple sclerosis and other diseases.
In tissue engineering, the chemical and topographical cues within three-dimensional (3D) scaffold... more In tissue engineering, the chemical and topographical cues within three-dimensional (3D) scaffolds are normally tested using static cell cultures but applied directly to tissue cultures in perfusion bioreactors. As human cells are very sensitive to the changes of culture environment, it is essential to evaluate the performance of any chemical, and topographical cues in a perfused environment before they are applied to tissue engineering. Thus the aim of this research was to bridge the gap between static and perfusion cultures by addressing the effect of perfusion on cell cultures within 3D scaffolds. For this we developed a scale down bioreactor system, which allows to evaluate the effectiveness of various chemical and topographical cues incorporated into our previously developed tubular ε-polycaprolactone scaffold under perfused conditions. Investigation of two exemplary cell types (fibroblasts and cortical astrocytes) using the miniaturized bioreactor indicated that: (1) quick and firm cell adhesion in 3D scaffold was critical for cell survival in perfusion culture compared with static culture, thus cell seeding procedures for static cultures might not be applicable. Therefore it was necessary to re-evaluate cell attachment on different surfaces under perfused conditions before a 3D scaffold was applied for tissue cultures, (2) continuous medium perfusion adversely influenced cell spread and survival, which could be balanced by intermittent perfusion, (3) micro-grooves still maintained its influences on cell alignment under perfused conditions, while medium perfusion demonstrated additional influence on fibroblast alignment but not on astrocyte alignment on grooved substrates. This research demonstrated that the mini-bioreactor system is crucial for the development 3 of functional scaffolds with suitable chemical and topographical cues by bridging the gap between static culture and perfusion culture.
Molecular and cellular neurosciences, 2000
Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors ... more Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors and high in differentiated cells. In this study we have carried out a detailed temporal analysis of AP-1 activity in oligodendrocyte-type-2 astrocyte (O-2A) lineage cells. We show that low AP-1 activity in progenitor cells depended on the application of growth factors. Treatment of cells with B104-conditioned medium induced high AP-1 activity, increased process length, and improved growth. The role of AP-1 in proliferation and process extension was emphasized when progenitor cells overexpressing a c-Jun dominant-negative mutant had impaired growth and shortened processes. AP-1 DNA-binding activity during O-2A differentiation in vitro showed an initial down-regulation followed by up-regulation after 2 days. Increased AP-1 levels in oligodendrocytes were inhibited by overexpression of bcl-2, indicating that AP-1 in mature oligodendrocytes is involved in the regulation of apoptosis. Prevent...
Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1995
Oncogenes represent altered versions of cellular genes instrumental for control of cell prolifera... more Oncogenes represent altered versions of cellular genes instrumental for control of cell proliferation and differentiation. Several oncogenes have been implicated in glial cell transformation and immortalization in culture (myc, src, mos, ras, and SV40 large T antigen). The purpose of this study is to further our understanding of glial cell neoplasia by investigating the effect of oncogenes on the growth and differentiation of central nervous system glial progenitor cells from the oligodendrocyte type 2 astrocyte (O-2A) lineage. This progenitor cell differentiates into an oligodendrocyte or a type-2 astrocyte according to environmental cues. Drug-selectable retroviral vectors were used to introduce oncogenes either alone or in combination into primary cultures of rat O-2A cells. Established O-2A progenitor cell lines were only obtained after infection with c-myc or SV40 large T antigen, suggesting that among the oncogenes tested only these were capable of immortalizing O-2A progenito...
Oncogene, 1990
Previous reports have demonstrated that E7 is the major transforming gene of HPV-16 and that cont... more Previous reports have demonstrated that E7 is the major transforming gene of HPV-16 and that continued expression of the gene is required to maintain the transformed phenotype of primary baby rat kidney cells transformed by HPV-16 E7 and EJ-ras. To investigate the point of action of E7 in the cell cycle we have utilised a system of inducible expression of the E7 gene. The studies reported here show that stimulation of cellular DNA synthesis by E7 is distinct from that observed with calf serum. In combination with cytofluorimetric analyses these results indicate that E7 functions at the transition from G1 to S phase of the cell cycle. This adds further support to the hypothesis of a common pathway of transformation shared by the DNA tumour viruses HPV, SV40 and Adenovirus.
Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors ... more Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors and high in differentiated cells. In this study we have carried out a detailed temporal analysis of AP-1 activity in oligodendrocytetype-2 astrocyte (O-2A) lineage cells. We show that low AP-1 activity in progenitor cells depended on the application of growth factors. Treatment of cells with B104-conditioned medium induced high AP-1 activity, increased process length, and improved growth. The role of AP-1 in proliferation and process extension was emphasized when progenitor cells overexpressing a c-Jun dominantnegative mutant had impaired growth and shortened processes. AP-1 DNA-binding activity during O-2A differentiation in vitro showed an initial down-regulation followed by up-regulation after 2 days. Increased AP-1 levels in oligodendrocytes were inhibited by overexpression of bcl-2, indicating that AP-1 in mature oligodendrocytes is involved in the regulation of apoptosis. Prevention of cell death by bcl-2 in oligodendrocytes was accompanied by progressive differentiation and expression of MOG and PLP.
Proceedings of the National Academy of Sciences, 1990
Cooperation between two growth factors promotes extended selfrenewal and inhibits differentiation... more Cooperation between two growth factors promotes extended selfrenewal and inhibits differentiation of oligodendrocyte-type-2 astrocyte (0-2A) progenitor cells (platelet-derived growth factor/fibroblast growth factor/maturation arrest/glia/precursor
Glia, 2001
Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann ce... more Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann cells, are able to generate myelin sheaths following transplantation into areas of CNS demyelination that are remarkably similar to those made by Schwann cells. The transcriptional control of Schwann cell myelination has been well documented, in particular the role of SCIP/Oct-6 and Krox-20. It is not known, however, whether these transcription factors are also expressed when OECs assume a myelinating phenotype. In this study, we addressed this question by using a transplantation approach to generate myelinating OECs and then examined the expression of SCIP/ Oct-6 and Krox-20 mRNA by in situ hybridization using oligonucleotide probes. We also examined the expression of desert hedgehog (Dhh), a Schwann cell-derived signaling molecule that is responsible for regulating the development of the connective tissue elements in peripheral nerve, which bear similarities to the morphologies adopted by nonmyelinating transplanted cells. Our results indicate that both Krox-20 and Dhh mRNA are strongly expressed by transplanted OECs, with SCIP mRNA present at much lower levels. The expression of Krox-20 relative to the expression of P0 mRNA by the transplanted OECs is consistent with its playing a similar role in OEC myelination to that in Schwann cell myelination, while the expression of Dhh suggests a possible mechanism for the diverse morphologies that cells adopt following OEC transplantation into the damaged CNS. Taken together, our results provide further evidence for the close similarity of OECs and Schwann cells and suggest that, despite their separate origins, the manner in which they generate a peripheral-type myelin sheath involves similar regulatory mechanisms.
Developmental Biology, 1993
Clinical & Experimental Metastasis, 1984
The biological and metastatic properties of cells from a murine mammary adenocarcinoma, MT1, were... more The biological and metastatic properties of cells from a murine mammary adenocarcinoma, MT1, were studied during serial transplantation in syngeneic hosts. Over 35 generations the tumour progressed from a well-differentiated, poorly metastatic neoplasm to an anaplastic highly metastatic state. At early passages the tumour yielded uniform cultures of cuboidal epithelial cells, at passage 17 both epithelioid and spindle type cells were present, and by passage 30 only spindle type cells were obtained. Epithelioid cell lines and clones when injected intravenously into syngeneic hosts produced lung colonies only, whereas spindle cell lines were capable of extensive extrapulmonary colonisation. Similar patterns of dissemination and growth were seen in spontaneous metastasis assays. In spite of the marked phenotypic differences in these 'subpopulations', their comparable ultrastructural features, oestrogen receptor levels, expression of MMTV antigens, DNA content and lectin binding profiles suggested a common cell lineage. It is proposed that these cell lines will be of use in the determination of tumour and host factors influencing tumour progression and the evolution of metastatic potential.
Cancer Immunology Immunotherapy, 1985
An aromatic retinoic acid analogue (Ro 10-9359) previously shown to be capable of inhibiting the ... more An aromatic retinoic acid analogue (Ro 10-9359) previously shown to be capable of inhibiting the growth and metastasis of immunogenic sarcomas and carcinomas (see accompanying paper) was tested for its anti-tumour effects in various categories of immune-deprived mice. 'Non-specific' immunosuppression evoked by sub-lethal whole-body X-irradiation abolished the inhibition of tumour growth induced by Ro 10-9359 in immunocompetent syngeneic hosts. Also, retinoid treatment of three categories of T-lymphocyte-deprived mice (nu/nu; thymectomized-irradiated," and cyclosporin A-treated) was ineffective in reducing the local growth rate or inhibiting spontaneous metastasis of their tumours; in fact, regardless of retinoid treatment the tumours grew faster and metastasized more widely in immunosuppressed animals than in controls. Silica and carrageenan (which are toxic to mononuclear phagocytes) did not interfere with the inhibitory effects of Ro 10-9359 on tumour growth, and did not themselves potentiate metastasis; however, both agents prevented the abolition of DM6 carcinoma metastasis by retinoids. APD, which inhibits the 'accessory cell' function of macrophages did not reduce the effectiveness o f R o 10-9359 against local tumours. However, in contrast to silica and carrageenan this agent did increase the incidence of metastasis of DM6 carcinoma from 40% to 60%, but in the presence of retinoids only 20% of mice succumbed to secondary disease. These results suggest an essential role for T Iymphocytes in retinoid-induced local tumour growth inhibition, and a further contribution of mononuclear phagocytes to the prevention of metastatic dise a s e .
Cancer Immunology Immunotherapy, 1985
Aromatic retinoic acid analogues selected for their favourable therapeutic ratios were tested for... more Aromatic retinoic acid analogues selected for their favourable therapeutic ratios were tested for their effects on the growth (in vivo and in vitro) and spontaneous metastasis of a variety of murine sarcomas and carcinomas. Ro 10-1670 (a trimethylmethoxyphenyl analogue of retinoic acid) was used in in vitro studies, while its corresponding ethyl ester Ro 10-9359 was used for oral administration. Four of six fibrosarcomas, one of three squamous cell carcinomas, and one of five mammary adenocarcinomas responded to retinoid treatment in vivo by reduced growth rates (first detectable after 8-10 days), and in some cases by complete regression. The magnitude of the response was directly proportional to tumour immunogenicity, and eight tumours which failed to respond to retinoids did not evoke detectable transplantation immunity in syngeneic recipients. Retinoid administration did not significantly inhibit the development of spontaneous metastasis of non-immunogenic tumours, but decreased the incidence of secondary disease in the case of tumours of moderate immunogenicity. In vitro, retinoid treatments were generally without significant effects on tumour cell growth rate or morphology, and where growth inhibition was obtained it did not correlate with in vivo tumour responsiveness. No evidence of increased differentiation of retinoid-treated tumours was obtained either in vitro or in vivo. Taken together, the data suggest that in the 14 transplantable syngeneic tumours studied the inhibitory effects of retinoids on tumour growth and metastasis in vivo were mediated indirectly by potentiation of cell-mediated immunity directed against antigenic determinants on the tumour cell surface.
Clinical and Experimental Metastasis, 1984
Annals of the New York Academy of Sciences, 1991
Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann ce... more Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann cells, are able to generate myelin sheaths following transplantation into areas of CNS demyelination that are remarkably similar to those made by Schwann cells. The transcriptional control of Schwann cell myelination has been well documented, in particular the role of SCIP/Oct-6 and Krox-20. It is not known, however, whether these transcription factors are also expressed when OECs assume a myelinating phenotype. In this study, we addressed this question by using a transplantation approach to generate myelinating OECs and then examined the expression of SCIP/ Oct-6 and Krox-20 mRNA by in situ hybridization using oligonucleotide probes. We also examined the expression of desert hedgehog (Dhh), a Schwann cell-derived signaling molecule that is responsible for regulating the development of the connective tissue elements in peripheral nerve, which bear similarities to the morphologies adopted by nonmyelinating transplanted cells. Our results indicate that both Krox-20 and Dhh mRNA are strongly expressed by transplanted OECs, with SCIP mRNA present at much lower levels. The expression of Krox-20 relative to the expression of P0 mRNA by the transplanted OECs is consistent with its playing a similar role in OEC myelination to that in Schwann cell myelination, while the expression of Dhh suggests a possible mechanism for the diverse morphologies that cells adopt following OEC transplantation into the damaged CNS. Taken together, our results provide further evidence for the close similarity of OECs and Schwann cells and suggest that, despite their separate origins, the manner in which they generate a peripheral-type myelin sheath involves similar regulatory mechanisms.
Acta Neurochirurgica, 2007
Background. Implantation of neural cells has been proposed as a therapeutic strategy for repairin... more Background. Implantation of neural cells has been proposed as a therapeutic strategy for repairing the injured or diseased brain. In the present study we have examined the potential of olfactory ensheathing cells (OEC) to promote brain repair after surgical implantation in a rodent model of parkinsonism. Methods. Neonatal OECs were implanted in the striatum after a 6-hydroxydopamine lesion of the ipsilateral substantia nigra. Amphetamine-induced rotational asymmetry scores were determined 48 hours before and 4, 6 and 8 weeks after OEC implantation. The density of immunostaining for tyrosine hydroxylase and synaptophysin in the striatum and the number of tyrosine hydroxylase-positive cells remaining in the substantia nigra were also determined. Results. Rotational asymmetry scores were similar in OEC-implanted and vehicle-treated groups at all time points examined, and at each time were similar to those observed prior to implantation. Levels of striatal tyrosine-hydroxylase and synaptophysin immunoreactivity were similar in OEC-and vehicle-treated groups. The number of tyrosine-hydroxylase-positive cells in the substantia nigra was similar in both groups indicating that severity of the lesion was similar. Visualisation of GFP-labelled OECs one week after implantation in a separate group of animals revealed the cells to be located in the area immediately surrounding the needle tract. Conclusion. This study demonstrates that implantation of OECs alone is not sufficient to promote tissue repair and functional recovery in a rodent model of parkinsonism. The results add to a growing number of studies that propose a caveat for the use of pure OECs as a neurosurgical strategy for the treatment of brain disease or injury.
Proceedings of the National Academy of Sciences, Aug 1, 1990
Bipotential oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, which give rise to oligoden... more Bipotential oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, which give rise to oligodendrocytes and type-2 astrocytes in cultures of rat optic nerve, are one of the few cell types in which most aspects of proliferation and differentiation can be manipulated in a defined in vitro environment. Previous studies have shown that O-2A progenitors exposed to platelet-derived growth factor (PDGF) divide as migratory bipolar cells a limited number of times, with a cell cycle time of 18 hr, before clonally related progenitors differentiate into ...
Annals of the New York Academy of Sciences, Dec 17, 2006
BACKGROUND Our studies on glial development have focused, for the most part, on the optic nerve. ... more BACKGROUND Our studies on glial development have focused, for the most part, on the optic nerve. By studying this simple white matter tract, we have been able to analyze glial development in a relatively homogeneous tissue. Studies of this tissue are further simplified by the fact that the optic nerve contains no intrinsic neurons; thus, neuron-free preparations of glial cells can be obtained by simple dissection. In our initial studies on the glia of the optic nerve, we found that cultures derived from this simple tissue contained two ...
Molecular and Cellular Biology, 1996
Introduction of simian virus 40 T antigen into rodent fibroblasts gives rise to cells that can pr... more Introduction of simian virus 40 T antigen into rodent fibroblasts gives rise to cells that can proliferate indefinitely but are dependent upon it for maintenance of their growth once the normal mitotic life span has elapsed. Inactivation of T antigen in these immortalized cells causes rapid and irreversible cessation of growth. To determine whether this growth arrest is associated with entry into senescence, we have undertaken a genetic and biological analysis of conditionally immortal (tsa) cell lines derived by immortalizing rat embryo fibroblasts with the thermolabile tsA58 T antigen. This analysis has identified the following parallels between the tsa cells after inactivation of T antigen and senescent rat embryo fibroblasts: (i) growth arrest is irreversible; (ii) it occurs in G1 as well as G2; (iii) the G1 block can be partially overcome by stimulation with 20% fetal calf serum, but the G2 block cannot be overcome; (iv) 20% fetal calf serum induces c-fos, but c-myc is unaltere...
The Neuroscientist, 2012
Astrocytes are the most abundant cell type in the adult central nervous system (CNS), and their f... more Astrocytes are the most abundant cell type in the adult central nervous system (CNS), and their functional diversity in response to injury is now being appreciated. Astrocytes have long been considered the main player in the inhibition of CNS repair via the formation of the gliotic scar, but now it is accepted that astrocyte can play an important role in CNS repair and remyelination. Interest in the relationship between astrocytes and myelination focused initially on attempts to understand how the development of plaques of astroglial scar tissue in multiple sclerosis was related to the failure of these lesions to remyelinate. It is now considered that this is an end stage pathological response to injury, and that normally astrocytes play important roles in supporting the development and maintenance of CNS myelin. This review will focus on how this new understanding may be exploited to develop new strategies to enhance remyelination in multiple sclerosis and other diseases.
In tissue engineering, the chemical and topographical cues within three-dimensional (3D) scaffold... more In tissue engineering, the chemical and topographical cues within three-dimensional (3D) scaffolds are normally tested using static cell cultures but applied directly to tissue cultures in perfusion bioreactors. As human cells are very sensitive to the changes of culture environment, it is essential to evaluate the performance of any chemical, and topographical cues in a perfused environment before they are applied to tissue engineering. Thus the aim of this research was to bridge the gap between static and perfusion cultures by addressing the effect of perfusion on cell cultures within 3D scaffolds. For this we developed a scale down bioreactor system, which allows to evaluate the effectiveness of various chemical and topographical cues incorporated into our previously developed tubular ε-polycaprolactone scaffold under perfused conditions. Investigation of two exemplary cell types (fibroblasts and cortical astrocytes) using the miniaturized bioreactor indicated that: (1) quick and firm cell adhesion in 3D scaffold was critical for cell survival in perfusion culture compared with static culture, thus cell seeding procedures for static cultures might not be applicable. Therefore it was necessary to re-evaluate cell attachment on different surfaces under perfused conditions before a 3D scaffold was applied for tissue cultures, (2) continuous medium perfusion adversely influenced cell spread and survival, which could be balanced by intermittent perfusion, (3) micro-grooves still maintained its influences on cell alignment under perfused conditions, while medium perfusion demonstrated additional influence on fibroblast alignment but not on astrocyte alignment on grooved substrates. This research demonstrated that the mini-bioreactor system is crucial for the development 3 of functional scaffolds with suitable chemical and topographical cues by bridging the gap between static culture and perfusion culture.
Molecular and cellular neurosciences, 2000
Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors ... more Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors and high in differentiated cells. In this study we have carried out a detailed temporal analysis of AP-1 activity in oligodendrocyte-type-2 astrocyte (O-2A) lineage cells. We show that low AP-1 activity in progenitor cells depended on the application of growth factors. Treatment of cells with B104-conditioned medium induced high AP-1 activity, increased process length, and improved growth. The role of AP-1 in proliferation and process extension was emphasized when progenitor cells overexpressing a c-Jun dominant-negative mutant had impaired growth and shortened processes. AP-1 DNA-binding activity during O-2A differentiation in vitro showed an initial down-regulation followed by up-regulation after 2 days. Increased AP-1 levels in oligodendrocytes were inhibited by overexpression of bcl-2, indicating that AP-1 in mature oligodendrocytes is involved in the regulation of apoptosis. Prevent...
Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1995
Oncogenes represent altered versions of cellular genes instrumental for control of cell prolifera... more Oncogenes represent altered versions of cellular genes instrumental for control of cell proliferation and differentiation. Several oncogenes have been implicated in glial cell transformation and immortalization in culture (myc, src, mos, ras, and SV40 large T antigen). The purpose of this study is to further our understanding of glial cell neoplasia by investigating the effect of oncogenes on the growth and differentiation of central nervous system glial progenitor cells from the oligodendrocyte type 2 astrocyte (O-2A) lineage. This progenitor cell differentiates into an oligodendrocyte or a type-2 astrocyte according to environmental cues. Drug-selectable retroviral vectors were used to introduce oncogenes either alone or in combination into primary cultures of rat O-2A cells. Established O-2A progenitor cell lines were only obtained after infection with c-myc or SV40 large T antigen, suggesting that among the oncogenes tested only these were capable of immortalizing O-2A progenito...
Oncogene, 1990
Previous reports have demonstrated that E7 is the major transforming gene of HPV-16 and that cont... more Previous reports have demonstrated that E7 is the major transforming gene of HPV-16 and that continued expression of the gene is required to maintain the transformed phenotype of primary baby rat kidney cells transformed by HPV-16 E7 and EJ-ras. To investigate the point of action of E7 in the cell cycle we have utilised a system of inducible expression of the E7 gene. The studies reported here show that stimulation of cellular DNA synthesis by E7 is distinct from that observed with calf serum. In combination with cytofluorimetric analyses these results indicate that E7 functions at the transition from G1 to S phase of the cell cycle. This adds further support to the hypothesis of a common pathway of transformation shared by the DNA tumour viruses HPV, SV40 and Adenovirus.
Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors ... more Oligodendrocyte differentiation has been correlated with AP-1 activity, being low in progenitors and high in differentiated cells. In this study we have carried out a detailed temporal analysis of AP-1 activity in oligodendrocytetype-2 astrocyte (O-2A) lineage cells. We show that low AP-1 activity in progenitor cells depended on the application of growth factors. Treatment of cells with B104-conditioned medium induced high AP-1 activity, increased process length, and improved growth. The role of AP-1 in proliferation and process extension was emphasized when progenitor cells overexpressing a c-Jun dominantnegative mutant had impaired growth and shortened processes. AP-1 DNA-binding activity during O-2A differentiation in vitro showed an initial down-regulation followed by up-regulation after 2 days. Increased AP-1 levels in oligodendrocytes were inhibited by overexpression of bcl-2, indicating that AP-1 in mature oligodendrocytes is involved in the regulation of apoptosis. Prevention of cell death by bcl-2 in oligodendrocytes was accompanied by progressive differentiation and expression of MOG and PLP.
Proceedings of the National Academy of Sciences, 1990
Cooperation between two growth factors promotes extended selfrenewal and inhibits differentiation... more Cooperation between two growth factors promotes extended selfrenewal and inhibits differentiation of oligodendrocyte-type-2 astrocyte (0-2A) progenitor cells (platelet-derived growth factor/fibroblast growth factor/maturation arrest/glia/precursor
Glia, 2001
Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann ce... more Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann cells, are able to generate myelin sheaths following transplantation into areas of CNS demyelination that are remarkably similar to those made by Schwann cells. The transcriptional control of Schwann cell myelination has been well documented, in particular the role of SCIP/Oct-6 and Krox-20. It is not known, however, whether these transcription factors are also expressed when OECs assume a myelinating phenotype. In this study, we addressed this question by using a transplantation approach to generate myelinating OECs and then examined the expression of SCIP/ Oct-6 and Krox-20 mRNA by in situ hybridization using oligonucleotide probes. We also examined the expression of desert hedgehog (Dhh), a Schwann cell-derived signaling molecule that is responsible for regulating the development of the connective tissue elements in peripheral nerve, which bear similarities to the morphologies adopted by nonmyelinating transplanted cells. Our results indicate that both Krox-20 and Dhh mRNA are strongly expressed by transplanted OECs, with SCIP mRNA present at much lower levels. The expression of Krox-20 relative to the expression of P0 mRNA by the transplanted OECs is consistent with its playing a similar role in OEC myelination to that in Schwann cell myelination, while the expression of Dhh suggests a possible mechanism for the diverse morphologies that cells adopt following OEC transplantation into the damaged CNS. Taken together, our results provide further evidence for the close similarity of OECs and Schwann cells and suggest that, despite their separate origins, the manner in which they generate a peripheral-type myelin sheath involves similar regulatory mechanisms.
Developmental Biology, 1993
Clinical & Experimental Metastasis, 1984
The biological and metastatic properties of cells from a murine mammary adenocarcinoma, MT1, were... more The biological and metastatic properties of cells from a murine mammary adenocarcinoma, MT1, were studied during serial transplantation in syngeneic hosts. Over 35 generations the tumour progressed from a well-differentiated, poorly metastatic neoplasm to an anaplastic highly metastatic state. At early passages the tumour yielded uniform cultures of cuboidal epithelial cells, at passage 17 both epithelioid and spindle type cells were present, and by passage 30 only spindle type cells were obtained. Epithelioid cell lines and clones when injected intravenously into syngeneic hosts produced lung colonies only, whereas spindle cell lines were capable of extensive extrapulmonary colonisation. Similar patterns of dissemination and growth were seen in spontaneous metastasis assays. In spite of the marked phenotypic differences in these 'subpopulations', their comparable ultrastructural features, oestrogen receptor levels, expression of MMTV antigens, DNA content and lectin binding profiles suggested a common cell lineage. It is proposed that these cell lines will be of use in the determination of tumour and host factors influencing tumour progression and the evolution of metastatic potential.
Cancer Immunology Immunotherapy, 1985
An aromatic retinoic acid analogue (Ro 10-9359) previously shown to be capable of inhibiting the ... more An aromatic retinoic acid analogue (Ro 10-9359) previously shown to be capable of inhibiting the growth and metastasis of immunogenic sarcomas and carcinomas (see accompanying paper) was tested for its anti-tumour effects in various categories of immune-deprived mice. 'Non-specific' immunosuppression evoked by sub-lethal whole-body X-irradiation abolished the inhibition of tumour growth induced by Ro 10-9359 in immunocompetent syngeneic hosts. Also, retinoid treatment of three categories of T-lymphocyte-deprived mice (nu/nu; thymectomized-irradiated," and cyclosporin A-treated) was ineffective in reducing the local growth rate or inhibiting spontaneous metastasis of their tumours; in fact, regardless of retinoid treatment the tumours grew faster and metastasized more widely in immunosuppressed animals than in controls. Silica and carrageenan (which are toxic to mononuclear phagocytes) did not interfere with the inhibitory effects of Ro 10-9359 on tumour growth, and did not themselves potentiate metastasis; however, both agents prevented the abolition of DM6 carcinoma metastasis by retinoids. APD, which inhibits the 'accessory cell' function of macrophages did not reduce the effectiveness o f R o 10-9359 against local tumours. However, in contrast to silica and carrageenan this agent did increase the incidence of metastasis of DM6 carcinoma from 40% to 60%, but in the presence of retinoids only 20% of mice succumbed to secondary disease. These results suggest an essential role for T Iymphocytes in retinoid-induced local tumour growth inhibition, and a further contribution of mononuclear phagocytes to the prevention of metastatic dise a s e .
Cancer Immunology Immunotherapy, 1985
Aromatic retinoic acid analogues selected for their favourable therapeutic ratios were tested for... more Aromatic retinoic acid analogues selected for their favourable therapeutic ratios were tested for their effects on the growth (in vivo and in vitro) and spontaneous metastasis of a variety of murine sarcomas and carcinomas. Ro 10-1670 (a trimethylmethoxyphenyl analogue of retinoic acid) was used in in vitro studies, while its corresponding ethyl ester Ro 10-9359 was used for oral administration. Four of six fibrosarcomas, one of three squamous cell carcinomas, and one of five mammary adenocarcinomas responded to retinoid treatment in vivo by reduced growth rates (first detectable after 8-10 days), and in some cases by complete regression. The magnitude of the response was directly proportional to tumour immunogenicity, and eight tumours which failed to respond to retinoids did not evoke detectable transplantation immunity in syngeneic recipients. Retinoid administration did not significantly inhibit the development of spontaneous metastasis of non-immunogenic tumours, but decreased the incidence of secondary disease in the case of tumours of moderate immunogenicity. In vitro, retinoid treatments were generally without significant effects on tumour cell growth rate or morphology, and where growth inhibition was obtained it did not correlate with in vivo tumour responsiveness. No evidence of increased differentiation of retinoid-treated tumours was obtained either in vitro or in vivo. Taken together, the data suggest that in the 14 transplantable syngeneic tumours studied the inhibitory effects of retinoids on tumour growth and metastasis in vivo were mediated indirectly by potentiation of cell-mediated immunity directed against antigenic determinants on the tumour cell surface.
Clinical and Experimental Metastasis, 1984
Annals of the New York Academy of Sciences, 1991
Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann ce... more Olfactory ensheathing cells (OECs), although having a separate developmental origin to Schwann cells, are able to generate myelin sheaths following transplantation into areas of CNS demyelination that are remarkably similar to those made by Schwann cells. The transcriptional control of Schwann cell myelination has been well documented, in particular the role of SCIP/Oct-6 and Krox-20. It is not known, however, whether these transcription factors are also expressed when OECs assume a myelinating phenotype. In this study, we addressed this question by using a transplantation approach to generate myelinating OECs and then examined the expression of SCIP/ Oct-6 and Krox-20 mRNA by in situ hybridization using oligonucleotide probes. We also examined the expression of desert hedgehog (Dhh), a Schwann cell-derived signaling molecule that is responsible for regulating the development of the connective tissue elements in peripheral nerve, which bear similarities to the morphologies adopted by nonmyelinating transplanted cells. Our results indicate that both Krox-20 and Dhh mRNA are strongly expressed by transplanted OECs, with SCIP mRNA present at much lower levels. The expression of Krox-20 relative to the expression of P0 mRNA by the transplanted OECs is consistent with its playing a similar role in OEC myelination to that in Schwann cell myelination, while the expression of Dhh suggests a possible mechanism for the diverse morphologies that cells adopt following OEC transplantation into the damaged CNS. Taken together, our results provide further evidence for the close similarity of OECs and Schwann cells and suggest that, despite their separate origins, the manner in which they generate a peripheral-type myelin sheath involves similar regulatory mechanisms.
Acta Neurochirurgica, 2007
Background. Implantation of neural cells has been proposed as a therapeutic strategy for repairin... more Background. Implantation of neural cells has been proposed as a therapeutic strategy for repairing the injured or diseased brain. In the present study we have examined the potential of olfactory ensheathing cells (OEC) to promote brain repair after surgical implantation in a rodent model of parkinsonism. Methods. Neonatal OECs were implanted in the striatum after a 6-hydroxydopamine lesion of the ipsilateral substantia nigra. Amphetamine-induced rotational asymmetry scores were determined 48 hours before and 4, 6 and 8 weeks after OEC implantation. The density of immunostaining for tyrosine hydroxylase and synaptophysin in the striatum and the number of tyrosine hydroxylase-positive cells remaining in the substantia nigra were also determined. Results. Rotational asymmetry scores were similar in OEC-implanted and vehicle-treated groups at all time points examined, and at each time were similar to those observed prior to implantation. Levels of striatal tyrosine-hydroxylase and synaptophysin immunoreactivity were similar in OEC-and vehicle-treated groups. The number of tyrosine-hydroxylase-positive cells in the substantia nigra was similar in both groups indicating that severity of the lesion was similar. Visualisation of GFP-labelled OECs one week after implantation in a separate group of animals revealed the cells to be located in the area immediately surrounding the needle tract. Conclusion. This study demonstrates that implantation of OECs alone is not sufficient to promote tissue repair and functional recovery in a rodent model of parkinsonism. The results add to a growing number of studies that propose a caveat for the use of pure OECs as a neurosurgical strategy for the treatment of brain disease or injury.
Proceedings of the National Academy of Sciences, Aug 1, 1990
Bipotential oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, which give rise to oligoden... more Bipotential oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, which give rise to oligodendrocytes and type-2 astrocytes in cultures of rat optic nerve, are one of the few cell types in which most aspects of proliferation and differentiation can be manipulated in a defined in vitro environment. Previous studies have shown that O-2A progenitors exposed to platelet-derived growth factor (PDGF) divide as migratory bipolar cells a limited number of times, with a cell cycle time of 18 hr, before clonally related progenitors differentiate into ...
Annals of the New York Academy of Sciences, Dec 17, 2006
BACKGROUND Our studies on glial development have focused, for the most part, on the optic nerve. ... more BACKGROUND Our studies on glial development have focused, for the most part, on the optic nerve. By studying this simple white matter tract, we have been able to analyze glial development in a relatively homogeneous tissue. Studies of this tissue are further simplified by the fact that the optic nerve contains no intrinsic neurons; thus, neuron-free preparations of glial cells can be obtained by simple dissection. In our initial studies on the glia of the optic nerve, we found that cultures derived from this simple tissue contained two ...