Abstract 3376: Cord blood stem cells revert EMT to MET in glioma stem cells by downregulating synergistic transcriptional activation of Sox2 and Twist1

The dynamic nature of cancer stem cells that underlie metastasis or their ability to switch between different cellular identities, as in epithelial to mesenchymal transition and mesenchymal to epithelial transition has profound implications for cancer therapy. The functional relationship between molecules involved in cancer cell stemness and metastasis is not clear. In this regard, our studies on human glioblastoma tissue grade IV specimens showed significant expression of Twist1 and Sox2, known mesenchymal and stemness related markers, respectively, indicating their association with glial tumorigenesis and metastasis. The glioma stem cells obtained from CD133+ cells demonstrated increased expression of Twist1 and Sox2 accompanied by significant increase in the mesenchymal markers such as N-cadherin, vimentin and β-catenin. Our studies on glioma stem cells treatment with human umbilical cord blood derived mesenchymal stem cells, showed down regulation of Twist1 and Sox2 proteins, apart from other mesenchymal stem cell markers. Based on the in vitro experiments and in vivo intracranial xenograft mouse model studies we elucidated the potential therapeutic role of hUCBSC in suppressing glioma cancer stemness by the induction of mesenchymal to epithelial transition.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3376. doi:1538-7445.AM2012-3376

Cord blood stem cells inhibit epidermal growth factor receptor translocation to mitochondria in glioblastoma

BACKGROUND

Overexpression of EGFR is one of the most frequently diagnosed genetic aberrations of glioblastoma multiforme (GBM). EGFR signaling is involved in diverse cellular functions and is dependent on the type of preferred receptor complexes. EGFR translocation to mitochondria has been reported recently in different cancer types. However, mechanistic aspects of EGFR translocation to mitochondria in GBM have not been evaluated to date.

METHODOLOGY/PRINCIPLE FINDINGS

In the present study, we analyzed the expression of EGFR in GBM-patient derived specimens using immunohistochemistry, reverse-transcription based PCR and Western blotting techniques. In clinical samples, EGFR co-localizes with FAK in mitochondria. We evaluated this previous observation in standard glioma cell lines and in vivo mice xenografts. We further analyzed the effect of human umbilical cord blood stem cells (hUCBSC) on the inhibition of EGFR expression and EGFR signaling in glioma cells and xenografts. Treatment with hUCBSC inhibited the expression of EGFR and its co-localization with FAK in glioma cells. Also, hUCBSC inhibited the co-localization of activated forms of EGFR, FAK and c-Src in mitochondria of glioma cells and xenografts. In addition, hUCBSC also inhibited EGFR signaling proteins in glioma cells both in vitro and in vivo.

CONCLUSIONS/SIGNIFICANCE

We have shown that hUCBSC treatments inhibit phosphorylation of EGFR, FAK and c-Src forms. Our findings associate EGFR expression and its localization to mitochondria with specific biological functions in GBM cells and provide relevant preclinical information that can be used for the development of effective hUCBSC-based therapies.

Transcriptional repression of Mad-Max complex by human umbilical cord blood stem cells downregulates extracellular signal-regulated kinase in glioblastoma

Previously, we have shown that human umbilical cord blood stem cell (hUCBSC) treatment downregulate cyclin D1 in glioma cells. To study the cell cycle progression and investigate the upstream molecules regulating cyclin D1 expression, we analyzed the involvement of extracellular signal-regulated kinase (ERK) and its functionality after treatment with hUCBSC. We observed downregulation of pERK after hUCBSC treatment at both transcriptional and translational levels. Increased translocation of ERK from cytoplasm to the nucleus was observed in glioma cells, whereas hUCBSC cocultures with glioma cells showed suppressed nuclear translocation. This finding suggests that hUCBSC regulates ERK by suppressing its phosphorylation at phospho-Thr(202)/Tyr(204) retarding pERK nuclear translocation. ERK promoter analysis has shown c-Myc binding sites, indicative of possible transcriptional interactions that regulate cyclin D1 and ERK expression levels. Treatment of U251 and 5310 glioma cells with U0126, a MEK/ERK inhibitor receded pERK and c-Myc levels. In another experiment, U251 and 5310 cells treated with 10074-G5, c-Myc/Max inhibitor displayed reduction in pERK and c-Myc levels suggestive of a positive feedback loop between ERK/c-Myc/Max molecules. In the present study, we show that glioma cells exhibit abundant c-Myc expression and increased c-Myc/Max activity. In contrast, the glioma cells cocultured with hUCBSC demonstrated high Mad1 expression that competitively binds to Max to repress the c-Myc/Max mediated gene transcription. Our studies thus elucidate the potential role of hUCBSC in controlling glioma cell cycle progression and invasion by limiting Max binding to c-Myc, thus regulating the expression of glioma cell cycle and invasion associated molecules such as ERK, integrins via increased levels of Mad1 expression.

p53- and Bax-mediated apoptosis in injured rat spinal cord

Spinal cord injury (SCI) induces a series of endogenous biochemical changes that lead to secondary degeneration, including apoptosis. p53-mediated mitochondrial apoptosis is likely to be an important mechanism of cell death in spinal cord injury. However, the signaling cascades that are activated before DNA fragmentation have not yet been determined. DNA damage-induced, p53-activated neuronal cell death has already been identified in several neurodegenerative diseases. To determine DNA damage-induced, p53-mediated apoptosis in spinal cord injury, we performed RT-PCR microarray and analyzed 84 DNA damaging and apoptotic genes. Genes involved in DNA damage and apoptosis were upregulated whereas anti-apoptotic genes were downregulated in injured spinal cords. Western blot analysis showed the upregulation of DNA damage-inducing protein such as ATM, cell cycle checkpoint kinases, 8-hydroxy-2'-deoxyguanosine (8-OHdG), BRCA2 and H2AX in injured spinal cord tissues. Detection of phospho-H2AX in the nucleus and release of 8-OHdG in cytosol were demonstrated by immunohistochemistry. Expression of p53 was observed in the neurons, oligodendrocytes and astrocytes after spinal cord injury. Upregulation of phospho-p53, Bax and downregulation of Bcl2 were detected after spinal cord injury. Sub-cellular distribution of Bax and cytochrome c indicated mitochondrial-mediated apoptosis taking place after spinal cord injury. In addition, we carried out immunohistochemical analysis to confirm Bax translocation into the mitochondria and activated p53 at Ser³⁹². Expression of APAF1, caspase 9 and caspase 3 activities confirmed the intrinsic apoptotic pathway after SCI. Activated p53 and Bax mitochondrial translocation were detected in injured spinal neurons. Taken together, the in vitro data strengthened the in vivo observations of DNA damage-induced p53-mediated mitochondrial apoptosis in the injured spinal cord.

Abstract 3319: Cell cycle regulation of glioblastoma progression by cord blood stem cells is mediated by downregulation of cyclin D1

Normal progression of the cell cycle requires sequential expression of cyclins. Rapid induction of cyclin D1 and its associated binding with cyclin-dependent kinases, in the presence or absence of mitogenic signals, is considered a rate-limiting step during cell cycle progression through the G1 phase. In the present study, human umbilical cord blood stem cells (hUCBSC) co-cultured with glioblastoma cells (U251 and 5310) not only induced G0-G1 phase arrest, but also reduced the number of cells at the S and G2-M phases of the cell cycle. Western and FACS analyses of cell cycle regulatory proteins showed decreased expression levels upon treatment with hUCBSC. Co-localization experiments under in vivo conditions in nude mice brain xenografts with cyclin D1 and CD81 antibodies demonstrated decreased expression of cyclin D1 in the presence of hUCBSC. Treatment with hUCBSC decreased expression of the cyclin D1 and CDK4 complex as well as cyclin D1 and CDK6 complexes. However, there was no significant change in the CDK4 and CDK6 complex. Our results indicate that hUCBSC can attenuate uncontrolled cell cycle progression of glioma cells by downregulating the expression levels of cyclin D1 and its partner kinases CDK4 and CDK6 at the cell cycle level. Our data elucidate a model to regulate glioma cell cycle progression in which hUCBSC act to control cyclin D1 induction and its partner kinases, CDK4 and CDK6, by mediating cell cycle arrest via G0-G1 arrest.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3319. doi:10.1158/1538-7445.AM2011-3319

Abstract 3322: Downregulation of XIAP by cord blood stem cells is associated with inhibition of heat shock protein 90 in glioblastoma

Heat shock protein 90 (HSP90) is highly expressed under stressful conditions in eukaryotic cells showing chaperone activity including the suppression of protein aggregation and signaling pathways. HSP90 is upregulated in various human tumors, including glioblastoma, and targeting its function might provide new therapeutic opportunities. Previously, we have shown that human umbilical cord blood-derived mesenchymal stem cells (hUCBSC) downregulate XIAP in glioblastoma cells in vitro and in vivo. In the present study, we report that downregulation of XIAP by hUCBSC is associated with inhibition of HSP90. Under in vivo conditions, hUCBSC induce apoptosis by downregulation of XIAP in which XIAP migrates from the cytosol to the nucleus in mice brain xenografts. Immunoprecipitation experiments proved that SMAC is associated with Cytochrome C and XIAP in the mitochondria, indicating mitochondrial apoptosis. Simultaneously, cytosolic HSP90 is downregulated and co-localized with TNFR2 in hUCBSC-treated tumors, proving that TRAIL-mediated apoptosis is taking place in hUCBSC-treated tumor xenografts. Also, expression of mitochondrial HSP90 (TRAP-1) is downregulated in glioma cells. The downregulation of XIAP by hUCBSC is shown to be under the transcriptional control of SP1 under both in vitro and in vivo conditions. These results have been confirmed by using shRNA for XIAP. Taken together, these results prove that hUCBSC are efficient in the inhibition of HSP90, and hUCBSC have the potential to be therapeutic tools for the treatment of glioblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3322. doi:10.1158/1538-7445.AM2011-3322

Downregulation of Focal Adhesion Kinase (FAK) by cord blood stem cells inhibits angiogenesis in glioblastoma

Angiogenesis involves the formation of new blood vessels by rerouting or remodeling existing ones and is believed to be the primary method of vessel formation in gliomas. To study the mechanisms by which angiogenesis of glioma cells can be inhibited by human umbilical cord blood stem cells (hUCBSC), we studied two glioma cell lines (SNB19, U251) and a glioma xenograft cell line (5310) alone and in co-culture with hUCBSC. Conditioned media from co-cultures of glioma cells with hUCBSC showed reduced angiogenesis as evaluated by in vitro angiogenesis assay using HMEC cells. Reduction in angiogenesis was associated with downregulation of FAK and integrin α_vβ₃ in the co-cultures of glioma cells. Downregulation of FAK gene is correlated with downregulation of many angiogenesis-related genes, including Ang1, VEGFA and Akt. Under in vivo conditions, neovascularization by glioma cells was inhibited by hUCBSC. Further, intracranial tumor growth was inhibited by hUCBSC in athymic nude mice. Similar to in vitro results, we observed downregulation of FAK, VEGF and Akt molecules to inhibit angiogenesis in the hUCBSC-treated nude mice brains. Taken together, our results suggest that hUCBSC have the potential to inhibit the angiogenesis of glioma cells both in vitro and in vivo.

Human umbilical cord blood-derived mesenchymal stem cells upregulate myelin basic protein in shiverer mice

Human umbilical cord blood is a rich source of pluripotent mesenchymal stem cells and possesses significant advantages over other stem cell sources such as the embryo and bone marrow. In the present study, we aimed to investigate the potential of human umbilical cord blood-derived pluripotent mesenchymal stem cells (hUCB) to myelinate the axons of shiverer mice brains. We also investigated the effect of hUCB treatment on regulation of myelin basic protein in vitro in PC-12 cells, which are normally not myelinated. The results of our study clearly demonstrated that hUCB survive and migrate in vivo and has the potential to myelinate shiverer mice brains. The expression level of myelin basic protein, a major component of the myelin sheath, has been significantly increased in vivo and in vitro as revealed by Western blot, reverse transcription (RT)-polymerase chain reaction, immunohistochemistry, immunocytochemistry, and fluorescent in situ hybridization results. Further, transmission electron microscopic images of hUCB-treated shiverer mice brains showed several layers of myelin around the axons compared with a thin and fragmented layer of myelin in untreated animals. Moreover, the frequency of shivering was diminished 1 month after hUCB treatment in shiverer mice. Our results strongly indicated that hUCB transplantation could be an effective means of treating demyelinating or hypomyelinating disorders.

Cord blood stem cell-mediated induction of apoptosis in glioma downregulates X-linked inhibitor of apoptosis protein (XIAP)

BACKGROUND

XIAP (X-linked inhibitor of apoptosis protein) is one of the most important members of the apoptosis inhibitor family. XIAP is upregulated in various malignancies, including human glioblastoma. It promotes invasion, metastasis, growth and survival of malignant cells. We hypothesized that downregulation of XIAP by human umbilical cord blood mesenchymal stem cells (hUCBSC) in glioma cells would cause them to undergo apoptotic death.

METHODOLOGY/PRINCIPAL FINDINGS

We observed the effect of hUCBSC on two malignant glioma cell lines (SNB19 and U251) and two glioma xenograft cell lines (4910 and 5310). In co-cultures of glioma cells with hUCBSC, proliferation of glioma cells was significantly inhibited. This is associated with increased cytotoxicity of glioma cells, which led to glioma cell death. Stem cells induced apoptosis in glioma cells, which was evaluated by TUNEL assay, FACS analyses and immunoblotting. The induction of apoptosis is associated with inhibition of XIAP in co-cultures of hUCBSC. Similar results were obtained by the treatment of glioma cells with shRNA to downregulate XIAP (siXIAP). Downregulation of XIAP resulted in activation of caspase-3 and caspase-9 to trigger apoptosis in glioma cells. Apoptosis is characterized by the loss of mitochondrial membrane potential and upregulation of mitochondrial apoptotic proteins Bax and Bad. Cell death of glioma cells was marked by downregulation of Akt and phospho-Akt molecules. We observed similar results under in vivo conditions in U251- and 5310-injected nude mice brains, which were treated with hUCBSC. Under in vivo conditions, Smac/DIABLO was found to be colocalized in the nucleus, showing that hUCBSC induced apoptosis is mediated by inhibition of XIAP and activation of Smac/DIABLO.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that downregulation of XIAP by hUCBSC treatment induces apoptosis, which led to the death of the glioma cells and xenograft cells. This study demonstrates the therapeutic potential of XIAP and hUCBSC to treat malignant gliomas.

Epigenetic upregulation of urokinase plasminogen activator promotes the tropism of mesenchymal stem cells for tumor cells

A major obstacle for the effective treatment of cancer is the invasive capacity of the tumor cells. Previous studies have shown the capability of mesenchymal stem cells (MSC) to target these disseminated tumor cells and to serve as therapeutic delivery vehicles. However, the molecular mechanisms that would enhance the migration of MSCs toward tumor areas are not well understood. In particular, very little is known about the role that epigenetic mechanisms play in cell migration and tropism of MSCs. In this study, we investigated whether histone deacetylation was involved in the repression of urokinase plasminogen activator (uPA) expression in MSCs derived from umbilical cord blood (CB) and bone marrow (BM). Induction of uPA expression by histone deacetylase inhibitors trichostatin A and sodium butyrate was observed in CB- and BM-derived MSCs examined. In vitro migration assays showed that induction of uPA expression by histone deacetylase inhibitors in CB- and BM-derived MSCs significantly enhanced tumor tropism of these cells. Furthermore, overexpression of uPA in CB-MSCs induced migration capacity toward human cancer cells in vitro. In addition, our results showed that uPA-uPAR knockdown in PC3 prostate cancer cells significantly inhibited tumor-specific migration of uPA-overexpressing MSCs. These results have significant implications for the development of MSC-mediated, tumor-selective gene therapies.

Upregulation of PTEN in glioma cells by cord blood mesenchymal stem cells inhibits migration via downregulation of the PI3K/Akt pathway

Background

PTEN (phosphatase and tensin homologue deleted on chromosome ten) is a tumor suppressor gene implicated in a wide variety of human cancers, including glioblastoma. PTEN is a major negative regulator of the PI3K/Akt signaling pathway. Most human gliomas show high levels of activated Akt, whereas less than half of these tumors carry PTEN mutations or homozygous deletions. The unique ability of mesenchymal stem cells to track down tumor cells makes them as potential therapeutic agents. Based on this capability, new therapeutic approaches have been developed using mesenchymal stem cells to cure glioblastoma. However, molecular mechanisms of interactions between glioma cells and stem cells are still unknown.

Methodology/Principal Findings

In order to study the mechanisms by which migration of glioma cells can be inhibited by the upregulation of the PTEN gene, we studied two glioma cell lines (SNB19 and U251) and two glioma xenograft cell lines (4910 and 5310) alone and in co-culture with human umbilical cord blood-derived mesenchymal stem cells (hUCBSC). Co-cultures of glioma cells showed increased expression of PTEN as evaluated by immunofluorescence and immunoblotting assays. Upregulation of PTEN gene is correlated with the downregulation of many genes including Akt, JUN, MAPK14, PDK2, PI3K, PTK2, RAS and RAF1 as revealed by cDNA microarray analysis. These results have been confirmed by reverse-transcription based PCR analysis of PTEN and Akt genes. Upregulation of PTEN resulted in the inhibition of migration capability of glioma cells under in vitro conditions. Also, wound healing capability of glioma cells was significantly inhibited in co-culture with hUCBSC. Under in vivo conditions, intracranial tumor growth was inhibited by hUCBSC in nude mice. Further, hUCBSC upregulated PTEN and decreased the levels of XIAP and Akt, which are responsible for the inhibition of tumor growth in the mouse brain.

Conclusions/Significance

Our studies indicated that upregulation of PTEN by hUCBSC in glioma cells and in the nude mice tumors downregulated Akt and PI3K signaling pathway molecules. This resulted in the inhibition of migration as well as wound healing property of the glioma cells. Taken together, our results suggest hUCBSC as a therapeutic agent in treating malignant gliomas.

Abstract 3323: Induction of apoptosis in glioma cells by downregulation of X-linked inhibitor of apoptosis protein (XIAP)

XIAP (X-linked inhibitor of apoptosis protein) is one of the most important members of the family of apoptosis inhibitors. XIAP blocks apoptosis by inhibiting both the initiator (caspase 9) and effector (caspase 3) caspases, and therefore, prevents cell death induced by various triggers. One mechanism through which tumor cells are believed to acquire resistance to apoptosis is by overexpression of XIAP. When XIAP is overexpressed, cancer cells are rendered resistant to apoptosis, both intrinsically and in response to chemotherapy and radiotherapy. It is upregulated in various malignancies, including human glioblastoma. It promotes invasion, metastasis, growth, and survival of malignant cells. In order to downregulate XIAP in glioma cells, we used human umbilical cord blood mesenchymal stem cells (hUCB) and siRNA of XIAP (siXIAP). We observed the effect of both hUCB and siXIAP on two malignant glioma cell lines (SNB19 and U251) and two glioma xenograft cell lines (4910 and 5310). In either case, proliferation of the glioma cells was significantly inhibited. Both treatments increased cytotoxicity of glioma cells and led to cell death. However, cytotoxicity is more significant in siXIAP treatments compared to hUCB cocultures. Both hUCB and siXIAP induced TNF-alpha-mediated apoptosis in glioma cells, which was confirmed by TUNEL assay, FACS analyses and immunoblotting. Apoptosis is characterized by loss of mitochondrial membrane potential and upregulation of mitochondrial apoptotic protein BAD. Cell death of glioma cells is marked by downregulation of Akt and phospho-Akt molecules. Taken together, our results indicate the therapeutic potential of XIAP and hUCB in treating malignant gliomas.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3323.

Neuronal apoptosis is inhibited by cord blood stem cells after spinal cord injury

Spinal cord injury (SCI) induces a series of endogenous biochemical changes that lead to secondary damage involving apoptosis as one of the major events. To understand the molecular basis of apoptosis after spinal cord injury, we subjected male rats to spinal cord injury using a weight drop device (NYU impactor) and evaluated the therapeutic potential of human umbilical cord blood stem cells (hUCB), which were stereotactically transplanted into the injury epicenter 1 week after SCI. We identified genes that render the adult-injured spinal cord nonconducive and the hUCB-treated spinal cord conducive to regeneration and repair at 3 weeks post-injury using an RT-PCR microarray by analyzing 84 apoptotic genes. Genes involved in inflammation and apoptosis were upregulated in injured spinal cords of rats, whereas genes involved in neuroprotection were upregulated in the hUCB-treated rats. Quantitative RT-PCR verified mRNA changes in the apoptotic genes of TNF-alpha, TNFR1, TNFR2, Fas, Lta, and CD40. Based on these results, we evaluated the role of TNF-alpha and its related apoptotic genes in neuronal death after SCI. Changes in the expression of TNF-alpha, TNFR1, and TNFR2 were observed over a period of 3 weeks post-SCI and after treatment with hUCB. Expression of P50 and P65 on neurons after SCI was efficiently downregulated by hUCB. These results were confirmed by the evaluation of apoptotic proteins of co-cultures of spinal neurons with hUCB under in-vitro conditions. The results of this study suggest that hUCB have therapeutic potential in inhibiting neuronal apoptosis during the repair of injured spinal cord.

Human umbilical cord blood stem cells upregulate matrix metalloproteinase-2 in rats after spinal cord injury

Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes involved in inflammation, wound healing and other pathological processes after neurological disorders. MMP-2 promotes functional recovery after spinal cord injury (SCI) by regulating the formation of a glial scar. In the present study, we aimed to investigate the expression and/or activity of several MMPs, after SCI and human umbilical cord blood mesenchymal stem cell (hUCB) treatment in rats with a special emphasis on MMP-2. Treatment with hUCB after SCI altered the expression of several MMPs in rats. MMP-2 is upregulated after hUCB treatment in spinal cord injured rats and in spinal neurons injured either with staurosporine or hydrogen peroxide. Further, hUCB induced upregulation of MMP-2 reduced formation of the glial scar at the site of injury along with reduced immunoreactivity to chondroitin sulfate proteoglycans. Blockade of MMP-2 activity in hUCB cocultured injured spinal neurons reduced the protection offered by hUCB which indicated the involvement of MMP-2 in the neuroprotection offered by hUCB. Based on these results, we conclude that hUCB treatment after SCI upregulates MMP-2 levels and reduces the formation of the glial scar thereby creating an environment suitable for endogenous repair mechanisms.

Stem cells downregulate the elevated levels of tissue plasminogen activator in rats after spinal cord injury

We investigated the involvement of tPA after SCI in rats and effect of treatment with human umbilical cord blood derived stem cells. tPA expression and activity were determined in vivo after SCI in rats and in vitro in rat embryonic spinal neurons in response to injury with staurosporine, hydrogen peroxide and glutamate. The activity and/or expression of tPA increased after SCI and reached peak levels on day 21 post-SCI. Notably, the tPA mRNA activity was upregulated by 310-fold compared to controls on day 21 post-SCI. As expected, MBP expression is minimal at the time of peak tPA activity and vice versa. Implantation of hUCB after SCI resulted in the downregulation of elevated tPA activity/expression in vivo in rats as well as in vitro in spinal neurons. Our results demonstrated the involvement of tPA in the secondary pathogenesis after SCI as well as the therapeutic potential of hUCB.

Neuroprotection by cord blood stem cells against glutamate-induced apoptosis is mediated by Akt pathway

The neurotransmitter glutamate mediates excitatory synaptic transmission in the brain and spinal cord. In pathological conditions massive glutamate release reaches near millimolar concentrations in the extracellular space and contributes to neuron degeneration and death. In the present study, we demonstrate a neuroprotective role for human umbilical cord blood stem cells (hUCB) against glutamate-induced apoptosis in cultured rat cortical neurons. Microarray analysis shows the upregulation of stress pathway genes after glutamate toxicity of neurons, while in cocultures with hUCB, survival pathway genes were upregulated. Real time-PCR analysis shows the expression of genes for NMDA receptors after glutamate toxicity in neurons. The neuroprotection of hUCB against glutamate toxicity is similar to the application of the glutamate receptor antagonist MK-801. Cocultures of hUCB protected neurons against glutamate-induced apoptosis as revealed by APO-BrdU TUNEL and FACS analyses. Immunoblot analysis shows that apoptosis is mediated by the cleavage of caspase-3 and caspase-7 in glutamate treated neurons. Cocultures with hUCB indicate the upregulation of Akt signaling pathway to protect neurons. Blocking of the Akt pathway by a dominant-negative Akt and using Akt-inhibitor IV, we confirm that the mechanism underlying hUCB neuroprotection involves activation of Akt signaling pathway. These results suggest the neuroprotective potential of hUCB against glutamate-induced apoptosis of cultured cortical neurons.

Umbilical cord blood stem cell mediated downregulation of fas improves functional recovery of rats after spinal cord injury

Human umbilical cord blood stem cells (hUCB), due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, represent a potentially useful source for cell-based therapies after spinal cord injury (SCI). To evaluate their therapeutic potential, hUCB were stereotactically transplanted into the injury epicenter, one week after SCI in rats. Our results show the presence of a substantial number of surviving hUCB in the injured spinal cord up to five weeks after transplantation. Three weeks after SCI, apoptotic cells were found especially in the dorsal white matter and gray matter, which are positive for both neuron and oligodendrocyte markers. Expression of Fas on both neurons and oligodendrocytes was efficiently downregulated by hUCB. This ultimately resulted in downregulation of caspase-3 extrinsic pathway proteins involving increased expression of FLIP, XIAP and inhibition of PARP cleavage. In hUCB-treated rats, the PI3K/Akt pathway was also involved in antiapoptotic actions. Further, structural integrity of the cytoskeletal proteins alpha-tubulin, MAP2A&2B and NF-200 has been preserved in hUCB treatments. The behavioral scores of hind limbs of hUCB-treated rats improved significantly than those of the injured group, showing functional recovery. Taken together, our results indicate that hUCB-mediated downregulation of Fas and caspases leads to functional recovery of hind limbs of rats after SCI.

Axonal remyelination by cord blood stem cells after spinal cord injury

Human umbilical cord blood stem cells (hUCB) hold great promise for therapeutic repair after spinal cord injury (SCI). Here, we present our preliminary investigations on axonal remyelination of injured spinal cord by transplanted hUCB. Adult male rats were subjected to moderate SCI using NYU Impactor, and hUCB were grafted into the site of injury one week after SCI. Immunohistochemical data provides evidence of differentiation of hUCB into several neural phenotypes including neurons, oligodendrocytes and astrocytes. Ultrastructural analysis of axons reveals that hUCB form morphologically normal appearing myelin sheaths around axons in the injured areas of spinal cord. Colocalization studies prove that oligodendrocytes derived from hUCB secrete neurotrophic hormones neurotrophin-3 (NT3) and brain-derived neurotrophic factor (BDNF). Cord blood stem cells aid in the synthesis of myelin basic protein (MBP) and proteolipid protein (PLP) of myelin in the injured areas, thereby facilitating the process of remyelination. Elevated levels of mRNA expression were observed for NT3, BDNF, MBP and PLP in hUCB-treated rats as revealed by fluorescent in situ hybridization (FISH) analysis. Recovery of hind limb locomotor function was also significantly enhanced in the hUCB-treated rats based on Basso-Beattie-Bresnahan (BBB) scores assessed 14 days after transplantation. These findings demonstrate that hUCB, when transplanted into the spinal cord 7 days after weight-drop injury, survive for at least 2 weeks, differentiate into oligodendrocytes and neurons, and enable improved locomotor function. Therefore, hUCB facilitate functional recovery after moderate SCI and may prove to be a useful therapeutic strategy to repair the injured spinal cord.

Mesenchymal stem cells from rat bone marrow downregulate caspase-3-mediated apoptotic pathway after spinal cord injury in rats

Mesenchymal stem cells have been intensively studied for their potential use in reparative strategies for neurodegenerative diseases and traumatic injuries. We used mesenchymal stem cells (rMSC) from rat bone marrow to evaluate the therapeutic potential after spinal cord injury (SCI). Immunohistochemistry confirmed a large number of apoptotic neurons and oligodendrocytes in caudal segments 2 mm away from the lesion site. Expression of caspase-3 on both neurons and oligodendrocytes after SCI was significantly downregulated by rMSC. Caspase-3 downregulation by rMSC involves increased expression of FLIP and XIAP in the cytosol and inhibition of PARP cleavage in the nucleus. Animals treated with rMSC had higher Basso, Beattie, Bresnahan (BBB) locomotor scoring and better recovery of hind limb sensitivity. Treatment with rMSC had a positive effect on behavioral outcome and histopathological assessment after SCI. The ability of rMSC to incorporate into the spinal cord, differentiate and to improve locomotor recovery hold promise for a potential cure after SCI.

Role of protein kinase C-mediated protein phosphorylation in mitochondrial translocation of mouse CYP1A1, which contains a non-canonical targeting signal

A large number of mitochondrial proteins lack canonical mitochondrial-targeting signals. The bimodal transport of cytochromes P450 (CYPs) to endoplasmic reticulum and mitochondria (MT), reported previously by us, likely represents one mode of non-canonical protein targeting to MT. Herein, we have studied the mechanism of mouse MT-CYP1A1 targeting to gain insight into the regulatory features and evolutionary conservation of bimodal targeting mechanism. Mouse MT-CYP1A1 consists of two NH2-terminal-truncated molecular species, +91A1 and +331A1. Mutations Pro-2 --> Leu and Tyr-5 --> Leu, which increase the signal recognition particle (SRP) binding, diminished MT targeting of the protein in intact cells. By contrast, mutations Leu-7 --> Asn and Leu-17 --> Asn, which decreased SRP-binding affinity, enhanced MT targeting, thus suggesting that SRP binding is an important regulatory step that modulates bimodal targeting. Protein kinase C (PKC)-mediated phosphorylation of nascent chains at Thr-35 vastly decreased affinity for SRP binding suggesting an important regulatory step. In support of these results, COS cell transfection experiments show that phosphomimetic mutation Thr-35 --> Asp or induced cellular PKC caused increased CYP1A1 targeting to MT and correspondingly lower levels to the endoplasmic reticulum. Results suggest evolutionary conservation of chimeric signals and bimodal targeting of CYP1A1 in different species. The mouse MT-CYP1A1 is an extrinsic membrane protein, which exhibited high FDX1 plus FDXR-mediated N-demethylation of a number of tricyclic antidepressants, pain killers, anti-psychotics, and narcotics that are poor substrates for microsomal CYP1A1.

A binding site for the kringle II domain of prothrombin in the apple 1 domain of factor XI

Previously we defined binding sites for high molecular weight kininogen (HK) and thrombin in the Apple 1 (A1) domain of factor XI (FXI). Since prothrombin (and Ca(2+)) can bind FXI and can substitute for HK (and Zn(2+)) as a cofactor for FXI binding to platelets, we have attempted to identify a prothrombin-binding site in FXI. The recombinant A1 domain (rA1, Glu(1)-Ser(90)) inhibited the saturable, specific and reversible binding of prothrombin to FXI, whereas neither the rA2 domain (Ser(90)-Ala(181)), rA3 domain (Ala(181)-Val(271)), nor rA4 domain (Phe(272)-Glu(361)) inhibited prothrombin binding to FXI. Kinetic binding studies using surface plasmon resonance showed binding of FXI (K(d) approximately 71 nm) and the rA1 domain (K(d) approximately 239 nm) but not rA2, rA3, or rA4 to immobilized prothrombin. Reciprocal binding studies revealed that synthetic peptides (encompassing residues Ala(45)-Ser(86)) containing both HK- and thrombin-binding sites, inhibit (125)I-rA1 (Glu(1)-Ser(90)) binding to prothrombin, (125)I-prothrombin binding to FXI, and (125)I-prothrombin fragment 2 (Ser(156)-Arg(271)) binding to FXI. However, homologous prekallikrein-derived peptides (encompassing Pro(45)-Gly(86)) did not inhibit FXI rA1 binding to prothrombin. The peptides Ala(45)-Arg(54), Phe(56)-Val(71), and Asp(72)-Ser(86), derived from sequences of the A1 domain of FXI, acted synergistically to inhibit (125)I-rA1 binding to prothrombin. Mutant rA1 peptides (V64A and I77A), which did not inhibit FXI binding to HK, retained full capacity to inhibit rA1 domain binding to prothrombin, and mutant rA1 peptides Ala(45)-Ala(54) (D51A) and Val(59)-Arg(70) (E66A), which did not inhibit FXI binding to thrombin, retained full capacity to inhibit rA1 domain binding to prothrombin. Thus, these experiments demonstrate that a prothrombin binding site exists in the A1 domain of FXI spanning residues Ala(45)-Ser(86) that is contiguous with but separate and distinct from the HK- and thrombin-binding sites and that this interaction occurs through the kringle II domain of prothrombin.

Distribution of leukotriene B4 receptors in human hematopoietic cells

Leukotriene B4 (LTB4), a product of arachidonic acid metabolism, plays an important role in inflammatory responses. We have cloned from human erythroleukemia cells, a G protein-coupled receptor, designated P2Y(7), which was later identified as the receptor for LTB4 (B-LTR). We have investigated the distribution of LTB4 receptors in various hematopoietic cells. Northern blotting and reverse transcription-coupled polymerase chain reaction (RT-PCR) analyses using radiolabeled LTB4 receptor cDNA as a probe indicated the presence of LTB4 receptor mRNA in peripheral blood leukocytes but not in platelets. Flow cytometry analysis of peripheral blood cells using specific LTB4 receptor antibodies revealed that monocytes, granulocytes, and lymphocytes, but not platelets, express LTB4 receptors. RT-PCR-Southern hybridization analysis revealed that peripheral blood leukocytes and human umbilical vein endothelial cells express the LTB4 receptor. Of the hematopoietic cell lines tested, promonocytic U937 cells, promyelocytic HL-60 cells, K562 cells, and human erythroleukemia cells express the LTB4 receptor. These results suggest a physiological role for the LTB4 receptor in the stimulation of monocytes, neutrophils, and endothelial cells.

Computer-based oral health records on the World Wide Web

Recently, the World Wide Web has emerged as a platform for computer-based oral health records. Web-based patient records can make teledentistry an instant reality. Because an increasing number of dental care providers can access Web pages, traditional barriers to exchanging information are dropping. Web-based records also make cumulative, longitudinal patient records possible. Sophisticated security mechanisms can ensure the integrity and confidentiality of patient information. Because Web-based systems are simpler to install and configure, the cost of operating them may be reduced. However, their development is complex, difficult, and expensive because the Web was not developed as a programming environment. Furthermore, the technologies underlying the Web are constantly evolving, forcing developers to continuously reengineer their systems. In addition, several policy questions, such as storage of and access to computer-based patient records, have to be answered. This article describes CMSWeb, a Web-based clinical information system implemented at Temple University School of Dentistry.

Distribution of P2Y receptor subtypes on haematopoietic cells

1. RT-PCR-southern hybridization analyses with radiolabelled P2Y receptor cDNAs as probes indicated that the peripheral blood leukocytes and the human umbilical vein endothelial cells express P2Y1, P2Y2, P2Y4 and P2Y6 receptors. 2. Of the haematopoietic cell lines tested, promonocytic U937 cells express P2Y2 and P2Y6, but not P2Y1 or P2Y4; promyelocytic HL-60 cells express the P2Y1, P2Y2 and P2Y6 receptors but not the P2Y4 receptor; K562 cells express P2Y1 but not P2Y2, P2Y4 or P2Y6; and Dami cells express P2Y1, P2Y2, P2Y4 and P2Y6 receptors. 3. Of the peripheral blood leukocytes tested, polymorphonuclear cells express P2Y4 and P2Y6 but not P2Y1 or P2Y2 receptors; monocytes express P2Y1, P2Y2, P2Y4 and P2Y6 receptors and lymphocytes express P2Y1, P2Y2, P2Y4 and P2Y6 receptors. 4. These results suggest a physiological role for different P2Y receptor subtypes in the extracellular nucleotide-mediated stimulation of monocytes, neutrophils, lymphocytes and endothelial cells.