Investigation of multipotent postnatal stem cells from human periodontal ligament

BACKGROUND

Periodontal diseases that lead to the destruction of periodontal tissues--including periodontal ligament (PDL), cementum, and bone--are a major cause of tooth loss in adults and are a substantial public-health burden worldwide. PDL is a specialised connective tissue that connects cementum and alveolar bone to maintain and support teeth in situ and preserve tissue homoeostasis. We investigated the notion that human PDL contains stem cells that could be used to regenerate periodontal tissue.

METHODS

PDL tissue was obtained from 25 surgically extracted human third molars and used to isolate PDL stem cells (PDLSCs) by single-colony selection and magnetic activated cell sorting. Immunohistochemical staining, RT-PCR, and northern and western blot analyses were used to identify putative stem-cell markers. Human PDLSCs were transplanted into immunocompromised mice (n=12) and rats (n=6) to assess capacity for tissue regeneration and periodontal repair. Findings PDLSCs expressed the mesenchymal stem-cell markers STRO-1 and CD146/MUC18. Under defined culture conditions, PDLSCs differentiated into cementoblast-like cells, adipocytes, and collagen-forming cells. When transplanted into immunocompromised rodents, PDLSCs showed the capacity to generate a cementum/PDL-like structure and contribute to periodontal tissue repair.

INTERPRETATION

Our findings suggest that PDL contains stem cells that have the potential to generate cementum/PDL-like tissue in vivo. Transplantation of these cells, which can be obtained from an easily accessible tissue resource and expanded ex vivo, might hold promise as a therapeutic approach for reconstruction of tissues destroyed by periodontal diseases.

SHED: stem cells from human exfoliated deciduous teeth

To isolate high-quality human postnatal stem cells from accessible resources is an important goal for stem-cell research. In this study we found that exfoliated human deciduous tooth contains multipotent stem cells [stem cells from human exfoliated deciduous teeth (SHED)]. SHED were identified to be a population of highly proliferative, clonogenic cells capable of differentiating into a variety of cell types including neural cells, adipocytes, and odontoblasts. After in vivo transplantation, SHED were found to be able to induce bone formation, generate dentin, and survive in mouse brain along with expression of neural markers. Here we show that a naturally exfoliated human organ contains a population of stem cells that are completely different from previously identified stem cells. SHED are not only derived from a very accessible tissue resource but are also capable of providing enough cells for potential clinical application. Thus, exfoliated teeth may be an unexpected unique resource for stem-cell therapies including autologous stem-cell transplantation and tissue engineering.

Induction of apoptosis in fibroblasts by IL-1 beta-converting enzyme, a mammalian homolog of the C. elegans cell death gene ced-3

The mammalian interleukin-1 beta-converting enzyme (ICE) has sequence similarity to the C. elegans cell death gene ced-3. We show here that overexpression of the murine ICE (mICE) gene or of the C. elegans ced-3 gene causes Rat-1 cells to undergo programmed cell death. Point mutations in a region homologous between mICE and CED-3 eliminate the ability of mICE and ced-3 to cause cell death. The cell death caused by mICE can be suppressed by overexpression of the crmA gene, a specific inhibitor of ICE, as well as by bcl-2, a mammalian oncogene that can act to prevent programmed cell death. Our results suggest that ICE may function during mammalian development to cause programmed cell death.

Ich-1, an Ice/ced-3-related gene, encodes both positive and negative regulators of programmed cell death

We report here the isolation and characterization of Ich-1, a gene related to the C. elegans cell death gene ced-3 and the mammalian homolog of ced-3, interleukin-1 beta-converting enzyme (ICE). Alternative splicing results in two distinct Ich-1 mRNA species. One mRNA species encodes a protein product of 435 amino acids (ICH-1L) that is homologous to both the P20 and P10 subunits of ICE (27% identity) and the entire CED-3 protein (28% identity). The other mRNA encodes a 312 amino acid truncated version of ICH-1L protein (ICH-1S). Overexpression of IchL induces programmed cell death, suggesting that Ich-1 is also a mammalian programmed cell death gene. More interestingly, overexpression of the Ich-1S suppresses Rat-1 cell death induced by serum deprivation. These observations suggest that Ich-1 plays an important role in both positive and negative regulation of programmed cell death in vertebrate animals.

Enhanced expression of PAI-1 in visceral fat: possible contributor to vascular disease in obesity

The presence of obesity increases the risk of thrombotic vascular diseases. The role of fat accumulation and its effect on plasminogen activator inhibitor-1 (PAI-1) levels was investigated in humans and animals. Plasma PAI-1 levels were closely correlated with visceral fat area but not with subcutaneous fat area in human subjects. PAI-1 mRNA was detected in both types of fat tissue in obese rats but increased only in visceral fat during the development of obesity. These data suggest that an enhanced expression of the PAI-1 gene in visceral fat may increase plasma levels and may have a role in the development of vascular disease in visceral obesity.

Murine caspase-11, an ICE-interacting protease, is essential for the activation of ICE

We report here the inactivation of a member of the Ice/Ced-3 (caspase) family of cell death genes, casp-11, by gene targeting. Like Ice-deficient mice, casp-11 mutant mice are resistant to endotoxic shock induced by lipopolysaccharide. Production of both IL-1alpha and IL-1beta after lipopolysaccharide stimulation, a crucial event during septic shock and an indication of ICE activation, is blocked in casp-11 mutant mice. casp-11 mutant embryonic fibroblast cells are resistant to apoptosis induced by overexpression of ICE. Furthermore, we found that pro-caspase-11 physically interacts with pro-ICE in cells, and the expression of casp-11 is essential for activation of ICE. Our data suggest that caspase-11 is a component of ICE complex and is required for the activation of ICE.

Accumulated chromosomal instability in murine bone marrow mesenchymal stem cells leads to malignant transformation

Despite recent emerging evidence suggesting that cancer stem cells subsist in a variety of tumors, it is not yet fully elucidated whether postnatal stem cells are directly involved in tumorigenesis. We used murine bone marrow-derived mesenchymal stem cells (BMMSCs) as a model to test a hypothesis that tumorigenesis may originate from spontaneous mutation of stem cells. In this study, we demonstrated that murine BMMSCs, after numerous passages, obtained unlimited population doublings and proceeded to a malignant transformation state, resulting in fibrosarcoma formation in vivo. Transformed BMMSCs colonized to multiple organs when delivered systemically through the tail vein. Fibrosarcoma cells formed by transformed BMMSCs contained cancer progenitors, which were capable of generating colony clusters in vitro and fibrosarcoma in vivo by the second administration. The mechanism by which BMMSCs transformed to malignant cells was associated with accumulated chromosomal abnormalities, gradual elevation in telomerase activity, and increased c-myc expression. Moreover, BMMSCs and their transformed counterpart, fibrosarcoma-forming cells, demonstrated different sensitivity to anti-cancer drugs. BMMSCs/fibrosarcoma transformation system may provide an ideal system to elucidate the mechanism of how stem cells become cancer cells and to screen anti-sarcoma drugs.

The efficacy of mesenchymal stem cells to regenerate and repair dental structures

OBJECTIVES

Identification, characterization, and potential application of mesenchymal stem cells (MSC) derived from human dental tissues.

METHODS

Dental pulp and periodontal ligament were obtained from normal human impacted third molars. The tissues were digested in collagenase/dispase to generate single cell suspensions. Cells were cultured in alpha-MEM supplemented with 20% fetal bovine serum, 2 mM l-glutamine, 100 microM l-ascorbate-2-phosphate. Magnetic and fluorescence activated cell sorting were employed to characterize the phenotype of freshly isolated and ex vivo expanded cell populations. The developmental potential of cultured cells was assessed following co-transplantation with hydroxyapetite/tricalcium phosphate (HA/TCP) particles into immunocompromised mice for 8 weeks.

RESULTS

MSC were identified in adult human dental pulp (dental pulp stem cells, DPSC), human primary teeth (stem cells from human exfoliated deciduous teeth, SHED), and periodontal ligament (periodontal ligament stem cells, PDLSC) by their capacity to generate clongenic cell clusters in culture. Ex vivo expanded DPSC, SHED, and PDLSC populations expressed a heterogeneous assortment of makers associated with MSC, dentin, bone, smooth muscle, neural tissue, and endothelium. PDLSC were also found to express the tendon specific marker, Scleraxis. Xenogeneic transplants containing HA/TCP with either DPSC or SHED generated donor-derived dentin-pulp-like tissues with distinct odontoblast layers lining the mineralized dentin-matrix. In parallel studies, PDLSC generated cementum-like structures associated with PDL-like connective tissue when transplanted with HA/TCP into immunocompromised mice.

CONCLUSION

Collectively, these data revealed the presence of distinct MSC populations associated with dental structures with the potential of stem cells to regenerate living human dental tissues in vivo.

Overexpression of CNP in chondrocytes rescues achondroplasia through a MAPK-dependent pathway

Achondroplasia is the most common genetic form of human dwarfism, for which there is presently no effective therapy. C-type natriuretic peptide (CNP) is a newly identified molecule that regulates endochondral bone growth through GC-B, a subtype of particulate guanylyl cyclase. Here we show that targeted overexpression of CNP in chondrocytes counteracts dwarfism in a mouse model of achondroplasia with activated fibroblast growth factor receptor 3 (FGFR-3) in the cartilage. CNP prevented the shortening of achondroplastic bones by correcting the decreased extracellular matrix synthesis in the growth plate through inhibition of the MAPK pathway of FGF signaling. CNP had no effect on the STAT-1 pathway of FGF signaling that mediates the decreased proliferation and the delayed differentiation of achondroplastic chondrocytes. These results demonstrate that activation of the CNP-GC-B system in endochondral bone formation constitutes a new therapeutic strategy for human achondroplasia.

Founder's Award, Society for Biomaterials. Sixth World Biomaterials Congress 2000, Kamuela, HI,May 15-20, 2000. Really smart bioconjugates of smart polymers and receptor proteins

Over the past 18 years we have been deeply involved with the synthesis and applications of stimuli-responsive polymer systems, especially polymer-biomolecule conjugates. This article summarizes our work with one of these conjugate systems, specifically polymer-protein conjugates. We include conjugates prepared by random polymer conjugation to lysine amino groups, and also those prepared by site-specific conjugation of the polymer to specific amino acid sites that are genetically engineered into the known amino acid sequence of the protein. We describe the preparation and properties of thermally sensitive random conjugates to enzymes and several affinity recognition proteins. We have also prepared site-specific conjugates to streptavidin with temperature-sensitive polymers, pH-sensitive polymers, and light-sensitive polymers. The preparation of these conjugates and their many fascinating applications are reviewed in this article.

Resistance to Fas-mediated apoptosis: activation of caspase 3 is regulated by cell cycle regulator p21WAF1 and IAP gene family ILP

The death receptor Fas transduces apoptotic death signaling mediated by caspases. In the present study, human hepatoma HepG2 cells showed the Fas-mediated apoptosis mediated by caspase, especially caspase 3, only in the presence of actinomycin D. Interestingly, cytosolic proteins extracted from intact HepG2 cells induced caspase 3 inactivation. Our results reveal that this inactivation was triggered by the direct inhibition of activated caspase 3 by IAP gene family ILP. In addition, a 53 kDa protein was co-immunoprecipitated with anti-human caspase 3 antibody from intact HepG2 cells. This protein was a complex-protein of procaspase 3 and the cell cycle regulator p21WAF1 (p21). P21 bound to only procaspase 3, but not to activated caspase 3. We also demonstrate that p21 protein-loaded HepG2 cells resist to Fas-mediated apoptosis even in the presence of actinomycin D. Here we report that caspase 3 inactivation for the resistance to Fas-mediated apoptosis is induced by a procaspase 3/p21 complex formation and direct inhibition of activated caspase 3 by ILP.

Comparison of stem-cell-mediated osteogenesis and dentinogenesis

The difference between stem-cell-mediated bone and dentin regeneration is not yet well-understood. Here we use an in vivo stem cell transplantation system to investigate differential regulation mechanisms of bone marrow stromal stem cells (BMSSCs) and dental pulp stem cells (DPSCs). Elevated expression of basic fibroblast growth factor (bFGF) and matrix metalloproteinase 9 (MMP-9, gelatinase B) was found to be associated with the formation of hematopoietic marrow in BMSSC transplants, but not in the connective tissue of DPSC transplants. The expression of dentin sialoprotein (DSP) specifically marked dentin synthesis in DPSC transplants. Moreover, DPSCs were found to be able to generate reparative dentin-like tissue on the surface of human dentin in vivo. This study provided direct evidence to suggest that osteogenesis and dentinogenesis mediated by BMSSCs and DPSCs, respectively, may be regulated by distinct mechanisms, leading to the different organization of the mineralized and non-mineralized tissues.

Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis

We attempted to investigate whether vitamin K2 (menatetrenone) treatment effectively prevents the incidence of new fractures in osteoporosis. A total of 241 osteoporotic patients were enrolled in a 24-month randomized open label study. The control group (without treatment; n = 121) and the vitamin K2-treated group (n = 120), which received 45 mg/day orally vitamin K2, were followed for lumbar bone mineral density (LBMD; measured by dual-energy X-ray absorptiometry [DXA]) and occurrence of new clinical fractures. Serum level of Glu-osteocalcin (Glu-OC) and menaquinone-4 levels were measured at the end of the follow-up period. Serum level of OC and urinary excretion of deoxypyridinoline (DPD) were measured before and after the treatment. The background data of these two groups were identical. The incidence of clinical fractures during the 2 years of treatment in the control was higher than the vitamin K2-treated group (chi2 = 10.935; p = 0.0273). The percentages of change from the initial value of LBMD at 6, 12, and 24 months after the initiation of the study were -1.8 +/- 0.6%, -2.4 +/- 0.7%, and -3.3 +/- 0.8% for the control group, and 1.4 +/- 0.7%, -0.1 +/- 0.6%, and -0.5 +/- 1.0% for the vitamin K2-treated group, respectively. The changes in LBMD at each time point were significantly different between the control and the treated group (p = 0.0010 for 6 months, p = 0.0153 for 12 months, and p = 0.0339 for 24 months). The serum levels of Glu-OC at the end of the observation period in the control and the treated group were 3.0 +/- 0.3 ng/ml and 1.6 +/- 0.1 ng/ml, respectively (p < 0.0001), while the serum level of OC measured by the conventional radioimmunoassay (RIA) showed a significant rise (42.4 +/-6.9% from the basal value) in the treated group at 24 months (18.2 +/- 6.1% for the controls;p = 0.0081). There was no significant change in urinary DPD excretion in the treated group. These findings suggest that vitamin K2 treatment effectively prevents the occurrence of new fractures, although the vitamin K2-treated group failed to increase in LBMD. Furthermore, vitamin K2 treatment enhances gamma-carboxylation of the OC molecule.

Catecholaminergic polymorphic ventricular tachycardia: electrocardiographic characteristics and optimal therapeutic strategies to prevent sudden death

OBJECTIVE

To investigate the clinical outcome, ECG characteristics, and optimal treatment of catecholaminergic polymorphic ventricular tachycardia (CPVT), a malignant and rare ventricular tachycardia.

PATIENTS AND METHODS

Questionnaire responses and ECGs of 29 patients with CPVT were evaluated. Mean (SD) age of onset was 10.3 (6.1) years.

RESULTS

The initial CPVT manifestations were syncope (79%), cardiac arrest (7%), and a family history (14%). ECGs showed sinus bradycardia and a normal QTc. Mean heart rate during CPVT was 192 (30) beats/min. Most cases were non-sustained (72%), but 21% were sustained and 7% were associated with ventricular fibrillation. The morphology of CPVT was polymorphic (62%), polymorphic and bidirectional (21%), bidirectional (10%), or polymorphic with ventricular fibrillation (7%). There was 100% inducement of CPVT by exercise, 75% by catecholamine infusion, and none by programmed stimulation. No late potential was recorded. Onset was in the right ventricular outflow tract in more than half the cases. During a follow up of 6.8 (4.9) years, sudden death occurred in 24% of the patients, 7% of whom had anoxic brain damage. Autosomal dominant inheritance was seen in 8% of the patients' families. beta Blockers completely controlled CPVT in only 31% of cases. Calcium antagonists partially suppressed CPVT in autosomal dominant cases.

CONCLUSIONS

CPVT may arise in certain distinct areas but the prognosis is poor. The onset of CPVT may be an indication for an implanted cardioverter-defibrillator.

The role of the solitary and paramedian reticular nuclei in mediating cardiovascular reflex responses from carotid baro- and chemoreceptors

1. With dye-filled micro-electrodes single neurones in the medulla of anaesthetized paralysed cats were identified which: (a) fired rhythmically in synchrony with or were modulated by the cardiac cycle, and which ceased firing with occlusion of the ipsilateral common carotid artery (carotid sinus baroreceptor neurones); (b) were excited by stimulation of carotid body chemoreceptors by close intra-arterial injection of lobeline into the thyroid artery (carotid body chemoreceptor neurones).2. Twelve carotid baroreceptor neurones were identified, in thirty-three cats, nine of which were localized in the intermediate area of the nucleus of the solitary tract (NTS) within 1 mm ahead of or behind the obex; three units were located either in the parahypoglossal area or the dorsal portion of the paramedian reticular nucleus (PRN).3. Of the twenty-one carotid chemoreceptor neurones which were identified, thirteen were localized in the NTS, three in the parahypoglossal area and four in the dorsal PRN.4. Bilateral lesions of the paramedian reticular area of medulla destroying the PRN, abolished or reversed the depressor response to electrical stimulation of myelinated fibres of the carotid sinus nerve (CSN), attenuated the depressor response to carotid sinus stretch and augmented the pressor response to chemoreceptor stimulation by lobeline. Such lesions did not significantly alter the reflex heart rate responses.5. Small lesions of the NTS within an area 1 mm rostral to the obex abolished all reflex blood pressure and heart rate responses to electrical stimulation of the CSN or natural stimulation of carotid baro- or chemoreceptors.6. Baroreceptors and chemoreceptors of the CSN project both to the intermediate zone of the NTS and to more medial areas of the medulla, particularly the dorsal PRN and parahypoglossal area.7. The PRN serves to mediate the reflex depressor, but not cardio-vagal, response from myelinated baroreceptors and buffers the pressor responses from chemoreceptors; it may serve as an important area integrating cardiovascular activity descending from forebrain, brain stem and cerebellum with baroreceptor reflexes.8. Cardiovascular reflex responses arising from non-myelinated baroreceptors and all chemoreceptors are mediated by neurones in the intermediate area of the NTS.

Tau in cerebrospinal fluid: a potential diagnostic marker in Alzheimer's disease

Cerebrospinal fluid from 70 patients with Alzheimer's disease (AD) and 96 patients with non-AD neurological diseases as well as 19 normal control subjects was surveyed by sandwich enzyme-linked immunosorbent assay to quantitate levels of the microtubule-associated protein tau in cerebrospinal fluid. The tau level was significantly increased in AD patients as compared with that in patients with non-AD neurological diseases and control subjects. Increased tau levels were found irrespective of age at onset, apolipoprotein E genotype, and clinical stage. Western blots of AD cerebrospinal fluid proteins revealed two to three tau-immunoreactive bands with an apparent molecular mass between 50 and 65 kd consistent with phosphorylated cerebrospinal fluid tau. Taken together, our results suggest that cerebrospinal fluid tau might reflect the progressive accumulation of altered tau due to the progressive death of neurons in the AD brain, and that the enzyme-linked immunosorbent assay of cerebrospinal fluid tau may prove to be a reliable and early diagnostic test for AD.

Identification and characterization of Ich-3, a member of the interleukin-1beta converting enzyme (ICE)/Ced-3 family and an upstream regulator of ICE

We report here the isolation and characterization of a new member of the ice/ced-3 family of cell death genes, named ich-3. The predicted amino acid sequence of Ich-3 protein shares 54% identity with murine interleukin-1beta converting enzyme (ICE). Overexpression of ich-3 in Rat-1 and HeLa cells induces apoptosis, which can be inhibited by CrmA and Bcl-2. The mRNA and proteins of ich-3 are dramatically induced in vivo upon stimulation with lipopolysaccharide, an inducer of septic shock. The ich-3 gene product can be cleaved by cytotoxic T cells granule serine protease granzyme B, suggesting that Ich-3 may mediate apoptosis induced by granzyme B. Ich-3 does not process proIL-1beta directly but does promote proIL-1beta processing by ICE. These results suggest that Ich-3 may play a very important role in apoptosis and inflammatory responses and may be an upstream regulator of ICE.

A crucial role of caspase-3 in osteogenic differentiation of bone marrow stromal stem cells

Caspase-3 is a critical enzyme for apoptosis and cell survival. Here we report delayed ossification and decreased bone mineral density in caspase-3-deficient (Casp3(-/-) and Casp3(+/-)) mice due to an attenuated osteogenic differentiation of bone marrow stromal stem cells (BMSSCs). The mechanism involved in the impaired differentiation of BMSSCs is due, at least partially, to the overactivated TGF-beta/Smad2 signaling pathway and the upregulated expressions of p53 and p21 along with the downregulated expressions of Cdk2 and Cdc2, and ultimately increased replicative senescence. In addition, the overactivated TGF-beta/Smad2 signaling may result in the compromised Runx2/Cbfa1 expression in preosteoblasts. Furthermore, we demonstrate that caspase-3 inhibitor, a potential agent for clinical treatment of human diseases, caused accelerated bone loss in ovariectomized mice, which is also associated with the overactivated TGF-beta/Smad2 signaling in BMSSCs. This study demonstrates that caspase-3 is crucial for the differentiation of BMSSCs by influencing TGF-beta/Smad2 pathway and cell cycle progression.

Mammalian ELAV-like neuronal RNA-binding proteins HuB and HuC promote neuronal development in both the central and the peripheral nervous systems

Hu proteins are mammalian embryonic lethal abnormal visual system (ELAV)-like neuronal RNA-binding proteins that contain three RNA recognition motifs. Although Drosophila ELAV is required for the correct differentiation and survival of neurons, the roles played by the Hu genes in the mammalian nervous system remain largely unknown. To explore the in vivo functions of mouse Hu proteins, we overexpressed them in rat pheochromocytoma PC12 cells, where they induced neuronal phenotype in the absence of nerve growth factor. We have characterized the functions of various forms of mHuB and mHuC bearing point mutations or deletions. Mutants of mHuC that had amino acid exchanges in the RNP1 domain of the first or second RNA recognition motifs (RRMs) lost biologic activity as well as RNA-binding activity. In addition, the mutants containing only the third RRM failed to induce the neuronal phenotype in PC12 cells and inhibited the biologic activity of cotransfected wild-type mHuB and mHuC, thus acting as a dominant-negative form. However, these mutants could not suppress the nerve growth factor-induced differentiation of PC12 cells. Further, we misexpressed wild-type and dominant-negative Hu in E9.5 mouse embryos, by using electroporation into the neural tube at the level of the rhombencephalon. mHuB and mHuC induced the ectopic expression of neuronal markers, whereas the dominant-negative forms of mHuB and mHuC suppressed the differentiation of central nervous system motor neurons. From these results, we suggest that Hu proteins are required for neuronal differentiation in the mammalian nervous system.

Control of the cell death pathway by Dapaf-1, a Drosophila Apaf-1/CED-4-related caspase activator

We identified a Drosophila Apaf-1/CED-4 homolog gene, dapaf-1. Alternative splicing results in two dapaf-1 mRNA species, which encode distinct forms of caspase activator, Dapaf-1L (Apaf-1 type) and Dapaf-1S (CED-4 type). Distinct caspases were activated by these Dapaf-1 isoforms. Loss of Dapaf-1 function resulted in defective cytochrome c-dependent caspase activities and reduced apoptosis in embryo and in larval brain. Dapaf-1 activities were also involved in cell death induced by ectopic expression of reaper in the compound eye. These data suggest that Dapaf-1/cytochrome c-dependent cell death-inducing machinery is present in Drosophila, and the requirement of Dapaf-1/Apaf-1 in neural cell death is conserved through evolution.

Survivin initiates procaspase 3/p21 complex formation as a result of interaction with Cdk4 to resist Fas-mediated cell death

Caspase 3 is an essential death factor for the Fas-mediated cell death, and its inactivation in cells is initiated by an interaction with p21 on mitochondria or with IAP family member ILP. Survivin is also a member of IAP family and is specifically expressed during embryogenesis and in tumor cells and suppresses cell death signaling. In our current study, we demonstrated that Survivin translocation into the nucleus is dependent on Fas stimulation and cell proliferation. Survivin also interacts with the cell cycle regulator Cdk4, leading to Cdk2/Cyclin E activation and Rb phosphorylation. As a result of Survivin/Cdk4 complex formation, p21 is released from its complex with Cdk4 and interacts with mitochondrial procaspase 3 to suppress Fas-mediated cell death. Here, we propose that Survivin supports procaspase 3/p21 complex formation as a result of interaction with Cdk4 resulting in suppression of cell death signaling.

Flow-induced dilation of human coronary arterioles: important role of Ca(2+)-activated K(+) channels

BACKGROUND

Flow-induced vasodilation (FID) is a physiological mechanism for regulating coronary flow and is mediated largely by nitric oxide (NO) in animals. Because hyperpolarizing mechanisms may play a greater role than NO in the microcirculation, we hypothesized that hyperpolarization contributes importantly to FID of human coronary arterioles.

METHODS AND RESULTS

Arterioles from atria or ventricles were cannulated for videomicroscopy. Membrane potential of vascular smooth muscle cells (VSMCs) was measured simultaneously. After constriction with endothelin-1, increases in flow induced an endothelium-dependent vasodilation. Nomega-Nitro-L-arginine methyl ester 10(-4) mol/L modestly impaired FID of arterioles from patients without coronary artery disease (CAD), whereas no inhibition was seen in arterioles from patients with CAD. Indomethacin 10(-5) mol/L was without effect, but 40 mmol/L KCl attenuated maximal FID. Tetraethylammonium 10(-3) mol/L but not glibenclamide 10(-6) mol/L reduced FID. Charybdotoxin 10(-8) mol/L impaired both FID (15+/-3% versus 75+/-12%, P<0.05) and hyperpolarization (-32+/-2 mV [from -28+/-2 mV after endothelin-1] versus -42+/-2 mV [-27+/-2 mV], P<0.05). Miconazole 10(-6) mol/L or 17-octadecynoic acid 10(-5) mol/L reduced FID. By multivariate analysis, age was an independent predictor for the reduced FID. Conclusions-We conclude that shear stress induces endothelium-dependent vasodilation, hyperpolarizing VSMCs through opening Ca(2+)-activated K(+) channels in human coronary arterioles. In subjects without CAD, NO contributes to FID. NO and prostaglandins play no role in patients with CAD; rather, cytochrome P450 metabolites are involved. This is consistent with a role for endothelium-derived hyperpolarizing factor in FID of the human coronary microcirculation.