Proliferation of parathyroid cells negatively correlates with expression of parathyroid hormone-related protein in secondary parathyroid hyperplasia

BACKGROUND

Parathyroid hormone-related protein (PTHrP) is now suspected to act as an autocrine or paracrine regulator of cell growth or differentiation, although it was originally reported as a hypercalcemic substance in malignancies. This study was performed to assess the relationship between PTHrP expression and cell proliferation in human parathyroid glands.

METHODS

The localization of PTH and PTHrP was studied in 42 samples of hyperplastic parathyroid from 14 long-term hemodialysis cases with immunohistochemistry and in situ hybridization. Results were compared with proliferative activity (proliferating cell nuclear antigen index: counts of proliferating cell nuclear antigen-positive cells/100 cells). The localization of the PTH/PTHrP receptor was also examined. Ten normal glands were studied as controls.

RESULTS

In hyperplasia, cells positive for PTH, PTHrP, or both were observed immunohistochemically. The areas expressing PTHrP mRNA completely coincided with those positive for PTHrP immunohistochemically. Oxyphilic or transitional oxyphilic cells were consistently positive for PTHrP. PTH/PTHrP receptors were located in the cytoplasmic membrane in most parathyroid cells. Proliferating cell nuclear antigen-positive cells were rare in normal glands with an index of 0. 22 +/- 0.09 (mean +/- sem). They were significantly increased in hyperplastic cases but less for PTHrP-positive than for -negative cells (1.25 +/- 0.16 as compared with 7.80 +/- 0.52; P < 0.0001).

CONCLUSION

The observed low level of proliferation of PTHrP-positive cells suggests a functional role for PTHrP as a possible growth suppressor in the human parathyroid.

[Lung cancer accompanying sarcoidosis with diffuse myocardial involvement]

We describe an interesting case of adenocarcinoma of the lung accompanying sarcoidosis with diffuse myocardial involvement. A 69-year-old man had a tumor shadow on chest X-ray films of the right upper lung field. Bronchofiberscopy was performed in Jan. 1997. Because transbronchial biopsy specimens disclosed granuloma, the patient was treated with isoniazid, rifampicin, and streptomycin sulfate for tuberculosis, but did not show any improvement. In March 1997, the patient was examined by an ophthalmologist for blurred vision. He was given a diagnosis of uveitis and referred to us for evaluation because his serum ACE and lysozyme levels were elevated. Bronchofiberscopy was performed again, and a diagnosis of lung cancer accompanying sarcoidosis was made based on the findings of transbronchial biopsy and bronchoalveolar lavage. The disease progressed rapidly, and the patient died 47 days after admission. Autopsy disclosed sarcoid granulomas in cardiac muscle tissue and lung tissue. There have been very few reports on the co-existence of sarcoidosis and lung cancer, and the relationship between the two diseases is unclear.

Vulnerability to aging in the rat serotonergic system

Distributional changes of serotonergic fibers associated with aging were demonstrated immunohistochemically. Old rat brains were morphologically characterized by the presence of peculiar features of serotonergic fibers not found in the young adult brain. In 24-month-old rats, these aberrant serotonergic fibers were subdivided into two groups according to morphological alterations: type 1 fibers consisting of thin fibers with moderately enlarged varicosities, and type 2 fibers consisting of much thicker fibers that have even larger varicosities and a tortuous course. These two types of fibers were distributed differentially in the forebrain. Type 1 fibers were found mainly in the striatum and frontoparietal cortex, whereas type 2 fibers were found in the posterior cingulate cortex and dentate gyrus of the hippocampal formation. Both types of aberrant fibers were seen in amygdala, frontoparietal cortex, hypothalamus, and thalamus. In 36-month-old rats, more highly degenerating arborizations were detected, and these aberrant ramifications were classified as follows based on shape as: type 3 fibers consisting of highly arborized thin fibers with a larger number of larger varicosities, and type 4 fibers consisting of thick fibers with abundant larger varicosities. Distributional difference indicated that type 1 fibers progress into type 3 fibers, whereas type 2 develop into type 4 fibers. These findings suggest the possibility that one set of pathological fibers emanate from the dorsal raphe nucleus and the other from the median raphe. Moreover, both two sets of serotonergic fibers show age-related aberrations in their morphology over same time course.

[Three cases of pulmonary embolism incorrectly diagnosed as lung cancer]

Pulmonary embolism is commonly misdiagnosed as lung cancer, since sputum cytological tests often show atypical or malignant cells. We report three operated cases of pulmonary embolism incorrectly diagnosed as lung cancer. The first patient is a 39-year-old male with chest pain an bloody sputum. Chest x-ray revealed abnormal shadows and subsequent sputum cytological tests identified malignant cells. The second patient is a 63-year-old male with the same diagnostic pattern as the first case. The third patient is a 72-year-old male whose routine chest x-ray showed an abnormal shadow; malignant cells were identified by cytological tests on transbronchial fiberscope brushings. These three patients were histopathologically diagnosed as suffering pulmonary embolism by wedge resection under thoracotomy. When a patient has chest pain or bloody sputum with showing temporarily malignant cells on cytology, the possibility of pulmonary embolism should be taken into consideration.

[Present and future cancer risk assessment of carcinogenic heterocyclic amines in humans]

Heterocyclic amines are formed during high temperature cooking of foods such as meat and fish. Although heterocyclic amines are known mutagens and some of them are shown to be carcinogenic to experimental animals, the carcinogenic potential of heterocyclic amines in humans has yet to be established. The most important criteria in determining the relationship between heterocyclic amines and human cancers are the strength and consistency of the association, the presence of a dose-response relationship, and the biological plausibility of heterocyclic amines being human carcinogens. To date, there are too few data to evaluate the strength, consistency, and dose response of this relationship in humans. To investigate cancer risk posed by heterocyclic amines to humans, an accurate estimation of exposure is needed. Validated methods for exposure assessment of heterocyclic amines are not available. At present, without any available long-term biomarkers of heterocyclic amines, it is crucial to improve exposure assessment. Most studies concerning the cancer risk assessment of heterocyclic amines are based on the exposure levels calculated only by information on the consumption of cooked foods and the mean levels of heterocyclic amines in cooked foods. Inaccurate exposure assessment can lead to incorrect cancer risk. This review describes the present and future problems of the exposure assessment and cancer risk assessment of heterocyclic amines.

Contribution of a vascular modulator, hepatocyte growth factor (HGF), to the pathogenesis of cardiovascular disease

HGF is a mesenchyme-derived pleiotropic factor which regulates cell growth, cell motility, and morphogenesis of various types of cells, and is thus considered a humoral mediator of epithelial-mesenchymal interactions responsible for morphogenic tissue interactions during embryonic development and organogenesis. Although HGF is originally identified as a most potent mitogen for hepatocytes, HGF is also belonged to a member of endothelium-specific growth factors. Since endothelial cells are known to secrete various anti-proliferative and vasodilating factors, an agent that promotes seeding or regeneration of endothelium may have potential therapeutic value against vascular smooth muscle cell proliferation. The mitogenic action of HGF on human endothelial cells was most potent among growth factors. Moreover, the presence of local HGF system (HGF and its specific receptor, c-met) was observed in vascular cells and cardiac myocytes in vitro as well as in vivo. Production of local HGF production in vascular cells was regulated by various cytokines including transforming growth factor (TGF)-beta and Ang II. Furthermore, HGF may be therapeutic growth factors for the treatment of restenosis after angioplasty and arteriosclerosis oblerance, etc., as gene therapy. On the other hand, serum HGF concentration was significantly correlated with blood pressure. These results suggest that HGF secretion might be elevated in response to high blood pressure as a counter-system against endothelial dysfunction, and may be considered as an index of severity of hypertension. In this review, we discussed the potential role of HGF in cardiovascular disease.

B-cell lymphoma of mucosa-associated lymphoid tissue of the thymus: a report of two cases with a background of Sjögren's syndrome and monoclonal gammopathy

Two rare cases of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arising in the thymus are reported. Both patients (a 61-year-old man and a 75-year-old woman) were suffering from Sjögren's syndrome and immunoglobulin (Ig)A kappa monoclonal gammopathy. Mixed IgA-IgG cryoglobulinemia was also present in the male case. Tumor cells expressed IgA and kappa antibody reactive proteins identical with serum IgA kappa M. Moreover, we could demonstrate rearrangements of the immunoglobulin heavy and light chain genes, which supported the monoclonal origin of tumor cells. Immunological abnormalities improved after thymectomy in one case in which the tumor cells were confined to the thymus, but not the other with regional lymph node involvement, suggesting a causal role for the tumor. MALT lymphomas of the thymus thus appear to be associated with immunological disorders such as Sjögren's syndrome or monoclonal gammopathy.

Stimulatory effect of lipoprotein (a) on proliferation of human mesangial cells: role of lipoprotein (a) in renal disease

As lipoprotein (a) [Lp(a)] abnormalities would accelerate glomerular injury, we studied the effect of Lp (a) on proliferation of cultured human mesangial cells (MC). Transfection of human apo (a) gene into human hepatoma cells, HepG2 cells, producing human apo B, resulted in the formation of Lp (a), while no Lp (a) was detected in control cells. In contrast, free apo (a) was detected in the medium of apo (a)-transfected MC. Incubation of cultured medium of HepG2 cells transfected with apo (a) gene with MC resulted in a significant increase in cell number compared to control (P<0.01). In contrast, little effect of transfection of apo (a) gene directly into MC on growth of MC was observed. Of importance, addition of LDL into the medium of MC transfected with apo (a) vector resulted in a significant increase in number of MC compared to control, whereas LDL did not show any effects on MC growth. As active TGF-beta was not detected in the medium of MC, and addition of neutralizing anti-TGF-beta antibody did not alter growth of MC, Lp (a) stimulated growth of MC via the independent mechanisms from the inhibition of TGF-beta activation.

Oligonucleotide-based gene therapy for cardiovascular disease

Gene therapy is emerging as a potential strategy for the treatment of cardiovascular disease such as restenosis after angioplasty, vascular bypass graft occlusion, transplant coronary vasculopathy, homozygous familial hypercholesterolemia and cystic fibrosis, for which no known effective therapy exists. Gene therapy requires efficient in vivo gene transfer technology. During the past decade, many gene transfer methods including viral transfer techniques have been developed, and some are being applied clinically in human gene therapy studies. Molecular biology and pathophysiology of the cardiovascular system have started to emerge, and the time is ripe for the introduction of gene therapy to the management of cardiovascular disorders. In this review, we have focused on the future potential of oligonucleotide-based gene therapy for the treatment of cardiovascular disease.

Fatal hemorrhage in irradiated esophageal cancer patients

Between 1980 and 1994, 423 patients with esophageal cancer were given curative radiation therapy. Of these patients, 31 died of massive hemorrhage and were used as the subjects of analysis in this study. The incidence of massive hemorrhage in all patients was 7% (31/423). In the 31 patients who died of massive hemorrhage, 27 had local tumors and two had no tumors at hemorrhage (two unknown cases). The mean time interval from the start of radiation to hemorrhage was 9.2 months. In 9 autopsy cases the origin of hemorrhage was a tear of the aorta in 5 cases, necrotic local tumor in 3 cases and esophageal ulcer in 1 case. The positive risk factors for this complication seemed to be excess total dose, infection, metallic stent, and tracheoesophageal fistula. Chest pain or sentinel hemorrhage proceeding to massive hemorrhage was observed in about half of the patients.

Vesicle exocytosis stimulated by alpha-latrotoxin is mediated by latrophilin and requires both external and stored Ca2+

alpha-Latrotoxin (LTX) stimulates massive neurotransmitter release by two mechanisms: Ca2+-dependent and -independent. Our studies on norepinephrine secretion from nerve terminals now reveal the different molecular basis of these two actions. The Ca2+-dependent LTX-evoked vesicle exocytosis (abolished by botulinum neurotoxins) is 10-fold more sensitive to external Ca2+ than secretion triggered by depolarization or A23187; it does not, however, depend on the cation entry into terminals but requires intracellular Ca2+ and is blocked by drugs depleting Ca2+ stores and by inhibitors of phospholipase C (PLC). These data, together with binding studies, prove that latrophilin, which is linked to G proteins and inositol polyphosphate production, is the major functional LTX receptor. The Ca2+-independent LTX-stimulated release is not inhibited by botulinum neurotoxins or drugs interfering with Ca2+ metabolism and occurs via pores in the presynaptic membrane, large enough to allow efflux of neurotransmitters and other small molecules from the cytoplasm. Our results unite previously contradictory data about the toxin's effects and suggest that LTX-stimulated exocytosis depends upon the co-operative action of external and intracellular Ca2+ involving G proteins and PLC, whereas the Ca2+-independent release is largely non-vesicular.

Transcription factor decoy for nuclear factor-kappaB inhibits tumor necrosis factor-alpha-induced expression of interleukin-6 and intracellular adhesion molecule-1 in endothelial cells

BACKGROUND

Several cytokines and adhesion molecules released from endothelium play an important role in inflammation, immune responses, and probably atherogenesis.

OBJECTIVE

To determine whether the transcription factor nuclear factor-kappaB mediated expression of these genes involved in the inflammatory response of endothelial cells to tumor necrosis factor-alpha, by using transcription factor decoy oligodeoxynucleotides.

DESIGN AND METHODS

We first transfected fluorescein isothiocyanate (FITC)-labeled double-stranded oligodeoxynucleotides into endothelial cells by a cationic liposome-mediated method of gene transfer. We then confirmed that the decoy oligodeoxynucleotides could block binding of nuclear factor-kappaB to its specific cis element effectively. In addition, we transfected the reporter gene chloramphenicol acetyltransferase driven by three repeated nuclear factor-kappaB binding sequences in the promoter and enhancer region.

RESULTS

FITC-labeled oligodeoxynucleotides were detected in the nuclei of approximately 70% of the total cells. Tumor necrosis factor--stimulated expression of chloramphenicol acetyltransferase was partially inhibited by transfection of nuclear factor-kappaB decoy oligodeoxynucleotides, but not by transfection of scrambled oligodeoxynucleotides. Also nuclear factor-kappaB decoy oligodeoxynucleotides but not scrambled oligodeoxynucleotides inhibited tumor necrosis factor-induced expression of interleukin-6 and intracellular adhesion molecule-1 both at the messenger RNA and at protein level (assessed by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay).

CONCLUSION

Our results demonstrate that nuclear factor-kappaB decoy oligodeoxynucleotides transfected by cationic liposome method inhibited tumor necrosis factor--induced expression of interleukin-6 and intracellular adhesion molecule-1 in endothelial cells.

Clinical study on localization-related epilepsy in infancy without underlying disorders

A clinical study of 15 patients without underlying disorders whose first seizures occurred before 1 year of age was performed to determine the characteristics of localization-related epilepsies in infancy. The patients were retrospectively divided into two groups: the seizure-controlled group (10 patients) and the refractory group (five patients). The seizure-controlled group included patients whose seizures were controlled completely within 1 year after onset; the refractory group included all other patients. The characteristics of the refractory group were as follows: (1) interictal electroencephalography showed focal abnormalities, particularly on the left side, and (2) all of the patients exhibited developmental retardation. Even in the seizure-controlled group, 40% of the patients exhibited developmental retardation, and all of them were indistinguishable from patients with benign complex partial epilepsies in infancy at the onset of the seizures. Aggressive treatment should be re-evaluated for early-onset localization-related epilepsies.

A novel retinoic acid receptor (RAR)-selective antagonist inhibits differentiation and apoptosis of HL-60 cells: implications of RARalpha-mediated signals in myeloid leukemic cells

Retinoic acid (RA) induces HL-60 cells to differentiate terminally into mature granulocytes, which subsequently die by apoptosis. The biological effects of RA are mediated by two distinct families of transcription factors: retinoic acid receptors (RARs) and retinoid X receptors (RXRs). RARs and RXRs form heterodimers and regulate retinoid-mediated gene expression. We have recently developed a novel RAR-selective antagonist (ER27191) which prevents RAR activation by retinoids. Using this RAR-selective antagonist, and RXR and RAR agonist, we demonstrate the RAR-mediated signaling pathway is important for differentiation and apoptosis of myeloid leukemic cells. Simple activation of RXRs is not sufficient to induce apoptosis of the cells. Interestingly, the combination of the RAR-selective antagonist and 9-cis RA resulted in partial differentiation and apoptosis of HL-60 and NB4 cells, whereas the RAR antagonist completely blocked all-trans RA-induced differentiation and apoptosis of the cells. Additional experiments showed that levels of BCL-2 protein decreased during differentiation of myeloid leukemic cells. Furthermore, HL-60 cells transduced with a bcl-2 expression vector showed the same differentiation response to retinoids as did parental HL-60 cells even though apoptosis was inhibited in these bcl-2-transduced cells, suggesting that differentiation and apoptosis are regulated independently in myeloid leukemic cells.

Inhibition of intimal hyperplasia after vein grafting by in vivo transfer of human senescent cell-derived inhibitor-1 gene

The senescent cell-derived inhibitor (sdi)-1 (p21) protein has been identified as a downstream mediator of the tumor suppressor p53 in the cell cycle regulation. In this study, we focused on the function of sdi-1 gene in inhibiting vascular smooth muscle cell (VSMC) proliferation after vein grafting in a rabbit model. To test the hypothesis, we transfected human sdi-1 gene by an intra-operative approach. Accompanied by markedly increased sdi-1 protein, the significant increase in PCNA-stained VSMCs in vein grafts was inhibited by transfection of sdi-1 gene. Moreover, at 2 weeks after transfection, transfer of sdi-1 gene resulted in a significant inhibition in neointimal formation, compared with control vector. Of importance, immunohistological studies determining the expression pattern of myosin heavy isoforms, adult type specific SM2 and embryonic specific SMemb/NMHC-B, demonstrated expression of the adult phenotype of VSMCs in the neointima of sdi-1 gene-transfected vein grafts at 2 weeks after the operation, while the neointima was predominantly composed of embryonic phenotype of VSMCs in the control grafts. Overall, these results demonstrate that a single intraluminal incubation of human sdi-1 gene can result in a significant inhibition of neointimal formation after vein grafting, associated with phenotypic change of VSMCs from neonatal to adult type in a rabbit model. Inhibition of hyperplasia in a graft model by transfection of sdi-1 gene may be due to the change in VSMC phenotype from neonatal to adult, in addition to the inhibition of VSMC growth.

Potential role of a novel vascular modulator, hepatocyte growth factor (HGF), in cardiovascular disease: characterization and regulation of local HGF system

Since endothelial cells (EC) are known to secrete various anti-proliferative and vasodilating factors, an agent that promotes seeding or regeneration of EC may have potential therapeutic value against vascular smooth muscle cell (VSMC) proliferation. To seek an endothelium specific growth factor, we have focused on hepatocyte growth factor (HGF). HGF is belonged to a member of endothelium specific growth factors, whose mitogenic action on EC was most potent among growth factors. Moreover, the presence of local HGF system (HGF and its specific receptor, c-met) was observed in EC and VSMC of rat and human in vitro as well as in vivo. Production of local HGF production in vascular cells was regulated by various cytokines including transforming growth factor (TGF)-beta and angiotensin II (Ang II). Furthermore, HGF may be a therapeutic growth factor for the treatment of restenosis after angioplasty and arteriosclerosis obliterance, etc., as gene therapy. From these characteristics of HGF, we hypothesized that HGF might contribute to the protection or repair of vascular endothelial cells. Indeed, serum HGF concentration was significantly correlated with blood pressure, suggesting that HGF secretion might be elevated in response to high blood pressure as a counter-system against endothelial dysfunction. In this review, we discussed that HGF is a member of the endothelium specific growth factors whose serum concentration is significantly associated with blood pressure.

Detection of varicella-zoster virus genome in the vitreous humor from two patients with acute retinal necrosis; lacking or having a PstI cleavage site

Using polymerase chain reaction, we detected the varicella-zoster virus genome in the vitreous humor of two patients with clinically diagnosed acute retinal necrosis. One of the two cases was thought to be caused by infection with a varicella-zoster virus lacking a PstI cleavage site. We could not find any clinical differences between the two substrains. The presence of a PstI cleavage site on the varicella-zoster virus genome might not be associated with the occurrence of acute retinal necrosis.

Evaluation of fungal DNA sequence using polymerase chain reaction in infection-free vitreous humor

We evaluated the vitreous bodies from 14 clinically nonfungal infectious eyes to establish a baseline for the presence of a fungal genome using polymerase chain reaction (PCR). The vitreous samples were all PCR negative, except for one eye with chronic uveitis. Blood samples examined were all PCR negative. We concluded that fungal DNA sequences could not be amplified in vitreous specimens obtained from patients with clinically diagnosed proliferative diabetic retinopathy, macular hole, or epiretinal membrane.

[Heerfordt's syndrome remitting without corticosteroid therapy]

A 25-year-old woman presented with low-grade fever, uveitis, and bilateral swelling of the parotid glands. Her older sister had a history of sarcoidosis. A chest X-ray film showed bilateral hilar lymphadenopathy. The low-grade fever persisted after admission. Ga scintigraphy showed abnormal uptake in the parotid glands and hilar lymph nodes bilaterally. Sarcoidosis was diagnosed histologically after epithelioid cell granulomas without caseous necrosis were found in a specimen obtained by transbronchial biopsy. Heerfordt's syndrome was the final diagnosis. Six days after admission, left facial and left trigeminal nerve paralysis developed. The symptoms remitted without steroid therapy and, as of eight months after discharge there had been no evidence of recurrence.

Restoration of retinoid sensitivity by MDR1 ribozymes in retinoic acid-resistant myeloid leukemic cells

Complete remission is achieved in a high proportion of patients with acute promyelocytic leukemia (APL) after all-trans retinoic acid (RA) treatment, but most patients relapse and develop RA-resistant APL. We have previously reported that both RA-resistant HL-60 (HL-60R) and APL cells express P-glycoprotein and MDR1 transcripts; and these cells differentiate to mature granulocytes after culture with RA and P-glycoprotein antagonist. Ribozymes have been shown to be able to intercept a target RNA by catalytic activity. To address the role of MDR1 in overcoming RA-resistance in APL cells, we investigated the biologic effects of ribozymes against the MDR1 transcript in HL-60R cells. These ribozymes efficiently cleaved MDR1 mRNA at a specific site in vitro. The 196 MDR1 ribozyme was cloned into an expression vector, and stably transfected (HL-60R/196Rz) cells were obtained. Expression of MDR1 transcripts was decreased in HL-60R/196Rz cells compared with parental HL-60R and empty vector-transfected (HL-60R/neo) cells. Interestingly, RA inhibited cellular proliferation and induced differentiation of HL-60R/196Rz cells in a dose-dependent manner, suggesting reversal of drug resistance in HL-60R cells by the MDR1 ribozyme. These data are direct evidence that P-glycoprotein/MDR1 is responsible in part for acquired resistance to RA in myeloid leukemic cells. The MDR1 ribozyme may be a useful tool for investigating the biology of retinoid resistance and may have therapeutic potential for patients with RA-resistant APL.

Serum deprivation-induced apoptosis accompanied by up-regulation of p53 and bax in human aortic vascular smooth muscle cells

Vascular remodeling, which plays an important role in atherosclerosis and hypertension, is determined in large part by the balance between cell growth and cell death by apoptosis. In this study, we studied the apoptosis of human aortic vascular smooth muscle cells (VSMC) induced by serum deprivation. Serum deprivation induced apoptosis of VSMC in a time-dependent manner. Serum deprivation resulted in the up-regulation of p53 protein, compared to treatment with 10% serum (P < 0.01), suggesting that apoptosis induced by serum deprivation may be due to the up-regulation of p53. Of importance, the protein of bax, a promoter of apoptosis, was significantly increased in VSMC treated by serum deprivation compared to treatment with 10% serum (P < 0.01). Overall, these findings demonstrated that serum deprivation induced apoptosis in human aortic VSMC, accompanied by the induction of p53 and bax, suggesting that apoptosis induced by serum deprivation may be mediated by the p53-bax pathway.

Inhibition of growth of human vascular smooth muscle cells by overexpression of p21 gene through induction of apoptosis

The senescent cell-derived inhibitor (sdi)-1 protein (p21 product) has been identified as a downstream mediator of the tumor suppressor p53 in the regulation of cell cycle progression through a G1 phase checkpoint. Given the importance of cell cycle inhibition for the treatment of restenosis, in this study we focused on the function of p21 gene in inhibiting proliferation of vascular smooth muscle cells (VSMC). To test the hypothesis, we transfected human p21 gene into human aortic VSMC using hemagglutinating virus of Japan-liposome-mediated transfer. Initially, we examined the successful transfection of human p21 gene into VSMC. p21 protein was increased in VSMC transfected with p21 vector as compared with control vector. Accompanied by increased p21 protein, transfection of p21 vector resulted in a significant decrease in number of VSMC induced by 2% serum (P<.01). Although p21 has been reported to play an important role in the regulation of apoptosis in some cells, apoptosis mediated by p21 is still controversial. Therefore, we hypothesized that overexpression of p21 mediates apoptosis in human VSMC, in addition to the blockade of cell cycle progression. First, we assessed the concordance between morphologic analysis and apoptosis as determined by nuclear staining with Hoechst 33342. Cells transfected with p21 gene exhibited the characteristic features of cell shrinkage, membrane blebbing, and rounding that are typical of apoptotic death. Of greater interest, a significant increase in apoptotic cells was observed in VSMC transfected with p21 vector as compared with control vector (P<.01). These results were confirmed by the measurement of DNA fragmentation. Consistent with nuclear staining, DNA fragmentation in VSMC transfected with human p21 gene was significantly increased as compared with that in VSMC transfected with control vector (P<.05). To study the molecular mechanisms of apoptosis mediated by overexpression of p21 gene, the protein levels of bax, a promoter of apoptosis, and bcl-2, an inhibitor of apoptosis, were also measured by Western blotting. Overexpression of p21 gene significantly increased protein of bax (P<.05), whereas transfection of p21 gene did not alter bcl-2 protein. Importantly, the ratio of bax to bcl-2 was significantly increased in VSMC transfected with human p21 vector as compared with control vector (P<.05). Overall, these results demonstrated that inhibition of VSMC growth by overexpression of human p21 gene was accompanied by induction of apoptosis through an inappropriate increase in bax protein. These results suggest that regulation of cell cycle by p21 may be closely linked to programmed cell death/apoptosis in human VSMC.