Pulmonary hypertension as a risk factor for death in patients with sickle cell disease

BACKGROUND

The prevalence of pulmonary hypertension in adults with sickle cell disease, the mechanism of its development, and its prospective prognostic significance are unknown.

METHODS

We performed Doppler echocardiographic assessments of pulmonary-artery systolic pressure in 195 consecutive patients (82 men and 113 women; mean [+/-SD] age, 36+/-12 years). Pulmonary hypertension was prospectively defined as a tricuspid regurgitant jet velocity of at least 2.5 m per second. Patients were followed for a mean of 18 months, and data were censored at the time of death or loss to follow-up.

RESULTS

Doppler-defined pulmonary hypertension occurred in 32 percent of patients. Multiple logistic-regression analysis, with the use of the dichotomous variable of a tricuspid regurgitant jet velocity of less than 2.5 m per second or 2.5 m per second or more, identified a self-reported history of cardiovascular or renal complications, increased systolic blood pressure, high lactate dehydrogenase levels (a marker of hemolysis), high levels of alkaline phosphatase, and low transferrin levels as significant independent correlates of pulmonary hypertension. The fetal hemoglobin level, white-cell count, and platelet count and the use of hydroxyurea therapy were unrelated to pulmonary hypertension. A tricuspid regurgitant jet velocity of at least 2.5 m per second, as compared with a velocity of less than 2.5 m per second, was strongly associated with an increased risk of death (rate ratio, 10.1; 95 percent confidence interval, 2.2 to 47.0; P<0.001) and remained so after adjustment for other possible risk factors in a proportional-hazards regression model.

CONCLUSIONS

Pulmonary hypertension, diagnosed by Doppler echocardiography, is common in adults with sickle cell disease. It appears to be a complication of chronic hemolysis, is resistant to hydroxyurea therapy, and confers a high risk of death. Therapeutic trials targeting this population of patients are indicated.

Allogeneic hematopoietic stem-cell transplantation for sickle cell disease

BACKGROUND

Myeloablative allogeneic hematopoietic stem-cell transplantation is curative in children with sickle cell disease, but in adults the procedure is unduly toxic. Graft rejection and graft-versus-host disease (GVHD) are additional barriers to its success. We performed nonmyeloablative stem-cell transplantation in adults with sickle cell disease.

METHODS

Ten adults (age range, 16 to 45 years) with severe sickle cell disease underwent nonmyeloablative transplantation with CD34+ peripheral-blood stem cells, mobilized by granulocyte colony-stimulating factor (G-CSF), which were obtained from HLA-matched siblings. The patients received 300 cGy of total-body irradiation plus alemtuzumab before transplantation, and sirolimus was administered afterward.

RESULTS

All 10 patients were alive at a median follow-up of 30 months after transplantation (range, 15 to 54). Nine patients had long-term, stable donor lymphohematopoietic engraftment at levels that sufficed to reverse the sickle cell disease phenotype. Mean (+/-SE) donor-recipient chimerism for T cells (CD3+) and myeloid cells (CD14+15+) was 53.3+/-8.6% and 83.3+/-10.3%, respectively, in the nine patients whose grafts were successful. Hemoglobin values before transplantation and at the last follow-up assessment were 9.0+/-0.3 and 12.6+/-0.5 g per deciliter, respectively. Serious adverse events included the narcotic-withdrawal syndrome and sirolimus-associated pneumonitis and arthralgia. Neither acute nor chronic GVHD developed in any patient.

CONCLUSIONS

A protocol for nonmyeloablative allogeneic hematopoietic stem-cell transplantation that includes total-body irradiation and treatment with alemtuzumab and sirolimus can achieve stable, mixed donor-recipient chimerism and reverse the sickle cell phenotype. (ClinicalTrials.gov number, NCT00061568.)

Prevalence of neutropenia in the U.S. population: age, sex, smoking status, and ethnic differences

BACKGROUND

Benign reductions in neutrophil counts may be more common at certain ages and in certain ethnic groups and may be affected by sex and smoking status.

OBJECTIVE

To determine differences in neutrophil counts in the U.S. population according to ethnicity, age, sex, and smoking status.

DESIGN

Population-based, cross-sectional study.

SETTING

Various locations in the United States.

PARTICIPANTS

25,222 participants in the 1999 to 2004 National Health and Nutrition Examination Survey who were 1 year of age or older.

MEASUREMENTS

Complete blood counts and comparison of means and the proportion of participants with neutropenia.

RESULTS

Relative to white participants, black participants had lower leukocyte counts (mean difference, 0.89 x 10(9) cells/L; P < 0.001), lower neutrophil counts (0.83 x 10(9) cells/L; P < 0.001), and similar lymphocyte counts (0.022 x 10(9) cells/L; P = 0.36), whereas Mexican-American participants had slightly higher mean leukocyte counts (0.16 x 10(9) cells/L; P = 0.014), higher neutrophil counts (0.11 x 10(9) cells/L; P = 0.026), and higher lymphocyte counts (0.095 x 10(9) cells/L; P < 0.001). The prevalence of neutropenia (neutrophil count <1.5 x 10(9) cells/L) was 4.5% among black participants, 0.79% among white participants, and 0.38% among Mexican-American participants. The prevalence of neutropenia was higher among males and children younger than 5 years of age. Neutrophil counts less than 1.0 x 10(9) cells/L were observed in fewer than 1% of the overall sample (0.57% in black participants, 0.11% in white participants, and 0.08% in Mexican-American participants). Smoking was associated with higher leukocyte and neutrophil counts but had a smaller effect among black and Mexican-American participants than among white participants.

LIMITATION

Because estimates are based on single measures, fluctuations over time could not be determined.

CONCLUSIONS

In the United States, neutrophil counts are lower in black persons than in white persons and neutropenia is more prevalent in black persons. Neutrophil counts are slightly higher in Mexican-American persons than in white persons, and neutropenia is uncommon in both groups. The clinical implications of these findings are unclear, but they suggest that when determining the need for a diagnostic evaluation for neutropenia, clinicians should consider the patient's age, sex, ethnicity, and smoking status.

Nonmyeloablative HLA-matched sibling allogeneic hematopoietic stem cell transplantation for severe sickle cell phenotype

IMPORTANCE

Myeloablative allogeneic hematopoietic stem cell transplantation (HSCT) is curative for children with severe sickle cell disease, but toxicity may be prohibitive for adults. Nonmyeloablative transplantation has been attempted with degrees of preparative regimen intensity, but graft rejection and graft-vs-host disease remain significant.

OBJECTIVE

To determine the efficacy, safety, and outcome on end-organ function with this low-intensity regimen for sickle cell phenotype with or without thalassemia.

DESIGN, SETTING, AND PARTICIPANTS

From July 16, 2004, to October 25, 2013, 30 patients aged 16-65 years with severe disease enrolled in this nonmyeloablative transplant study, consisting of alemtuzumab (1 mg/kg in divided doses), total-body irradiation (300 cGy), sirolimus, and infusion of unmanipulated filgrastim mobilized peripheral blood stem cells (5.5-31.7 × 10(6) cells/kg) from human leukocyte antigen-matched siblings.

MAIN OUTCOMES AND MEASURES

The primary end point was treatment success at 1 year after the transplant, defined as a full donor-type hemoglobin for patients with sickle cell disease and transfusion independence for patients with thalassemia. The secondary end points were the level of donor leukocyte chimerism; incidence of acute and chronic graft-vs-host disease; and sickle cell-thalassemia disease-free survival, immunologic recovery, and changes in organ function, assessed by annual brain imaging, pulmonary function, echocardiographic image, and laboratory testing.

RESULTS

Twenty-nine patients survived a median 3.4 years (range, 1-8.6), with no nonrelapse mortality. One patient died from intracranial bleeding after relapse. As of October 25, 2013, 26 patients (87%) had long-term stable donor engraftment without acute or chronic graft-vs-host disease. The mean donor T-cell level was 48% (95% CI, 34%-62%); the myeloid chimerism levels, 86% (95% CI, 70%-100%). Fifteen engrafted patients discontinued immunosuppression medication with continued stable donor chimerism and no graft-vs-host disease. The normalized hemoglobin and resolution of hemolysis among engrafted patients were accompanied by stabilization in brain imaging, a reduction of echocardiographic estimates of pulmonary pressure, and allowed for phlebotomy to reduce hepatic iron. The mean annual hospitalization rate was 3.23 (95% CI, 1.83-4.63) the year before, 0.63 (95% CI, 0.26-1.01) the first year after, 0.19 (95% CI, 0-0.45) the second year after, and 0.11 (95% CI, 0.04-0.19) the third year after transplant. For patients taking long-term narcotics, the mean use per week was 639 mg (95% CI, 220-1058) of intravenous morphine-equivalent dose the week of their transplants and 140 mg (95% CI, 56-225) 6 months after transplant. There were 38 serious adverse events: pain and related management, infections, abdominal events, and sirolimus related toxic effects.

CONCLUSIONS AND RELEVANCE

Among 30 patients with sickle cell phenotype with or without thalassemia who underwent nonmyeloablative allogeneic HSCT, the rate of stable mixed-donor chimerism was high and allowed for complete replacement with circulating donor red blood cells among engrafted participants. Further accrual and follow-up are required to assess longer-term clinical outcomes, adverse events, and transplant tolerance.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00061568.

Hematologic responses of patients with sickle cell disease to treatment with hydroxyurea

Because fetal hemoglobin contains gammaglobin chains instead of beta chains, it is not affected by the genetic defect that causes sickle cell disease. Increased levels of fetal hemoglobin decrease the tendency toward intracellular polymerization of sickle hemoglobin that characterizes this disease. Hydroxyurea is one of several cytostatic agents that have been shown to increase the production of fetal hemoglobin in some patients with sickle cell disease. We studied the effects of hydroxyurea administration in 10 hospitalized patients with sickle cell disease, each of whom was treated for three months. Seven patients responded with a 2- to 10-fold increase in fetal hemoglobin, from a mean (+/- SD) of 1.6 +/- 1.6 percent of total hemoglobin to 6.8 +/- 4.7 percent; three patients had fetal-hemoglobin levels of 10 to 15 percent of total hemoglobin. Three did not respond to treatment. Four of the patients who responded were retreated with hydroxyurea after one to four months without treatment and were found to have larger increases in fetal-hemoglobin levels. In most patients, levels were still rising at the end of the study, even after 90 days of therapy. Fetal-hemoglobin levels tended to peak at dosages of hydroxyurea that were myelosuppressive. In the patients who responded to treatment, there were significant increases in the percentage of reticulocytes and erythrocytes containing fetal hemoglobin and in the amount of fetal hemoglobin within these cells. The percentage of dense red cells decreased in the patients who responded to treatment. The tendency toward intracellular polymerization at physiologic oxygen saturation was reduced by about 33 percent in the cells containing fetal hemoglobin, whereas there was no change in the other cells. We conclude that hydroxyurea is effective in increasing the production of fetal hemoglobin, which in this study was found to be associated with a small decrease in hemolysis and an increase in hemoglobin levels despite myelosuppression. Controlled, prospective trials are necessary to establish whether these effects will lead to clinical benefit.

Social Determinants of Racial Disparities in CKD

Significant disparities in CKD rates and outcomes exist between black and white Americans. Health disparities are defined as health differences that adversely affect disadvantaged populations, on the basis of one or more health outcomes. CKD is the complex result of genetic and environmental factors, reflecting the balance of nature and nurture. Social determinants of health have an important role as environmental components, especially for black populations, who are disproportionately disadvantaged. Understanding the social determinants of health and appreciating the underlying differences associated with meaningful clinical outcomes may help nephrologists treat all their patients with CKD in an optimal manner. Altering the social determinants of health, although difficult, may embody important policy and research efforts, with the ultimate goal of improving outcomes for patients with kidney diseases, and minimizing the disparities between groups.

Augmentation by erythropoietin of the fetal-hemoglobin response to hydroxyurea in sickle cell disease

BACKGROUND

Hydroxyurea increases the production of fetal hemoglobin in patients with sickle cell anemia, inhibiting the polymerization of hemoglobin S and potentially improving vaso-occlusive manifestations and hemolysis. Recombinant erythropoietin increases the number of reticulocytes containing fetal hemoglobin in laboratory animals and in humans. We studied whether hydroxyurea and erythropoietin might have a potentiating effect on the production of fetal hemoglobin in patients with sickle cell disease.

METHODS

We treated four patients who were receiving hydroxyurea for sickle cell disease (three who were homozygous for sickle cell anemia and one with sickle beta zero-thalassemia) with escalating doses of intravenous erythropoietin for seven weeks, along with oral iron sulfate. Doses of hydroxyurea on four consecutive days were alternated with doses of erythropoietin on three consecutive days.

RESULTS

There was a 28 percent increase in the number of reticulocytes containing fetal hemoglobin and a 48 percent increase in the percentage of fetal hemoglobin, as compared with the maximal values obtained with hydroxyurea alone. The percentage of erythrocytes containing fetal hemoglobin (F cells) increased from 64 to 78 percent. As compared with hydroxyurea alone, treatment with hydroxyurea and erythropoietin decreased the mean (+/- SD) serum indirect bilirubin level from 0.8 +/- 0.2 to 0.5 +/- 0.1 mg per deciliter (13.3 +/- 2.9 to 8.9 +/- 2.2 mumol per liter) (P = 0.02), suggesting a further decrease in hemolysis. Red-cell filterability improved.

CONCLUSIONS

Intravenous recombinant erythropoietin with iron supplementation alternating with hydroxyurea elevates fetal-hemoglobin and F-cell levels more than hydroxyurea alone. Such increases decrease intracellular polymerization of hemoglobin S and improve the overall rheologic characteristics of erythrocytes. A reduced dosage of hydroxyurea alternating with erythropoietin may prove less myelotoxic than hydroxyurea given daily or in pulsed-dose regimens. It may also increase levels of fetal hemoglobin in patients with sickle cell disease who have not been helped by hydroxyurea alone.

Nitric oxide donor properties of hydroxyurea in patients with sickle cell disease

Hydroxyurea therapy reduces the rates of vaso-occlusive crisis in patients with sickle cell anaemia and recent data suggest that hydroxyurea treatment can generate nitric oxide (NO). Nitric oxide has been proposed as a novel therapy for sickle cell disease via a number of pathways. We therefore sought to determine whether hydroxyurea has NO donor properties in patients with sickle cell anaemia and explore potential mechanisms by which NO production could be therapeutic. Venous blood was collected from 19 fasting sickle cell anaemia patients, on chronic hydroxyurea therapy, at baseline and 2 and 4 h after a single morning dose of hydroxyurea, as well as 10 patients not taking hydroxyurea. The plasma and red cell NO reaction products nitrate, nitrite and nitrosylated- haemoglobin were measured using ozone-based chemiluminescent assays (using vanadium, KI and I3- reductants respectively). Consistent with NO release from hydroxyurea, baseline levels of total nitrosylated haemoglobin increased from 300 nmol/l to 500 nmol/l (P = 0.01). Plasma nitrate and nitrite levels also significantly increased with peak levels observed at 2 h. Glutathionyl-haemoglobin levels were unchanged, while plasma secretory vascular cellular adhesion molecule-1 levels were reduced in patients taking hydroxyurea (419 +/- 40 ng/ml) compared with control patients with sickle cell anaemia (653 +/- 55 ng/ml; P = 0.003), and were inversely correlated with fetal haemoglobin levels (r = -0.72; P = 0.002). These results demonstrate that hydroxyurea therapy is associated with the intravascular and intraerythrocytic generation of NO. The role of NO in the induction of fetal haemoglobin and possible synergy between NO donor therapy and classic cytostatic and differentiating medications should be explored.

HIF prolyl hydroxylase inhibition results in endogenous erythropoietin induction, erythrocytosis, and modest fetal hemoglobin expression in rhesus macaques

The hypoxia-inducible factor (HIF) pathway is crucial in mitigating the deleterious effects of oxygen deprivation. HIF-alpha is an essential component of the oxygen-sensing mechanisms and under normoxic conditions is targeted for degradation via hydroxylation by HIF-prolyl hydroxylases. Several HIF-prolyl hydroxylase inhibitors (PHIs) induced erythropoietin (epo) expression in vitro and in mice, with peak epo expression ranging from 5.6- to 207-fold above control animals. Furthermore, several PHIs induced fetal hemoglobin (HbF) expression in primary human erythroid cells in vitro, as determined by flow cytometry. One PHI, FG-2216, was further tested in a nonhuman primate model without and with chronic phlebotomy. FG-2216 was orally bioavailable and induced significant and reversible Epo induction in vivo (82- to 309-fold at 60 mg/kg). Chronic oral dosing in male rhesus macaques was well tolerated, significantly increased erythropoiesis, and prevented anemia induced by weekly phlebotomy. Furthermore, modest increases in HbF-containing red cells and reticulocytes were demonstrated by flow cytometry, though significant increases in HbF were not demonstrated by high-pressure liquid chromatography (HPLC). HIF PHIs represent a novel class of molecules with broad potential clinical application for congenital and acquired anemias.

Periodic microcirculatory flow in patients with sickle-cell disease

We have applied the technique of laser-Doppler velocimetry to compare patterns of cutaneous blood flow in the forearms of patients with stable sickle-cell disease, with the patterns in normal subjects matched for age, race, and sex, and in patients with anemia due to beta+-thalassemia. The mean resting blood flow in the patients with sickle-cell disease was comparable to that of the control groups but was associated with large, local oscillations in flow with periods of 7 to 10 seconds and peak-to-trough magnitudes about half the mean flow. Oscillations occurred simultaneously at sites separated by 1 cm but were independent in phase and frequency. Since these laser-Doppler measurements represent the average flow pattern in about 1 mm3 of skin (i.e., in approximately 50 to 70 capillary loops), these results suggest that microcirculatory flow in patients with sickle-cell disease proceeds by synchronization of rhythmic flow in large domains of microvessels. These findings indicate that periodic flow may be a compensatory mechanism to offset the deleterious altered rheology of erythrocytes containing polymerized hemoglobin S, and suggest that laser-Doppler velocimetry may be a useful method to investigate microvascular physiology in patients with sickle-cell disease.

Identification and characterization of a novel member of olfactomedin-related protein family, hGC-1, expressed during myeloid lineage development

We have cloned a novel hematopoietic granulocyte colony-stimulating factor (G-CSF)-induced olfactomedin-related glycoprotein, termed hGC-1 (human G-CSF-stimulated clone-1). mRNA differential display was used in conjunction with a modified two-phase liquid culture system. Cultures were enriched for early precursors of erythroid, myeloid, and megakaryocytic lineages, which were isolated after induction with erythropoietin, G-CSF, and thrombopoietin, respectively. RNA from the enriched cells was subjected to differential display analysis to identify lineage-specific expressed genes. One clone specifically induced by G-CSF, hGC-1, was characterized. The 2861 bp cDNA clone of hGC-1 contained an open reading frame of 1530 nucleotides, translating into a protein of 510 amino acids with a signal peptide and six N-linked glycosylation motifs. The protein sequence of hGC-1 showed it to be a glycoprotein of the olfactomedin family, which includes olfactomedin, TIGR, Noelin-2 and latrophilin-1. Olfactomedin-like genes show characteristic tissue-restricted patterns of expression; the specific tissues expressing these genes differ among the family members. hGC-1 was strongly expressed in the prostate, small intestine, and colon, moderately expressed in the bone marrow and stomach, and not detectable in other tissues. In vitro translation and ex vivo expression showed hGC-1 to be an N-linked glycoprotein. The hGC-1 gene locus mapped to chromosome 13q14.3. Together, our findings indicate that hGC-1 is primarily expressed as an extracellular olfactomedin-related glycoprotein during normal myeloid-specific lineage differentiation, suggesting the possibility of a matrix-related function for hGC-1 in differentiation.

Thalidomide induces gamma-globin gene expression through increased reactive oxygen species-mediated p38 MAPK signaling and histone H4 acetylation in adult erythropoiesis

Although thalidomide has been shown to improve anemia in some patients with myelodysplastic syndromes and stimulates erythropoietin in patients with multiple myeloma, thalidomide's specific effects on gamma-globin gene expression during erythroid differentiation have not been studied. Here, we investigated the effects of thalidomide on gamma-globin gene expression and the involved signaling pathway using an ex vivo culture system of primary human CD34+ cells. We found that thalidomide induced gamma-globin mRNA expression in a dose-dependent manner, but had no effect on beta-globin expression. We also demonstrated that intracellular reactive oxygen species (ROS) levels were increased by treatment with thalidomide for 48 hours (from day 3 to day 5). Western blot analysis demonstrated that thalidomide activated the p38 mitogen-activated protein kinase (MAPK) signaling pathway in a time- and dose-dependent manner and increased histone H4 acetylation. Pretreatment of cells with the antioxidant enzyme catalase and the intracellular hydroxyl scavenger dimethylthiourea (DMTU) abrogated the thalidomide-induced p38 MAPK activation and histone H4 acetylation. Moreover, pretreatment with catalase and DMTU diminished thalidomide-induced gamma-globin gene expression. These data indicate that thalidomide induces increased expression of the gamma-globin gene via ROS-dependent activation of the p38 MAPK signaling pathway and histone H4 acetylation.

von Hippel-Lindau disease-associated hemangioblastomas are derived from embryologic multipotent cells

BACKGROUND

To determine the origin of the neoplastic cell in central nervous system (CNS) hemangioblastomas in von Hippel-Lindau disease (VHL) and its role in tumor formation and distribution, we characterized and differentiated neoplastic cells from hemangioblastomas removed from VHL patients.

METHODS AND FINDINGS

A total of 31 CNS hemangioblastomas from 25 VHL patients were resected and analyzed. Tumor cells from the hemangioblastomas were characterized, grown, and differentiated into multiple lineages. Resected hemangioblastomas were located in the cerebellum (11 tumors), brainstem (five tumors), and spinal cord (15 tumors). Consistent with an embryologically derived hemangioblast, the neoplastic cells demonstrated coexpression of the mesodermal markers brachyury, Flk-1 (vascular endothelial growth factor-2), and stem cell leukemia (Scl). The neoplastic cells also expressed hematopoietic stem cell antigens and receptors including CD133, CD34, c-kit, Scl, erythropoietin, and erythropoietin receptor. Under specific microenvironments, neoplastic cells (hemangioblasts) were expanded and differentiated into erythrocytic, granulocytic, and endothelial progenitors. Deletion of the wild-type VHL allele in the hematopoietic and endothelial progeny confirmed their neoplastic origin.

CONCLUSIONS

The neoplastic cell of origin for CNS hemangioblastomas in VHL patients is the mesoderm-derived, embryologically arrested hemangioblast. The hematopoietic and endothelial differentiation potential of these cells can be reactivated under suitable conditions. These findings may also explain the unique tissue distribution of tumor involvement.

Pathophysiology of sickle cell disease: role of cellular and genetic modifiers

Sickle hemoglobin (HbS), caused by a point mutation in the beta-globin gene of hemoglobin, polymerizes when deoxygenated. The pathophysiology of sickle cell disease results from cellular defects caused directly by the hemoglobin mutation interacting with the environment and many other gene products--a few known, but most yet unidentified--a typical example of epistasis. How normal tissue perfusion is interrupted is complex and why the phenotype of sickle cell disease differs from patient to patient is poorly understood. We review the "classic" aspects of the pathophysiology of sickle cell disease and focus on known and potential modulators of the phenotype of this disorder.

Inhaled nitric oxide augments nitric oxide transport on sickle cell hemoglobin without affecting oxygen affinity

Nitric oxide (NO) inhalation has been reported to increase the oxygen affinity of sickle cell erythrocytes. Also, proposed allosteric mechanisms for hemoglobin, based on S-nitrosation of beta-chain cysteine 93, raise the possibility of altering the pathophysiology of sickle cell disease by inhibiting polymerization or by increasing NO delivery to the tissue. We studied the effects of a 2-hour treatment, using varying concentrations of inhaled NO. Oxygen affinity, as measured by P(50), did not respond to inhaled NO, either in controls or in individuals with sickle cell disease. At baseline, the arterial and venous levels of nitrosylated hemoglobin were not significantly different, but NO inhalation led to a dose-dependent increase in mean nitrosylated hemoglobin, and at the highest dosage, a significant arterial-venous difference emerged. The levels of nitrosylated hemoglobin are too low to affect overall hemoglobin oxygen affinity, but augmented NO transport to the microvasculature seems a promising strategy for improving microvascular perfusion.

Percutaneous transluminal in vivo gene transfer by recombinant adenovirus in normal porcine coronary arteries, atherosclerotic arteries, and two models of coronary restenosis

BACKGROUND

Gene therapy has been proposed as a possible solution to the problem of restenosis after coronary angioplasty. The current study was undertaken to assess conventional methods of gene transfer and to develop percutaneous techniques for introducing genes directly into the coronary arteries of large mammals. Since the anticipated targets of gene therapy against restenosis include atherosclerotic and previously instrumented arteries, we also evaluated gene transfer in atherosclerotic coronary arteries and in two porcine models of restenosis: one using intracoronary stents and a second using balloon overstretch angioplasty.

METHODS AND RESULTS

The conventional method of using perforated balloon catheters to deliver Lipofectin-DNA complexes directly into the coronary arteries of intact animals was applied to 18 porcine coronary arteries including normal arteries, hypercholesterolemic arteries, and those simulating restenosis. The results of this study were consistent with previously published results indicating that only low levels of luciferase gene expression could be obtained by Lipofectin-mediated gene transfer. We therefore undertook a second, parallel study to evaluate percutaneous transluminal in vivo gene transfer using a replication-deficient adenoviral vector. A comparison of the two studies revealed that the mean level of reporter gene expression in the cohort undergoing adenoviral infection was 100-fold higher than in the cohort undergoing Lipofection. Analysis of luciferase activity over time in normal arteries revealed that recombinant gene expression was half-maximal after 1 day, peaked within 1 week, was still half-maximal at 2 weeks, and declined to low levels by 4 weeks. Histochemical analysis of coronary arteries treated with a second adenovirus expressing a nuclear-localized beta-galactosidase gene demonstrated gene transfer to a limited number of cells in the media and adventitia. Immunohistochemical analysis of Ad5-infused arteries using a monoclonal antibody directed against CD44 identified a periadventitial infiltrate composed of leukocytes.

CONCLUSIONS

The recombinant adenoviral vectors proved to be far more effective than Lipofectin at delivering foreign genes directly into the coronary arteries of living mammals. Furthermore, the influences of hypercholesterolemia and arterial injury appeared to have little effect on the levels of gene expression obtained using either method. The results demonstrate that low-level recombinant gene expression, the major obstacle impeding gene therapy for the prevention of restenosis, can potentially be overcome by using adenoviral vectors to mediate coronary gene transfer in vivo. The duration of gene expression provided by these vectors and their effective deployment in atherosclerotic, balloon-overstretched, and stented coronary arteries suggest that recombinant adenovirus may have potential for evaluating gene therapy in the clinically informative porcine models of coronary restenosis.

Sparing effect of hemoglobin F and hemoglobin A2 on the polymerization of hemoglobin S at physiologic ligand saturations

Recent interest in therapies for sickle cell anemia based on elevating fetal Hb has made accurate estimates of the sparing effect of fetal Hb (Hb F) and other non-sickle Hbs on sickle Hb (Hb S) polymerization essential. We have developed a technique, using HbCO as surrogate for HbO2, that enables us to assess the solubility of Hb S as a function of ligand saturation under conditions that mimic those of the sickling disorders. Equimolar mixtures of unliganded Hb S with Hb F or normal Hb A2 were isosoluble. Solubilities for equimolar mixtures with normal (Hb A) or abnormal (Hb C) Hbs were also identical but were lower than in the prior case. Thus, the sparing effect of both Hb F and Hb A2 should be considered in therapeutic strategies designed to modify Hb S polymerization. Hemolysates, stripped of 2,3-bisphosphoglycerate, from sickle cell disease patients with Hb (F + A2) levels varying from 6 to 25%, as well as from a sickle trait individual, were used to evaluate equilibrium solubility as a function of ligand saturation over the range of pathophysiologic interest (25-70%). Our results show that the sparing effect of Hb (F + A2) increases relative to that of Hb A as ligand saturation increases, and that in the absence of ligand, approximately 30% Hb (F + A2) is essentially isosoluble with the 60% Hb A of sickle trait. Although detailed knowledge of expected therapeutic benefits is confounded by the heterogeneity of Hb F distribution and other variables, these data should provide a framework for estimating likely clinical benefit from pharmacologic efforts to modulate globin gene expression.

Two-phase liquid culture system models normal human adult erythropoiesis at the molecular level

We have studied the patterns of expression of various genes during maturation of normal human adult erythroid precursors cultured in a two-phase liquid culture method. In the first phase, peripheral blood mononuclear cells are cultured for one week in the presence of a combination of growth factors, but not erythropoietin (Epo). In Phase II, Epo is included in the medium. Cell samples were taken throughout phase II, and expression of globins, transcription factors, and cytokine receptors was assayed by RT-PCR and quantified by phosphor imaging. We have divided phase II into stages: early (days 0-5), intermediate (days 6-10) and late (days 11-15) and measured maximum expression of each gene. During early phase II, gamma-globin, Spl, and GATA-2 mRNAs were expressed at their highest levels. As the cells matured during the intermediate period, GATA-2 levels remained high, and then declined, while the transcription factors GATA-1, EKLF, NF-E2, and the Epo receptor (EpoR) reached maximum expression. In late phase II, beta-globin increased and reached its maximum level of expression. This erythroid culture system appears to recapitulate normal adult erythropoiesis at the molecular level, and thus may be a suitable model to examine the molecular basis of severe congenital or acquired disorders of erythropoiesis.

Olfactomedin 4 inhibits cathepsin C-mediated protease activities, thereby modulating neutrophil killing of Staphylococcus aureus and Escherichia coli in mice

Neutrophils kill bacteria generally through oxidative and nonoxidative mechanisms. Whereas much research has focused on the enzymes essential for neutrophil killing, little is known about the regulatory molecules responsible for such killing. In this study, we investigated the role of olfactomedin 4 (OLFM4), an olfactomedin-related glycoprotein, in neutrophil bactericidal capability and host innate immunity. Neutrophils from OLFM4⁻/⁻ mice have increased intracellular killing of Staphylococcus aureus and Escherichia coli in vitro. The OLFM4⁻/⁻ mice have enhanced in vivo bacterial clearance and are more resistant to sepsis when challenged with S. aureus or E. coli by i.p. injection. OLFM4 was found to interact with cathepsin C, a cysteine protease that plays an important role in bacterial killing and immune regulation. We demonstrated that OLFM4 inhibited cathepsin C activity in vitro and in vivo. The cathepsin C activity in neutrophils from OLFM4⁻/⁻ mice was significantly higher than that in neutrophils from wild-type littermate mice. The activities of three serine proteases (neutrophil elastase, cathepsin G, and proteinase 3), which require cathepsin C activity for processing and maturity, were also significantly higher in OLFM4⁻/⁻ neutrophils. The bacterial killing and clearance capabilities observed in OLFM4⁻/⁻ mice that were enhanced relative to wild-type mice were significantly compromised by the additional loss of cathepsin C in mice with OLFM4 and cathepsin C double deficiency. These results indicate that OLFM4 is an important negative regulator of neutrophil bactericidal activity by restricting cathepsin C activity and its downstream granule-associated serine proteases.

The glycoprotein hGC-1 binds to cadherin and lectins

Human granulocyte colony stimulating factor stimulated clone-1 (hGC-1, also known as GW112, OLM4, and hOlfD) is an olfactomedin-related glycoprotein of unknown function. We performed a series of biochemical studies to characterize its function. Using hGC-1 purified from baculovirus Sf9 cells we demonstrated that hGC-1 is a secreted glycoprotein containing N-linked carbohydrate chains and forms disulfide-bonded multimers. It binds to cell surfaces and to the locutions ricinus communis agglutinin I, concanavalin A and wheat germ agglutinin. Purified hGC-1 enhanced NIH3T3 and 293T/17 cell spreading and attachment, as did hGC-1-enriched culture supernatants of 293T/17 cells transfected with an hGC-1 expression vector. Coimmunoprecipitation studies demonstrated that hGC-1 interacts with cadherin in 293T/17 cells. This interaction depends on the C-terminal olfactomedin domain, but does not require the five well-conserved cysteine residues. However, cysteine residues at 83, 85, 246 and 437 are essential for secretion, and cysteine 226 is critical for hGC-1 multimer formation. Our studies demonstrated that hGC-1, an extracellular matrix glycoprotein, facilitates cell adhesion. Its potential interaction with endogenous cell surface lectins and cadherin may mediate this function.

Variants in the VCAM1 gene and risk for symptomatic stroke in sickle cell disease

Stroke is a major cause of morbidity and mortality in sickle cell (SS) disease. Genetic risk factors have been postulated to contribute to this clinical outcome. The human genome project has substantially increased the catalog of variations in genes, many of which could modify the risk for manifestations of disease outcome in a monogenic disease, namely SS. VCAM1 is a cell adhesion molecule postulated to play a critical role in the pathogenesis of SS disease. We identified a total of 33 single nucleotide polymorphisms (SNPs) by sequencing the entire coding region, 2134 bp upstream of the 5' end of the published cDNA, 217 bp downstream of the 3' end of the cDNA, and selected intronic regions of the VCAM1 locus. Allelic frequencies for selected SNPs were determined in a healthy population. We subsequently analyzed 4 nonsynonymous coding, 2 synonymous coding, and 4 common promoter SNPs in a genetic association study of clinically apparent stroke in SS disease conducted in a cohort derived from a single institution in Jamaica (51 symptomatic cases and 51 matched controls). Of the 10 candidate SNPs analyzed in this pilot study, the variant allele of the nonsynonymous SNP, VCAM1 G1238C, may be associated with protection from stroke (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.15-0.83, P =.04). Further study is required to confirm the importance of this variant in VCAM1 as a clinically useful modifier of outcome in SS disease.

Hydroxyurea therapy in beta-thalassaemia intermedia: improvement in haematological parameters due to enhanced beta-globin synthesis

The beta-thalassaemias represent a heterogenous group of diseases resulting from decreased erythroid beta-globin mRNA expression and imbalanced alpha/beta-globin chain synthesis which are manifest clinically by ineffective erythropoiesis and excessive haemolysis. Increasing levels of haemoglobin F (HbF) by pharmacological agents has been proposed to ameliorate the severity of the disease by improving the balance in globin chain synthesis. Hydroxyurea (HU), as an effective agent with low toxicity for activating gamma-globin gene, has been shown to enhance HbF synthesis in experimental animals and in patients with sickle cell anaemia. However, previous trials of HU in beta-thalassaemia patients are ambiguous, with a small number having increased HbF synthesis. In a recent study of HU effects in Chinese beta-thalassaemia patients we unexpectedly found that two unrelated patients with beta-thalassaemia intermedia demonstrated an improvement in the effectiveness of erythropoiesis reflected by an increase in haemoglobin concentration (from 4.1 to 6.3 g/dl, patient 1; from 6.5 to 9.7 g/dl, patient 2) and in red cell volume (from 68 to 104 fl, patient 1; from 68 to 85 fl, patient 2) after a period of excess of 300d of low-dosage HU treatment. These effects, however, appear to be due to increased beta-globin biosynthesis, because the percentage of HbF decreased in each patient as total Hb increased. This was reflected by changes in the beta/alpha ratio (from 0.301 to 0.581, patient 1; from 0.348 to 0.487, patient 2) with minimal changes in gamma-globin biosynthesis. We conclude that in addition to its known effects in stimulating gamma-globin production, hydroxyurea may have a more general role in augmenting globin synthesis, including beta-globin in some thalassaemia intermedia patients who maintain the capacity to express normal beta-globin chains.