Characterization of hematopoietic cells arising on the textured surface of left ventricular assist devices

BACKGROUND

Textured biomaterial surfaces in implantable left ventricular assist devices induce development of a nonthrombotic neointimal surface and allow elimination of anticoagulation therapy in device recipients. Characterization of the hematopoietic cells formed within the neointimal surfaces of these devices will contribute to our understanding of this unique neointima.

METHODS

The blood-contacting surface of seven ThermoCardiosystems left ventricular assist devices was removed, washed with phosphate-buffered saline solution, and digested with 0.1% collagenase for 15 to 20 minutes. The hematopoietic cells released from the explants were isolated and analyzed by flow cytometry and immuno-histochemical staining.

RESULTS

More than 80% +/- 6% of hematopoietic cells isolated in this fashion are of myelomonocytic origin and express CD14, CD15, and CD33 surface molecules. Four percent of cells express the CD34 surface marker, which suggests that the neointima is colonized by pluripotent hematopoietic stem cells. Continuous culture of these hematopoietic cells in the presence of the cytokines interleukin-3, c-kit ligand, granulocyte colony-stimulating factor resulted in tenfold expansion by day 7 and 25-fold expansion by day 14.

CONCLUSIONS

Pluripotent hematopoietic cells with a high proliferative capacity colonize textured surfaces of left ventricular assist devices and may contribute to the development of a biologically nonthrombogenic neointima.

Human bone marrow microvascular endothelial cells support long-term proliferation and differentiation of myeloid and megakaryocytic progenitors

Endothelial cells are a major component of the bone marrow (BM) microenvironment that regulate the trafficking and homing of hematopoietic progenitor and stem cells. In this paper, we provide evidence that BM endothelial cells (BMECs) also support multilineage hematopoiesis by elaboration of soluble cytokines. Hematopoietic progenitor cells incubated in direct contact with BMEC monolayers, or physically separated by microporous membrane, expanded five-fold to sevenfold at 7 days, in the absence of exogenous cytokines. Flow cytometric analysis of proliferating progenitor cells grown in the presence of BMEC monolayers showed that by day 14 of coculture, 70% to 80% of hematopoietic cells were myeloid, expressing CD15 or CD14, and 14% to 19% were megakaryocytic, expressing GPIIb/IIIa or GPIb. CD34+ cells derived from umbilical cord blood, cultured in the upper chamber of transwell culture plates, as well as the cells grown in direct contact with BMEC monolayers, generated progenitors for up to 70 days. Unstimulated BMEC monolayers constitutively produce interleukin-6, Kit-ligand, granulocyte colony-stimulating factor, and granulocyte macrophage colony-stimulating factor. These data suggest that BMEC regulate proliferation of hematopoietic progenitor cells and long-term culture initiating cells by elaboration of lineage-specific cytokines.

Isolation and characterization of human bone marrow microvascular endothelial cells: hematopoietic progenitor cell adhesion

To examine potential mechanisms by which hematopoiesis may be regulated by endothelial cells within the bone marrow (BM) microenvironment, we have devised a technique for the in vitro study of the interaction of human BM microvascular endothelial cells (BMEC) with hematopoietic cells. Microvessels isolated by collagenase digestion of spicules obtained from filtered BM aspirate were plated on gelatin-coated plastic dishes, and colonies of endothelial cells grown from microvessel explants were further purified by Ulex europaeus lectin affinity separation. BMEC monolayers isolated by this technique grew in typical cobblestone fashion, stained positively with antibody to factor VIII/von Willebrand factor, and incorporated acetylated LDL. Immunohistochemical studies showed that BM microvessels and BMEC monolayers express CD34, PECAM, and thrombospondin. Incubation of resting BMEC with BM mononuclear hematopoietic cells resulted in the selective adhesion of relatively large numbers of CD34+ progenitor cells and megakaryocytes. The binding of purified BM-derived CD34+ progenitor cells to BMEC was dependent on divalent cations and was partially blocked by antibodies to CD34. IL-1 beta treatment of BMEC monolayers resulted in an increase of CD34+ progenitor cell adhesion by mechanisms independent of CD34 or divalent cations. BMEC exhibit specific affinity for CD34+ progenitor cells and megakaryocytes, suggesting that the BM microvasculature may play a role in regulating the trafficking, proliferation, and differentiation of lineage specific hematopoietic elements, and possibly of pluripotent stem cells within the CD34+ population.

Longitudinal height velocity standards for U.S. adolescents

Longitudinally based height velocity centiles for U.S. children, appropriate for paediatric clinical use, were derived for growth from ages 7 to 18 years. A series of gender- and race-specific figures present the median velocity curves for children by year of maturation. Smooth 3rd to 97th centile curves, for blacks and whites together, are provided for children who are early, average, and late maturers. The data were taken from 6532 black and white children participating in the Six Cities Study from 1974 to 1989.

Congenital hip dislocation or dysplasia with subluxation: a radiologic study

We studied the behavior of hips in congenital hip dislocation. Two types were identified: those that developed normally after closed reduction and those that required an osteotomy. Children with hips that required an osteotomy were older at presentation and at follow-up had worse subluxation, with shallower acetabula. In this group, the younger the age at which reduction was achieved, the less the residual subluxation of the hip at follow-up. The age at which the late osteotomy was performed did not appear to affect the residual hip subluxation or the acetabular development. We could not find any radiologic parameter that would predict the need for an osteotomy.

The orthopaedic management of hypophosphataemic rickets

The orthopaedic management of 19 patients with hypophosphataemic rickets was reviewed. Three groups of patients could be identified: teenagers or young adults without knee problems, those with knee problems, and adults or elderly patients with stiff joints due to mineralisation of ligaments. Osteotomies were best staged. Diaphyseal osteotomies were performed at all ages with stabilisation over an intramedullary nail; metaphyseal osteotomies were most successful at or close to maturity. Early degeneration of the knees with shedding of the articular cartilage was seen in young adults, and osteochondritis-like lesions were seen in some teenagers. Stiffness and bone pain were a feature in elderly patients.

Daily diaries of respiratory symptoms and air pollution: methodological issues and results

Daily diaries of respiratory symptoms are a powerful technique for detecting acute effects of air pollution exposure. While conceptually simple, these diary studies can be difficult to analyze. The daily symptom rates are highly correlated, even after adjustment for covariates, and this lack of independence must be considered in the analysis. Possible approaches include the use of incidence instead of prevalence rates and autoregressive models. Heterogeneity among subjects also induces dependencies in the data. These can be addressed by stratification and by two-stage models such as those developed by Korn and Whittemore. These approaches have been applied to two data sets: a cohort of school children participating in the Harvard Six Cities Study and a cohort of student nurses in Los Angeles. Both data sets provide evidence of autocorrelation and heterogeneity. Controlling for autocorrelation corrects the precision estimates, and because diary data are usually positively autocorrelated, this leads to larger variance estimates. Controlling for heterogeneity among subjects appears to increase the effect sizes for air pollution exposure. Preliminary results indicate associations between sulfur dioxide and cough incidence in children and between nitrogen dioxide and phlegm incidence in student nurses.

Effect of intensity of physical activity on body fatness and fat distribution

To evaluate the effect of intensity of physical activity on body fatness and fat distribution, observations of 1366 women and 1257 men who participated in the 1981 Canada Fitness Survey were analyzed. Subjects were tested for energy expenditure of leisure-time activities and estimated maximal oxygen uptake (VO2max), body fatness was measured by subcutaneous skinfold thicknesses, and anthropometric measurements were made. Subjects of both sexes were categorized into four subgroups on the basis of their participation in leisure-time activities of various intensities. In general, subjects practicing vigorous activities on a regular basis had lower subcutaneous skinfold thicknesses and waist-to-hip ratios (WHRs) than those not performing these activities. These differences remained statistically significant after a covariance analysis was used to remove the effect of total energy expenditure of leisure-time activities on subcutaneous fat and fat distribution. Moreover, the WHR remained significantly lower in subjects performing high-intensity exercise after the effect of subcutaneous fat on fat distribution was adjusted for.

Screening for scoliosis

We compared two groups of consecutive patients presenting to a scoliosis center: viz., 214 children from 1974 to 1978 and 100 children from 1984 to 1986. The number of curves detected by school screening increased from 10 percent to 33 percent, and the size of the curves at presentation decreased from 49 to 33 degrees. Half the curves were still detected by families and friends. School screening for scoliosis has increased detection of curves at an early stage when bracing may be successful.

The treatment of congenital knee dislocation. A review of nineteen knees

The treatment of 19 congenitally dislocated knees in 11 patients is reviewed. The knees were subdivided into genu recurvatum, subluxation and dislocation. Nine knees were treated conservatively and ten surgically. A good result was obtained with conservative treatment if started before the age of three months; after this, surgery was likely to be required and was satisfactory if undertaken before two years of age. A successful surgical result was achieved with quadriceps lengthening. If the quadriceps tendon and the anterior cruciate ligament were divided, then only fair results were achieved. Untreated, patients developed stiff, unstable knees.

Paraplegia due to aspergillosis. Successful conservative treatment of two cases

Aspergillus infection of the spine is rare; for it to lead to paraplegia is still more rare. When this does occur it is usually treated by decompression and antifungal agents, but the results have usually been poor. We report two cases of successful conservative treatment of Aspergillus paraplegia in patients with chronic granulomatous disease.

The health effects of automobile exhaust. VI. Relationship of respiratory symptoms and pulmonary function in tunnel and turnpike workers

To examine the effect of automobile exhaust on respiratory symptoms and pulmonary function, the authors studied 175 tunnel and turnpike workers employed by the Massachusetts Turnpike Authority on two occasions 3 yr apart beginning in 1972. A standard respiratory symptom and illness questionnaire was administered, spirometry was performed, and proximal hair lead and blood lead content were measured as biologic indices of automobile exhaust exposure. One hundred nine (63%) workers were current cigarette smokers, 41 (23%) were exsmokers, and 24 (14%) had never smoked. Smoking was strongly related to respiratory symptoms of cough (P less than .001) and phlegm production (P less than .001), but not to wheezing (P = .41), breathlessness (P = .14), bronchial asthma (P = .13), or frequent chest colds (P = .14). When workers were stratified by smoking status, no effect could be seen between high automobile exhaust exposure as measured by a variety of parameters and all of the above respiratory symptoms and illnesses. The level of pulmonary function [forced expiratory volume in 1 sec (FEV1.0) and forced vital capacity (FVC)] was not related to past or current exhaust exposure in a cross-sectional analysis when we controlled for age, height, and cigarette consumption. In a prospective analysis of 84 of these workers, the observed changes in FEV1.0 and FVC over 3 yr were unrelated to exhaust exposure after controlling for age, height, cigarette consumption, and initial level of pulmonary function.

Multiple molecular forms of endothelial cell factor VIII related antigen

Heterogeneous factor VIII related antigen isolated from endothelial cell postculture medium was characterized. On crossed immunoelectrophoresis, slow moving less anodal populations of factor VIII related antigen molecules were more prominent in endothelial cell postculture medium than in plasma. The protein synthesized by endothelial cells appeared as two discrete protein bands of different molecular weight in sodium dodecyl sulfate polyacrylamide gels. In contrast the factor VIII related antigen isolated from plasma moved as a single protein band in an identical gel system. The factor VIII related antigen from endothelial cell postculture medium was immunoisolated using monospecific rabbit antibody to normal human plasma factor VIII related antigen, electrophoresed on sodium dodecyl sulfate polyacrylamide gels, radiolabeled with 125I, trypsinized and subjected to peptide mapping using two-dimensional high voltage electrophoresis and thin-layer chromatography. The two forms of endothelial cell factor VIII antigen had virtually identical peptide maps. These studies suggest that the molecular heterogeneity of the factor VIII related antigen system reflects polymeric associations of identical subunits. Circulation in vivo may alter the ratio of polymer subsets.

Respiratory disease rates and pulmonary function in children associated with NO2 exposure

As part of a long-range, prospective study of the health effects of air pollution, approximately 8,000 children from 6 yrs to 10 yrs of age from 6 communities had questionnaires completed by their parents and had simple spirometry performed in school. Comparisons were made between children living in homes with gas stoves and those living in homes with electric stoves. Children from households with gas stoves had a greater history of respiratory illness before age 2 (average difference, 32.5/1,000 children) and small but significantly lower levels of FEV1 and FVC corrected for height (average difference, 16 ml and 18 ml, respectively). These findings were not explained by differences in social class or by parental smoking habits. Measurements taken in the homes for 24-h periods showed that NO2 levels were 4 to 7 times higher in homes with gas stoves than in homes with electric stoves. However, these 24-h measurements were generally well below the current federal 24-h outdoor standard of 100 micrograms/m3. Short-term peak exposures, which were in excess of 1,100 micrograms/m3, regularly occurred in kitchens. Further work will be required to determine the importance of these short-term peaks in explaining the effects noted.

Structural analysis of human platelet membrane glycoprotein I complex

The glycoprotein I complex, consisting of two polypeptides of Mr 210,000 and 150,000, was isolated from human platelet membranes by wheat germ lectin affinity chromatography. Glycocalicin, a soluble loosely bound membrane glycoprotein of Mr 150,000 related to the glycoprotein I system, was also purified. The isolated polypeptides were radioiodinated in sodium dodecyl sulfate/polyacrylamide gels and digested with trypsin, and the labeled peptide digest was analyzed by two-dimensional high-voltage electrophoresis and thin-layer chromatography. The two polypeptides of Mr 210,000 and 150,000 in the glycoprotein I complex had essentially identical radioactive peptide maps. Glycocalicin had a completely different tryptic peptide map. These studies shed light on the molecular relationships of some of the components of the platelet membrane glycoprotein I system. The possibility is raised that the receptorlike function of the intrinsic platelet membrane glycoproteins may be related to the polymeric subunit associations of the constituent polypeptides.