HIV envelope gp120 activates human arterial smooth muscle cells.

There have been increasing reports of acute coronary thrombotic events in patients with HIV. Although these clinical events have been attributed primarily to dyslipidemia associated with protease inhibitor therapy, autopsy studies in children with HIV suggest the presence of an underlying arteriopathy. This study demonstrates that the HIV envelope protein, gp120, activates human arterial smooth muscle cells to express tissue factor, the initiator of the coagulation cascade. The induction of tissue factor by gp120 is mediated by two biologically relevant coreceptors for HIV infection, CXCR4 and CCR5, and is also dependent on the presence of functional CD4. Induction of tissue factor by gp120 requires activation of mitogen-activating protein kinases, activation of protein kinase C, and generation of reactive oxygen species, signaling pathways that have protean effects on smooth muscle cell physiology. The activation of smooth muscle cells by gp120 may play an important role in the vascular, thrombotic, and inflammatory responses to HIV infection.

Prevention of loosening in total hip replacements using guided bone regeneration.

The aim of this study was to prevent wear debris from reaching the interface of the acetabular cup and femoral component by using a partially occlusive expanded polytetrafluoroethylene membrane. This membrane initially acted as a physical seal, which became incorporated by bone and soft tissue, forming a secondary biologic seal, preventing loosening. An animal model was developed to test the hypothesis. The model replicated the mechanisms of loosening where the effects of wear debris were studied. Using femoral heads with the appropriate roughness, a goat model produced the radiologic and histologic presentation of loosening as observed in total hip replacements in humans. Loosening was assessed by measurement of the radiolucent lines, and was attributed to wear debris by histologic investigation. The expanded polytetrafluoroethylene membrane prevented acetabular implant loosening to a statistical significance of 0.02 in a blinded assessment when compared with the control groups. Loosening of the first 5 mm of the proximomedial aspect of the femur also was prevented. The authors of the current study prevented wear particle-induced osteolysis in the acetabular component by using an expanded polytetrafluoroethylene membrane to seal the bone-cement interface.

Human vascular smooth muscle cells possess functional CCR5.

CC chemokine receptors are important modulators of inflammation. Although CC chemokine receptors have been found predominantly on leukocytes, recent studies have suggested that vascular smooth muscle cells respond to CC chemokines. We now report that human smooth muscle cells express CCR5, a co-receptor for human immunodeficiency virus. CCR5 mRNA was detectable by RNA blot hybridization in human aortic and coronary artery smooth muscle cells. The cDNA generated by reverse transcription-polymerase chain reaction from aortic smooth muscle cells had 100% identity throughout the entire coding region with the CCR5 cloned from THP-1 cells. By immunohistochemistry, CCR5 and the CCR5 ligand, macrophage inflammatory protein-1beta (MIP-1beta), were detected in smooth muscle cells and macrophages of the atherosclerotic plaque. In smooth muscle cell culture, MIP-1beta induced a significant increase in intracellular calcium concentrations, which was blocked by an antibody to CCR5. In addition, MIP-1beta caused a calcium-dependent increase in tissue factor activity. Tissue factor is the initiator of coagulation and is thought to play a key role in arterial thrombosis. These data suggest that human arterial smooth muscle cells express functional CCR5 receptors and MIP-1beta is an agonist for these cells.

Enhanced bone regeneration and formation around implants using guided bone regeneration.

This study investigated the use of a prototype expanded polytetrafluoroethylene membrane attached to bone with butyl-cyanoacrylate, in facilitating guided bone regeneration into bone defects and around titanium screws in rabbit femora. Two experimental models were used to assess bone growth. The first model investigated two unicortical defects in each femora. The second was bone growth in a 500-micron engineered space around one transcortical titanium screw. In the first model there was a significant increase in bone formation at 1 and 2 months in the membrane groups (p < 0.01) as compared to the controls. In the second model the percentage of bone in contact with the implant was significant at 1 and 2 months in the defects covered with membrane compared to the uncovered defects. The uncovered defects had fibrous tissue adherent to the implant continuous with the overlying soft tissue. Our study demonstrated three points: this membrane can be used to increase bone regeneration into defects, this technique allows bone to grow directly around an implant, and butyl-cyanoacrylate can be used in deep soft tissue and bone applications without any apparent deleterious effects.

A monoclonal antibody (3G5)-defined ganglioside antigen is expressed on the cell surface of microvascular pericytes.

The identification of microvascular pericytes in vitro relies principally on morphological characteristics and growth dynamics, as there is a paucity of immunochemical markers for these cells. Consequently, an attempt was made to identify mAb reagents that would aid in both the rapid identification and enrichment of retinal capillary pericytes in vascular cell cultures. A panel of mAbs raised by xenogeneic immunization of mice with various tissues was screened for immunoreactivity with dissociated cultures of bovine retinal capillary pericytes. Two antibodies from the panel (3G5 and HISL-8) were seen to react with pericytes by indirect immunofluorescence. The mAb 3G5 was selected for further study. mAb 3G5 did not react with dissociated cultures of smooth muscle cells, endothelial cells, or retinal pigmented endothelial cells. The pericyte 3G5 antigen was insensitive to the action of trypsin; therefore, mAb 3G5 was used to selectively purify pericytes from trypsinized mixed retinal cell cultures by flow cytometry. 3G5+ pericytes (representing 8% of cells in a mixed retinal cell culture) were enriched at least nine-fold to represent greater than 70% of cells. The mAb 3G5 stained retinal capillaries in vivo with a fluorescence distribution consistent with pericyte staining. The 3G5 antigen of cultured pericytes was found to be a glycolipid of mobility intermediate between ganglioside markers GM1 and GM2.

Regulation of vascular permeability in cell culture.

Although one of the earliest findings of diabetic retinopathy is altered capillary permeability, metabolic factors in diabetes that may increase the permeability of capillaries to fluorescein are unknown. We have studied the effect of a variety of vascular and retinal cells and hyperglycemia on the diffusion rate of fluorescein. These studies were performed with a cell culture system that mimics the cross-section of a capillary by having two chambers separated with a porous membrane that can support the growth of cells on either side of the membrane. The addition of a confluent layer of endothelial cells or retinal pigmented epithelial (RPE) cells inhibited fluorescein diffusion between the two chambers 20- and 300-fold, respectively, after cells were cultured for greater than 5 days. Exposure of endothelial cells to 400 mg/dl glucose for either 3 or 100 days did not affect the barrier function of these cells. The barrier function of capillary endothelial cells isolated from BB rats with chronic diabetes and from nondiabetic animals did not differ. In contrast to endothelial cells and RPE cells, arterial smooth muscle and pericytes, which are not known to form tight junctions, did not inhibit the diffusion of fluorescein more than 2-fold. Surprisingly, the dual culture of endothelial cells with either retinal pericytes or smooth muscle cells resulted in a 50-fold increase in the rate of fluorescein diffusion, showing a disruption of the endothelial barrier. In summary, the intercellular connections between endothelial and epithelial cells that are responsible for the barrier to fluorescein diffusion are not functionally affected by chronic exposure to hyperglycemia or diabetic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)