Human macrophage cathepsin B-mediated C-terminal cleavage of apolipoprotein A-I at Ser228 severely impairs antiatherogenic capacity.

Apolipoprotein A-I (apoA-I) is the major component of HDL and central to the ability of HDL to stimulate ATP-binding cassette transporter A1 (ABCA1)-dependent, antiatherogenic export of cholesterol from macrophage foam cells, a key player in the pathology of atherosclerosis. Cell-mediated modifications of apoA-I, such as chlorination, nitration, oxidation, and proteolysis, can impair its antiatherogenic function, although it is unknown whether macrophages themselves contribute to such modifications. To investigate this, human monocyte-derived macrophages (HMDMs) were incubated with human apoA-I under conditions used to induce cholesterol export.

Cholesterol accumulation inhibits ER to Golgi transport and protein secretion: studies of apolipoprotein E and VSVGt.

Cholesterol excess is typical of various diseases including atherosclerosis. We have investigated whether cholesterol accumulation in the ER (endoplasmic reticulum) can inhibit exit of vesicular cargo and secretion of proteins by studying apoE (apolipoprotein E), a significant glycoprotein in human health and disease. CHO (Chinese hamster ovary) cells expressing human apoE under a cholesterol-independent promoter incubated with cholesterol-cyclodextrin complexes showed increased levels of cellular free and esterified cholesterol, inhibition of SREBP-2 (sterol-regulatory-element-binding protein 2) processing, and a mild induction of ER stress, indicating significant accumulation of cholesterol in the ER.

Effects of biomimetic surfaces and oxygen tension on redifferentiation of passaged human fibrochondrocytes in 2D and 3D cultures.

Due to its limited healing potential within the inner avascular region, functional repair of the meniscus remains a significant challenge in orthopaedic surgery. Tissue engineering of a meniscus implant using meniscal cells offers the promise of enhancing the reparative process and achieving functional meniscal repair. In this work, using quantitative real-time reverse transcriptase polymerase chain reaction (RT-qPCR) analysis, we show that human fibrochondrocytes rapidly dedifferentiate during monolayer expansion on standard tissue culture flasks, representing a significant limit to clinical use of this cell population for meniscal repair.

Modulation of collagen II fiber formation in 3-D porous scaffold environments.

Collagen II, a major extracellular matrix component in cartilaginous tissues, undergoes fibrillogenesis under physiological conditions. The present study explored collagen II fiber formation in solution and in two- (coverslip) and three-dimensional (scaffold) environments under different incubation conditions. These conditions include variations in adsorption buffers, the presence of 1-ethyl-3-(3-dimenthylaminopropyl) carbodiimide/N-hydroxysuccinimide crosslinker and the nature of the material surfaces.

Interactions between meniscal cells and a self assembled biomimetic surface composed of hyaluronic acid, chitosan and meniscal extracellular matrix molecules.

Menisci are one of the most commonly injured parts of the knee with a limited healing potential. This study focuses on fabrication and characterization of biomimetic surfaces for meniscal tissue engineering. To achieve this, a combination of hyaluronic acid/chitosan (HA/CH) mutilayers with covalently immobilized major extracellular matrix (ECM) components of native meniscus, namely collagen I/II (COL.

Expression and stability of two isoforms of ABCG1 in human vascular cells.

Objective: To evaluate the expression of two ABCG1 isoforms that differ in the presence or absence of a 12 amino acid (AA) peptide between the ABC cassette and the transmembrane region, termed ABCG1(+12) and ABCG1(-12), respectively, in human vascular cells and tissues.

Methods And Results: mRNA for both isoforms was expressed in human macrophages, vascular endothelial and smooth muscle cells as well as whole human spleen, lung, liver and brain tissue. However, ABCG1(+12) was not expressed in mouse tissues.

Influence of biodegradable and non-biodegradable material surfaces on the differentiation of human monocyte-derived macrophages.

Monocyte-derived macrophages (MDM) and multinucleated foreign body giant cells (FBGC) are the primary cell types that remain at the cell-material interface of polyurethane (PU)-based medical devices as a result of chronic inflammatory responses. In vitro studies have demonstrated that MDM possess degradative potential toward PU, which can result in device failure. Because most studies have followed the degradation potential, morphology, and function of these cells only once fully differentiated, the current study investigated the influence of a non-degradable control tissue culture-grade polystyrene (TCPS) surface relative to two degradable model polycarbonate-urethanes (PCNU), of different chemistry, on various parameters of MDM morphology and function during a 14-day differentiation time course.

Intracellular phospholipase A2 expression and location in human macrophages: influence of synthetic material surface chemistry.

Phospholipase A(2) (PLA(2)) enzymes participate in a potent inflammatory pathway through the liberation of arachidonic acid upon hydrolysis of membrane glycerophospholipids. The presence of implanted polycarbonate-urethane (PCNU) materials, used in several medical applications, has the ability to influence inflammatory responses of human macrophages that are recruited to a tissue-material interface; however, the specific inflammatory pathways that are activated upon macrophage attachment to PCNU are largely unknown. Previous studies suggested the participation of PLA(2) pathways in material degradation with the use of chemical inhibitors, such as aristolochic acid (ARIST), however not accurately defining the specific PLA(2) enzymes involved.

Material surfaces affect the protein expression patterns of human macrophages: A proteomics approach.

Monocyte-derived macrophages (MDM) are key inflammatory cells and are central to the foreign body response to implant materials. MDM have been shown to exhibit changes in actin cytoskeleton, multinucleation, cell size, and function in response to small alterations in polycarbonate-urethane (PCNU) surface chemistry. Although PCNU chemistry has an influence on de novo protein synthesis, no assessments of the protein expression profiles of MDM have yet been reported.

The human macrophage response during differentiation and biodegradation on polycarbonate-based polyurethanes: dependence on hard segment chemistry.

Human monocytes, isolated from whole blood, were seeded onto tissue culture grade polystyrene (PS) and three polycarbonate-based polyurethanes (PCNUs) (synthesized with either 1,6-hexane diisocyanate (HDI) or 4,4'-methylene bis-phenyl diisocyanate (MDI), poly(1,6-hexyl 1,2-ethyl carbonate) diol (PCN) and 1,4-butanediol (BD) in different stoichiometric ratios (HDI:PCN:BD 4:3:1 or 3:2:1 and MDI:PCN:BD 3:2:1) (referred to as HDI431, HDI321 and MDI321, respectively). Following their differentiation to monocyte-derived macrophages (MDMs) the cells were trypsinized and reseeded onto each of the PCNUs synthesized with either 14C-HDI or 14C-BD and degradation was measured by radiolabel release (RR). When the differentiation surface was MDI321, there was more RR from 14C-HDI431 than from any other surface (p < 0.

Phospholipase A2 pathway association with macrophage-mediated polycarbonate-urethane biodegradation.

Activation of the phospholipase A2 (PLA2) pathway is a key cell signaling event in the inflammatory response. The PLA2 family consists of a group of enzymes that hydrolyze membrane phospholipids, resulting in the liberation of arachidonic acid (AA), a precursor to pro-inflammatory molecules. Given the well-documented activating role of biomaterials in the inflammatory response to medical implants, the present study investigated the link between PLA2 and polycarbonate-based polyurethane (PCNU) biodegradation, and the effect that material surface had on PLA2 activation in the U937 cell line.