The influence of calcium ions on the synthesis of collagen and glycosaminoglycans in human diploid cells in culture

The two faces of titanium dioxide nanoparticles bio-camouflage in 3D bone spheroids

Titanium (Ti) and its alloys are widely used in dental implants and hip-prostheses due to their excellent biocompatibility. Growing evidence support that surface degradation due to corrosion and wear processes, contribute to implant failure, since the release of metallic ions and wear particles generate local tissue reactions (peri-implant inflammatory reactions). The generated ions and wear debris (particles at the micron and nanoscale) stay, in a first moment, at the interface implant-bone. However, depending on their size, they can enter blood circulation possibly contributing to systemic reactions and toxicities. Most of the nanotoxicological studies with titanium dioxide nanoparticles (TiO2 NPs) use conventional two-dimensional cell culture monolayers to explore macrophage and monocyte activation, where limited information regarding bone cells is available. Recently three-dimensional models have been gaining prominence since they present a greater anatomical and physiological relevance. Taking this into consideration, in this work we developed a human osteoblast-like spheroid model, which closely mimics bone cell-cell interactions, providing a more realistic scenario for nanotoxicological studies. The treatment of spheroids with different concentrations of TiO2 NPs during 72 h did not change their viability significantly. Though, higher concentrations of TiO2 NPs influenced osteoblast cell cycle without interfering in their ability to differentiate and mineralize. For higher concentration of TiO2 NPs, collagen deposition and pro-inflammatory cytokine, chemokine and growth factor secretion (involved in osteolysis and bone homeostasis) increased. These results raise the possible use of this model in nanotoxicological studies of osseointegrated devices and demonstrate a possible therapeutic potential of this TiO2 NPs to prevent or reverse bone resorption.

Detection of Co-expressed Pathway Modules Associated With Mineral Concentration and Meat Quality in Nelore Cattle

Meat quality is a complex trait that is influenced by genetic and environmental factors, which includes mineral concentration. However, the association between mineral concentration and meat quality, and the specific molecular pathways underlying this association, are not well explored. We therefore analyzed gene expression as measured with RNA-seq in Longissimus thoracis muscle of 194 Nelore steers for association with three meat quality traits (intramuscular fat, meat pH, and tenderness) and the concentration of 13 minerals (Ca, Cr, Co, Cu, Fe, K, Mg, Mn, Na, P, S, Se, and Zn). We identified seven sets of co-expressed genes (modules) associated with at least two traits, which indicates that common pathways influence these traits. From pathway analysis of module hub genes, we further found an over-representation for energy and protein metabolism (AMPK and mTOR signaling pathways) in addition to muscle growth, and protein turnover pathways. Among the identified hub genes FASN, ELOV5, and PDE3B are involved with lipid metabolism and were affected by previously identified eQTLs associated to fat deposition. The reported hub genes and over-represented pathways provide evidence of interplay among gene expression, mineral concentration, and meat quality traits. Future studies investigating the effect of different levels of mineral supplementation in the gene expression and meat quality traits could help us to elucidate the regulatory mechanism by which the genes/pathways are affected.

Epiretinal Membrane: Prevalence and Risk Factors from the Korea National Health and Nutrition Examination Survey, 2008 through 2012

PURPOSE

To investigate the prevalence and risk factors for an epiretinal membrane (ERM) in Korean population.

METHODS

Using the database of the Korea National Health and Nutrition Examination Survey from 2008 through 2012, 14,772 participants 40 years of age or older with gradable fundus photographs were included. The presence of ERM was determined by using fundus photographs. The prevalence of ERM was estimated and possible risk factors including systemic factors, nutritional status, and blood tests were analyzed via multiple logistic regression analyses.

RESULTS

The prevalence of ERM was 2.9% (95% confidence interval [CI], 2.6% to 3.3%). On multiple logistic regression analysis, the prevalence of ERM was affected by age. The odds ratios (ORs) against the forties were 2.70, 5.48, and 5.69 in the fifties, sixties, and seventies, respectively. ERM was also significantly affected by cataract surgery (OR, 2.82; 95% CI, 2.08 to 3.81) and by the increase in intake of 100-mg calcium (OR, 1.05; 95% CI, 1.00 to 1.11). ERM had negative associations with red blood cell count (OR, 0.66; 95% CI, 0.45 to 0.95).

CONCLUSIONS

The estimated nation-wide prevalence of ERM in Korea is 2.9%. The presence of ERM in the general population is associated with age, cataract surgery, increased dietary calcium, and a low red blood cell count.

Stress reactions in connective tissues: a molecular hypothesis

The proper qualitative and quantitative stimuli necessary to maintain bone, cartilage, tendon, and ligament ability to bear load has yet to be completely elucidated. Substantially greater investigation of these requirements has been accomplished for muscle than for dense and ordinary connective tissues; inferential proposals from these muscle observations have been made regarding connective tissues. This hypothesis postulates there is a highly structured inter-relationship in terms of the homeostatic stimuli which are shared in common by these different tissues as suggested by the close anatomic and functional relationship they have evolved. The evolutionary influence of man's exercise patterns upon these stimuli, their mode of transduction into adaptive cellular response, and the vulnerability to over-use injury their loss creates is hypothesized.

A molecular basis for low back pain in Western industrialized cultures

In spite of billions of dollars spent annually on research and treatment of low back pain (LBP) in Western industrialized cultures, the cause(s) of this complaint remain obscure. The modern sedentary lifestyle is hypothesized to create disuse changes beginning with muscle, which ultimately causes interference with the adaptive and structural dynamics of specialized connective tissue. Calcium-glycosaminoglycan kinetics play a central role in the proposed sequence of events leading to collagen dehydration, fibrillation, and ultimately gross structural incompetence.

Analysis of cell-growth-phase-related variations in hyaluronate synthase activity of isolated plasma-membrane fractions of cultured human skin fibroblasts

Hyaluronate synthase activity is localized exclusively in plasma-membrane fractions of cultured human skin fibroblasts. The enzyme activity of plasma membranes prepared from exponential-growth-phase cells was about 6.5 times that of stationary-growth-phase cells. Hyaluronate synthase from exponential-growth-phase cells exhibited lower Km and higher Vmax. values for both UDP-N-acetylglucosamine and UDP-glucuronic acid and higher rate of elongation of hyaluronate chains compared with the enzyme from stationary-growth-phase cells. Hyaluronate synthase exhibited an extremely short half-life, 2.2 h and 3.8 h respectively when cells were treated with cycloheximide and actinomycin D. The cell-growth-phase-dependent variations in hyaluronate synthase activity appear to be due to its high turnover rate as well as due to some post-translational modification of the enzyme protein as cells progress from early exponential to stationary growth phase. The isolated plasma membranes contained a protein (Mr approx. 450,000) that was selectively autophosphorylated from [gamma-32P]ATP in vitro in the presence of hyaluronate precursors in the reaction mixture and that also exhibited some hyaluronate-synthesis-related properties. The 32P-labelled protein isolated from plasma membranes of exponentially growing cells expressed an efficient UDP-[14C]glucuronic acid- and UDP-N-acetyl[3H]glucosamine-binding activity and was able to synthesize oligosaccharides (Mr 5000) of [14C]glucuronic acid and N-acetyl[3H]glucosamine residues. The corresponding protein of stationary-growth-phase cells, which expressed much higher nucleotide-sugar-precursor-binding activity, appeared to have lost its oligosaccharide-synthesizing activity.

Effect of calcium on cell proliferation and extracellular matrix synthesis in arterial smooth muscle cells and dermal fibroblasts

The effect of calcium on cell proliferation and connective tissue formation was studied in cultured vascular smooth muscle cells (SMC) and dermal fibroblasts. Calcium deficiency caused a modest decrease in proliferation of smooth muscle cells but this effect was small compared to that previously observed with fibroblasts. Synthesis of connective tissue components was affected differently in the two cell types. Biosynthesis of proteoglycans was assessed by metabolic labeling of their glycosaminoglycan side chains. Different levels of extracellular calcium did not affect proteoglycan production by fibroblasts, but it was significantly reduced in smooth muscle cells incubated in calcium-deficient medium. Both smooth muscle cells and fibroblasts were able to produce appreciable amounts of collagen in the complete absence of calcium and in both cell types collagen synthesis was increased when calcium was present. Fibroblasts, however, showed a much smaller response to calcium than did smooth muscle cells. In fibroblasts the maximum rate of collagen synthesis was achieved in a narrow range of calcium concentration which was slightly below that found commonly in the tissue culture medium. By contrast, in smooth muscle cells the rate of collagen synthesis increased greatly when calcium was present and this elevated rate persisted even when the cells were exposed to high levels of extracellular calcium. We conclude that these findings may be of significance to the development of atherosclerotic lesions.

Influence of calcium concentration in the medium on the cell proliferation and glycosaminoglycan synthesis of human diploid skin fibroblasts in culture

Changes of the glycosaminoglycan (GAGs) fractions in the medium, the cell surface of human diploid skin fibroblasts and the relation between GAGs synthesis and cell growth in cultured media containing various Ca++ concentrations were investigated by means of electrophoretic fractionation. The results demonstrated that the synthesis of the hyaluronic acid (HA) fraction was increased with increase of the Ca++ concentration in the medium, and this change appeared to be linked to the condition of cell growth. The synthesis of the heparan sulfate and dermatan sulfate (HS + DS) fraction was decreased with increase of the Ca++ concentration in the medium, and this change depended largely on the Ca++ concentration in the medium rather than the cell growth. The synthesis of the chondroitin sulfate (Ch-s) fraction was also decreased with increase of the Ca++ concentration in the medium. However, this change was neither controlled especially by the Ca++ concentration in the medium nor by the condition of cell growth, but reflected the decrease of total GAGs synthesis by the increase of the Ca++ concentration in the medium.