Role of zinc in cellular zinc trafficking and mineralization in a murine osteoblast-like cell line

Low-level laser therapy influences mouse odontoblast-like cell response in vitro

OBJECTIVE

The purpose of this study was to analyze the influence of two different irradiation times with 85 mW/cm(2) 830 nm laser on the behavior of mouse odontoblast-like cells.

BACKGROUND DATA

The use of low-level laser therapy (LLLT) to stimulate pulp tissue is a reality, but few reports relate odontoblastic responses to irradiation in in vitro models.

METHODS

Odontoblast-like cells (MDPC-23) were cultivated and divided into three groups: control/nonirradiated (group 1); or irradiated with 85 mW/cm(2), 830 nm laser for 10 sec (0.8 J/cm(2)) (group 2); or for 50 sec (4.2 J/cm(2)) (group 3) with a wavelength of 830 nm. After 3, 7, and 10 days, it was analyzed: growth curve and cell viability, total protein content, alkaline phosphatase (ALP) activity, calcified nodules detection and quantification, collagen immunolocalization, vascular endothelial growth factor (VEGF) expression, and real-time polymerase chain reaction (PCR) for DMP1 gene. Data were analyzed by Kruskall-Wallis test (α=0.05).

RESULTS

Cell growth was smaller in group 2 (p<0.01), whereas viability was similar in all groups and at all periods. Total protein content and ALP activity increased on the 10th day with 0.8 J/cm(2) (p<0.01), as well as the detection and quantification of mineralization nodules (p<0.05), collagen, and VEGF expression (p<0.01). The expression of DMP1 increased in all groups (p<0.05) compared with control at 3 days, except for 0.8 J/cm(2) at 3 days and control at 10 days.

CONCLUSIONS

LLLT influenced the behavior of odontoblast-like cells; the shorter time/smallest energy density promoted the expression of odontoblastic phenotype in a more significant way.

Bio-composite scaffolds containing chitosan/nano-hydroxyapatite/nano-copper-zinc for bone tissue engineering

The current study involves fabrication and characterization of bio-composite scaffolds containing chitosan (CS), nano-hydroxyapatite (nHAp) and Cu-Zn alloy nanoparticles (nCu-Zn) by freeze drying technique. The fabricated composite scaffolds (CS/nHAp and CS/nHAp/nCu-Zn) were characterized by SEM, EDX, XRD and FT-IR studies. The addition of nCu-Zn in the CS/nHAp scaffolds significantly increased swelling, decreased degradation, increased protein adsorption, and increased antibacterial activity. The CS/nHAp/nCu-Zn scaffolds had no toxicity towards rat osteoprogenitor cells. So the developed CS/nHAp/nCu-Zn scaffolds have advantageous and potential applications over the CS-nHAp scaffolds for bone tissue engineering.

Composite membranes of poly(lactic acid) with zinc-added bioactive glass as a guiding matrix for osteogenic differentiation of bone marrow mesenchymal stem cells

This study aims to produce a degradable and bone-bioactive membrane for guiding bone regeneration by combining a degradable polymer, poly(lactic acid) (PLA), with a bioactive inorganic zinc-containing bioactive glass (ZnBG). The in vitro osteogenic development of rat bone marrow mesenchymal stem cells (rBMSCs) upon different membrane substrates (pure PLA control, PLA–BG, and PLA–ZnBG) was investigated in terms of bone cell phenotype syntheses and mineralization. Results showed significantly stimulated production of alkaline phosphatase and osteocalcin at days 14 and 21 in the membranes containing BG and ZnBG, with more in the samples containing ZnBG. The addition of ZnBG in PLA allowed the rBMSCs to express a high level of bone sialoprotein as confirmed by immunostaining. Cellular mineralization of the secreted extracellular matrix showed a significantly higher Ca level on the BG- and ZnBG-added membrane than on the PLA, and the more so in the ZnBG-added one. Based on the in vitro assessments using rBMSCs, the ZnBG-added PLA is considered to be of potential use in guiding active bone regeneration within the periodontal pocket.

Zinc deprivation inhibits extracellular matrix calcification through decreased synthesis of matrix proteins in osteoblasts

SCOPE

Zinc is implicated as an activator for bone formation, however, its influence on bone calcification has not been reported. This study examined how zinc regulates the bone matrix calcification in osteoblasts.

METHODS AND RESULTS

Two osteoblastic MC3T3-E1 cell subclones (SC 4 and SC 24 as high and low osteogenic differentiation, respectively) were cultured in normal osteogenic (OSM), Zinc deficient (Zn-, 1 μM), or adequate (Zn+, 15 μM) media up to 20 days. Cells (SC 4) were also supplemented with (50 μg/mL) or no ascorbic acid (AA) in combination with Zinc treatment. Zn- decreased collagen synthesis and matrix accumulation. Although AA is essential for collagen formation, its supplementation could not compensate for Zinc deficiency-induced detrimental effects on extracellular matrix mineralization. Zn- also decreased the medium and cell layer alkaline phosphatase ALP activity. This decreased ALP activity might cause the decrease of Pi accumulation in response to Zn-, as measured by von Kossa staining. Ca deposition in cell layers, measured by Alizarin red S staining, was also decreased by Zn(-) .

CONCLUSION

Our findings suggest that zinc deprivation inhibits extracellular matrix calcification in osteoblasts by decreasing the synthesis and activity of matrix proteins, type I collagen and ALP, and decreasing Ca and Pi accumulation. Therefore zinc deficiency can be considered as risk factor for poor extracellular matrix calcification.

Zinc as an essential trace element in the acceleration of matrix vesicles-mediated mineral deposition

BACKGROUND

Zinc (Zn) has a potent stimulatory effect on osteoblastic bone formation and an inhibitory effect on osteoclastic bone resorption.

PURPOSE

The effect of Zn on the function of matrix vesicles (MVs) remains controversial. The purpose of this study was to investigate the effect of Zn on alkaline phosphatase (ALP) activity of osteoblasts and in the initial biological MVs-mediated mineral deposition.

STUDY DESIGN

Osteoblasts were treated with varying concentrations of Zn dissolved in culture medium. After three, five, and seven days of culture, ALP activity was assayed. For the detection of a low level of calcium concentration in MVs, X-ray fluorescence (XRF) analyses were applied. The effect of Zn for the transformation of calcium phosphate was analyzed using a scanning electron microscope fitted with an energy dispersive X-ray microanalysis (EDX) system.

RESULTS

The ALP activity of osteoblasts in culture medium supplemented with 1 × 10(-5) M of Zn was significantly increased at both five and seven days. XRF data demonstrated higher levels of calcium concentration over time in the Zn-supplemented group. EDX data showed that mineral deposits beginning on day 3 were transformed from whitlockite to calcium phosphate near hydroxyapatite, and that Zn accelerated this transformation.

CONCLUSIONS

The proper concentration of Zn increased the ALP activity of osteoblasts after five and seven days of incubation. The present XRF and EDX data suggest that the increase of mineral deposition with Zn exposure for one to five days might be mediated by the activation of ALP and calcium-binding proteins.