Abstract
Calcium phosphate (CaP) materials are among the best bone graft substitutes, but their use in the repair of damaged bone in tumor patients is still unclear. The human Jurkat T lymphoblast leukemia-derived cell line (Jurkat T cells) was exposed in vitro to a titanium (Ti) substrate (10 × 10 × 1 mm3) with a bilateral rough (average roughness index (Ra) = 2–5 μm) CaP coating applied via the microarc oxidation (MAO) technique, and the morphofunctional response of the cells was studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscope (EDX) analyses showed voltage-dependent (150–300 V) growth of structural (Ra index, mass, and thickness) and morphological surface and volume elements, a low Ca/PaT ratio (0.3–0.6), and the appearance of crystalline phases of CaHPO4 (monetite) and β-Ca2P2O7 (calcium pyrophosphate). Cell and molecular reactions in 2-day and 14-day cultures differed strongly and correlated with the Ra values. There was significant upregulation of hTERT expression (1.7-fold), IL-17 secretion, the presentation of the activation antigens CD25 (by 2.7%) and CD95 (by 5.15%) on CD4+ cells, and 1.5–2-fold increased cell apoptosis and necrosis after two days of culture. Hyperactivation-dependent death of CD4+ cells triggered by the surface roughness of the CaP coating was proposed. Conversely, a 3.2-fold downregulation in hTERT expression increased the percentages of CD4+ cells and their CD95+ subset (by 15.5% and 22.9%, respectively) and inhibited the secretion of 17 of 27 test cytokines/chemokines without a reduction in Jurkat T cell survival after 14 days of coculture. Thereafter, cell hypoergy and the selection of an hTERT-independent viable CD4+ subset of tumor cells were proposed. The possible role of negative zeta potentials and Ca2+ as effectors of CaP roughness was discussed. The continuous (2–14 days) 1.5–6-fold reductions in the secretion of vascular endothelial growth factor (VEGF) by tumor cells correlated with the Ra values of microarc CaP-coated Ti substrates seems to limit surgical stress-induced metastasis of lymphoid malignancies.
Highlights
Calcium phosphate (CaP) materials are among the best bone graft substitutes because they promote rapid bone formation and remodeling within their volume and on their surface and may ensure bone healing within a year
Scanning electron microscopy (SEM) images represent the surface and cross-section morphology of the CaP coatings deposited by the microarc oxidation (MAO) method under the different applied voltages (Figure 1)
This study showed voltage-dependent (150–300 V) growth of structural (Ra index, mass, and thickness) and morphological surface and volume elements, low calcium content (Ca/PaT = 0.3–0.6), the appearance of crystalline phases of CaHPO4 and β-Ca2 P2 O7, and an increased magnitude of negative electrostatic voltage in the CaP coatings deposited via MAO on Ti substrate
Summary
Calcium phosphate (CaP) materials are among the best bone graft substitutes because they promote rapid bone formation and remodeling within their volume and on their surface and may ensure bone healing within a year. Despite these achievements, the mechanisms behind the CaP features (structure, size, and solubility) that induce healthy bone formation are still incompletely understood [1]. Plasma electrolytic or microarc oxidation (MAO) is one the most applicable techniques to prepare metal-oxide and CaP coatings [3,4,5,6] that can be relatively improved and innovate traumatological and orthopedic practice. We have previously detected the synthetic microterritories in microarc CaP coating which promote osteogenic differentiation and maturation of mesenchymal stem cells in vitro [7]
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