Can Bone-Specific Alkaline Phosphatase and Osteocalcine Levels Be Used to Determine the Age in Children?

Functionalized Decellularized Bone Matrix Promotes Bone Regeneration by Releasing Osteogenic Peptides

The decellularized bone matrix (DCB) provides a promising bone substitute for the treatment of bone defects because of its similar biochemical, biophysical, and mechanical properties to normal bone tissue. However, the decellularized procedure also greatly reduced its osteogenic induction activity. In this study, peptides derived from the knuckle epitope of bone morphogenetic protein-2 were incorporated into the thermo-sensitive hydrogel poloxamer 407, and the peptide-loaded hydrogel was then filled into the pores of DCB to construct a functionalized scaffold with enhanced osteogenesis. In vitro studies have shown that the functionalized DCB scaffold possessed appropriate mechanical properties and biocompatibility and exhibited a sustained release profile of osteogenic peptide. These performances critically facilitated cell proliferation and cell spreading of bone marrow mesenchymal stem cells and upregulated the expression of osteogenic-related genes by activating the Smad/Runx2 signaling pathway, thereby promoting osteogenic differentiation and extracellular matrix mineralization. Further in vivo studies demonstrated that the functionalized DCB scaffold accelerated the repair of critical radial defects in rabbits without inducing excessive graft-related inflammatory responses. These results suggest a clinically meaningful strategy for the treatment of large segmental bone defects, and the prepared osteogenic peptide modified composite DCB scaffold has great application potential for bone regeneration.

Bone Turnover Markers in Children: From Laboratory Challenges to Clinical Interpretation

Bone turnover markers (BTMs) have been developed many years ago to study, in combination with imaging techniques, bone remodeling in adults. In children and adolescents, bone metabolism differs from adults since it implies both growth and bone remodeling, suggesting an age- and gender-dependent BTM concentration. Therefore, specific studies have evaluated BTMs in not only physiological but also pathological conditions. However, in pediatrics, the use of BTMs in clinical practice is still limited due to these many children-related specificities. This review will discuss about physiological levels of BTMs as well as their modifications under pathological conditions in children and adolescents. A focus is also given on analytical and clinical challenges that restrain BTM usefulness in pediatrics.

Effect of hydroxyapatite bioceramics on the growth of osteoblasts and HIF-α/VEGF signal axis in partial hypoxia environment in vitro

BACKGROUND:

Hydroxyapatite bioceramic is a kind of bone implant commonly used in oral clinic treatment. In the early stage of tissue repair, cells will suffer hypoxic due to the interruption of blood supply.

OBJECTIVE:

Studying the expression of osteoblasts in hypoxic environment will help us to understand the expression and response mechanism of osteoblasts at the implantation site of hydroxyapatite in the early stage of hypoxia.

METHODS:

MG63 osteoblast cell line was used in this study. The cells of normal group were incubated under normal oxygen and hydroxyapatite ceramics condition. The cells of hypoxia group were incubated under hypoxia (37∘C, 8% CO2, 8% O2, 86% N2) and hydroxyapatite ceramics condition. Cell proliferation was measured by CCK8 assay. Apoptosis was measured by flow cytometry. Serum alkaline phosphatase (ALP) activity was measured by ALP kit. Hypoxia inducible factor (HIF-α) and vascular endothelial growth factor (VEGF) were detected by Western blot.

RESULTS:

Compared to the normal group, the cells of hypoxia group showed a dramatically higher proliferation ability, especially at 48 h (P< 0.05). Due to hypoxia, cell apoptosis was induced, but there is no difference between these two groups. Interestingly, the ALP activity of hypoxia group was higher than that of normal group at 24 h and 48 h (P< 0.05). Mechanically, western blot result showed that the protein level of both HIF-α and VEGF were up-regulated in hypoxia group.

CONCLUSIONS:

Under hypoxia condition, hydroxyapatite bioceramics can promote the proliferation of MG63 osteoblasts, elevate the activity of alkaline phosphatase and upregulate HIF-α and VEGF expression without effect on apoptosis.