Abstract
The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials.
Highlights
Mg-based biodegradable materials have garnered increasing attention for their potential applications as biodegradable and bioabsorbable implant materials in the field of orthopedics
The phase identification of Mg-1Ca-x wt.% Sr alloys were characterized by XRD (Fig. 3), and the results showed that all alloys were composed of α-Mg phase, α-Mg2Ca and α-Mg17Sr2 intermetallic phase
Many previous studies have discussed the relationship between mitogen-activated protein kinases (MAPK) family and RUNX2/OSX, the results indicated that ERK1/2 mediated RUNX2 phosphorylation and transcriptional activity in bone[46]
Summary
Mg-based biodegradable materials have garnered increasing attention for their potential applications as biodegradable and bioabsorbable implant materials in the field of orthopedics. Ida S. et al has synthesized and characterized Mg-xCa-xSr (x = 0.5–7.0 wt%; y = 0.5–3.5 wt%) alloys for biodegradable orthopedic implant applications, and indicated that the Mg-1.0Ca-0.5Sr alloy is the most promising alloy since it showed the lowest degradation rate along with no significant toxicity to osteoblasts[20], the blood compatibility, cyto-compatibility and the osteoinductivity as well as the corresponding mechanisms were not involved completely. These beneficial effects of Ca and Sr prompted us to research the feasibility of Ca, Sr alloying within Mg and the corresponding effects on the biology functions. The purposes of our present study were: (1) to prepare Mg-1Ca alloys with different Sr contents; (2) to seek the optimal amount of Sr content added in Mg-1Ca alloys with respect to the osteogenic induction effects; (3) to illuminate the potential molecular mechanism of osteogenic differentiation about the Mg alloys with Ca and Sr
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