In vitro and in vivo study on the osseointegration of magnesium and strontium ion with two different proportions of mineralized collagen and its mechanism

Abstract

To explore the optimal combination of Mg2+, Sr2+ and mineralized collagen (nHAC) with two different proportions of hydroxyapatite (HA) and collagen (COL) on differentiation of MC3T3-E1 and the underlying mechanism, as well as achieve bone osseointegration. MC3T3-E1 cells were cultured in a complete medium with Mg2+ at the concentration of 0, 4, 8, 12, 16, 20 mmol/L, Sr2+ at the concentration of 0, 3, 6, 12 mmol/L, and the impregnation solution of 3:7 and 5:5nHAC. The differentiation of MC3T3-E1 was measured by expression of osteogenic genes and proteins including Runx-2, BMP-2 and OCN and determined the activation of PI3K/AKT/GSK3β/β-catenin signaling pathway in 12 mmol/LMg 2 ++3 mmol/LSr 2 ++3:7nHAC group. Osteoporosis was induced in 18 female rats by means of ovariectomy, the implants were immersed in 60 mmol/LMg 2 ++15 mmol/LSr 2 ++3:7nHAC impregnation solution and implanted into the mesial alveolar fossa for immediate implantation. The osseointegration of the implants was observed by Confocal laser scanning microscopy (CLSM) and histology at 4 and 8 weeks. The groups cultured with 12 mmol/LMg 2 +, 3 mmol/LSr 2 + and 3:7nHAC impregnation solution showed the osteogenic genes and proteins were significantly higher respectively (P < 0.05), as well as p-Akt, p-GSK3β and β-catenin proteins (P < 0.05). CLSM and histology showed that the implant surface was surrounded by thick lamellar bone plate, and the trabecular bone were dense and continuous in the impregnation solution. These results found that magnesium and strontium ion-loaded mineralized collagen play an critical role in up-regulating the cells activity through PI3K/AKT/GSK3β/β-catenin signaling pathway and could be promote the formation of osseointegration.

Advances in osseointegration of biomimetic mineralized collagen and inorganic metal elements of natural bone for bone repair

“…The content of Mg in the composite and the sustained release of Mg too high and too low will affect its bone repair effect. Sun et al [ 54 ] found that MC3T3-E1 cells significantly promoted Runx-2, OCN and BMP-2 gene expression when cultured in a medium containing 12 mmol/l Mg 2+ . Therefore, when the Mg content in the implantation site of the composite is close to that in 12 mmol/ Mg 2+ medium, it can significantly promote the osteogenic properties of the scaffold.…”

“…In vivo studies have found that the MHA/Coll scaffold is effective in recruiting progenitors and osteocytes and contributes to the assembly of the hematopoietic ecosystem. Sun et al [ 54 ] demonstrated that MC scaffolds loaded with Mg–Sr ions could activate PI3K/AKT/GSK3b/b-catenin signaling pathway to promote osteogenic differentiation of cells. So the MHA/Coll scaffold has good osteoinductive potential and provides a direction for clinical bone repair.…”

“…Osseointegration of elemental Sr with MC reduces nucleation barriers, regulates nucleation sites and promotes more homogeneous mineralization within fibrous regions [ 55 ]. The MC scaffold loaded with Sr ions also activates the PI3K/AKT/GSK3b/b-catenin signaling pathway and the MAPK pathway significantly enhancing the expression of osteogenic genes and proteins at the cellular level [ 54 , 71 ]. The composite scaffold can accelerate the reconstruction of bone tissue and promotes the formation of osseointegration between the implant and the new bone.…”

“…In addition, local controlled release of Sr ions is the focus of research. Sun et al [ 54 ] compared MC3T3-E1 cells cultured in medium containing Sr 2+ at 0, 3, 6 and 12 mmol/l. The results showed that 3 mmol/l could significantly promote the expression of osteogenic-related genes, such as Runx-2, BMP-2 and OCN.…”

“…Therefore, when the ratio of n-HA and collagen I is close to the composition of native bone, it tends to have a better ability to promote bone regeneration. Sun et al [ 54 ] investigated scaffolds with 3:7 and 5:5 volume ratios of n-HA and Col I and n-HA particles in scaffolds with 3:7 volume ratios were evenly distributed on the pore walls formed by collagen matrices to form stable and uniform porous structures. The scaffold also significantly promoted the expression of osteogenesis-related genes Runx-2, BMP-2 and OCN.…”