In vivo and in vitro study of resorbable magnesium wires for medical implants:Mg purity,surface quality,Zn alloying and polymer coating

Magnesium is an excellent material in terms of biocompatibility and its corrosion products can serve as an active source for new bone formation.However,localized corrosion and H_(2)generation limit the potential of Mg-based implants.Utilizing low-alloyed Mg-Zn wires can strongly reduce problems with large H_(2)bubbles and improve the mechanical properties considerably while maintaining excellent long-term biocompatibility.Acidic pickling and a polymer coating can be effectively used to lower the rate of in vivo degradation.In this work,microstructural,mechanical,and in vitro characterization of 250μm and 300μm extruded wires made from ultra-pure Mg,commercially pure Mg,Mg-0.15Zn,Mg-0.4Zn and Mg-1Zn was performed.Additionally,Mg-0.4Zn wires together with a variant coated with a copolymer of L-lactide andε-caprolactone were tested in vivo on artificially damaged Wistar rat femurs.Based on the observed Mg-induced osteogenesis,polymer-coated Mg wires with a small addition of Zn are a perspective material for bone-support applications,such as cerclage and fixation wires.

Vitamin D receptor expression in human bone tissue and dose-dependent activation in resorbing osteoclasts

The effects of vitamin D on osteoblast mineralization are well documented. Reports of the effects of vitamin D on osteoclasts, however, are conflicting, showing both inhibition and stimulation. Finding that resorbing osteoclasts in human bone express vitamin D receptor （VDR）, we examined their response to different concentrations of 25-hydroxy vitamin D3 [25（OH）D3] （100 or 500 nmol·L^-1） and 1,25-dihydroxy vitamin D3 [1,25（OH）2D3] （0.1 or 0.5 nmol·L^-1） metabolites in cell cultures. Specifically, CD14＋ monocytes were cultured in charcoal-stripped serum in the presence of receptor activator of nuclear factor kappa-B ligand （RANKL） and macrophage colony-stimulating factor （M-CSF）. Tartrate-resistant acid phosphatase （TRAP） histochemical staining assays and dentine resorption analysis were used to identify the size and number of osteoclast cells, number of nuclei per cell and resorption activity. The expression of VDR was detected in human bone tissue （ex vivo） by immunohistochemistry and in vitro cell cultures by western blotting. Quantitative reverse transcription-PCR （qRT-PCR） was used to determine the level of expression of vitamin D-related genes in response to vitamin D metabolites. VDR-related genes during osteoclastogenesis, shown by qRT-PCR, was stimulated in response to 500 nmol·L^-1 of 25（OH）D3 and 0.1-0.5 nmol·L^-1 of 1,25（OH）2D3, upregulating cytochrome P450 family 27 subfamily B member I （CYP27B1） and cytochrome P450 family 24 subfamily A member I （CYP24A1）. Osteoclast fusion transcripts transmembrane 7 subfamily member 4 （tm7sf4） and nuclear factor of activated T-cell cytoplasmic 1 （nfatcl） where downregulated in response to vitamin D metabolites. Osteoclast number and resorption activity were also increased. Both 25（OH）D3 and 1,25（OH）2D3 reduced osteoclast size and number when co-treated with RANKL and M-CSF. The evidence for VDR expression in resorbing osteoclasts in vivo and low-dose effects of 1,25（OH）2D3 on osteoclasts in vitro may therefore provide insight into the effects of clinical vitamin D treatments, further providing a counterpoint to the high-dose effects reported from in vitro experiments.

Simple Modifications to Standard TRIzol®Protocol Allow High-Yield RNA Extraction from Cells on Resorbable Materials

Resorbable bioceramics are attractive for medical applications such as bone substitution. Biochemical analysis on cells cultured on these biomaterials is vital to predict the impact of the materials in vivo and RNA extraction is an essential step in gene expression study using RT-qPCR. In this study, we describe simple modifications to the TRIzol? RNA extraction protocol widely used in biology and these allow high-yield extraction of RNA from cells on resorbable calcium phosphates. Without the modifications, RNA is trapped in the co-precipitated calcium compounds, rendering TRIzol? extraction method infeasible. Among the modifications, the use of extra TRIzol? to dilute the lysate before the RNA precipitation step is critical for extraction of RNA from porous ?-tricalcium phosphate (?-TCP) discs. We also investigate the rationale behind the undesirable precipitation so as to provide clues about the modifications required for other resorbable materials with high application potential in bone tissue engineering.

RESORBABLE HIGH-STRENGTH ROD FOR FRACTURE INTERNAL FIXATION

Objective To find an ideal biomaterial for internal fixation. Methods Forty rabbits with fracture of the femur diaphysis (superiorcondyle) were treated by intramedullary nailing of femur with composites rod of resorbable DL-polylactic acid (PDLLA)-calcium metaphosphate (CMP), while steinmann's pin as control. The fracture healing, the material degradation and its mechanical properties were studied by X-ray films, macroscopic, microscopic and electron microscopic observations. Results No significant inflammatory reaction was found, and all the osteotomies were healed, while material was resorbed. Conclusion The PDLLA-CMP has excellent biocompatibility and mechanical properties, and it can be a promising implant material in orthopaedics surgery.

Resorbable polymer electrospun nanofibers:History,shapes and application for tissue engineering

Resorbable polymer electrospun nanofiber-based materials/devices have high surface-to-volume ratio and often have a porous structure with excellent pore interconnectivity,which are suitable for growth and development of different types of cells.Due to the huge advantages of both resorbable polymers and electrospun nano fibers,re sorbable polymer electrospun nanofibers(RPENs)have been widely applied in the field of tissue engineering.In this paper,we will mainly introduce RPENs for tissue engineering.Firstly,the electrospinning technique and electrospun nanofiber architectures are briefly introduced.Secondly,the application of RPENs in the field of tissue engineering is mainly reviewed.Finally,the advantages and disadvantages of RPENs for tissue engineering are discussed.This review will provide a comprehensive guide to apply resorbable polymer electrospun nanofibers for tissue engineering.

Prophylactic vertebroplasty procedure applied with a resorbable bone cement can decrease the fracture risk of sandwich vertebrae:long-term evaluation of clinical outcomes

A sandwich vertebra is formed after multiple osteoporotic vertebral fractures treated by percutaneous vertebroplasty,which has a risk of developing new fractures.The purpose of our study was to(i)investigate the occurrence of new fractures in sandwich vertebra after cement augmentation procedures and to(ii)evaluate the clinical outcomes after prophylactic vertebral reinforcement applied with resorbable bone cement.From June 2011 to 2014,we analysed 55 patients with at least one sandwich vertebrae and treated with percutaneous vertebroplasty.Eighteen patients were treated by prophylactic vertebroplasty with a resorbable bone cement to strengthen the sandwich vertebrae as the prevention group.The others were the non-prevention group.All patients were examined by spinal radiographs within 1 day,6 months,12 months,24 months and thereafter.The incidence of sandwich vertebra is 8.25%(55/667)in our study.Most sandwich vertebrae(69.01%,49/71)are distributed in the thoracic-lumbar junction.There are 24 sandwich vertebrae(18 patients)and 47 sandwich vertebrae(37 patients)in either prevention group or non-prevention group,respectively.No significant difference is found between age,sex,body mass index,bone mineral density,cement disk leakage,sandwich vertebrae distribution or Cobb angle in the two groups.In the follow-up,8 out of 37(21.6%)patients(with eight sandwich vertebrae)developed new fractures in non-prevention’group,whereas no new fractures were detected in the prevention group.Neither Cobb angle nor vertebral compression rate showed significant change in the prevention group during the follow-up.However,in the non-prevention group,we found that Cobb angle increased and vertebral height lost significantly(P<0.05).Prophylactic vertebroplasty procedure applied with resorbable bone cement could decrease the rate of new fractures of sandwich vertebrae.