Thor Friis - Academia.edu (original) (raw)

Papers by Thor Friis

Tissue Engineering Part C-methods, Oct 1, 2014

The sheep (Ovis aries) is favored by many musculoskeletal tissue engineering groups as a large an... more The sheep (Ovis aries) is favored by many musculoskeletal tissue engineering groups as a large animal model because of its docile temperament and ease of husbandry. The size and weight of sheep are comparable to humans, which allows for the use of implants and fixation devices used in human clinical practice. The construction of a complimentary DNA (cDNA) library can capture the expression of genes in both a tissue-and time-specific manner. cDNA libraries have been a consistent source of gene discovery ever since the technology became commonplace more than three decades ago. Here, we describe the construction of a cDNA library using cells derived from sheep bones based on the pBluescript cDNA kit. Thirty clones were picked at random and sequenced. This led to the identification of a novel gene, C12orf29, which our initial experiments indicate is involved in skeletal biology. We also describe a polymerase chain reaction-based cDNA clone isolation method that allows the isolation of genes of interest from a cDNA library pool. The techniques outlined here can be applied in-house by smaller tissue engineering groups to generate tools for biomolecular research for large preclinical animal studies and highlights the power of standard cDNA library protocols to uncover novel genes.

Nanoscale, Jan 17, 2017

Current major obstacles for translating the nanoparticle (NP) morphology-related function into th... more Current major obstacles for translating the nanoparticle (NP) morphology-related function into therapeutic purposes come from the challenges in understanding the mechanisms that determine cell lineage commitment and constructing a NP-based 3D functional structure, and few studies have successfully demonstrated clear evidence of regulating in vivo tissue regeneration by NP morphology so far. Here, we show that nanoparticle geometry can be harnessed to mediate bone regeneration in a rat cranial defect model. We successfully synthesized hydroxyapatite NPs with well-defined morphologies using a modified liquid-solution-solid (LSS) method. The NPs showed differential effects on stem cell behaviors such as particle uptake, autophagy activation and osteogenic differentiation. By integrating nanoparticles within gelatin, we achieved 3D scaffolds with uniformly-distributed nano-topologies which, can mediate in vivo osteogenesis through stimulation of autophagy, with spherical particles demon...

Faculty of Built Environment and Engineering; Institute of Health and Biomedical Innovation, May 1, 2011

The efficient loading and sustained release of proteins from bioactive microspheres remain a sign... more The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS-A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS-A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS-A microspheres prepared by non-in situ method, which lack a core-shell structure. CS-A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS-A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS-A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS-A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.

Journal of Materials Chemistry B, 2018

When a bone substitute biomaterial is implanted into the body, the material's surface comes i... more When a bone substitute biomaterial is implanted into the body, the material's surface comes into contact with circulating blood, which results in the formation of a peri-implant hematoma or blood clot.

composite microspheres with core-shell structure alginate − preparation and protein delivery of s... more composite microspheres with core-shell structure alginate − preparation and protein delivery of silicateIn situ

J. Mater. Chem. B, 2016

Calcium phosphates (CAPs) can be produced from either biologically sourced materials or mineral d... more Calcium phosphates (CAPs) can be produced from either biologically sourced materials or mineral deposits.

Journal of The Royal Society Interface, 2011

The efficient loading and sustained release of proteins from bioactive microspheres remain a sign... more The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS–A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS–A microspheres with a core-shell...

Journal of Cellular and Molecular Medicine, 2010

Proliferative behaviour is a critical features regarding the survival of cells, as such, they are... more Proliferative behaviour is a critical features regarding the survival of cells, as such, they are frequently analysed in cancer research. Therefore, robust and reliable methods are required to determine cell proliferation during experiments. Several methods are commonly used to quantify cell proliferation, and each has its advantages and limitations [1] whereas no method is suitable for all areas of application. There seems to be a general lack of understanding amongst many users as to which assay is the most appropriate for their specific application (Table 1). Direct visual cell counting using a haemocytometer combined with a cell viability dye, is the simplest and most inexpensive method to determine cell numbers. However, it is a time consuming method, subject to operator errors, and therefore of limited value for medium to high-throughput applications [2]. Colorimetric assays such as MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3carboxymethoxyphenyl)-2-(4-sulfonyl)-2H-tetrazolium), watersoluble tetrazolium salt (WST-1) (4-(3-(4-Iodophenyl)-2-(4-nitrophenyl)2H-5-tetrazolio)-1,3-benzene disulfonate) and AlamarBlue were originally developed to measure reagent cytotoxicity and destabilization. MTT, MTS and WST-1 are assays based on the bioreduction of tetrazolium salts from pale yellow to the dark blue formazan dye by mitochondrial dehydrogenases and are end-point assays by nature [3, 4]. AlamarBlue, also known as resazurin, is transformed from blue colour to the highly fluorescent resorufin (pink) within a redox reaction process. The exact cellular location of this reaction remains unknown, although various reaction sites have been suggested [5]. Resazurin is a water soluble and non-toxic dye that allows continuous monitoring of cultures over time, and has the advantage that further analytic assays can be performed on the same samples compared to the tetrazolium salt-based assays

Bone, 2010

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production... more Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK-ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Bone, 2010

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production... more Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK-ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Biomaterials, 2010

Porous mesopore-bioglass (MBG) scaffolds have been proposed as a new class of bone regeneration m... more Porous mesopore-bioglass (MBG) scaffolds have been proposed as a new class of bone regeneration materials due to their apatite-formation and drug-delivery properties; however, the material's inherent brittleness and high degradation and surface instability are major disadvantages, which compromise its mechanical strength and cytocompatibility as a biological scaffold. Silk, on the other hand, is a native biomaterial and is well characterized with respect to biocompatibility and tensile strength. In this study we set out to investigate what effects blending silk with MBG had on the physiochemical, drug-delivery and biological properties of MBG scaffolds with a view to bone tissue engineering applications. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were the methods used to analyze the inner microstructure, pore size and morphology, and composition of MBG scaffolds, before and after addition of silk. The effect of silk modification on the mechanical property of MBG scaffolds was determined by testing the compressive strength of the scaffolds and also compressive strength after degradation over time. The drug-delivery potential was evaluated by the release of dexamethasone (DEX) from the scaffolds. Finally, the cytocompatibility of silk-modified scaffolds was investigated by the attachment, morphology, proliferation, differentiation and bone-relative gene expression of bone marrow stromal cells (BMSCs). The results showed that silk modification improved the uniformity and continuity of pore network of MBG scaffolds, and maintained high porosity (94%) and large-pore size (200-400 mm). There was a significant improvement in mechanical strength, mechanical stability, and control of burst release of DEX in silkmodified MBG scaffolds. Silk modification also appeared to provide a better environment for BMSC attachment, spreading, proliferation, and osteogenic differentiation on MBG scaffolds.

Biomaterials, 2010

The rationale for the present study was to develop porous CaP/silk composite scaffolds with an op... more The rationale for the present study was to develop porous CaP/silk composite scaffolds with an optimized CaP-phase distribution and pore architecture, to facilitate osteogenic properties of human bone mesenchymal stromal cells (BMSCs) and in vivo bone formation abilities. This was achieved by first preparing CaP/silk hybrid powders which were then incorporated into silk to obtain uniform CaP/silk composite scaffolds, by means of a freeze drying method. The composition, microstructure and mechanical properties of the CaP/silk composite scaffolds were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscope (SEM) and a universal mechanical testing machine. BMSCs were cultured in these scaffolds and cell proliferation analyzed by confocal microscopy and MTS assay. Alkaline phosphatase (ALP) activity and osteogenic gene expression were assayed to determine if osteogenic differentiation had taken place. A calvarial defect model in SCID mice was used to determine the in vivo bone forming ability of the hybrid CaP/silk scaffolds. Our results showed that incorporating the hybrid CaP/silk powders into silk scaffolds improved both pore structure architecture and distribution of CaP powders in the composite scaffolds. By incorporating the CaP phase into silk scaffolds in vitro osteogenic differentiation of BMSCs was enhanced and there was increased in vivo cancellous bone formation. Here we report a novel method to prepare Ca/P composite scaffolds with an optimum pore structure and Ca/P distribution to facilitate BMSC differentiation and bone formation.

Arthritis & Rheumatism, 2010

ERK1/2 and p38 in the regulation of hypertrophic changes of normal articular cartilage chondrocyt... more ERK1/2 and p38 in the regulation of hypertrophic changes of normal articular cartilage chondrocytes induced by osteoarthritic subchondral osteoblasts

Analytical Biochemistry, 1992

ABSTRACT

Journal of Analytical & Bioanalytical Techniques

One of the most challenging aspects of interpreting quantitative information of biological sample... more One of the most challenging aspects of interpreting quantitative information of biological samples from laser inductively coupled plasma mass spectrometry (LA-ICP-MS) is a lack of appropriate matrix-matched internal standards that is needed for calibrations. There are standards available; however, most certified reference standard materials are suboptimal, due to the high variability and complexity of biological materials, especially for calcified tissues. In the present study, we described an approach in which bovine bone pellets are used as reliable matrixmatched standards for quantitative analysis of bone samples. Bovine tibial bones, sourced from a local butcher shop, were treated with or without autoclave sterilization. The samples were lyophilized over a 24 hour period, after which the elemental distributions in autoclaved, non-autoclaved bone pellets and naive bone fragments were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and LA-ICP-MS methods, in addition to homogeneity analysis of non-autoclaved bone pellets. The results demonstrated that non-autoclaved and autoclaved bone pellets shared similar average elemental concentrations after correcting for background signal; natural bone fragments, on the other hand, showed large sample variations. Factors such as low cost and ease of manufacture, “home-made” non-autoclaved bone pellets are the preferred option and these were subjected to further investigations. The homogeneity analysis revealed that non-autoclaved bone pellets had a higher degree of homogeneity, with minimal standard deviations and a uniform particle size of less than 100 μm. These results show that non-autoclaved bovine bone pellets are reliable and easy-to-make alternative to matrix-matched reference material with which to analyse calcified tissues by LA-ICP-MS.

BioMed Research International

World neurosurgery, Oct 1, 2018

Tissue Engineering Part C-methods, Oct 1, 2014

The sheep (Ovis aries) is favored by many musculoskeletal tissue engineering groups as a large an... more The sheep (Ovis aries) is favored by many musculoskeletal tissue engineering groups as a large animal model because of its docile temperament and ease of husbandry. The size and weight of sheep are comparable to humans, which allows for the use of implants and fixation devices used in human clinical practice. The construction of a complimentary DNA (cDNA) library can capture the expression of genes in both a tissue-and time-specific manner. cDNA libraries have been a consistent source of gene discovery ever since the technology became commonplace more than three decades ago. Here, we describe the construction of a cDNA library using cells derived from sheep bones based on the pBluescript cDNA kit. Thirty clones were picked at random and sequenced. This led to the identification of a novel gene, C12orf29, which our initial experiments indicate is involved in skeletal biology. We also describe a polymerase chain reaction-based cDNA clone isolation method that allows the isolation of genes of interest from a cDNA library pool. The techniques outlined here can be applied in-house by smaller tissue engineering groups to generate tools for biomolecular research for large preclinical animal studies and highlights the power of standard cDNA library protocols to uncover novel genes.

Nanoscale, Jan 17, 2017

Current major obstacles for translating the nanoparticle (NP) morphology-related function into th... more Current major obstacles for translating the nanoparticle (NP) morphology-related function into therapeutic purposes come from the challenges in understanding the mechanisms that determine cell lineage commitment and constructing a NP-based 3D functional structure, and few studies have successfully demonstrated clear evidence of regulating in vivo tissue regeneration by NP morphology so far. Here, we show that nanoparticle geometry can be harnessed to mediate bone regeneration in a rat cranial defect model. We successfully synthesized hydroxyapatite NPs with well-defined morphologies using a modified liquid-solution-solid (LSS) method. The NPs showed differential effects on stem cell behaviors such as particle uptake, autophagy activation and osteogenic differentiation. By integrating nanoparticles within gelatin, we achieved 3D scaffolds with uniformly-distributed nano-topologies which, can mediate in vivo osteogenesis through stimulation of autophagy, with spherical particles demon...

Faculty of Built Environment and Engineering; Institute of Health and Biomedical Innovation, May 1, 2011

The efficient loading and sustained release of proteins from bioactive microspheres remain a sign... more The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS-A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS-A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS-A microspheres prepared by non-in situ method, which lack a core-shell structure. CS-A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS-A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS-A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS-A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.

Journal of Materials Chemistry B, 2018

When a bone substitute biomaterial is implanted into the body, the material's surface comes i... more When a bone substitute biomaterial is implanted into the body, the material's surface comes into contact with circulating blood, which results in the formation of a peri-implant hematoma or blood clot.

composite microspheres with core-shell structure alginate − preparation and protein delivery of s... more composite microspheres with core-shell structure alginate − preparation and protein delivery of silicateIn situ

J. Mater. Chem. B, 2016

Calcium phosphates (CAPs) can be produced from either biologically sourced materials or mineral d... more Calcium phosphates (CAPs) can be produced from either biologically sourced materials or mineral deposits.

Journal of The Royal Society Interface, 2011

The efficient loading and sustained release of proteins from bioactive microspheres remain a sign... more The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS–A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS–A microspheres with a core-shell...

Journal of Cellular and Molecular Medicine, 2010

Proliferative behaviour is a critical features regarding the survival of cells, as such, they are... more Proliferative behaviour is a critical features regarding the survival of cells, as such, they are frequently analysed in cancer research. Therefore, robust and reliable methods are required to determine cell proliferation during experiments. Several methods are commonly used to quantify cell proliferation, and each has its advantages and limitations [1] whereas no method is suitable for all areas of application. There seems to be a general lack of understanding amongst many users as to which assay is the most appropriate for their specific application (Table 1). Direct visual cell counting using a haemocytometer combined with a cell viability dye, is the simplest and most inexpensive method to determine cell numbers. However, it is a time consuming method, subject to operator errors, and therefore of limited value for medium to high-throughput applications [2]. Colorimetric assays such as MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3carboxymethoxyphenyl)-2-(4-sulfonyl)-2H-tetrazolium), watersoluble tetrazolium salt (WST-1) (4-(3-(4-Iodophenyl)-2-(4-nitrophenyl)2H-5-tetrazolio)-1,3-benzene disulfonate) and AlamarBlue were originally developed to measure reagent cytotoxicity and destabilization. MTT, MTS and WST-1 are assays based on the bioreduction of tetrazolium salts from pale yellow to the dark blue formazan dye by mitochondrial dehydrogenases and are end-point assays by nature [3, 4]. AlamarBlue, also known as resazurin, is transformed from blue colour to the highly fluorescent resorufin (pink) within a redox reaction process. The exact cellular location of this reaction remains unknown, although various reaction sites have been suggested [5]. Resazurin is a water soluble and non-toxic dye that allows continuous monitoring of cultures over time, and has the advantage that further analytic assays can be performed on the same samples compared to the tetrazolium salt-based assays

Bone, 2010

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production... more Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK-ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Bone, 2010

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production... more Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK-ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Biomaterials, 2010

Porous mesopore-bioglass (MBG) scaffolds have been proposed as a new class of bone regeneration m... more Porous mesopore-bioglass (MBG) scaffolds have been proposed as a new class of bone regeneration materials due to their apatite-formation and drug-delivery properties; however, the material's inherent brittleness and high degradation and surface instability are major disadvantages, which compromise its mechanical strength and cytocompatibility as a biological scaffold. Silk, on the other hand, is a native biomaterial and is well characterized with respect to biocompatibility and tensile strength. In this study we set out to investigate what effects blending silk with MBG had on the physiochemical, drug-delivery and biological properties of MBG scaffolds with a view to bone tissue engineering applications. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were the methods used to analyze the inner microstructure, pore size and morphology, and composition of MBG scaffolds, before and after addition of silk. The effect of silk modification on the mechanical property of MBG scaffolds was determined by testing the compressive strength of the scaffolds and also compressive strength after degradation over time. The drug-delivery potential was evaluated by the release of dexamethasone (DEX) from the scaffolds. Finally, the cytocompatibility of silk-modified scaffolds was investigated by the attachment, morphology, proliferation, differentiation and bone-relative gene expression of bone marrow stromal cells (BMSCs). The results showed that silk modification improved the uniformity and continuity of pore network of MBG scaffolds, and maintained high porosity (94%) and large-pore size (200-400 mm). There was a significant improvement in mechanical strength, mechanical stability, and control of burst release of DEX in silkmodified MBG scaffolds. Silk modification also appeared to provide a better environment for BMSC attachment, spreading, proliferation, and osteogenic differentiation on MBG scaffolds.

Biomaterials, 2010

The rationale for the present study was to develop porous CaP/silk composite scaffolds with an op... more The rationale for the present study was to develop porous CaP/silk composite scaffolds with an optimized CaP-phase distribution and pore architecture, to facilitate osteogenic properties of human bone mesenchymal stromal cells (BMSCs) and in vivo bone formation abilities. This was achieved by first preparing CaP/silk hybrid powders which were then incorporated into silk to obtain uniform CaP/silk composite scaffolds, by means of a freeze drying method. The composition, microstructure and mechanical properties of the CaP/silk composite scaffolds were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscope (SEM) and a universal mechanical testing machine. BMSCs were cultured in these scaffolds and cell proliferation analyzed by confocal microscopy and MTS assay. Alkaline phosphatase (ALP) activity and osteogenic gene expression were assayed to determine if osteogenic differentiation had taken place. A calvarial defect model in SCID mice was used to determine the in vivo bone forming ability of the hybrid CaP/silk scaffolds. Our results showed that incorporating the hybrid CaP/silk powders into silk scaffolds improved both pore structure architecture and distribution of CaP powders in the composite scaffolds. By incorporating the CaP phase into silk scaffolds in vitro osteogenic differentiation of BMSCs was enhanced and there was increased in vivo cancellous bone formation. Here we report a novel method to prepare Ca/P composite scaffolds with an optimum pore structure and Ca/P distribution to facilitate BMSC differentiation and bone formation.

Arthritis & Rheumatism, 2010

ERK1/2 and p38 in the regulation of hypertrophic changes of normal articular cartilage chondrocyt... more ERK1/2 and p38 in the regulation of hypertrophic changes of normal articular cartilage chondrocytes induced by osteoarthritic subchondral osteoblasts

Analytical Biochemistry, 1992

ABSTRACT

Journal of Analytical & Bioanalytical Techniques

One of the most challenging aspects of interpreting quantitative information of biological sample... more One of the most challenging aspects of interpreting quantitative information of biological samples from laser inductively coupled plasma mass spectrometry (LA-ICP-MS) is a lack of appropriate matrix-matched internal standards that is needed for calibrations. There are standards available; however, most certified reference standard materials are suboptimal, due to the high variability and complexity of biological materials, especially for calcified tissues. In the present study, we described an approach in which bovine bone pellets are used as reliable matrixmatched standards for quantitative analysis of bone samples. Bovine tibial bones, sourced from a local butcher shop, were treated with or without autoclave sterilization. The samples were lyophilized over a 24 hour period, after which the elemental distributions in autoclaved, non-autoclaved bone pellets and naive bone fragments were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and LA-ICP-MS methods, in addition to homogeneity analysis of non-autoclaved bone pellets. The results demonstrated that non-autoclaved and autoclaved bone pellets shared similar average elemental concentrations after correcting for background signal; natural bone fragments, on the other hand, showed large sample variations. Factors such as low cost and ease of manufacture, “home-made” non-autoclaved bone pellets are the preferred option and these were subjected to further investigations. The homogeneity analysis revealed that non-autoclaved bone pellets had a higher degree of homogeneity, with minimal standard deviations and a uniform particle size of less than 100 μm. These results show that non-autoclaved bovine bone pellets are reliable and easy-to-make alternative to matrix-matched reference material with which to analyse calcified tissues by LA-ICP-MS.

BioMed Research International

World neurosurgery, Oct 1, 2018