Mikael J. Turunen
University of Eastern Finland
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Featured researches published by Mikael J. Turunen.
Journal of Bone and Mineral Research | 2010
Hanna Isaksson; Mikael J. Turunen; Lassi Rieppo; Simo Saarakkala; Inari S. Tamminen; Jarno Rieppo; Heikki Kröger; Jukka S. Jurvelin
Renal osteodystrophy alters metabolic activity and remodeling rate of bone and also may lead to different bone composition. The objective of this study was to characterize the composition of bone in high‐turnover renal osteodystrophy patients by means of Fourier transform infrared spectroscopic imaging (FTIRI). Iliac crest biopsies from healthy bone (n = 11) and patients with renal osteodystrophy (ROD, n = 11) were used in this study. The ROD samples were from patients with hyperparathyroid disease. By using FTIRI, phosphate‐to‐amide I ratio (mineral‐to‐matrix ratio), carbonate‐to‐phosphate ratio, and carbonate‐to‐amide I ratio (turnover rate/remodeling activity), as well as the collagen cross‐link ratio (collagen maturity), were quantified. Histomorphometric analyses were conducted for comparison. The ROD samples showed significantly lower carbonate‐to‐phosphate (p < .01) and carbonate‐to‐amide I (p < .001) ratios. The spatial variation across the trabeculae highlighted a significantly lower degree of mineralization (p < .05) at the edges of the trabeculae in the ROD samples than in normal bone. Statistically significant linear correlations were found between histomorphometric parameters related to bone‐remodeling activity and number of bone cells and FTIRI‐calculated parameters based on carbonate‐to‐phosphate and carbonate‐to‐amide I ratios. Hence the results suggested that FTIRI parameters related to carbonate may be indicative of turnover and remodeling rate of bone.
Applied Spectroscopy | 2011
Mikael J. Turunen; Simo Saarakkala; Lassi Rieppo; Heikki J. Helminen; Jukka S. Jurvelin; Hanna Isaksson
The molecular composition of the organic and inorganic matrices of bone undergoes alterations during maturation. The aim of this study was to compare Fourier transform infrared (FT-IR) and near-infrared (NIR) Raman microspectroscopy techniques for characterization of the composition of growing and developing bone from young to skeletally mature rabbits. Moreover, the specificity and differences of the techniques for determining bone composition were clarified. The humeri of female New Zealand White rabbits, with age range from young to skeletally mature animals (four age groups, n = 7 per group), were studied. Spectral peak areas, intensities, and ratios related to organic and inorganic matrices of bone were analyzed and compared between the age groups and between FT-IR and Raman microspectroscopic techniques. Specifically, the degree of mineralization, type-B carbonate substitution, crystallinity of hydroxyapatite (HA), mineral content, and collagen maturity were examined. Significant changes during maturation were observed in various compositional parameters with one or both techniques. Overall, the compositional parameters calculated from the Raman spectra correlated with analogous parameters calculated from the IR spectra. Collagen cross-linking (XLR), as determined through peak fitting and directly from the IR spectra, were highly correlated. The mineral/matrix ratio in the Raman spectra was evaluated with multiple different peaks representing the organic matrix. The results showed high correlation with each other. After comparison with the bone mineral density (BMD) values from micro-computed tomography (micro-CT) imaging measurements and crystal size from XRD measurements, it is suggested that Raman microspectroscopy is more sensitive than FT-IR microspectroscopy for the inorganic matrix of the bone. In the literature, similar spectroscopic parameters obtained with FT-IR and NIR Raman microspectroscopic techniques are often compared. According to the present results, however, caution is required when performing this kind of comparison.
Bone | 2013
Mikael J. Turunen; Viktoria Prantner; Jukka S. Jurvelin; Heikki Kröger; Hanna Isaksson
The microarchitecture of trabecular bone adapts to its mechanical loading environment according to Wolffs law and alters with age. Trabecular bone is a metabolically active tissue, thus, its molecular composition and microarchitecture may vary between anatomical locations as a result of the local mechanical loading environment. No comprehensive comparison of composition and microarchitecture of trabecular bone in different anatomical locations has been conducted. Therefore, the objective of this study was to compare the molecular composition and microarchitecture, evaluated with Fourier transform infrared (FTIR) microspectroscopy and micro-computed tomography (μCT), respectively, in the femoral neck, greater trochanter and calcaneus of human cadavers. Specimens were harvested from 20 male human cadavers (aged 17-82 years) with no known metabolic bone diseases. Significant differences were found in composition and microarchitecture of trabecular bone between the anatomical locations. Compositional differences were primarily observed between the calcaneus and the proximal femur sites. Mineralization was higher in the greater trochanter than in the calcaneus (+2%, p<0.05) and crystallinity was lowest in the calcaneus (-24%, p<0.05 as compared to the femoral neck). Variation in the composition of trabecular bone within different parts of the proximal femur was only minor. Collagen maturity was significantly lower in greater trochanter than in femoral neck (-8%, p<0.01) and calcaneus (-5%, p<0.05). The greater trochanter possessed a less dense trabecular bone microarchitecture compared to femoral neck or calcaneus. Age related changes were mainly found in the greater trochanter. Significant correlations were found between the composition and microarchitecture of trabecular bone in the greater trochanter and calcaneus, indicating that both composition and microarchitecture alter similarly. This study provides new information about composition and microarchitecture of trabecular bone in different anatomical locations and their alterations with age with respect to the anatomical loading environments.
Journal of Biomechanics | 2015
Xiaowei Ojanen; Hanna Isaksson; Juha Töyräs; Mikael J. Turunen; Markus K. H. Malo; A Halvari; Jukka S. Jurvelin
Trabecular bone is a metabolically active tissue with a high surface to volume ratio. It exhibits viscoelastic properties that may change during aging. Changes in bone properties due to altered metabolism are sensitively revealed in trabecular bone. However, the relationships between material composition and viscoelastic properties of bone, and their changes during aging have not yet been elucidated. In this study, trabecular bone samples from the femoral neck of male cadavers (n=21) aged 17-82 years were collected and the tissue level composition and its associations with the tissue viscoelastic properties were evaluated by using Raman microspectroscopy and nanoindentation, respectively. For composition, collagen content, mineralization, carbonate substitution and mineral crystallinity were evaluated. The calculated mechanical properties included reduced modulus (Er), hardness (H) and the creep parameters (E1, E2, η1and η2), as obtained by fitting the experimental data to the Burgers model. The results indicated that the creep parameters, E1, E2, η1and η2, were linearly correlated with mineral crystallinity (r=0.769-0.924, p<0.001). Creep time constant (η2/E2) tended to increase with crystallinity (r=0.422, p=0.057). With age, the mineralization decreased (r=-0.587, p=0.005) while the carbonate substitution increased (r=0.728, p<0.001). Age showed no significant associations with nanoindentation parameters. The present findings suggest that, at the tissue-level, the viscoelastic properties of trabecular bone are related to the changes in characteristics of bone mineral. This association may be independent of human age.
Journal of Orthopaedic Research | 2012
Mikael J. Turunen; Simo Saarakkala; Heikki J. Helminen; Jukka S. Jurvelin; Hanna Isaksson
The organization and composition of the collagen matrix of cortical bone changes as the bone matures due to growth and mechanical loading. We aimed to investigate the composition and organization of the collagen matrix in rabbit cortical bone during maturation using Fourier transform infrared (FTIR) microspectroscopy and polarized light microscopy (PLM). FTIR and PLM findings were compared to biochemical analysis from an earlier study. Mid‐diaphyseal samples from left femora of female New Zealand White rabbits were used. The animal age ranged from newborn to 18‐month old (5 age groups, n = 10 per group). The bones had earlier been decalcified and evaluated with biochemistry. In this study, collagen content, orientation, collagen cross‐linking and spatial heterogeneity of all parameters was evaluated. Similar results were obtained when collagen content was evaluated with FTIR and PLM compared to the collagen content assessed with BA. Collagen content, orientation and collagen maturity increased significantly until the age of 3 months and remained similar thereafter. Simultaneously, spatial heterogeneity of the measured parameters decreased. Based on these findings, it seems that the collagen matrix of rabbit bone attains its mature state around 3 months of age, which is before the overall skeletal maturity is reached.
Journal of Biomechanics | 2012
Mikael J. Turunen; Juha Töyräs; Mikko J. Lammi; Jukka S. Jurvelin; Rami K. Korhonen
In clinical arthrographic examination, strong hypertonic contrast agents are injected directly into the joint space. This may reduce the stiffness of articular cartilage, which is further hypothesized to lead to overload-induced cell death. We investigated the cell death in articular cartilage while the tissue was compressed in situ in physiological saline solution and in full strength hypertonic X-ray contrast agent Hexabrix(TM). Samples were prepared from bovine patellae and stored in Dulbeccos Modified Eagles Medium overnight. Further, impact tests with or without creep were conducted for the samples with contact stresses and creep times changing from 1 MPa to 10 MPa and from 0 min to 15 min, respectively. Finally, depth-dependent cell viability was assessed with a confocal microscope. In order to characterize changes in the biomechanical properties of cartilage as a result of the use of Hexabrix™, stress-relaxation tests were conducted for the samples immersed in Hexabrix™ and phosphate buffered saline (PBS). Both dynamic and equilibrium modulus of the samples immersed in Hexabrix™ were significantly (p<0.05) lower than those of the samples immersed in PBS. Cartilage samples immersed in physiological saline solution showed load-induced cell death primarily in the superficial and middle zones. However, under high 8-10 MPa contact stresses, the samples immersed in full strength Hexabrix™ showed significantly (p<0.05) higher number of dead cells than the samples compressed in physiological saline, especially in the deep zone of cartilage. In conclusion, excessive loading stresses followed by tissue creep might increase the risk for chondrocyte death in articular cartilage when immersed in hypertonic X-ray contrast agent, especially in the deep zone of cartilage.
Journal of Biomedical Optics | 2014
Mikael J. Turunen; Sebastian Lages; Ana Labrador; Ulf Olsson; Magnus Tägil; Jukka S. Jurvelin; Hanna Isaksson
Abstract. Callus formation is a critical step for successful fracture healing. Little is known about the molecular composition and mineral structure of the newly formed tissue in the callus. The aim was to evaluate the feasibility of small angle x-ray scattering (SAXS) to assess mineral structure of callus and cortical bone and if it could provide complementary information with the compositional analyses from Fourier transform infrared (FTIR) microspectroscopy. Femurs of 12 male Sprague–Dawley rats at 9 weeks of age were fractured and fixed with an intramedullary 1.1 mm K-wire. Fractures were treated with the combinations of bone morphogenetic protein-7 and/or zoledronate. Rats were sacrificed after 6 weeks and both femurs were prepared for FTIR and SAXS analysis. Significant differences were found in the molecular composition and mineral structure between the fracture callus, fracture cortex, and control cortex. The degree of mineralization, collagen maturity, and degree of orientation of the mineral plates were lower in the callus tissue than in the cortices. The results indicate the feasibility of SAXS in the investigation of mineral structure of bone fracture callus and provide complementary information with the composition analyzed with FTIR. Moreover, this study contributes to the limited FTIR and SAXS data in the field.
Journal of Structural Biology | 2016
Mikael J. Turunen; Jørn Døvling Kaspersen; Ulf Olsson; Manuel Guizar-Sicairos; Martin Bech; Florian Schaff; Magnus Tägil; Jukka S. Jurvelin; Hanna Isaksson
The macro- and micro-features of bone can be assessed by using imaging methods. However, nano- and molecular features require more detailed characterization, such as use of e.g., vibrational spectroscopy and X-ray scattering. Nano- and molecular features also affect the mechanical competence of bone tissue. The aim of the present study was to reveal the effects of mineralization and its alterations on the mineral crystal scale, by investigating the spatial variation of molecular composition and mineral crystal structure across the cross-section of femur diaphyses in young rats, and healthy and osteoporotic mature rats (N=5). Fourier transform infrared spectroscopy and scanning small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with high spatial resolution were used at identical locations over the whole cross-section. This allowed quantification of point-by-point information about the spatial distribution of mineral crystal volume. All measured parameters (crystal dimensions, degree of orientation and predominant orientation) varied across the cortex. Specifically, the crystal dimensions were lower in the central cortex than in the endosteal and periosteal regions. Mineral crystal orientation followed the cortical circumference in the periosteal and endosteal regions, but was less well-oriented in the central regions. Central cortex is formed rapidly during development through endochondral ossification. Since rats possess no osteonal remodeling, this bone remains (until old age). Significant linear correlations were observed between the dimensional and organizational parameters, e.g., between crystal length and degree of orientation (R(2)=0.83, p<0.001). Application of SAXS/WAXS provides valuable information on bone nanostructure and its constituents, effects of diseases and, prospectively, mechanical competence.
IEEE Transactions on Medical Imaging | 2015
Mikael J. Turunen; Juha Töyräs; Harri T. Kokkonen; Jukka S. Jurvelin
Contrast agent enhanced cone beam computed tomography (CE-CBCT), a technique capable of high-resolution in vivo imaging with small radiation dose, has been applied successfully for clinical diagnostics of cartilage degeneration, i.e., osteoarthritis (OA). As an X-ray technique, CE-CBCT may also detect changes in mineral density of subchondral bone (volumetric bone mineral density, vBMD), known to be characteristic for OA. However, its feasibility for density measurements is not clear due to limited signal-to-noise ratio and contrast of CBCT images. In the present study, we created clinically applicable hydroxyapatite phantoms and determined vBMDs of cortical bone, trabecular bone, subchondral trabecular bone and subchondral plate of 10 cadaver (ex vivo) and 10 volunteer (in vivo) distal femora using a clinical CBCT scanner, and for reference, also using a conventional CT scanner. Our results indicated strong linear correlations between the vBMD values measured with the CT and CBCT scanners , however, absolute vBMD values were dependent on the scanner in use. Further, the differences between the vBMDs of cortical bone, trabecular bone and subchondral bone were similar and independent of the scanner. The present results indicate that vBMD values might not be directly comparable between different instruments. However, based on our present and previous results, we propose that, for OA diagnostics, clinical CBCT enables not only quantitative analysis of articular cartilage but also subchondral bone vBMD. Quantitative information on both cartilage and subchondral bone could be beneficial in OA diagnostics.
Journal of Bone and Mineral Research | 2011
Inari S. Tamminen; Mervi K Mäyränpää; Mikael J. Turunen; Hanna Isaksson; Outi Mäkitie; Jukka S. Jurvelin; Heikki Kröger
Primary osteoporosis in children often leads to vertebral fractures, but it remains unknown whether these fractures associate with changes in bone composition. This study aimed to determine the differences in bone composition in fracture‐prone children with and without vertebral fractures, as assessed by Fourier transform infrared spectroscopic imaging (FTIRI) and bone histomorphometry. Iliac crest bone biopsies (n = 24) were obtained from children who were suspected of primary osteoporosis based on evidence from the fracture history and/or low bone mineral density (BMD) by dual‐energy X‐ray absorptiometry. Vertebral morphology was determined by radiography. Bone biopsies were analyzed using histomorphometry and FTIRI. Phosphate‐to‐amide I, carbonate‐to‐phosphate, carbonate‐to‐amide I, and cross‐link ratio (collagen maturity) were calculated. Children with (n = 14) and without (n = 10) vertebral fracture were compared. Low cancellous bone volume (BV/TV) was detected by histomorphometry in 36% of the children with vertebral fracture, and bone turnover rate was abnormal in 64% of them. Children with vertebral fractures had lower carbonate‐to‐phosphate ratios (p < .05) and higher collagen maturity (p < .05) than children without vertebral fracture. The children with low BV/TV in biopsy showed lower carbonate‐to‐amide I ratios (p < .05) than the children with normal bone volume. This study showed changes in bone composition among fracture‐prone children who had sustained a vertebral fracture. The observed changes in bone composition in these children may contribute to their greater propensity to sustain vertebral fractures.