Impairment of chondrocyte biosynthetic activity by exposure to 3-tesla high-field magnetic resonance imaging is temporary

Effect of pulsed electromagnetic fields on the bioactivity of human osteoarthritic chondrocytes

Low-frequency pulsed electromagnetic fields (PEMFs) are used for the treatment of human osteoarthritic cells in vivo without knowledge of underling principles. The authors evaluated the effect of PEMFs on human chondrocytes of the osteoarthritic knee in vitro. Biopsies of the cut femoral condyles after total knee arthroplasty were kept in a standard cell culture medium consisting of Dulbecco's modified Eagle's medium: nutrient mixture F-12, 10% fetal calf serum, PenStrept (Mediatech, Inc, Manassas, Virginia), and ascorbic acid for 4 days and randomly split into an exposed group (PEMF for 4 hours daily for 4 days at 75 Hz and 1.6 mT) and a control group. Both groups were retained for biochemical and polymerase chain reaction analysis (glycosaminoglycan and DNA levels). A P value less than .05 was considered significant.DNA analysis revealed no differences between groups and no increase in content after exposure (P=.88 and .66, respectively). The increase of glycosaminoglycans was 0.4±1.6 ng (95% confidence interval [CI], 1.4 to 0.5) and -0.5±1.8 ng (95% CI, 0.6 to -1.5) in the exposed and control groups, respectively, with no significant difference (P=.24). A smaller decrease of glycosaminoglycan and DNA levels was observed over 4 days in the exposed group compared with the control group, with no statistical significance. The authors concluded that low-frequency PEMFs do not significantly influence the biosynthetic activity of explantcultures of human osteoarthritic cells in vitro. Nevertheless, they may be suitable as an adjuvant to a larger treatment regimen.

Electromagnetic fields enhance chondrogenesis of human adipose-derived stem cells in a chondrogenic microenvironment in vitro

We tested the hypothesis that electromagnetic field (EMF) stimulation enhances chondrogenesis in human adipose-derived stem cells (ADSCs) in a chondrogenic microenvironment. A two-dimensional hyaluronan (HA)-coated well (2D-HA) and a three-dimensional pellet culture system (3D-pellet) were used as chondrogenic microenvironments. The ADSCs were cultured in 2D-HA or 3D-pellet, and then treated with clinical-use pulse electromagnetic field (PEMF) or the innovative single-pulse electromagnetic field (SPEMF) stimulation. The cytotoxicity, cell viability, and chondrogenic and osteogenic differentiations were analyzed after PEMF or SPEMF treatment. The modules of PEMF and SPEMF stimulations used in this study did not cause cytotoxicity or alter cell viability in ADSCs. Both PEMF and SPEMF enhanced the chondrogenic gene expression (SOX-9, collagen type II, and aggrecan) of ADSCs cultured in 2D-HA and 3D-pellet. The expressions of bone matrix genes (osteocalcin and collagen type I) of ADSCs were not changed after SPEMF treatment in 2D-HA and 3D-pellet; however, they were enhanced by PEMF treatment. Both PEMF and SPEMF increased the cartilaginous matrix (sulfated glycosaminoglycan) deposition of ADSCs. However, PEMF treatment also increased mineralization of ADSCs, but SPEMF treatment did not. Both PEMF and SPEMF enhanced chondrogenic differentiation of ADSCs cultured in a chondrogenic microenvironment. SPEMF treatment enhanced ADSC chondrogenesis, but not osteogenesis, when the cells were cultured in a chondrogenic microenvironment. However, PEMF enhanced both osteogenesis and chondrogenesis under the same conditions. Thus the combination of a chondrogenic microenvironment with SPEMF stimulation can promote chondrogenic differentiation of ADSCs and may be applicable to articular cartilage tissue engineering.

Manipulation of Suspended Single Cells by Microfluidics and Optical Tweezers

Chondrocytes and osteoblasts experience multiple stresses in vivo. The optimum mechanical conditions for cell health are not fully understood. This paper describes the optical and microfluidic mechanical manipulation of single suspended cells enabled by the μPIVOT, an integrated micron resolution particle image velocimeter (μPIV) and dual optical tweezers instrument (OT). In this study, we examine the viability and trap stiffness of cartilage cells, identify the maximum fluid-induced stresses possible in uniform and extensional flows, and compare the deformation characteristics of bone and muscle cells. These results indicate cell photodamage of chondrocytes is negligible for at least 20 min for laser powers below 30 mW, a dead cell presents less resistance to internal organelle rearrangement and deforms globally more than a viable cell, the maximum fluid-induced shear stresses are limited to ~15 mPa for uniform flows but may exceed 1 Pa for extensional flows, and osteoblasts show no deformation for shear stresses up to 250 mPa while myoblasts are more easily deformed and exhibit a modulated response to increasing stress. This suggests that global and/or local stresses can be applied to single cells without physical contact. Coupled with microfluidic sensors, these manipulations may provide unique methods to explore single cell biomechanics.

Can low frequency electromagnetic field help cartilage tissue engineering?

To understand whether a low-frequency pulsed electromagnetic field (EMF) could help cartilage tissue repair in the scope of tissue engineering, we tested how EMF affected collagen gel properties and the behaviors of chondrocyte cells embedded in collagen constructs. Collagen gel and primary chondrocytes embedded in collagen were exposed to EMF for 24 h. Gel and cells that were not exposed to EMF served as controls. Collagen gel exposed to EMF was more hydrophobic and less susceptible to enzymatic degradation (both p < 0.05) than control. Three weeks after EMF exposure, chondrocytes showed higher proliferation and lower glycosaminoglycan (GAG) production (both p < 0.05) than control. By the end of the third week, aggrecan, type I, II, and X collagen mRNA expressions in the EMF group were 1.8 times higher (p < 0.05), except for type II collagen) than control. The increase in gene expression did not show up in aggrecan histological staining and type II and type X collagen immunohistochemical staining. Cells from both groups kept a normal polygonal shape through out the test period. Our results suggested that one-time EMF exposure could promote collagen-embedded chondrocytes proliferation and their gene expressions. It also promoted short-term (week 1) GAG production and lacuna formation. No apparent GAG and type II collagen production was seen in histological staining three weeks after the EMF exposure.

Deleterious effects of MRI on chondrocytes

OBJECTIVE

To assess how magnetic fields (MFs), with or without concurrent radio frequency (RF), influence chondrocytes and knee joint repair, we applied an MF strength via magnetic resonance imaging (MRI) slightly greater than the frequently used dosage in the clinics and examined the effects of these treatments in vitro on human chondrocytes and in vivo in pigs.

METHODS

Human chondrocytes were directly exposed to a 3-tesla (T) magnetic field (MF group) or a 3-T static magnetic field plus 125.3 MHz radio frequency (MF+RF group), and cell proliferation, apoptosis, cytosolic Ca2+ ([Ca2+]i) fluxes and expression of the apoptosis-related proteins of the treated cells were examined to assess the effects of the treatments. In the pig study, we examined the effects of the treatments on the recovery of surgically damaged pig knees.

RESULTS

A 3-T static MF and RF suppressed cell growth and induced apoptosis through p53, p21, p27 and Bax protein expression. In the pig model, we found that MRI surveillance had a deleterious effect on the recovery of the damaged knee cartilage.

CONCLUSION

Magnetic strength, with or without concurrent RF, suppressed chondrocyte growth in vitro and affected recovery of damaged knee cartilage in vivo in the pig model. These results may be specific to the parameters used in this study and may not apply to other situations, field strengths, forms of cartilage injury, or animal species.

Do static or time-varying magnetic fields in magnetic resonance imaging (3.0 T) alter protein-gene expression?-A study on human embryonic lung fibroblasts

PURPOSE

To evaluate the influence of magnetic resonance imaging (MRI) on gene expression in embryonic human lung fibroblasts (Hel 299).

MATERIALS AND METHODS

The cells were exposed to the static magnetic field and to a turbo spin-echo sequence of an MR scanner at 3.0 Tesla. An MR group (exposed) and a control group (sham-exposed) were set up using a special MR-compatible incubation system. The exposure time was two hours. Gene expression profiles were studied using a complementary deoxyribonucleic acid (cDNA) microarray containing 498 known genes involved in transcription, intracellular transport, structure/junction/adhesion or extracellular matrix, signaling, host defense, energetics, metabolism, cell shape, and death.

RESULTS

No changes in gene expression were found in either group (exposed or sham-exposed cells) at the end of a two-hour exposure for any of the 498 tested protein genes.

CONCLUSION

The results suggest that MRI has no influence on protein-gene expression in eugenic human lung cells.