Magnetic resonance elastography methodology for the evaluation of tissue engineered construct growth

Area of Science:

• Biomedical Engineering
• Materials Science
• Regenerative Medicine

Background:

• Traditional mechanical testing of engineered tissues is destructive and unsuitable for long-term studies.
• Noninvasive imaging techniques like magnetic resonance imaging (MRI) are increasingly used to monitor tissue development.
• Magnetic resonance (MR) techniques such as diffusion and relaxometry have characterized chemical and physical property changes in developing tissues.

Purpose of the Study:

• To introduce and validate microscopic magnetic resonance elastography (μMRE) as a noninvasive method for measuring mechanical properties of small soft tissues.
• To demonstrate the application of μMRE in monitoring the differentiation of human mesenchymal stem cells (hMSC) into adipogenic and osteogenic constructs.
• To provide a protocol for using μMRE in tissue engineering research.

Main Methods:

• Utilized a modified Hahn spin-echo sequence synchronized with a mechanical actuator to generate and image shear waves.
• Employed oscillating bipolar pairs for motion sensitization during MR image acquisition.
• Applied an inversion algorithm to shear wave images to generate quantitative shear stiffness maps.

Main Results:

• Developed a μMRE protocol for noninvasive mechanical property assessment of engineered tissues.
• Demonstrated strong correlation (R(2)>0.9914) between μMRE measurements and dynamic mechanical analysis.
• Successfully monitored hMSC differentiation into adipogenic and osteogenic constructs using μMRE.

Conclusions:

• μMRE is a viable, nondestructive alternative to traditional mechanical testing for engineered tissues.
• This technique provides essential data on local mechanical properties, crucial for assessing tissue structure and function.
• μMRE integration into tissue development processes offers valuable insights into construct maturation and quality.