Monitoring Tissue Engineering and Regeneration by Magnetic Resonance Imaging and Spectroscopy

Abstract

In this article, based on the invited talk at the "Tissue Science 2012" meeting in Chicago on October 1-3, 2012, we describe some examples of characterization of engineered cartilage and bone tissue using magnetic resonance spectroscopy and imaging. Two different models of engineered cartilage and engineered bone tissue constructs were used for these studies: 1) chondrocyte based cartilage tissue engineering constructs: human and bovine chondrocytes seeded in alginate beads (Hydrogel scaffold model) or bovine chondrocytes grown as pellets (scaffold free model); 2) mesenchymal stem cell (MSC) based cartilage and bone tissue engineering constructs: human mesenchymal stem cell (HMSCs) seeded in cartilage biomimetic scaffolds (collagen/chitosan scaffold integrated with extracellular matrix of cartilage) or HMSCs seeded in collagen/chitosan scaffolds. Magnetic resonance spectroscopy and imaging experiments using 9.4 T (400 MHz proton frequency), 11.7 T (500 MHz proton frequency) or 14.1 T (600 MHz proton frequency) MR spectrometers/Imager were performed on these constructs over two to four weeks of tissue culture time. Specifically, water suppressed proton NMR spectroscopy; proton and sodium multi-quantum coherence spectroscopy and proton T1, T2 and ADC parametric MRI were used to study the chondrogenesis and osteogenesis of these tissues. We found that the change in MR relaxation and diffusion coefficient parameters correlate well with the growth of engineered tissues. We found that the MR parameters and the change in these parameters in growing tissue are strongly influenced by the choice of scaffolds. We also found as expected that the tissue-engineered cartilage lacked order or preference in collagen orientation. Further work is underway to elucidate these findings. We anticipate that in future, MRI will augment histological and immunohistochemical techniques by providing a complimentary and real time quantitative assessment of engineered tissue growth at all growth stages: (i) cell seeding to pre implantation; (ii) preclinical validation studies post implantation in small and large animal models; (iii) clinical studies of performance of engineered tissues.

Imaging Strategies for Tissue Engineering Applications

“…40 In addition, it was demonstrated in vitro that changes in MR parameters correlated to cell 36 Color images available online at www.liebertpub.com/teb behaviors, such as differentiation of mesenchymal stem cells and growth of chondrocytes in the gels. 41,42 As fat tissues have a short T1 relaxation time, resorption of adipose tissueengineered constructs was longitudinally monitored in vivo using MRI. 43 Also, articular cartilage repair in a rabbit osteochondral defect model was monitored over time after thrombin peptide (TP)-508 treatment using quantitative T2 mapping, as shown in Figure 5A.…”

High contrast microstructural visualization of natural acellular matrices by means of phase-based x-ray tomography

“…Validation of the decellularization process requires understanding whether the native tissue microarchitecture has been preserved. While this would be achieved by visualizing scaffolds after decellularization, the TE community currently lacks an imaging modality capable of producing images of sufficiently high contrast and resolution while being non-destructive 7 . Most established imaging modalities can only be used to a limited extent.…”

NMR techniques in studying water in biotechnological systems

“…Thus, effective anisotropic molecular motion can be studied (Ikoma et al 2001;Navon et al 2001). For instance, the MQF methodology on protons and sodium atoms (Shinar and Navon 2006) and T 1 and T 2 relaxation times were applied to investigate the chondrogenesis and osteogenesis of collagen tissues (Kotecha et al 2013b).…”

“…In addition to MQF NMR methods, the present work considers also 1D and 2D NMR diffusion methods in studying tissueengineering materials (Kotecha et al 2013a(Kotecha et al , 2013bPothirajan et al 2014;Rodin 2018a) showing how to observe an anisotropy and restriction diffusion with estimates of a restricted distance and water permeability (Tanner 1979;Rodin et al 2014;Rodin 2018c). NMR parameters (T 1 , T 2 , and measured diffusion coefficient) studied in tissue-engineering processes correlated with the growth of tissues.…”

“…NMR parameters (T 1 , T 2 , and measured diffusion coefficient) studied in tissue-engineering processes correlated with the growth of tissues. Thus, they can be used in characterizing the scaffolds (Pothirajan et al 2014;Kotecha et al 2013aKotecha et al , 2013bKotecha et al , 2013c. MQF NMR has been applied for the study of the tissueengineered cartilage and showed that collagen molecules in such a cartilage have no order in orientation (Kotecha 2013b, c).…”