Non-invasive quantification of myocardial fibrosis in diabetic mice using in-vivo high-resolution MRI

Introduction

There is an established role for magnetic resonance imaging in the assessment of myocardial fibrosis, in ischaemic and non-ischaemic cardiomyopathies. The amount of fibrosis is of importance because of its prognostic value, in terms of arrhythmias occurrence, and haemodynamic consequences.

T2 relaxation time directly depends on physico-chemical properties of each tissue. Thus, myocardial T2 time determination can help in quantifying fibrosis. Diabetic cardiomyopathy is characterized by myocardial structural modifications including hypertrophy, microcirculation impairment and interstitial fibrosis.

Purpose

To describe a non-invasive MRI method using high-resolution myocardial T2 time measurement to assess myocardial fibrosis in a model of diabetic mice in vivo.

Methods

Two multi-slice spin-echo sequences were performed for T2 time assessment respectively at 20 and 9 ms echo time (resolution 85 × 85 μm2, slice thickness 1.0 mm, imaging time 15 minutes), in ten 16-week old C57Bl/6J after 8 weeks of streptozotocin-induced diabetes, and ten control mice, under isoflurane anesthesia using a 11.75 T vertical scanner (Bruker, Rheinstetten, Germany). All images were acquired in short-axis view. MRI measurements were then compared with histological quantification of fibrosis using picrosirius red staining.

Results

T2 relaxation time was significantly lower in diabetic mice (13.8 +/- 2.8 ms versus 18.9 +/- 2.3 ms in the control group, p < 0.05). This was associated with a significant increase of myocardial fibrosis as evaluated by picro-sirius red staining, in diabetic mice.

Conclusion

We describe here a non-invasive and accurate MRI method to quantify myocardial fibrosis in vivo in diabetic mice, using T2 relaxation time measurement. This method can be applied in many ischaemic or non-ischaemic cardiomyopathies in which a fibrotic phenomenon is involved.