Treatment of stroke with bone marrow stromal cells (BMSC) significantly reduces vascular permeability in the ischemic brain within two weeks after stroke in non-diabetic rats ¹. Diabetes increases risk of ischemic stroke, stroke recurrence and long-term mortality from stroke, and worsens the overall neurological outcomes after stroke ². Surprisingly, BMSC therapy administered at 24h after stroke in rats with type 1 diabetes mellitus adversely increases BBB leakage and intracranial hemorrhage two weeks after stroke ³. In the clinic, the vast majority (90-95%) of diabetic patients have type 2 diabetes mellitus (T2DM) ⁴. Thus, further investigations are therefore warranted on the effects of BMSC treatment of stroke in T2DM subjects.T2DM was induced in adult male Wistar rats. Right middle cerebral artery occlusion (MCAo) was then induced for 2 hours using the filament model. Rats were treated with either BMSC at a dose of 5 million (5x10⁶) cells or an equal volume of phosphate-buffered saline (PBS) as the vehicle via tail vein injection at 3 days after MCAo. The treated (BMSC, n=9) and control (PBS, n=9) groups of T2DM rats with stroke were age and body weight matched. MRI was performed with ClinScan 7T system at one day and then weekly for 5 weeks after ischemia-reperfusion for all rats. MRI sequences included T2-weighted imaging, susceptibility weighted imaging (SWI), diffusion spectrum imaging and contrast enhanced T1-weighted imaging (CE-T1WI) with Gd-DTPA, as the image contrast agent.

As indicated in figure 1 from two representative rats, The contrast enhanced images exhibited regions with elevated intensity in ischemic cerebral tissue, persisted for 5 weeks after stroke in the control T2DM rat. However, for the BMSC treated T2DM rat, hyperintensity, excluding the ventricle, in the ischemic brain tissue was present from 1 day to 3 weeks, rapidly faded at 4 weeks, and was hardly detectable at 5 weeks after stroke. Figure 2 shows the longitudinal SWI images from the two representative T2DM rats with and without BMSC treatments. The SWI images exhibited much more severe hemorrhage in the control T2DM rat than in the BMSC treated T2DM rat during 1d to 5w after stroke. Typical MRI images of the six diffusion maps, obtained at 5 weeks after stroke, are shown in figure 3.

According to the quantitative measurements, as shown in figure 4, BBB disruption volumes with Gd-DTPA enhancement were significantly smaller in the BMSC treated T2DM rats than in the control rats from 1w after stroke. SWI demonstrated that BMSC treatment marginally reduces hemorrhagic volumes at 5w, but significantly decreases hemorrhagic spots starting 3w, after stroke in T2DM rats. MRI diffusion metrics of fraction anisotropy (FA) and entropy provide complementary information of white matter and demonstrated by the diffusion MRI metrics starting from 2w to 5w after stroke in T2DM rat, that BMSC treatment significantly improves white matter features compared with the PBS treated control rats.

By using histological methods, BBB disruption and permeability rate in diabetic animals were regionally measured shortly after stroke from stained cerebral tissue sections, and limited to a one time measurement. In contrast, by employing MRI in the present study, longitudinal measurements were performed in stroke T2DM rats with or without BMSC treatment from 1 day to 5 weeks post stroke. MRI demonstrated that, compared with the PBS treated control rats, BMSC treatment of stroke in T2DM rats significantly reduced BBB leakage and hemorrhagic spots starting from 1 week and 3 weeks after stroke (p<0.05) measured by CE-T1WI with Gd-DTPA and identified by SWI, respectively; BMSC treatment also significantly improves white matter features.