Magnetic Resonance Imaging Investigation of Neuroplasticity After Ischemic Stroke in Tetramethylpyrazine-Treated Rats

Xue-Feng Feng; Jian-Feng Lei; Man-Zhong Li; Yu Zhan; Le Yang; Yun Lu; Ming-Cong Li; Yu-Ming Zhuang; Lei Wang; Hui Zhao

doi:10.3389/fphar.2022.851746

Magnetic Resonance Imaging Investigation of Neuroplasticity After Ischemic Stroke in Tetramethylpyrazine-Treated Rats

Front Pharmacol. 2022 Apr 26:13:851746. doi: 10.3389/fphar.2022.851746. eCollection 2022.

Authors

Xue-Feng Feng^{1

2}, Jian-Feng Lei³, Man-Zhong Li^{1

2}, Yu Zhan^{1

2}, Le Yang^{1

2}, Yun Lu^{1

2}, Ming-Cong Li^{1

2}, Yu-Ming Zhuang^{1

2}, Lei Wang^{1

2}, Hui Zhao^{1

2}

Affiliations

¹ School of Traditional Chinese Medicine, Capital Medical University, Beijing, China.
² Beijing Key Lab of TCM Collateral Disease Theory Research, Beijing, China.
³ Medical Imaging Laboratory of Core Facility Center, Capital Medical University, Beijing, China.

Abstract

Ischemic stroke elicits white matter injury typically signed by axonal disintegration and demyelination; thus, the development of white matter reorganization is needed. 2,3,5,6-Tetramethylpyrazine (TMP) is widely used to treat ischemic stroke. This study was aimed to investigate whether TMP could protect the white matter and promote axonal repair after cerebral ischemia. Male Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion (MCAO) and treated with TMP (10, 20, 40 mg/kg) intraperitoneally for 14 days. The motor function related to gait was evaluated by the gait analysis system. Multiparametric magnetic resonance imaging (MRI) was conducted to noninvasively identify gray-white matter structural integrity, axonal reorganization, and cerebral blood flow (CBF), followed by histological analysis. The expressions of axonal growth-associated protein 43 (GAP-43), synaptophysin (SYN), axonal growth-inhibitory signals, and guidance factors were measured by Western blot. Our results showed TMP reduced infarct volume, relieved gray-white matter damage, promoted axonal remodeling, and restored CBF along the peri-infarct cortex, external capsule, and internal capsule. These MRI findings were confirmed by histopathological data. Moreover, motor function, especially gait impairment, was improved by TMP treatment. Notably, TMP upregulated GAP-43 and SYN and enhanced axonal guidance cues such as Netrin-1/DCC and Slit-2/Robo-1 but downregulated intrinsic growth-inhibitory signals NogoA/NgR/RhoA/ROCK-2. Taken together, our data indicated that TMP facilitated poststroke axonal remodeling and motor functional recovery. Moreover, our findings suggested that TMP restored local CBF, augmented guidance cues, and restrained intrinsic growth-inhibitory signals, all of which might improve the intracerebral microenvironment of ischemic areas and then benefit white matter remodeling.

Keywords: axonal remodeling; ischemic stroke; synaptic plasticity; tetramethylpyrazine; white matter reorganization.