B Cells Directly Alter Adaptive Plasticity to Support Functional Recovery After Stroke

这项R01更新的中心假设集中在提供神经营养支持的B细胞亚群，以对抗缺血性卒中后的认知障碍和改善运动功能，这是血管促进认知障碍和痴呆（VCID）发展的关键危险因素。这些神经营养B细胞分泌脑源性神经营养因子（BDNF），可能对对抗VCID的发展至关重要。不幸的是，卒中风险最高的患者群体和VCID老年人的B细胞发育和生长因子分泌受损，这可能限制对卒中后抑郁和痴呆的保护。性别也是一个因素，因为老年妇女卒中后痴呆的循环BDNF水平最低，尽管之前没有研究直接将神经营养免疫细胞群的丧失与VCID的发展联系起来。基于我们的先导数据，我们将测试：脑卒中后B细胞的一个子集（即B细胞sbdnf +）是否在遇到谷氨酸后上调BDNF；如果B细胞sbdnf +限制VCID的发展并支持运动恢复；以及老年女性B细胞来源的BDNF是否受损。我们将使用4个。（“年轻”）和16岁以上。（“衰老”）雌性和雄性小鼠，测试B细胞sbdnf +是否支持脑卒中后神经元功能、可塑性、运动和多领域认知恢复。目的1将测试中风后，（1A）谷氨酸是否与B细胞结合以增加BDNF的产生并驱动恢复相关的细胞内Ca2+信号，这是性别和年龄依赖性的。我们将（1B）在体外使用B细胞sntrk2tm1ddg /J来测试BDNF受体TrkB是否需要BDNF的产生和体外神经保护。目的2将测试B细胞sbdnf +是否支持原发性运动皮质（M1）光血栓性卒中模型的远程可塑性以及认知和运动恢复。在年轻和老年雌性hCD20TamCre/ BDNFfl/fl小鼠和同鼠对照中，（2A）所有B细胞或（2B）特异性B细胞来源的BDNF的诱导耗尽将发生急性（第0天）或延迟（中风后第7天开始）。主要结果将包括1)在自动触屏任务中保留巴甫洛夫刺激强化学习，2)改善前肢精确到达，以及3)梗死周围和对侧M1可塑性。目的3将测试B细胞来源的BDNF是否增强长期认知和运动恢复。老年C57BL/6J雌性小鼠将在中风后第7天开始接受tMCAo或假手术，并过继移植（3A）过表达BDNF或（3B）缺乏BDNF的B细胞，后者来自hCD20TamCre/BDNFfl/fl供体小鼠。主要结果将包括1)通过触屏模式分离测试海马特异性认知缺陷的改善，2)熟练到达的精确度的提高，以及3)通过全脑系列双光子断层扫描确定的B细胞的局部ipsi和对侧发育，这与动物内脑回路特异性认知功能和运动恢复的大小相关。这些研究将证实，在发生VCID的女性中，一种新的B细胞亚群B细胞sbdnf +的年龄依赖性丧失。他们还将证实，治疗性靶向B细胞可以对抗中风后痴呆和运动缺陷，这是一种潜在的治疗方法，可以支持任何中枢神经系统损伤或疾病后的可塑性恢复。

The central hypothesis of this R01 renewal focuses on a subset of B cells that provide neurotrophic support to counter cognitive impairment and improve motor function after ischemic stroke, a key risk factor for the development of vascular contributions to cognitive impairment and dementia (VCID). These neurotrophic B cells secrete brain-derived neurotrophic factor (BDNF) and may be critical to countering the development of VCID. Unfortunately, the patient population most at risk for stroke and VCID aged individuals have impaired B cell development and secretion of growth factors that could limit protection from post-stroke depression and dementia. Sex is also a factor, as elderly women with post-stroke dementia have the lowest levels of circulating BDNF, though no prior studies have directly linked a loss of neurotrophic immune cell populations and the development of VCID. Based on our pilot data, we will test: if a subset of post-stroke B cells (i.e. B cellsBDNF+) upregulate BDNF after encountering glutamate; if B cellsBDNF+ limit the development of VCID and support motor recovery; and if B cell-derived BDNF is impaired in aged females. We will use 4 mos. (“young”) and 16 mos. (“aged”) female and male mice to test if B cellsBDNF+ support neuronal function, plasticity, motor, and multi-domain cognitive recovery post-stroke. Aim 1 will test if after stroke, (1A) glutamate binds to B cells to increase BDNF production and drive recovery-linked intracellular Ca2+ signaling that is sex- and age-dependent. We will (1B) use B cellsNtrk2tm1Ddg/J in vitro to test if the BDNF receptor TrkB is required for BDNF production and in vitro neuroprotection. Aim 2 will test if B cellsBDNF+ support remote plasticity, as well as cognitive and motor recovery in a primary motor cortex (M1) photothrombosis stroke model. Inducible depletion of (2A) all B cells or (2B) specific B cell-derived BDNF in young and aged female hCD20TamCre/ BDNFfl/fl mice and littermate controls will occur either acute (day 0) or delayed (beginning day 7 post-stroke). Primary outcomes will include 1) preservation of Pavlovian stimulus-reinforcer learning on an automated touchscreen task, 2) improved forelimb precision reaching, and 3) peri-infarct and contralesional M1 plasticity. Aim 3 will test if B cell-derived BDNF augments long-term cognitive and motor recovery. Aged C57BL/6J female mice will receive tMCAo or sham surgery and adoptive transfer of B cells that (3A) overexpress BDNF or (3B) lack BDNF, the latter derived from hCD20TamCre/BDNFfl/fl donor mice, beginning day 7 post-stroke. Primary outcomes will include 1) ameliorated hippocampal-specific cognitive deficits tested via touchscreen pattern separation, 2) improved precision skilled reaching, and 3) regional ipsi- and contralesional diapedesis of B cells, as determined via whole brain serial two-photon tomography, that correlates to within-animal magnitude of brain circuit-specific cognitive function and motor recovery. These studies will confirm an age-dependent loss of a novel subset of B cells, B cellsBDNF+, in females that develop VCID. They will also confirm that therapeutically targeting B cells can counter post-stroke dementia and motor deficits a potential treatment supporting plasticity-based recovery after any CNS injury or disease.