Progress in Human Brain Banking in China

Closing the gap in dementia research by community-based cohort studies in the Chinese population

China accounts for 1/5 of the global population and China faces a particularly heavy dementia burden due to its rapidly ageing population. Unique historical events, genetic background, sociocultural factors, lifestyle, and the COVID-19 pandemic further influence cognitive outcomes in the Chinese population. We searched PubMed, Web of Science, and Embase for community-based cohort studies related to dementia in the Chinese population, and summarized the characteristics, methodologies, and major findings published over the last 25 years from 39 cohorts. We identified critical research gaps and propose future directions, including enhancing sample representativeness, investigating China-specific risk factors, expanding exposure measurements to the whole life-span, collecting objective data, conducting administer-friendly domain-specific cognitive assessments, adopting pathological diagnostic criteria, standardizing biobank construction, verifying multi-modal biomarkers, examining social and genetic-environmental aspects, and monitoring post-COVID cognitive health, to approach high quality of dementia studies that can provide solid evidence to policy making and promote global brain health research.

The aldehyde dehydrogenase 2 rs671 variant enhances amyloid β pathology

In the ALDH2 rs671 variant, a guanine changes to an adenine, resulting in a dramatic decrease in the catalytic activity of the enzyme. Population-based data are contradictory about whether this variant increases the risk of Alzheimer's disease. In East Asian populations, the prevalence of the ALDH2 rs671 variant is 30-50%, making the National Human Brain Bank for Development and Function (the largest brain bank in East Asia) an important resource to explore the link between the ALDH2 rs671 polymorphism and Alzheimer's disease pathology. Here, using 469 postmortem brains, we find that while the ALDH2 rs671 variant is associated with increased plaque deposits and a higher Aβ40/42 ratio, it is not an independent risk factor for Alzheimer's disease. Mechanistically, we show that lower ALDH2 activity leads to 4-HNE accumulation in the brain. The (R)-4-HNE enantiomer adducts to residue Lys53 of C99, favoring Aβ40 generation in the Golgi apparatus. Decreased ALDH2 activity also lowers inflammatory factor secretion, as well as amyloid β phagocytosis and spread in brains of patients with Alzheimer's disease. We thus define the relationship between the ALDH2 rs671 polymorphism and amyloid β pathology, and find that ALDH2 rs671 is a key regulator of Aβ40 or Aβ42 generation.

Doublecortin-Expressing Neurons in Human Cerebral Cortex Layer II and Amygdala from Infancy to 100 Years Old

A cohort of morphologically heterogenous doublecortin immunoreactive (DCX +) "immature neurons" has been identified in the cerebral cortex largely around layer II and the amygdala largely in the paralaminar nucleus (PLN) among various mammals. To gain a wide spatiotemporal view on these neurons in humans, we examined layer II and amygdalar DCX + neurons in the brains of infants to 100-year-old individuals. Layer II DCX + neurons occurred throughout the cerebrum in the infants/toddlers, mainly in the temporal lobe in the adolescents and adults, and only in the temporal cortex surrounding the amygdala in the elderly. Amygdalar DCX + neurons occurred in all age groups, localized primarily to the PLN, and reduced in number with age. The small-sized DCX + neurons were unipolar or bipolar, and formed migratory chains extending tangentially, obliquely, and inwardly in layers I-III in the cortex, and from the PLN to other nuclei in the amygdala. Morphologically mature-looking neurons had a relatively larger soma and weaker DCX reactivity. In contrast to the above, DCX + neurons in the hippocampal dentate gyrus were only detected in the infant cases in parallelly processed cerebral sections. The present study reveals a broader regional distribution of the cortical layer II DCX + neurons than previously documented in human cerebrum, especially during childhood and adolescence, while both layer II and amygdalar DCX + neurons persist in the temporal lobe lifelong. Layer II and amygdalar DCX + neurons may serve as an essential immature neuronal system to support functional network plasticity in human cerebrum in an age/region-dependent manner.

Intraneuronal sortilin aggregation relative to granulovacuolar degeneration, tau pathogenesis and sorfra plaque formation in human hippocampal formation

Extracellular β-amyloid (Aβ) deposition and intraneuronal phosphorylated-tau (pTau) accumulation are the hallmark lesions of Alzheimer’s disease (AD). Recently, “sorfra” plaques, named for the extracellular deposition of sortilin c-terminal fragments, are reported as a new AD-related proteopathy, which develop in the human cerebrum resembling the spatiotemporal trajectory of tauopathy. Here, we identified intraneuronal sortilin aggregation as a change related to the development of granulovacuolar degeneration (GVD), tauopathy, and sorfra plaques in the human hippocampal formation. Intraneuronal sortilin aggregation occurred as cytoplasmic inclusions among the pyramidal neurons, co-labeled by antibodies to the extracellular domain and intracellular C-terminal of sortilin. They existed infrequently in the brains of adults, while their density as quantified in the subiculum/CA1 areas increased in the brains from elderly lacking Aβ/pTau, with pTau (i.e., primary age-related tauopathy, PART cases), and with Aβ/pTau (probably/definitive AD, pAD/AD cases) pathologies. In PART and pAD/AD cases, the intraneuronal sortilin aggregates colocalized partially with various GVD markers including casein kinase 1 delta (Ck1δ) and charged multivesicular body protein 2B (CHMP2B). Single-cell densitometry established an inverse correlation between sortilin immunoreactivity and that of Ck1δ, CHMP2B, p62, and pTau among pyramidal neurons. In pAD/AD cases, the sortilin aggregates were reduced in density as moving from the subiculum to CA subregions, wherein sorfra plaques became fewer and absent. Taken together, we consider intraneuronal sortilin aggregation an aging/stress-related change implicating protein sorting deficit, which can activate protein clearance responses including via enhanced phosphorylation and hydrolysis, thereby promoting GVD, sorfra, and Tau pathogenesis, and ultimately, neuronal destruction and death.

The top 100 most-cited articles citing human brain banking from 1970 to 2020: a bibliometric analysis

Many articles involving human brain banks have been published. Bibliometric analysis can determine the history of the development of research and future research trends in a specific field. Three independent researchers retrieved and reviewed articles from the Web of Science database using the following strategy: "TS = (((brain OR cerebral) AND (bank* OR biobank*)) OR brainbank*)." The top 100 most-cited articles were identified and listed in descending order by total citations. Web of Science was used to identify ten recent articles describing bank construction. GeenMedical ( https://www.geenmedical.com/ ) was used to identify ten recent articles from journals with an impact factor (IF) > 20. The top 100 most-cited articles citing human brain banks were published between 1991 and 2017. Fifty-two percent of the articles focused on a specific type of neurodegenerative disease, and 16% discussed the construction and development of human brain banks. Articles using brain tissue had more total and annual citations than those on bank construction. Ten articles with high IFs were published from 2017 to 2019, and they were primarily studies using novel research techniques such RNA sequencing and genome-wide association studies. Most studies were published in journals specializing in neurology or neuroscience such as Movement Disorders (10%), and had been conducted in the United States (52%) by neurologists (62%). The top 100 most-cited articles and recent publications citing human brain banks and their bibliometric characteristics were identified and analyzed, which may serve as a useful reference and pave the way for further research.

Perceptions and Attitudes toward Brain Donation among the Chinese People

Postmortem human brain donation is crucial to both anatomy education and research. The China Human Brain Banking Consortium was established recently to foster brain donation in China. The purpose of this study was to gain information about the public perception of and attitudes toward brain donation and to identify factors that may impact the willingness to participate in brain donation among the Chinese people. A specifically designed questionnaire was delivered to community residents in Changsha (the capital city of Hunan province) with a total of 1,249 completed forms returned and statistically analyzed. The majority of the participants considered that brain donation would help medical research and education, and 32.0% of respondents agreed that the brain donation would help change the traditional Chinese funeral belief in keeping the body intact after death. However, participants aged over 60 years old were less supportive of this concept. Among all participants, 63.7% stated that they were not knowledgeable about brain donation, while 26.4% explicitly expressed a willingness to participate in brain donation. Age, gender, monthly household income, and knowledge about brain donation significantly affected the willingness. Compared with other age groups, a higher proportion of participants aged over 60 years old preferred to be informed by a medical college. To promote brain donation in China, especially among the elderly, better communication of its medical benefits and a reinterpretation of the Confucius view of the human body should be provided. Efforts are also needed to provide appropriate forums and sources of brain donation information to targeted communities and society in general.