As the global population continues to age, neurological conditions like Parkinson’s disease, Alzheimer’s disease and cerebral small vessel disease impose heavy socioeconomic burdens. To advance diagnostic and treatment methods, pathological processes must be studied via the use of animal disease models and human brain tissues. However, currently available techniques for the visualisation of brain structures are limited and costly.

Aimed at overcoming this challenge, the Margaret K.L. Cheung Research Centre for Management of Parkinsonism at The Chinese University of Hong Kong (CUHK)’s Faculty of Medicine (CU Medicine) has developed a fast, user-friendly technique to make chemically stabilised antibodies for rapid labelling and imaging of molecules in biological tissues. The research findings have been selected as the cover story in the latest issue of the renowned peer-reviewed journal Nature Methods.

Technologies that enable the visualisation of biological tissue structures are crucial for the study of organs, like the brain, and their functions both in normal conditions and when suffering from a disease. A technique called immunostaining, which uses antibodies to target biological molecules in tissues, is immensely powerful and widely used for such purposes. However, antibodies cannot reach deep into the tissues, hindering their application to high-throughput, three-dimensional structural studies.

A research team led by Dr Lai Hei-ming, Assistant Professor in CU Medicine’s Department of Psychiatry and Principal Investigator of the Margaret K.L. Cheung Research Centre for Management of Parkinsonism; and Dr Ko Ho, Assistant Professor in CU Medicine’s Department of Medicine and Therapeutics and the School of Biomedical Sciences, and Associate Director of the Margaret K.L. Cheung Research Centre for Management of Parkinsonism, invented a 3D immunolabelling strategy named ThICK (thermal immunohistochemistry with optimised kinetics) staining to overcome the limitation.

Usually, antibodies are sensitive to heat and chemicals called denaturants. When used in immunostaining, these properties limit the choice of temperature and denaturants, since they can destabilise the antibodies and make them lose their functions.

Therefore, the team developed a chemical technology that can convert commercially available antibodies, making them much more resistant to heat and denaturants. The heat-stable antibodies, termed SPEARs (synergistically protected polyepoxide-crosslinked Fab-complexed antibody reagents), can be used to achieve immunolabelling of biological molecules deep inside intact tissues by flexibly choosing different incubation temperatures and denaturing chemicals. The use of SPEARs in ThICK staining can help to overcome the limitations of deep 3D immunostaining and optimise the visualisation of brain structures. 

The new chemical technology enables an innovative approach that is rapid, simple, and highly scalable. The study shows that ThICK staining with SPEARs can achieve whole mouse brain immunolabelling within 72 hours; when applied to human brain tissues, it can achieve fourfold deeper penetration with threefold fewer antibodies.

ThICK staining achieves whole organ immunolabelling faster than other state-of-the-art methods, from requiring one to eight weeks for each round of antibody staining to a much shorter time of one to three days.

The new tech is compatible with a wide range of commercially available antibodies, and different classes of tissue preservation and clearing methods. It can therefore be readily implemented in most laboratories.

Dr Ko remarked that SPEARs technology will particularly aid in the study of neurodegenerative diseases. It is hoped that the work can accelerate the path towards new tools for disease diagnosis and treatment paradigms in the future.

The study was also funded by the Croucher Foundation, the National Natural Science Foundation of China, the Innovation and Technology Commission, and the Research Grants Council of Hong Kong.