The Human Cell Atlas (HCA) project aims to catalogue every type of cell in a person. This is a huge challenge, given the human body is thought to contain more than 37 trillion cells. The project to decipher their functions and map their positions involves around 4000 scientists in 190 laboratories across 102 countries. A complete atlas would give scientists an unprecedented understanding of how cells develop, how they function, and how they go wrong. It would transform our understanding of the human body and its diseases.

More than 20 years ago. Scientists at the Sanger Institute completed a third of the international team that deciphered the very first human genome. That cost over $75m and took 9 months to sequence one person from one end to the other of each of the 24 types of chromosomes in that body. 

Now DNA sequencing can be done in 4 hours and costs about $200. Traditional methods would identify 1 to 4 genes in a tissue at a time. Currently, over 5000 genes are analysed at once.

Why the Human Atlas Project?

We know at a crude level where organs are and major cell types. They were worked out by people with microscopes and coloured stains over the 19th and 20th centuries. And it was thought there were a couple of hundred cell types in the body until quite recently. And now we know there are thousands because we have better techniques It gives us a much or that will in the future at least give us a much better idea of how bodies work.

We know cells such as a brain, skin, or heart cell. How many of those can there be? Research has shown that cells might look the same down a microscope but do processes quite differently. The project is trying to catalogue what’s happening at the molecular level to have 500 cells by 2025. 

The underlying data contains the molecular fingerprint of each cell, which means cells are defined not only by their location and shape but also by the genes that are switched on in that cell. And that’s important because the data is very rich in molecular breadth and depth.

Essentially every single cell in us has the same DNA or the same genome, which is pretty much nearly identical. However, only a component of that genome is active. The part that functions and is expressed into RNA and protein provides that cellular identity. Researchers look at the portion of the genome made functional by it being expressed, which confers the cellular identity.

The project aims to collect the maximum amount of human diversity.

 Recent Progress

Progress of the HCA is revealing groundbreaking insights into the human body. Key discoveries include

1. Detailed Mapping of Human Tissues and Organs:

• Digestive Tract: Researchers have created a detailed map of the digestive tract, from the esophagus to the colon.This map has identified a new cell type that may contribute to inflammation in ulcerative colitis and Crohn’s disease
• Other Organs: The HCA has also mapped various other organs, including the lungs, heart, and immune system. These maps have revealed new cell types and cellular interactions that were previously unknown.⁵

2. Understanding Human Development:

• Early Development: The HCA has provided insights into the early stages of human development, including the formation of the embryo and the development of various organs.
• Cellular Changes: By studying cellular changes during development, researchers can better understand how genetic and environmental factors influence human health and disease

3. Implications for Disease Diagnosis and Treatment:

• Disease Mechanisms: The HCA has revealed new insights into the cellular mechanisms underlying various diseases, including cancer, autoimmune disorders, and neurodegenerative diseases.
• Personalized Medicine: By understanding the cellular diversity of individuals, researchers can develop more targeted and personalised treatments for diseases.⁹

4. Advancing Regenerative Medicine:

• Cell Regeneration: The HCA’s knowledge of cell types and their interactions can help researchers develop new strategies for regenerating damaged tissues and organs.
• Tissue Engineering: By understanding the cellular composition of tissues, researchers can engineer functional tissues for transplantation.

Summary

The Human Cell Atlas project represents a significant advancement in biological research. By mapping every cell type in the human body, scientists can better understand health and disease. This knowledge has the potential to revolutionise medicine, leading to new treatments and therapies. Integrating artificial intelligence and advanced sequencing techniques is driving rapid progress in this field.

Read More

The podcast provides a comprehensive overview of the Human Cell Atlas project but needs to be more balanced with the complexity of biological systems. The human body is incredibly intricate, and the interactions between cells are multifaceted. It is important to note that the project is still in its early stages, and many challenges remain.

The various researchers have published over 40 peer-reviewed articles recently, and will draw the interim results later in 2025. Here is some more 

1. Why scientists are building an atlas of the human body Dec 2024 https://www.economist.com/podcasts/2024/12/04/why-scientists-are-building-an-atlas-of-the-human-body
2. A Journey into the Secrets of Human Cells – Helmholtz Zentrum München https://www.helmholtz-munich.de/en/newsroom/research-highlights/human-cell-atlas
3. Nature publishes results of the Human Cell Atlas – Science Media Centre España ciencemediacentre.es/en/nature-publishes-results-human-cell-atlas
4. Human Cell Atlas achieves leap in understanding of the human body https://www.humancellatlas.org/news/human-cell-atlas-achieves-leap-in-understanding-of-the-human-body
5. Mapping the human heart for the human cell atlas  https://www.imperial.ac.uk/news/192170/mapping-human-heart-human-cell-atlas/
6. Atlas of cells transforms understanding of human body – BBC https://www.bbc.com/news/articles/c23829l8kzro
7. Human Cell Atlas achieves leap in understanding of the human body https://www.humancellatlas.org/news/human-cell-atlas-achieves-leap-in-understanding-of-the-human-body