Researchers find strange 'mathematical pattern' throughout the human body
A fascinating insight into human cells' behavior, reveals a consistent pattern of cell size and count across the entire human body. (CREDIT: Creative Commons)
Research conducted by McGill University's Department of Earth and Planetary Sciences has uncovered a fascinating insight into human cells' behavior, revealing a consistent pattern of cell size and count across the entire human body.
Published in the Proceedings of the National Academy of Sciences, the paper titled "The human cell count and size distribution" sheds light on a mathematical symmetry observed across various types of human cell tissues.
This discovery hints at an undiscovered developmental mechanism that appears to follow a structured pattern commonly observed in nature.
The researchers found an intriguing inverse relationship between cell size and count. This means that as cell size increases, the cell count decreases, and vice versa.
Essentially, cells within a particular size class contribute equally to the overall cellular biomass of the body. This relationship holds true across different cell types and size classes, indicating a trade-off between these variables.
Cell size and count play crucial roles in the growth and functioning of the human body. However, prior to this study, no research had explored the relationship between these factors across the entire human organism.
To compile their findings, the team meticulously gathered data from over 1,500 published sources, resulting in a comprehensive dataset of cell size and count across major cell types.
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Their analysis revealed estimated total body cell counts of around 36 trillion cells for males, 28 trillion cells for females, and 17 trillion cells for a ten-year-old child.
Muscle and fat cells dominate the distribution of cell biomass in the human body, while red blood cells, platelets, and white blood cells significantly influence cell counts.
Interestingly, each cell type maintains a characteristic size range that remains consistent throughout an individual's development and is consistent across mammalian species.
Despite this uniformity, cell sizes vary drastically, spanning seven orders of magnitude from red blood cells to the largest muscle fibers. This vast difference in size is comparable to the mass ratio of a shrew to a blue whale, exceeding a million-fold.
Contrasting cell count and biomass distributions by cell type. Voronoi tree maps for all 400 investigated cell types of the reference male anatomical model (area represents relative cell number or biomass). (CREDIT: Proceedings of the National Academy of Sciences)
The distribution of cell sizes across the entire human body raises questions about whether it follows a lognormal distribution, similar to that of a single cell type, or if other distributions prevail and how this distribution is controlled remains unclear.
The observed patterns mirror statistical principles such as Zipf's law and Taylor's law, which are recurrent across various natural phenomena, including the distribution of bacteria in soil and the population of fish in the ocean.
Cell class distributions across select tissues. Cell count and biomass distributions across 18 broad cell classes (colored) are shown for the 32 most significant tissue systems of the body, representing about half of all 60 investigated tissue systems, including the vast majority of total cell biomass. (CREDIT: Proceedings of the National Academy of Sciences)
Zipf's law describes a power-law distribution where a small number of elements account for the majority of occurrences in a dataset. In this context, a small number of very large cells contribute significantly to cell biomass, while numerous smaller cells contribute to the overall cell count.
Taylor's law states that the variance in the number of individuals within a group scales with the mean of that measurement raised to a certain exponent. This law is relevant to the variations in size and count across different cell types.
In some cases, cells with broad size distributions (e.g., adipocytes; light blue) have counts of mean sizes that are higher than the size class sum (black points), since the counts of actual sizes are spread lognormally over multiple size classes. (CREDIT: Proceedings of the National Academy of Sciences)
The study found that the coefficient of variation in cell size remains relatively constant across cell types, indicating that cell mass variance scales with the mean cell mass raised to a certain power.
These patterns suggest recurring principles in the organization and distribution of cell sizes and counts, both within the human body and in natural systems more broadly. The authors stress the importance of adopting a whole-organism perspective to better understand human cell types, particularly in initiatives like the Human Cell Atlas.
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