Neighbours in the Womb: Kidneys and Gonads Keep Each Other Posted

Researchers have mapped how human urinary and reproductive organs develop together in the womb, revealing molecular signals between neighbouring tissues as the body's internal plumbing takes shape. ^[1]

The study, published in Science, places cells and their gene activity within the tissues where they grow. It brings developing gonads, kidney and adrenal tissues into a shared view, allowing researchers to examine relationships that are lost when cells are studied apart. ^[1]

Led by Guo Jingtao and Wang Xiaoyan at the Institute of Zoology of the Chinese Academy of Sciences, the team combined several ways of examining cells with experiments using human embryonic stem cells. Collaborators included Peking University Third Hospital and the Women and Children's Hospital, Qingdao University. ^[1]

The result is a resource for investigating a basic problem of human construction: how organs with different jobs develop alongside one another, exchanging signals while establishing their own identities. The urinary and reproductive systems share an embryonic origin and develop in close proximity. Their neighbours matter. ^[1]

Cells with an address

Earlier single-cell studies helped researchers identify the cells within individual developing organs and trace possible developmental paths. But separating tissue into individual cells removes a crucial piece of information: where each cell sat in relation to the others. The new study restores that geography to the molecular picture. ^[1]

The team examined male and female human embryos at three developmental points, known as Carnegie stages 15, 19 and 23. These stages classify embryos by their physical development, giving researchers a framework for comparing the construction of organs as it proceeds. ^[1]

Using a high-resolution technique called Stereo-seq, the researchers measured gene activity while preserving its location within tissue. They combined this spatial transcriptomics approach with single-cell multi-omics, which examines several layers of molecular information in individual cells, and protein imaging. Together, the methods connect what a cell is doing with where it is doing it. ^[1]

The team classified 33 cell types, identifying populations associated with the gonads, adrenal cortex, kidneys, connective tissues and nervous system. That breadth allows the atlas to follow relationships across developing organs rather than treating each organ as a separate project. ^[1]

There is important groundwork behind this effort. A separate atlas published in Nature in 2025 mapped the developing human reproductive tract using more than half a million cells from 89 donated embryonic and fetal tissue samples. The new study extends the view across the urogenital system, bringing kidney and adrenal tissues into the picture alongside the gonads. ^[1][2]

Messages from next door

At Carnegie stage 15, the researchers identified signals reaching the gonadal primordium, the early tissue from which a gonad develops. Those signals included pathways known as WNT, BMP and NCAM, with neighbouring tissues including the mesonephros, an embryonic kidney structure, and the adrenal primordium implicated as sources. ^[1]

This is where knowing a cell's address becomes useful. A molecular signal found in one tissue acquires a different meaning when researchers can locate nearby cells that may receive it. The atlas gives them a way to investigate those exchanges within the developing anatomy. ^[1]

The team then tested part of that picture in a stem-cell model. They treated intermediate-mesoderm cells, representing an early tissue involved in urogenital development, with a combination of BMP7, NCAM1 and the compound CHIR99021. ^[1]

After treatment, the cells increased their expression of genes used as markers of early gonadal development. Their overall gene-activity profile also moved towards an early gonadal state observed in embryos. The experiment connects the spatial findings with a response that researchers could produce in the laboratory. ^[1]

Another finding concerned rete cells, which the team located near the developing gonads. These cells expressed PAX8, a gene associated with their identity. The analyses suggested that some rete cells associated with the mesonephros might contribute to a subset of the gonad's supporting cells. ^[1]

That proposed relationship would connect neighbouring tissues through the cells themselves as well as through signals. Computational experiments and laboratory work that reduced PAX8 activity also suggested that the gene helps rete cells retain their identity. Both findings offer specific relationships for further testing. ^[1]

A reference for the next experiments

The atlas also distinguished three populations of cells involved in making steroid hormones: fetal Leydig cells in male gonads and two states of cells in the adrenal fetal zone. The two adrenal states showed different patterns of activity in genes related to cholesterol. Even cells grouped by a shared broad task had distinct molecular programmes. ^[1]

For medicine, the attraction is a reference against which disrupted development could eventually be examined. The researchers present the framework as a way to investigate congenital anomalies and differences of sex development, including questions about how coordination between tissues might go wrong. ^[1]

The sample count and its distribution across sexes and developmental stages were not specified in the Chinese Academy of Sciences account. How widely the proposed relationships apply across human embryos still needs testing. The study does not establish that these signals cause particular conditions, such as hypospadias or kidney malformations, and it supplies neither a clinical test nor a treatment. ^[1]

Its immediate value lies in making the next experiments more precise: identifying which neighbouring cells to examine, which signals to test and which developmental states to compare. The team has created an interactive platform for exploring the spatial and single-cell datasets, giving researchers a means to pursue those questions across the mapped tissues. ^[1]