Moo-ve Aside Mice: Exploring Cow Models in Research

For decades, mice have been a staple animal model for researchers, but nontraditional animal models are now getting their heyday. Gerlinde Van de Walle, a veterinarian virologist at Cornell University, studies the mesenchymal stromal cells (MSC) of large animals such as horses and cows, which are currently used to treat orthopedic injuries and have been shown to have regenerative properties.¹ 

“As a veterinarian, I’ve always very much been interested in studying naturally occurring diseases in our veterinary species and using that as a translational jump into human research,” remarked Van de Walle.

She and her team set out to characterize bovine MSC to ascertain the extent of similarities between cows and humans. Their findings, published in iScience, showed that human MSC share an extensive genetic overlap with their bovine counterparts, more so than with mice.² Understanding bovine MSC could improve therapeutic approaches and position cows as valuable models in regenerative medicine.

Few studies have examined the comparative characteristics of bovine MSC, emphasizing the need for robust identification and classification to advance MSC research. To bridge this gap, Van de Walle and her team collected samples from three sources within a single dairy cow: peripheral blood (PB), bone marrow (BM), and adipose tissue (AT). 

Microscopy revealed that the cells differentiated into adipocytes, chondrocytes, and osteocytes—these data were consistent with findings in humans. Then, the team used immunofluorescent imaging with three positive MSC cluster of differentiation (CD) markers: CD73, CD44, and CD29. Cells from all three tissue sources expressed these three markers.

Van de Walle’s team delved deeper into the heterogeneity of MSC, which is linked to variable treatment outcomes, and assessed shared and tissue-specific patterns. They used single-cell RNA sequencing (scRNA-seq) and verified the results with quantitative polymerase chain reaction.

Both MSC marker gene and protein expression patterns were largely similar between PB-, BM-, and AT-MSC. However, they noted heterogeneity in MSC with upregulated tissue-specific genes and distinct intercellular signaling pathways between the three sources. With these characteristics in mind, Van de Walle compared bovine MSC against human and murine MSC. 

The researchers drew from an online database of human and murine BM-MSC scRNA-seq datasets for comparison. When Van de Walle examined the transcriptomic profiles, she noted that BM-MSC shared 1,127 functionally relevant stem cell gene expression profiles with human BM-MSC, while murine and human BM-MSC shared 24 gene transcripts.

“[The results] were really exciting because that plays in our favor of promoting the value of nontraditional animal models and human research,” said Van de Walle.

“One advantage of veterinary species is that cows are outbred like humans, whereas mice are very inbred,” added Van de Walle. “By having this more diverse background, our nontraditional model organisms are more representative of the heterogeneity that exists in the human population.”

Javiera Bahamonde-Azcuy, a biomedical and veterinary scientist at the Austral University of Chile who was not involved in this study, noted her excitement in the robustness of the study’s large collection of information at the single cell level.

However, both Van de Walle and Bahamonde-Azcuy acknowledged the study’s major caveat: using a single donor animal. “The use of transcriptomics is very novel, but before drawing conclusions about differences between species, I would like to see repeated studies comparing more individuals from the same species,” emphasized Bahamonde-Azcuy.

Van de Walle and her team hope this preliminary wealth of transcriptomic data will inform future comparative analysis as they continue to study other bovine stem cells and their potential for treatment.

References

1. Harman RM, et al. Single-cell RNA sequencing of equine mesenchymal stromal cells from primary donor-matched tissue sources reveals functional heterogeneity in immune modulation and cell motility. Stem Cell Res Ther. 2020;11(1):524.
2. Danev N, et al. Comparative transcriptomic analysis of bovine mesenchymal stromal cells reveals tissue-source and species-specific differences. iScience. 2024;27(2):108886.