Single-cell transcriptomic analysis reveals transcriptional and cell subpopulation differences between human and pig immune cells

Abstract

Background: The pig is a promising donor candidate for xenotransplantation. Understanding the differences between human and swine immune systems is critical for addressing xenotransplant rejection and hematopoietic reconstitution. The gene transcriptional profile differences between human and pig immune cell subpopulations have not been studied. To assess the similarities and differences between pigs and humans at the levels of gene transcriptional profiles or cell subpopulations are important for better understanding the cross-species similarity of humans and pigs, and it would help establish the fundamental principles necessary to genetically engineer donor pigs and improve xenotransplantation.

Objective: To assess the gene transcriptional similarities and differences between pigs and humans.

Methods: Two pigs and two healthy humans' PBMCs were sorted for 10 × genomics single-cell sequence. We generated integrated human-pig scRNA-seq data from human and pig PBMCs and defined the overall gene expression landscape of pig peripheral blood immune cell subpopulations by updating the set of human-porcine homologous genes. The subsets of immune cells were detected by flow cytometry.

Results: There were significantly less T cells, NK cells and monocytes but more B cells in pig peripheral blood than those in human peripheral blood. High oxidative phosphorylation, HIF-1, glycolysis, and lysosome-related gene expressions in pig CD14⁺ monocytes were observed, whereas pig CD14⁺ monocytes exhibited lower levels of cytokine receptors and JAK-STAT-related genes. Pig activated CD4⁺T cells decreased cell adhesion and inflammation, while enriched for migration and activation processes. Porcine GNLY⁺CD8⁺T cells reduced cytotoxicity and increased proliferation compared with human GNLY⁺CD8⁺T cells. Pig CD2⁺CD8⁺γδT cells were functionally homologous to human CD2⁺CD4⁺ γδT cells. Pig CD2^-CD8^-γδT cells expressed genes with quiescent and precursor characteristics, while CD2^-CD8⁺γδT cells expressed migration and memory-related molecules. Pig CD24⁺ and CD5⁺B cells are associated with inflammatory responses.

Conclusion: Our research with integrated scRNA-seq assays identified the different distribution of pig immune cell subpopulations and the different transcriptional profiles of human and pig immune cells. This study enables a deeper understanding of the development and function of porcine immune cells.

Keywords: Cross-species; Human; Immune system; PBMCs; Pig; scRNA-seq.