Single Nucleotide Polymorphism Typing Going Spatial: In Situ Padlock Probes Targeting mRNA Variants to Identify Haploidentical Cells within the Tissue Environment.

BACKGROUND

Despite almost 3 decades of research, the mechanisms underlying the bidirectional trafficking of cells at the maternal-fetal interface that gives rise to microchimerism remain poorly understood. A major barrier to progress has been the lack of suitable detection methods capable of distinguishing maternal from fetal cells within the spatial context of the human placenta. To address this, we developed a novel detection method based on padlock probe technology to differentiate haploidentical cells in placental tissues.

METHODS

Padlock probes were designed to target single nucleotide polymorphisms (SNPs) present in messenger RNA transcripts. The assays were first validated in cell lines and subsequently applied to placental tissue to assess its ability to distinguish between maternal and fetal cells.

RESULTS

We established a panel of 27 assays targeting 3 human leukocyte antigen-A alleles and 12 biallelic SNPs. The method demonstrated high specificity and sensitivity, detecting minor cell populations at dilutions as low as 1:10 000. Proof of concept was obtained in a decidua basalis specimen, showing the assays' capability to distinguish maternal and fetal cells within placental tissue.

CONCLUSIONS

We present a novel, sex-unbiased methodology for the in situ visualization of haploidentical (microchimeric) cells. This approach enables the study of maternal-fetal cellular interactions within their native tissues at the maternal-fetal interface.