DSP aspirate was dried and resuspended in 10 µL DEPC-treated water, and 4 µL was used in a PCR reaction. NanoString SeqCode primers were used to amplify the tags and add Illumina adaptor sequences and sample demultiplexing barcodes. PCR products were pooled and purified with two rounds of AMPure XP beads (Beckman Coulter). Libraries were sequenced on an Illumina NextSeq 550, NextSeq 2000, or NovaSeq 6000 according to the manufacturer's instructions, with at least 27 × 27 paired end reads. FASTQ files were processed using the NanoString GeoMx NGS Pipeline  v2.2. Briefly, reads were trimmed to remove low quality bases and adapter sequences. Paired end reads were stitched and aligned, and the barcode and UMI sequences were extracted. Barcodes were matched to known probe barcodes with maximum one mismatch allowed. Reads matching the same barcode were deduplicated by UMI.