Background/Purpose: Histologic correlates of anti-Ro associated congenital heart block (CHB) are apoptosis and calcification of cardiomyocytes with fibrosis of the AV node surrounded by infiltrating macrophages and giant cells. This study leveraged an unprecedented opportunity to interrogate the transcriptome of different cell types in a fetal heart dying with CHB.

Methods: Aortas from a 19 wk CHB fetal heart and a healthy 22 wk heart were cannulated using a Langendorff preparation with proteolytic enzymes to yield a single cell suspension. DAPI negative cells were isolated by flow using antibodies to CD14/CD45, CD31, and podoplanin, to yield leukocytes, endothelial cells, and fibroblasts, respectively. After RNA isolation and cDNA library preparation, RNA-Seq and transcriptome analysis were performed. Expression of lineage markers was consistent with the isolates based on flow markers. Data are expressed as log2 transcripts per million.

Results: Transcriptomes of the two hearts for each isolated fraction were compared. For leukocytes, in CHB vs healthy there were 5000 genes greater than a threshold ratio of 0.78 (expressed as log2 difference). Based on the DAVID annotation, data were organized into clusters of closely related genes. Within the term inflammatory response (p=1.66E-4) for the ratio of CHB/healthy, the genes were IL8 (4.13), IL6 (6.72), TNFa (0.78), and EDN1 (5.17). In addition, leukocyte gene expression of FCGR3A, TLR7 and IRF5 was higher in CHB vs control (2.6,1.37 and 0.91, respectively), a result supporting that the requisite machinery is upregulated to effect anti-Ro-hYRNA ligation and activate macrophages via TLR signaling. For endothelial cells, 7000 genes exceeded a ratio of 0.78 for CHB/healthy. Within the term inflammatory response (p=1E-5), FOS, FOSB, NFKB1A, and NFKBIZ were expressed with ratios of 1.47, 2.46, 1.03, and 2.75. Within the categories IMMUNE (p=4E-2) and cell adhesion (p=1.42E-06) higher expressed genes included CTGF (2.06), PTGS2 (2.53), SOCS3 (1.56), and OAS3 (2.52) along with ICAM1 (2.12), CCL2 (2.75), IL32 (2.81), VCAM1 (3.85), and SELE (2.4). Likewise within the death category (2.62E-08), PPP1R15A (1.39), XAF1 (3.77), GADD45B (1.94), and TNFAIP3 (3.06) were increased in CHB. These data support endothelial cells in leukocyte recruitment. For the fibroblasts, 4500 genes were above the CHB/healthy threshold (Table 1). CHB fibroblasts showed increased expression of pro-fibrotic genes while attenuating anti-fibrotic genes. The cardiomyopathy marker, XIRP2 (3.15), as well as genes resisting and promoting vascular stiffness (ELN [-2.23] and TTN [2.12], respectively) were also identified.

Conclusion: These data support that autoimmune CHB is a complex disease with contributions from death pathways, inflammation and fibrosis. Scarring likely results from a multi pronged pro-fibrotic environment whereby fibrosis promoting genes undermine genes that forestall fibrosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/transcriptome-profile-of-cells-isolated-from-a-chb-heart-support-an-exuberant-inflammatory-%e2%81%84pro-fibrotic-cascade/