Vasoactive Management of Pulmonary Hypertension and Ventricular Dysfunction in Neonates Following Complicated Monochorionic Twin Pregnancies: A Single-Center Experience

OBJECTIVES

Twins resulting from a complicated monochorionic (MC) twin pregnancy are at risk for postnatal evolution of pulmonary hypertension (PH) and cardiac dysfunction (CD). Both pathologies are important contributors to short- and long-term morbidity in these infants. The aim of the present retrospective single-center cohort study was to evaluate the need for vasoactive treatment for PH and CD in these neonates.

METHODOLOGY

In-born neonates following a complicated MC twin pregnancy admitted to the department of neonatology of the University Children's Hospital Bonn (UKB) between October 2019 and December 2023 were screened for study inclusion. Finally, 70 neonates were included in the final analysis, with 37 neonates subclassified as recipient twins (group A) and 33 neonates as donor twins (group B).

RESULTS

The overall PH incidence at day of life (DOL) 1 was 17% and decreased to 6% at DOL 7 (p = 0.013), with no PH findings at DOL 28. The overall incidence of CD was 56% at DOL 1 and decreased strongly until DOL 7 (10%, p = 0.015), with no diagnosis of CD at DOL 28. The use of dobutamine, norepinephrine, and vasopressin at DOL 1 until DOL 7 did not differ between the subgroups, whereas the dosing of milrinone was significantly higher in Group B at DOL 1 (p = 0.043). Inhaled nitric oxide (iNO) was used in 16% of the cohort, and a levosimendan therapy was administered in 34% of the neonates. One-third of the cohort was treated with oral beta blockers, and in 10%, an intravenous beta blockade (landiolol) was administered. The maximum levosimendan vasoactive-inotropic score (LVISmax) increased from DOL 1 (12.4 [3/27]) to DOL 2 (14.6 [1/68], p = 0.777), with a significant decrease thereafter as measured at DOL 7 (9.5 [2/30], p = 0.011).

CONCLUSION

Early PH and CD are frequent diagnoses in neonates following a complicated MC twin pregnancy, and an individualized vasoactive treatment strategy is required in the management of these infants.

Immune Sensing of Synthetic, Bacterial, and Protozoan RNA by Toll-like Receptor 8 Requires Coordinated Processing by RNase T2 and RNase 2

Human toll-like receptor 8 (TLR8) activation induces a potent T helper-1 (Th1) cell response critical for defense against intracellular pathogens, including protozoa. The receptor harbors two distinct binding sites, uridine and di- and/or trinucleotides, but the RNases upstream of TLR8 remain poorly characterized. We identified two endolysosomal endoribonucleases, RNase T2 and RNase 2, that act synergistically to release uridine from oligoribonucleotides. RNase T2 cleaves preferentially before, and RNase 2 after, uridines. Live bacteria, P. falciparum-infected red blood cells, purified pathogen RNA, and synthetic oligoribonucleotides all required RNase 2 and T2 processing to activate TLR8. Uridine supplementation restored RNA recognition in RNASE2^-/- or RNASET2^-/- but not RNASE2^-/-RNASET2^-/- cells. Primary immune cells from RNase T2-hypomorphic patients lacked a response to bacterial RNA but responded robustly to small-molecule TLR8 ligands. Our data identify an essential function of RNase T2 and RNase 2 upstream of TLR8 and provide insight into TLR8 activation.

Immune sensing of synthetic, bacterial and protozoan RNA by TLR8 requires coordinated processing of RNA substrates by RNaseT2 and RNase2

Human TLR8 is an essential sensor of bacterial RNA which induces proinflammatory and Th1 cytokines. Crystallography revealed that TLR8 binds both uridine and short single-stranded RNA, but the RNases that process the RNA are still unknown. Herein, we demonstrate that two endosomal endoribonucleases, RNaseT2 and RNase2, can process RNA for TLR8 recognition. In the endosome, RNase2 and -T2 act synergistically to release uridine from oligoribonucleotides, with RNaseT2 cleaving preferentially before and RNase2 after uridines. Live bacteria, P. falciparum-infected red blood cells, purified pathogen RNA, and synthetic ligands all required RNase processing for TLR8 activation, and uridine supplementation restored RNA recognition in RNASE2−/− or RNASET2−/− but not double knockout cells. Strikingly, peripheral blood mononuclear cells from RNaseT2 hypomorphic patients did not respond to bacterial RNA but did to small-molecule TLR8 agonists. Our data provide a novel insight into TLR8 activation and its differences between cell types and species.

Experimental observations regarding the applicability of calf carotid xenograft in vascular surgery

The implantation process of Solcograft vascular prostheses in various positions was studied in 50 dogs between 7 and 600 postoperative days. It was shown that in the formation of a continuous endothelial layer, endothelium islets at the graft-vessel border and around ingrowing capillaries are of basic importance. Typical layers of the vessel wall have been formed between 4-6 months. Complications were mostly due to intimal proliferation and thrombosis.