Pulmonary arterial hypertension (PAH) is a devastating disease with poor prognosis and limited therapeutic options. We screened for pathways that may be responsible for the abnormal phenotype of pulmonary arterial smooth muscle cells (PASMCs), a major contributor of PAH pathobiology, and identified cyclin-dependent kinases (CDKs) as overactivated kinases in specimens derived from patients with idiopathic PAH. This increased CDK activity is confirmed at the level of mRNA and protein expression in human and experimental PAH, respectively. Specific CDK inhibition by dinaciclib and palbociclib decreases PASMC proliferation via cell cycle arrest and interference with the downstream CDK-Rb (retinoblastoma protein)-E2F signaling pathway. In two experimental models of PAH (i.e., monocrotaline and Su5416/hypoxia treated rats) palbociclib reverses the elevated right ventricular systolic pressure, reduces right heart hypertrophy, restores the cardiac index, and reduces pulmonary vascular remodeling. These results demonstrate that inhibition of CDKs by palbociclib may be a therapeutic strategy in PAH.

The pathogenetic role of angiogenesis in interstitial lung diseases (ILDs) is controversial. This study represents the first investigation of the spatial complexity and molecular motifs of microvascular architecture in important subsets of human ILD. The aim of our study was to identify specific variants of neoangiogenesis in three common pulmonary injury patterns in human ILD.We performed comprehensive and compartment-specific analysis of 24 human lung explants with usual intersitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP) and alveolar fibroelastosis (AFE) using histopathology, microvascular corrosion casting, micro-comupted tomography based volumetry and gene expression analysis using Nanostring as well as immunohistochemistry to assess remodelling-associated angiogenesis.Morphometrical assessment of vessel diameters and intervascular distances showed significant differences in neoangiogenesis in characteristically remodelled areas of UIP, NSIP and AFE lungs. Likewise, gene expression analysis revealed distinct and specific angiogenic profiles in UIP, NSIP and AFE lungs.Whereas UIP lungs showed a higher density of upstream vascularity and lower density in perifocal blood vessels, NSIP and AFE lungs revealed densely packed alveolar septal blood vessels. Vascular remodelling in NSIP and AFE is characterised by a prominent intussusceptive neoangiogenesis, in contrast to UIP, in which sprouting of new vessels into the fibrotic areas is characteristic. The molecular analyses of the gene expression provide a foundation for understanding these fundamental differences between AFE and UIP and give insight into the cellular functions involved.

Background. Unlike the vast amount of animal data available on the recellularization of allogenic decellularized heart valves (DHVs), there have only been sporadic histologic reports on such grafts in humans.Methods. Two experienced cardiac pathologists independently evaluated human specimens obtained during reoperation between December 2010 and April 2017 DHVs in seven categories after automated staining (scores: 0 to 6) in comparison with published data. An optimal result of 42 points was classified as 100%.Results. We found that 364 DHVs, 236 decellularized pulmonary homografts (DPHs), and 128 decellularized aortic homografts (DAHs) were implanted, and freedom from explantation was 96.1% (DAH) and 98.7% (DPH). Reoperations were because of (suspected) endocarditis in 5 of 11 patients, stenosis at the subvalvular or valvular or supravalvular level in 3 of 11 patients, planned staged reoperation in 2 of 11 patients, and 1 heart transplantation. Good reader agreement was reflected by an interagreement weighted k of 0.783 (95% confidence interval: 0.707 to 0.859). The relative histologic score in nonendocarditis specimens was 76% ± 4.3% (maximum 81%). Intracellular procollagen type 1 production was found in recipient mesenchymal cells within the transplanted grafts. In endocarditis specimens the histologic score was significantly lower with 48% ± 7.3% (minimum 41%, p [ 0.0004) because of leucocyte infiltration and matrix degradation. One DPH showed immune systemmediated graft failure. Grafts obtained during the first 12 months after implantation were not evenly repopulated with less recellularization in the inner parts; no difference was found between DAH and DPH with respect to extent of recellularization.Conclusions. Substantial in vivo recellularization with noninflammatory cells was observed in this study. Spontaneous recellularization appears to require multiple months, which correspondingly has an impact on size selection for growing patients.