Heparin-like molecules inhibit pulmonary vascular pericyte proliferation in vitro

RGS5 as a Biomarker of Pericytes, Involvement in Vascular Remodeling and Pulmonary Arterial Hypertension

Introduction

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained rise in mean pulmonary artery pressure. Pulmonary vascular remodeling serves an important role in PAH. Identifying a key driver gene to regulate vascular remodeling of the pulmonary microvasculature is critical for PAH management.

Methods

Differentially expressed genes were identified using the Gene Expression Omnibus (GEO) GSE117261, GSE48149, GSE113439, GSE53408 and GSE16947 datasets. A co-expression network was constructed using weighted gene co-expression network analysis. Novel and key signatures of PAH were screened using four algorithms, including weighted gene co-expression network analysis, GEO2R analysis, support vector machines recursive feature elimination and robust rank aggregation rank analysis. Regulator of G-protein signaling 5 (RGS5), a pro-apoptotic/anti-proliferative protein, which regulate arterial tone and blood pressure in vascular smooth muscle cells. The expression of RGS5 was determined using reverse transcription-quantitative PCR (RT-qPCR) in PAH and normal mice. The location of RGS5 and pericytes was detected using immunofluorescence.

Results

Compared with that in the normal group, RGS5 expression was upregulated in the PAH group based on GEO and RT-qPCR analyses. RGS5 expression in single cells was enriched in pericytes in single-cell RNA sequencing analysis. RGS5 co-localization with pericytes was detected in the pulmonary microvasculature of PAH.

Conclusion

RGS5 regulates vascular remodeling of the pulmonary microvasculature and the occurrence of PAH through pericytes, which has provided novel ideas and strategies regarding the occurrence and innovative treatment of PAH.

Platelets, extracellular vesicles and coagulation in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare disease of the pulmonary vasculature, characterised pathologically by proliferation, remodelling and thrombosis in situ. Unfortunately, existing therapeutic interventions do not reverse these findings and the disease continues to result in significant morbidity and premature mortality. A number of haematological derangements have been described in pulmonary arterial hypertension which may provide insights into the pathobiology of the disease and opportunities to explore new therapeutic pathways. These include quantitative and qualitative platelet abnormalities, such as thrombocytopaenia, increased mean platelet volume and altered platelet bioenergetics. Furthermore, a hypercoagulable state and aberrant negative regulatory pathways can be observed, which could contribute to thrombosis in situ in distal pulmonary arteries and arterioles. Finally, there is increasing interest in the role of extracellular vesicle autocrine and paracrine signalling in pulmonary arterial hypertension, and their potential utility as biomarkers and novel therapeutic targets. This review focuses on the potential role of platelets, extracellular vesicles and coagulation pathways in the pathobiology of pulmonary arterial hypertension. We highlight important unanswered clinical questions and the implications of these observations for future research and pulmonary arterial hypertension-directed therapies.

Heparin inhibits pulmonary artery smooth muscle cell proliferation through guanine nucleotide exchange factor-H1/RhoA/Rho kinase/p27

Ras homolog gene family member A (RhoA) through Rho kinase kinase (ROCK), one of its downstream effectors, regulates a wide range of cell physiological functions, including vascular smooth muscle cell (SMC) proliferation, by degrading cyclin-dependent kinase inhibitor, p27. Our previous studies found that heparin inhibition of pulmonary artery SMC (PASMC) proliferation and pulmonary hypertension was dependent on p27 up-regulation. To investigate whether ROCK, a regulator of p27, is involved in regulation of heparin inhibition of PASMC proliferation, we analyzed ROCK expression in the lungs from mice and from human PASMCs exposed to hypoxia, and investigated the effect of ROCK expression in vitro by RhoA cDNA transfection. We also investigated the effect of guanine nucleotide exchange factor (GEF)-H1, an upstream regulator of RhoA, on heparin inhibition of PASMC proliferation by GEF-H1 cDNA transfection. We found that: (1) hypoxia increased ROCK expression in mice and PASMCs; (2) overexpression of RhoA diminished the inhibitory effect of heparin on PASMC proliferation and down-regulated p27 expression; and (3) overexpression of GEF-H1 negated heparin inhibition of PASMC proliferation, which was accompanied by increased GTP-RhoA and decreased p27. This study demonstrates that the RhoA/ROCK pathway plays an important role in heparin inhibition on PASMC proliferation, and reveals that heparin inhibits PASMC proliferation through GEF-H1/RhoA/ROCK/p27 signaling pathway, by down-regulating GEF-H1, RhoA, and ROCK, and then up-regulating p27.

Growth inhibition of bovine pulmonary artery smooth muscle cells following long-term heparin treatment

Heparin (HP) inhibits pulmonary artery smooth muscle cell (PASMC) growth in vitro and vascular remodeling in vivo. Bârzu et al. (1994) suggested that the antiproliferative effect of HP on rat aortic smooth muscle cell in vitro diminishes with prolonged exposure to heparin. We exposed cultured bovine PASMC (BPASMC) to prolonged pretreatment with 20 microg/ml of 0-hexanoylated HP from passages 3 to13 and compared them to control (no pretreatment) cultures of identical passages. The pretreated BPASMC and control groups were growth arrested for 48 h, followed by treatment of 0-hexanoylated HP at different doses. On day 5, the growth inhibition of BPASMC was determined. The percent inhibition by 1 microg/ml of 0-hexanoylated HP was 46 +/- 14% versus 62 +/- 13%, for control and pretreated BPASMC, respectively. At 10 microg/ml the inhibition was 62 +/- 7% versus 84 +/- 6%. For 100 microg/ml the inhibition increased to 92 +/- 5% versus 100% and at 200 microg/ml the inhibition was 95 +/- 3% versus 100%. BPASMC (with or without preexposure to 0-hexanoylated HP), at passage 13, were sensitive to the growth inhibitory effect of 0-hexanoylated HP with no significant difference among the groups (95 +/- 3% inhibition vs. 100% for pretreated BPASMC). We found that 0-hexanoylated HP-induced necrosis as shown by flow cytometry and only minor apoptosis. Caspase-3 and PARP detection was insignificant between the groups. In summary, no cell subpopulation at long-term treatment exhibited resistance to 0-hexanoylated HP. The HP antiproliferative effect on SMC is potentially important in defining new approaches to the treatment of the remodeled vasculature of pulmonary hypertension. Liss, Inc.

Gene expression of cyclin-dependent kinase inhibitors and effect of heparin on their expression in mice with hypoxia-induced pulmonary hypertension

The balance between cell proliferation and cell quiescence is regulated delicately by a variety of mediators, in which cyclin-dependent kinases (CDK) and CDK inhibitors (CDKI) play a very important role. Heparin which inhibits pulmonary artery smooth muscle cell (PASMC) proliferation increases the levels of two CDKIs, p21 and p27, although only p27 is important in inhibition of PASMC growth in vitro and in vivo. In the present study we investigated the expression profile of all the cell cycle regulating genes, including all seven CDKIs (p21, p27, p57, p15, p16, p18, and p19), in the lungs of mice with hypoxia-induced pulmonary hypertension. A cell cycle pathway specific gene microarray was used to profile the 96 genes involved in cell cycle regulation. We also observed the effect of heparin on gene expression. We found that (a) hypoxic exposure for two weeks significantly inhibited p27 expression and stimulated p18 activity, showing a 98% decrease in p27 and 81% increase in p18; (b) other CDKIs, p21, p57, p15, p16, and p19 were not affected significantly in response to hypoxia; (c) heparin treatment restored p27 expression, but did not influence p18; (d) ERK1/2 and p38 were mediators in heparin upregulation of p27. This study provides an expression profile of cell cycle regulating genes under hypoxia in mice with hypoxia-induced pulmonary hypertension and strengthens the previous finding that p27 is the only CDKI involved in heparin regulation of PASMC proliferation and hypoxia-induced pulmonary hypertension.

Human endothelial cell interaction with biomimetic surfactant polymers containing Peptide ligands from the heparin binding domain of fibronectin

Biomimetic materials that mimic the extracellular matrix (ECM) provide a means to control cellular functions such as adhesion and growth, which are vital to successful engineering of tissue-incorporated biomaterials. Novel "ECM-like" biomimetic surfactant polymers consisting of a poly(vinyl amine) backbone with pendant cell-adhesive peptides derived from one of the heparin-binding domains of fibronectin were developed to improve endothelial cell adhesion and growth on vascular biomaterials. Heparin-binding peptide (HBP) sequences, alone and in combination with RGD peptides, were examined for their ability to promote human pulmonary artery endothelial cell (HPAEC) adhesion and growth (HBP1, WQPPRARI; HBP2, SPPRRARVT; HBP1:RGD; and HBP2:RGD) and compared with cell adhesion and growth on fibronectin and on negative control polymer surfaces in which alanines were substituted for the positively charged arginine residues in the two peptides. The results showed that HPAECs adhered and spread equally well on all HBP-containing polymers and the positive fibronectin control, showing similar stress fiber and focal adhesion formation. However, the HBP alone was unable to support long-term HPAEC growth and survival, showing a loss of focal adhesions and cytoskeletal disorganization by 24 h after seeding. With the addition of RGD, the surfaces behaved similarly or better than fibronectin. The negative control polymers showed little to no initial cell attachment, and the addition of soluble heparin to the medium reduced initial cell adhesion on both the HBP2 and HBP2:RGD surfaces. These results indicate that the HBP surfaces promote initial HPAEC adhesion and spreading, but not long-term survival.

Heparin affects signaling pathways stimulated by fibroblast growth factor-1 and -2 in type II cells

Undersulfation of the basement membrane matrix of alveolar type II (AT2) cells compared with that of neighboring type I cells is believed to account for some of the known morphological and functional differences between these pneumocytes. Heparin, a model for sulfated components of basement membrane matrices, is known to inhibit fibroblast growth factor (FGF)-2-stimulated DNA synthesis as well as gene expression of FGF-2 and its receptor in AT2 cells. To determine whether these end points result from specific effects of heparin on FGF-related signaling pathways, isolated rat AT2 cells were treated with 100 ng/ml FGF-1 or FGF-2 in the presence of up to 500 microg/ml heparin. In addition, experiments were done on cells grown in the presence of 20 mM sodium chlorate (sulfation inhibitor). High-dose heparin reduced FGF-1- or FGF-2-stimulated phosphorylation of mitogen-activated protein kinase kinases (MEK1/2), p44/42 mitogen-activated protein kinases (MAPK/ERK1/2), stress-activated protein kinase/c-Jun NH(2)-terminal kinase, Akt/protein kinase B, and p90(RSK). FGF-2-stimulated signaling was more sensitive to heparin's effects than was signaling stimulated by FGF-1. Heparin had an additive effect on the reduced [(3)H]thymidine incorporation in FGF-2-treated AT2 cells caused by inhibition of the MEK/ERK pathway by the MEK inhibitor PD-98059. The data suggest that heparin's known capacity to alter DNA synthesis and, possibly, other biological end points is realized via cross talk between multiple signaling pathways.

Heparin inhibits the motility and proliferation of human myometrial and leiomyoma smooth muscle cells

Uterine fibroids (leiomyomas) are a major women's health problem. Currently, the standard for treatment remains hysterectomy, because no other treatment modalities can reduce both symptoms and recurrence. As leiomyomas are a hyperproliferation of smooth muscle cells, we sought to understand the regulation of uterine smooth muscle cell mitogenesis by the glycosaminoglycan heparin, which has been extensively studied as an anti-proliferative molecule in vascular smooth muscle cells. Using matched pairs of human myometrial and leiomyoma smooth muscle cells from the same uterus, we demonstrate that the proliferation and motility of both cell types are inhibited by heparin. We report that the decrease in cell number seen in the presence of heparin is not because of cell death. Interestingly, there is significant patient-to-patient variability in the proliferation response but not in the motility response to heparin. Furthermore, nonanticoagulant and anticoagulant heparin were equally effective at inhibiting leiomyoma and myometrial smooth muscle cell proliferation. These results warrant further investigation into the possibility that heparin might be useful in the treatment of uterine fibroids.

Molecular and cellular basis of pulmonary vascular remodeling in pulmonary hypertension

Clinical pulmonary hypertension is characterized by a sustained elevation in pulmonary arterial pressure. Pulmonary vascular remodeling involves structural changes in the normal architecture of the walls of pulmonary arteries. The process of vascular remodeling can occur as a primary response to injury, or stimulus such as hypoxia, within the resistance vessels of the lung. Alternatively, the changes seen in more proximal vessels may arise secondary to a sustained increase in intravascular pressure. To withstand the chronic increase in intraluminal pressure, the vessel wall becomes thickened and stronger. This "armouring" of the vessel wall with extra-smooth muscle and extracellular matrix leads to a decrease in lumen diameter and reduced capacity for vasodilatation. This maladaptive response results in increased pulmonary vascular resistance and consequently, sustained pulmonary hypertension. The process of pulmonary vascular remodeling involves all layers of the vessel wall and is complicated by the finding that cellular heterogeneity exists within the traditional compartments of the vascular wall: intima, media, and adventitia. In addition, the developmental stage of the organism greatly modifies the response of the pulmonary circulation to injury. This review focuses on the latest advances in our knowledge of these processes as they relate to specific forms of pulmonary hypertension and particularly in the light of recent genetic studies that have identified specific pathways involved in the pathogenesis of severe pulmonary hypertension.