Seiichiro Sakao

Initial apoptosis is followed by increased proliferation of apoptosis-resistant endothelial cells

We have demonstrated that VEGF receptor blockade in combination with chronic hypoxia causes in rats severe angioproliferative pulmonary hypertension (SAPH) associated with arterial occlusion by proliferating endothelial cells, and we postulate that the established, lumen‐occluding lesions are the result of the emergence of apoptosis‐resistant proliferating cells. To study the dependence of exuberant endothelial cell proliferation on initial apoptosis, we adapted the CELLMAX artificial capillary system to analyze the effects of a VEGF receptor antagonist (SU5416) on human pulmonary microvascular endothelial cells under pulsatile shear stress. Immunohistochemical staining for caspase‐3 and PCNA and flow cytometry for Annexin‐V and BrdU supported our concept, since SU5416 caused initial apoptosis (35.8% at 24 h after the SU5416 addition and 4.8% in control cells) whereas the surviving cells became hyperproliferative (PCNA positive). Flow cytometry showed that apoptosis inhibition prevented the proliferation following the initial apoptosis. These lumen‐filling endothelial cells were apoptosis resistant, grew without serum, and were phenotypically altered in that they express the tumor marker survivin. Hyperproliferative apoptosis‐resistant cells were also generated by adding apoptosed cells instead of the VEGF receptor blocker to the CELLMAX system. In conclusion, endothelial cell death resulted in the selection of an apoptosis‐resistant, proliferating phenotypically altered endothelial cell phenotype.

VEGF-R blockade causes endothelial cell apoptosis, expansion of surviving CD34+ precursor cells and transdifferentiation to smooth muscle-like and neuronal-like cells

Severe pulmonary hypertension (PH) is characterized by complex precapillary arteriolar lesions, which contain phenotypically altered smooth muscle (SM) and endothelial cells (EC). We have demonstrated that VEGF receptor blockade by SU5416 {3‐[(2,4‐dimethylpyrrol‐5‐yl)methylidenyl]‐indolin 2‐one} in combination with chronic hypoxia causes severe angioproliferative PH associated with arterial occlusion in rats. We postulate that endothelial‐mesenchymal transdifferentiation can take place in the occlusive lesions and that endothelium‐derived mesenchymal cells can further differentiate toward a SM phenotype. To examine this hypothesis, we incubated human pulmonary microvascular endothelial cells (HPMVEC) with SU5416 and analyzed these cells utilizing quanti‐tative‐PCR, immunofluorescent staining and flow cytometry analysis. In vitro studies in HPMVEC demonstrated that SU5416 suppressed PGI2S gene expression while potently inducing COX‐2, VEGF, and TGF‐β1 expression;and caused transdifferentiation of mature vascular endothelial cells (defined by Dil‐ac‐LDL, Lectin and Factor VIII) to SM‐like (as defined by expression of α‐SM actin) “transitional” cells, coexpressing both endothelial and SM markers. SU5416 expanded the number of CD34 and/or c‐kit positive cells and caused transdifferentiation of CD34 positive cells but not negative cells. In conclusion, our data show that SU5416 generated a selection pressure that killed some EC and expanded progenitor‐like cells to transdiffer‐entiate to SM‐like and neuronal‐like cells.—Sakao, S., Taraseviciene‐Stewart, L., Cool, C. D., Tada, Y., Kasahara, Y., Kurosu, K., Tanabe, N., Takiguchi, Y., Tatsumi, K., Kuriyama, T., and Voelkel, N. F. VEGF‐R blockade causes endothelial cell apoptosis, expansion of surviving CD34+ precursor cells and transdifferentiation to smooth muscle‐like and neuronal‐like cells. FASEB J. 21, 3640–3652 (2007)

Identification of Annexin 1 as a Novel Autoantigen in Acute Exacerbation of Idiopathic Pulmonary Fibrosis

Consistent with the hypothesis that pulmonary epithelial apoptosis is the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we conducted serological identification of Ags by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify disease-related Abs. In a survey of Abs to the recombinant autoantigens identified by SEREX analysis, five Abs were identified as novel candidates for the acute exacerbation of IPF. Abs to annexin 1 were detected in 47 and 53% of the sera and bronchoalveolar lavage materials from patients with acute exacerbation of IPF. Some identical TCR Vβ genes were identified in sequential materials obtained at 1–3 mo in all 10 acute exacerbation IPF cases, suggesting that some infiltrating CD4-positive T cells sharing limited epitopes expand by Ag-driven stimulation during disease extension. The CDR3 region of these identical TCR Vβ genes showed high homology with the N-terminal portion of annexin 1, including in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and observation of the CD4-positive T cell responses in bronchoalveolar lavage samples, the N-terminal portion of annexin 1 was cleaved and found to induce marked proliferative responses of CD4-positive T cells in three patients. Our study demonstrates that annexin 1 is an autoantigen that raises both Ab production and T cell response in patients with acute exacerbation of IPF, and that the N-terminal portion of annexin 1 plays some role in the pathogenesis of acute exacerbation in IPF patients.

Adenovirus Vector-Mediated In Vivo Gene Transfer of Brain-Derived Neurotrophic Factor (BDNF) Promotes Rubrospinal Axonal Regeneration and Functional Recovery after Complete Transection of the Adult Rat Spinal Cord

Neurotrophins have been shown to promote axonal regeneration, but the techniques available for delivering neurotrophins have limited effectiveness. The aim of this study was to evaluate the effect of adenovirus vector mediated gene transfer of brain-derived neurotrophic factor (BDNF) on axonal regeneration after spinal cord injury. We prepared adenovirus vectors encoding either beta-galactosidase (AxCALacZ) or BDNF (AxCABDNF). AxCALacZ was used to assess infection levels of the adenovirus BDNF produced by AxCABDNF was detected by Western blotting and its bioactivity was confirmed by bioassay. As a model of spinal cord injury, the rat spinal cord was completely transected at the T8 level. Immediately after transection, the vectors were injected into both stumps of the spinal cord. Axonal regeneration after transection was assessed by retrograde and anterograde tracing. In AxCALacZ-injected rats, adenovirus-infected cells were observed not only at the injected site but also in brainstem nuclei, as shown by LacZ expression. After the injection of the retrograde tracer fluorogold (FG) distal portion to the transection, AxCABDNF-injected rats showed FG-labeled neurons in the red nucleus. The anterograde tracer biotinylated dextran amine (BDA) injected into the red nucleus was also found in regenerating rubrospinal fibers distal to the transection. These tracing experiments demonstrated the regeneration of descending axons. In addition, rats of the AxCABDNF group showed significant locomotor recovery of hindlimb function, which was completely abolished by re-transection. These results indicate that the recovery was caused by regeneration of rubrospinal axons, not by simple enhancement of the central pattern generator.

Adenovirus vector-mediated ex vivo gene transfer of brain-derived neurotrophic factor to bone marrow stromal cells promotes axonal regeneration after transplantation in completely transected adult rat spinal cord.

The aim of this study was to evaluate the efficacy in adult rat completely transected spinal cord of adenovirus vector-mediated brain-derived neurotrophic factor (BDNF) ex vivo gene transfer to bone marrow stromal cells (BMSC). BMSC were infected with adenovirus vectors carrying β-galactosidase (AxCALacZ) or BDNF (AxCABDNF) genes. The T8 segment of spinal cord was removed and replaced by graft containing Matrigel alone (MG group) or Matrigel and BMSC infected by AxCALacZ (BMSC-LacZ group) or AxCABDNF (BMSC-BDNF group). Axons in the graft were evaluated by immunohistochemistry and functional recovery was assessed with BBB locomotor scale. In the BMSC-BDNF group, the number of fibers positive for growth associated protein-43, tyrosine hydroxylase, and calcitonin gene-related peptide was significantly larger than numbers found for the MG and BMSC-LacZ groups. Rats from BMSC-BDNF and BMSC-LacZ groups showed significant recovery of hind limb function compared with MG rats; however, there was no significant difference between groups in degree of functional recovery. These findings demonstrate that adenovirus vector-mediated ex vivo gene transfer of BDNF enhances the capacity of BMSC to promote axonal regeneration in this completely transected spinal cord model; however, BDNF failed to enhance hind limb functional recovery. Further investigation is needed to establish an optimal combination of cell therapy and neurotrophin gene transfer for cases of spinal cord injury.

Vascular remodeling in pulmonary arterial hypertension: Multiple cancer-like pathways and possible treatment modalities

Most patients with severe pulmonary arterial hypertension (PAH) demonstrate persistent structural alterations in small pulmonary arterioles at the time of diagnosis, including marked proliferation of pulmonary artery endothelial cells (ECs), smooth muscle cells (SMCs) and fibroblasts. Rai et al. have recently proposed a paradigm shift to explain the pathobiology of small vessel disease in severe PAH patients as a quasi-neoplastic process. Indeed, the vascular lesions of patients with severe PAH exhibit some cancer-like characteristics: decreased population of apoptotic cells and overexpression of antiapoptotic proteins. Nevertheless they lack the capability for tissue invasion and metastasis. The article reviews pathomechanisms of vascular lesions in PAH comparing them with each of the cancer defining mechanisms and indicates the potential utility of antineoplastic drugs as antiproliferative treatment in PAH. PDGF has been identified as a novel potential therapeutic target and the successful treatment of experimental PAH with a PDGF receptor tyrosine kinase inhibitor has been demonstrated recently. These findings justify further clinical trials concerning thyrosine kinase inhibitors as future PAH therapies. However, the drugs currently developed for malignant neoplasms to target neoplastic proliferation should be tested carefully in PAH patients due to their cardiac and pulmonary toxicity.

The Effects of Antiangiogenic Compound SU5416 in a Rat Model of Pulmonary Arterial Hypertension

Several lines of evidence indicate that vascular endothelial growth factor (VEGF) plays a prosurvival and antiapoptotic role in endothelial cells. SU5416 is the first VEGF receptor 2 inhibitor to enter clinical development for cancer therapy. A phase I/II study of SU5416 has been completed, and the results show that SU5416 is well tolerated in patients with terminal cancers. It has been shown that VEGF receptor blockade using SU5416 combined with chronic hypoxia results in severe angioproliferative pulmonary hypertension (PAH) with neointimal changes in adult rats. Although classic animal models of pulmonary hypertension (that is, the monocrotaline and hypoxic models) do not form obstructive intimal lesions in the peripheral pulmonary arteries, the SU5416 model has shown pulmonary arterial changes resembling plexiform lesions. Therefore, the SU5416 model of PAH has been used for some time, and it has thus contributed to a better understanding of the pulmonary hypertensive process. However, the mechanism by which SU5416 combined with chronic hypoxia can result in PAH with plexiform-like lesions in adult rats is complex and still remains to be fully elucidated. The most likely explanation is that there is increased apoptosis of endothelial cells in response to the loss of the survival signaling, creating conditions favoring the emergence of apoptosis-resistant cells with increased growth potential, that is, the endothelial cell hyperproliferation that might characterize the plexiform lesions of human PAH. The aim of the present review is to provide information useful for understanding a potent inhibitor of VEGF receptor tyrosine kinase, SU5416, and to better understand its use for generating animal models of PAH.

Role of 320-Slice CT Imaging in the Diagnostic Workup of Patients With Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND Right-sided heart catheterization (RHC) and pulmonary digital subtraction angiography (PDSA) are the standard methods used in diagnosing suspected or defi nite chronic thromboembolic pulmonary hypertension (CTEPH). We studied the ability of 320-slice CT imaging to detect simultaneously chronic thromboembolic fi ndings in the pulmonary arteries and pulmonary hemodynamics based on the curvature of the interventricular septum (IVS) in CTEPH . METHODS Forty-four patients with high clinical suspicion of CTEPH underwent RHC, PDSA, and enhanced double-volume retrospective ECG-gated 320-slice CT scan. We measured the sensitivity and specificity of CT imaging to detect thrombi in the pulmonary arteries compared with PDSA. We also compared IVS bowing (expressed as curvature) measured on the short-axis cine heart image with pulmonary arterial pressure (PAP) obtained by RHC. RESULTS Compared with PDSA, the sensitivity and specificity of CT imaging to detect chronic thromboembolic findings were 97.0% and 97.1% at the main/lobar level and 85.8% and 94.6% at the segmental level, respectively. The correlation coefficients of IVS curvature with systolic PAP and mean PAP were 2 0.79 ( P , .001) and 2 0.86 ( P , .001), respectively. CONCLUSIONS The use of 320-slice CT imaging allows for less invasive and simultaneous detection of thrombi and evaluation of pulmonary hemodynamics for the diagnostic work-up of CTEPH.

The importance of epigenetics in the development of chronic obstructive pulmonary disease

It is generally accepted that genetic predisposition plays a role in COPD development in susceptible individuals. Therefore, many candidate genes that could be linked to the development of disease have been examined in COPD. However, inconsistent results in different study populations often limit this approach, suggesting that not only genetics, but also other factors, may be contributed to the susceptibility to COPD. Epigenetic mechanisms can affect the transcriptional activity of specific genes, at different points in time, and in different organs. Moreover, these mechanisms can have an effect on peoples health. Recently, there is emerging evidence supporting a role of epigenetics for the regulation of inflammatory genes in diseases such as asthma and COPD. Moreover, recent studies suggest that the currently used treatments including corticosteroids may work through epigenetic mechanisms. Epigenetic regulation can be reprogrammed, potentially affecting the risk, aetiology and treatment of various disease states. The epigenetically influenced phenotype could be reversed with demethylating or deacetylating agents, consistent with epigenetic plasticity. The postnatal reversibility of these methylation or acetylation events may therefore provide good opportunities for intervention.

Characterization of myofibroblasts in chronic thromboembolic pulmonary hypertension

BACKGROUND It has been generally accepted that chronic thromboembolic pulmonary hypertension (CTEPH) results from pulmonary embolism arising from deep vein thrombosis. An unresolved question regarding the etiology of CTEPH is why pulmonary thromboemboli are stable and resistant to effective anticoagulation. Recently non-resolving pulmonary thromboemboli in CTEPH have been shown to include myofibroblasts. This study investigates the cellular characteristics of myofibroblasts included in the organized thrombotic tissues of CTEPH. METHODS Organized thrombotic tissues of patients with CTEPH were obtained following pulmonary endarterectomy. We isolated cells from endarterectomized tissue from patients with CTEPH and identified them as endothelial-like cells and myofibroblast-like cells. RESULTS Myofibroblast-like cells were characterized as hyperproliferative, anchorage-independent, invasive and serum-independent. CONCLUSIONS Here we report the presence of active myofibroblast-like cells in endarterectomized tissue of CTEPH. We suggest that the formation of myofibroblasts with a high growth potential in the organized thrombotic tissues may be an important event in the pathobiology of this disease.