Morphological characterization of pulmonary microvascular disease in bronchopulmonary dysplasia caused by hyperoxia in newborn mice.

PURPOSE: Pulmonary microvascular injury is associated with the pathogenesis of bronchopulmonary dysplasia (BPD). To characterize the mechanisms of pulmonary vascular disease resulting from BPD, we studied the ultrastructural changes affecting pulmonary microvasculature. METHODS: Newborn ICR mice were exposed to 85% hyperoxia or normoxia for 14 days, and then normal air replacement conditions for the following 7 days. At postnatal day (P)14 and P21, lungs were harvested for ultrastructural examination and assessment of pulmonary hypertension. RESULTS: The ultrastructure of pulmonary microvasculature in the hyperoxia-exposed lungs revealed a collapsed capillary lumen. This was due to the abnormal morphology of endothelial cells (ECs) characterized by heterogeneously thick cytoplasm. Compared to normal air controls, the specimens displayed also remarkably thick blood-air barriers (BABs), most of which were occupied by EC layer components. Structural changes were accompanied by increased pulmonary artery medial thickness and right ventricular hypertrophy (RVH). Moreover, abnormalities in ECs persisted even after exposure to 7 days of normal air replacement conditions. Results were confirmed by morphometric quantification. CONCLUSION: Our results suggest that the abnormal morphology of capillary ECs and thick BABs correlates with pulmonary artery remodeling and RVH. These ultrastructural changes might represent possible mechanisms of secondary pulmonary hypertension in BPD.

Electron microscopic study of capillary network remodeling in the extensor digitorum longus muscle of normal adult rat.

Capillary networks demonstrate structural changes during maturation, aging, vascular disease, and cancer. Their morphological structure and function have an important influence on each other. Understanding the process of morphological vascular changes in the capillary network with advancing age may help overcome fatal vascular diseases. Aging-related structural changes of the capillary segments may accompany degeneration and regeneration of muscle fibers and serve to remodel the capillary network as a means of adapting to the changing environment. However, difficulty in obtaining human samples has hampered clarification of these microstructural changes. Herein, we examined serial ultrathin sections of capillary segments in the extensor digitorum longus muscle of normal mature (12 months old) rats in an attempt to analyze their structural changes. After bifurcation, a minimum of one capillary segment was filled with erythrocytes and was found to have fenestrations and plural endothelial disruptions, or pores, at the fenestrated portions. Some of the stagnated erythrocytes demonstrated extended protrusions, and their processes appeared to penetrate the basal lamina through the pores. These findings can also show that capillary segments are involved in partial remodeling of the capillary network. A better understanding of age-related structural changes of the capillary networks will help in fine-tuning novel vascular therapy for not only several fatal vascular diseases but also malignant tumors.

Endothelial cell transplantation in tumors restores normal vasculature, reduces tumor hypoxia, and suppresses tumor outgrowth.

OBJECTIVES: Vascular normalization, or restoration of the normal structure and function of blood vessels, using molecular-targeted therapy, has emerged as a potential strategy for treating malignant cancer and other vascular disorders. We hypothesized that restoring tumor blood vessels to their normal state would alleviate hypoxic conditions and potentially enhance the delivery of anticancer drugs. Our objective was to determine if transplanting normal endothelial cells into tumor-bearing mice could trigger vascular normalization. METHODS: Tumor cells were injected into the dorsal subcutis of severe combined immunodeficiency (SCID) mice (day 0). Tumor-bearing mice were injected intraperitoneally with cisplatin at day 14 to create scaffolds for blood vessel formation in the tumors. At day 28, human microvascular endothelial cells (HMVECs) or human embryonic stem-derived endothelial cells (ESECs) were transplanted into the necrotic regions of the tumor to induce normal angiogenesis. RESULTS: Microscopic observation revealed that the transplanted HMVECs or ESECs formed anastomoses with the host mouse vasculature. In addition, blood vessels with blood flow could be detected after 14d. Blood vessels reconstituted by HMVECs or ESECs exhibited normal vasculature, and tumor growth was significantly inhibited upon treatment. CONCLUSION: Reconstruction of tumor blood vessels to their normal state alleviated hypoxic conditions and improved the efficiency of drug delivery; the present approach provides a useful model for the development of new cancer therapies.

Role of uterine contraction in regeneration of the murine postpartum endometrium.

The endometrium undergoes continuous repair and regeneration without scarring throughout the reproductive life of women. However, the mechanisms responsible for this complete restoration remain mostly unexplored. We hypothesized that the ischemic state and local hypoxia present after parturition may create a special microenvironment for endometrial healing, and that this ischemia might be caused by reduction in organ volume via postpartum uterine contraction. Here, we developed a mouse model using a combination of cesarean section and the administration of a beta 2 adrenergic receptor agonist (ritodrine hydrochloride) in postpartum mice that had been ovariectomized to exclude the effect of ovarian hormones. Our results revealed that transient hypoxia indeed occurred in postpartum uteri. Furthermore, we found that the number of M2 macrophages, which play a central role in wound healing, peaked on Postpartum Day 3 and gradually decreased thereafter in hypoxic injury sites. Almost concurrently, significant upregulation of vascular endothelial growth factor and transforming growth factor beta (TGFbeta) was observed. In particular, the antifibrotic factor TGFbeta3 was released during the endometrial healing process. These changes were significantly suppressed by inhibition of uterine contraction. Taken together, these results suggest that uterine contraction is essential, not only for hemostasis, but also for endometrial regeneration, leading to a process that involves the activation of macrophages, increased endometrial cell proliferation, and upregulation of nonfibrotic growth factors. This study paves the way to a novel approach for investigating the process of scarless wound healing.

Vasohibin-2 modulates tumor onset in the gastrointestinal tract by normalizing tumor angiogenesis.

BACKGROUND: Vasohibin-2 (VASH2) has been identified as an endogenous and vascular endothelial growth factor (VEGF)-independent angiogenic factor that is highly expressed in tumor cells. In the present study, we aimed to determine whether pre-existing vascular changes can be used to predict tumor transformation as benign or malignant. We sought to characterize microvascular changes and tumor development in the intestinal tract of ApcMin/+ mice and ApcMin/+/Vash2-/- mice. METHODS: ApcMin/+ mice provide a unique orthotopic model for the development of spontaneous adenomatous polyposis and subsequent carcinomas, a phenomenon termed the adenoma-carcinoma sequence. ApcMin/+ mice were mated with Vash2-/- mice with a mixed C57BL/6 background and the resulting pups were screened for the Min mutation and for the Vash2-/- gene by PCR. Intestinal tumors from ApcMin/+ mice and ApcMin/+/Vash2-/- mice were removed and either frozen or epon-embedded for subsequent analyses. For 3-dimensional imaging using confocal laser-scanning microscopy and transmission electron microscopy, cryosections were made, and immunofluorescent staining for various markers was performed. RESULTS: We found that structural abnormalities in tumor vessels from benign tumors resembled those in malignant tumors. In addition, a novel angiogenic factor, vasohibin-2 (VASH2) protein, was detected around tumor blood vessels in late-stage adenomas and adenocarcinomas, but was absent from early-stage adenomas in ApcMin/+ mice. Tumors used to examine endogenous VASH2 (derived from CMT93 colon carcinomas) were less vascularized in Vash2-/- mice and were more regular than those seen in wild-type (WT) mice. In addition, tumors in Vash2-/- mice were smaller than those in WT mice. Furthermore, cross-breeding of mice homozygous for a deletion of Vash2 with mice heterozygous for the APC mutation resulted in animals that showed a significant decrease in the number of polyps in the small intestine. CONCLUSION: We propose that VASH2 may modulate the onset of tumors in the gastrointestinal tract by regulating tumor angiogenesis.

Malignant pericardial effusion and cardiac tamponade originating from uterine carcinosarcoma.

BACKGROUND: Cardiac tamponade caused by gynecologic malignancies are extremely rare. CASE: A 56-year-old woman was referred to our hospital with vaginal bleeding and abdominal distension. Computed tomography showed massive peritoneal fluid, peritoneal dissemination, swelling of the paraaortic lymph nodes and liver metastasis. Endometrial biopsy showed an admixture of both carcinomatous and sarcomatous elements. The final pathological diagnosis was uterine carcinosarcoma, homologous type. After four cycles of chemotherapy consisting of ifosfamide, adriamycin, and cisplatin, we performed laparotomy, and then two additional courses of chemotherapy were administered postoperatively. Eight months after chemotherapy, echocardiography demonstrated massive pericardial effusion with features of tamponade such as diastolic compression of the right ventricle. Cytological examination of the pericardial fluid showed two different cellular patterns, epithelial and non-epithelial components. CONCLUSION: Although cardiac tamponade is rare and has a poor prognosis, it is important for physicians to consider this possibility in the course of treating of uterine carcinosarcoma.