Sepsis
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KAIST Identifies the Cause of Sepsis-induced Lung Injury
(Professor Pilhan Kim from the Graduate School of Medical Science and Engineering)
A KAIST research team succeeded in visualizing pulmonary microcirculation and circulating cells in vivo with a custom-built 3D intravital lung microscopic imaging system. They found a type of leukocyte called neutrophils aggregate inside the capillaries during sepsis-induced acute lung injury (ALI), leading to disturbances and dead space in blood microcirculation.
According to the researchers, this phenomenon is responsible for tissue hypoxia causing lung damage in the sepsis model, and mitigating neutrophils improves microcirculation as well as hypoxia.
The lungs are responsible for exchanging oxygen with carbon dioxide gases during the breathing process, providing an essential function for sustaining life. This gas exchange occurs in the alveoli, each surrounded by many capillaries containing the circulating red blood cells.
Researchers have been making efforts to observe microcirculation in alveoli, but it has been technically challenging to capture high-resolution images of capillaries and red blood cells inside the lungs that are in constant breathing motion.
Professor Pilhan Kim from the Graduate School of Medical Science and Engineering and his team developed an ultra-fast laser scanning confocal microscope and an imaging chamber that could minimize the movement of a lung while preserving its respiratory state. They used this technology to successfully capture red blood cell circulation inside the capillaries of animal models with sepsis.
During the process, they found that hypoxia was induced by the increase of dead space inside the lungs of a sepsis model, a space where red blood cells do not circulate. This phenomenon is due to the neutrophils aggregating and trapping inside the capillaries and the arterioles. It was also shown that trapped neutrophils damage the lung tissue in the sepsis model by inhibiting microcirculation as well as releasing reactive oxygen species.
Further studies showed that the aggregated neutrophils inside pulmonary vessels exhibit a higher expression of the Mac-1 receptor (CD11b/CD18), which is a receptor involved in intercellular adhesion, compared to the neutrophils that normally circulate. Additionally, they confirmed that Mac-1 inhibitors can improve inhibited microcirculation, ameliorate hypoxia, while reducing pulmonary edema in the sepsis model.
Their high-resolution 3D intravital microscope technology allows the real-time imaging of living cells inside the lungs. This work is expected to be used in research on various lung diseases, including sepsis.
The research team’s pulmonary circulation imaging and precise analytical techniques will be used as the base technology for developing new diagnostic technologies, evaluating new therapeutic agents for various diseases related to microcirculation.
Professor Kim said, “In the ALI model, the inhibition of pulmonary microcirculation occurs due to neutrophils. By controlling this effect and improving microcirculation, it is possible to eliminate hypoxia and pulmonary edema – a new, effective strategy for treating patients with sepsis.”
Their 3D intravital microscope technology was commercialized through IVIM Technology, Inc., which is a faculty startup at KAIST. They released an all-in-one intravital microscope model called ‘IVM-CM’ and ‘IVM-C’. This next-generation imaging equipment for basic biomedical research on the complex pathophysiology of various human diseases will play a crucial role in the future global bio-health market.
This research, led by Dr. Inwon Park from the Department of Emergency Medicine at Seoul National University Bundang Hospital and formally the Graduate School of Medical Science and Engineering at KAIST, was published in the European Respiratory Journal (2019, 53:1800736) on March 28, 2019.
Figure 1. Custom-built high-speed real-time intravital microscope platform
Figure 2. Illustrative schematic and photo of a 3D intravital lung microscopic imaging system
Figure 3. Aggregation of neutrophils and consequent flow disturbance in pulmonary arteriole in sepsis-induced lung injury
2019.05.07 View 43475 -
The Antibody That Normalizes Tumor Vessels
Researchers also discover that their antisepsis antibody reduces glioma, lung and breast cancer progression in mice.
A research team at the Center for Vascular Research within the Institute for Basic Science (IBS) discovered that the antisepsis antibody ABTAA (Ang2-Binding and Tie2-Activating Antibody) reduces tumor volume and improves the delivery of anti-cancer drugs. Published in Cancer Cell, this study demonstrates that ABTAA restores the structural and functional integrity of tumor blood vessels in three different tumor models: breast, lungs, and brain.
Blood vessels inside and around an established tumor can be described as a chaotic and dysfunctional labyrinth. While the inner walls of healthy blood vessels are surrounded and supported by endothelial cells and other cells called pericytes, in the established tumor, the endothelial junctions are broken apart and pericytes are also detached. Blood flow into and from the tumor is severely retarded and tumor vessels lacking an intact vessel wall become leaky. This microenvironment causes limited drug delivery to the tumor and leads to inadequate oxygen supply (hypoxia) and even metastasis.
The research team led by Professor Gou-Young Koh at KAIST’s Graduate School of Medical Science and Engineering found that the antibody ABTAA normalizes the tumor vessels and hence, change the whole tumor microenvironment. “We call it normalization of tumor vessels, because it resembles closely the wall architecture of healthy, normal vessels,” explains PARK Jin-Sung, first author of the study. And continues: “Tumor can adapt to hypoxia and get more aggressive, so we tried to prevent this transition by normalizing tumor vessels. ABTAA changes the whole tumor environment, oxygenation status and level of lactate, so that the immune cells and drugs can reach the core regions of the tumor more easily. In this way, we create a favorable ground for tumor treatment.”
In an attempt to generate antibodies targeting the protein Ang2, which is specifically expressed by endothelial cells in stressful conditions like in tumor, the team unexpectedly discovered that ABTAA has a peculiar way of working and a dual function. ABTAA indeed not only blocks Ang2, but also activates Tie2 at the same time. Tie2 is a receptor present on the cell membrane of endothelial cells. ABTAA causes Ang2 to cluster together and to strongly activate Tie2 receptors. “If we activate Tie2, we can efficiently normalize tumor vessels, enhance drug delivery and change the whole microenvironment,” explains KOH Gou Young, Director of the Center for Vascular Research.
Several pharmaceutical companies are developing Ang2-blocking antibodies to cure cancer. However, even if these antibodies significantly inhibit tumor progression, they do not stop tumor hypoxia. Moreover, most of the anti-cancer drugs target the tumor at its early stage, when tumors are still hard to diagnose. ABTAA, instead, works with tumors that are already rooted: “When the tumor is established, hypoxia is the main driver of tumor progression. So, if we eliminate hypoxia, we make the tumor milder, by reducing its progression and metastasis,” comments Koh.
Figure: Schematic drawing of a blood vessel around tumors before and after treatment with ABTAA. The picture above shows a typical tumor vasculature characterized by damaged walls, red blood cells leakage and detached pericytes. Activating Tie2 on endothelial cells with the antibody ABTAA restores the normal vessel architecture: endothelial and pericytes on the vessel walls are stabilized, the delivery of blood is improved, and the anticancer drugs are more likely to reach the tumor core.
The researchers tested ABTAA in mice with three different types of tumors that show high levels of Ang2: glioma (a type of a brain tumor), lung carcinoma, and breast cancer. They also compared the effect of ABTAA with ABA, another antibody that blocks Ang2 but misses the Tie2 activating properties. In all three cases, ABTAA was superior to ABA in inducing tumor vessel normalization, which led to a better delivery of the anti-cancer drugs into the tumor core region.
Glioma is one of the so-called intractable diseases, because of its poor prognosis and treatment. Professor Koh’s team found that the glioma volume was reduced 39% by ABTAA and 17% by ABA. ABTAA profoundly reduced vascular leakage and edema formation in glioma through promoting vascular tightening. Moreover, when ABTAA was administered together with the chemotherapeutic drug temozolomide (TMZ), the tumor volume reduces further (76% by ABTAA+TMZ, 51% by ABA+TMZ, and 36% by TMZ).
In the Lewis Lung Carcinoma (LLC) tumor model, the team administered ABTAA together with a chemotherapeutic drug called cisplatin (Cpt) and observed a greater suppression of tumor growth (52%) compared with the controls and increased overall survival. Moreover, ABTAA+Cpt led to a marked increase in necrotic area within tumors.
Finally, in a spontaneous breast cancer model, ABTAA delayed tumor growth and enhanced the anti-tumor effect of Cpt.
Courtesy of the Institute for Basic Sciences (IBS)
Figure: The antibody ABTAA alone and in combination with other anti-cancer drugs have a beneficial effect in reducing tumor volume. ABTAA was tested in mice with brain tumor (glioma), lung or breast cancer. The image shows the improvements: reduction in glioma tumor size, reduction in metastatic colonies in lung tumor and decrease in necrotic regions in breast tumor.
In the future, the team would like to further understand the underlying relationship between faulty blood vessels and diseases. “We would like to apply this antibody to an organ that is rich in blood vessels, that is the eye, and see if this antibody can be useful to treat eye diseases such as age-related macular degeneration and diabetic retinopathy,” concludes Koh.
Professor Gou-Young Koh (left) and Jin-Sung Park (right)
2016.12.16 View 8227