Interstitial Pressure Research Articles

Numerical studies of the lymphatic uptake rate

Lymphatic uptake is essential for transporting nutrients, wastes, immune cells, and therapeutic proteins. Despite its importance, the literature lacks a quantitative analysis of the factors that affect lymphatic uptake, including interstitial pressure, downstream pressure, and tissue deformation. In this paper, we present a coupled model of a poroelastic tissue with initial lymphatics and quantify the impact of these factors on the rate of lymphatic uptake. Our results indicate that the lymphatic uptake increases with the amplitude of the oscillating downstream pressure when the amplitude exceeds a threshold. Additionally, the cross-sectional area of initial lymphatics increases with the volumetric strain of the tissue, while the interstitial pressure increases when the strain rate becomes negative. Therefore, the lymphatic uptake reaches its maximum when the tissue has positive volumetric strain while being compressed. We have also investigated the effect of intersection angles and positions of two initial lymphatics and concluded that they have minor impacts on lymphatic uptake. However, the lymphatic uptake per unit length of initial lymphatics decreases with their total length. These findings advance our understanding of lymphatic uptake and can guide the development of strategies to accelerate the transport of therapeutics.

Positive Chemotaxis of CREKA-Modified Ceria@Polydopamine Biomimetic Nanoswimmers for Enhanced Penetration and Chemo-photothermal Tumor Therapy.

Tumor interstitial pressure represents the greatest barrier against drug diffusion into the depth of the tumor. Biometric nanomotors highlight the possibility of enhanced deep penetration and improve cellular uptake. However, control of their directionality remains difficult to achieve. Herein, we report cysteine-arginine-glutamic acid-lysine-alanine (CREKA)-modified ceria@polydopamine nanobowls as tumor microenvironment-fueled nanoscale motors for positive chemotaxis into the tumor depth or toward tumor cells. Upon laser irradiation, this nanoswimmer rapidly depletes the tumor microenvironment-specific hydrogen peroxide (H2O2) in the nanobowl, contributing to a self-generated gradient and subsequently propulsion (9.5 μm/s at 46 °C). Moreover, the asymmetrical modification of CREKA on nanobowls could automatically reconfigure the motion direction toward tumor depth or tumor cells in response to receptor-ligand interaction, leading to a deep penetration (70 μm in multicellular spheroids) and enhanced antitumor effects over conventional nanomedicine-induced chemo-photothermal therapy (tumor growth inhibition rate: 84.2% versus 56.9%). Thus, controlling the direction of nanomotors holds considerable potential for improved antitumor responses, especially in solid tumors with high tumor interstitial pressure.

Nanomedicine Strategies for Targeting Tumor Stroma.

The tumor stroma, or the microenvironment surrounding solid tumors, can significantly impact the effectiveness of cancer therapies. The tumor microenvironment is characterized by high interstitial pressure, a consequence of leaky vasculature, and dense stroma created by excessive deposition of various macromolecules such as collagen, fibronectin, and hyaluronic acid (HA). In addition, non-cancerous cells such as cancer-associated fibroblasts (CAFs) and the extracellular matrix (ECM) itself can promote tumor growth. In recent years, there has been increased interest in combining standard cancer treatments with stromal-targeting strategies or stromal modulators to improve therapeutic outcomes. Furthermore, the use of nanomedicine, which can improve the delivery and retention of drugs in the tumor, has been proposed to target the stroma. This review focuses on how different stromal components contribute to tumor progression and impede chemotherapeutic delivery. Additionally, this review highlights recent advancements in nanomedicine-based stromal modulation and discusses potential future directions for developing more effective stroma-targeted cancer therapies.

Role of Alström syndrome 1 in the regulation of glomerular hemodynamics.

Inactivating mutations in the ALMS1 gene in humans cause Alström syndrome, characterized by the early onset of obesity, insulin resistance, and renal dysfunction. However, the role of ALMS1 in renal function and hemodynamics is unclear. We previously found that ALMS1 is expressed in thick ascending limbs, where it binds and decreases Na+-K+-2Cl- cotransporter activity. We hypothesized that ALMS1 is expressed in macula densa cells and that its deletion enhances tubuloglomerular feedback (TGF) and reduces glomerular filtration rate (GFR) in rats. To test this, homozygous ALMS1 knockout (KO) and littermate wild-type Dahl salt-sensitive rats were studied. TGF sensitivity was higher in ALMS1 KO rats as measured by in vivo renal micropuncture. Using confocal microscopy, we confirmed immunolabeling of ALMS1 in macula densa cells (nitric oxide synthase 1 positive), supporting a role for ALMS1 in TGF regulation. Baseline glomerular capillary pressure was higher in ALMS1 KO rats, as was mean arterial pressure. Renal interstitial hydrostatic pressure was lower in ALMS1 KO rats, which is linked to increased Na+ reabsorption and hypertension. GFR was reduced in ALMS1 KO rats. Seven-week-old ALMS1 KO rats were not proteinuric, but proteinuria was present in 18- to 22-wk-old ALMS1 KO rats. The glomerulosclerosis index was higher in 18-wk-old ALMS1 KO rats. In conclusion, ALMS1 is involved in the control of glomerular hemodynamics in part by enhancing TGF sensitivity, and this may contribute to decreased GFR. Increased TGF sensitivity, enhanced glomerular capillary pressure, and hypertension may lead to glomerular damage in ALMS1 KO rats. These are the first data supporting the role of ALMS1 in TGF and glomerular hemodynamics.NEW & NOTEWORTHY ALMS1 is a novel protein involved in regulating tubuloglomerular feedback (TGF) sensitivity, glomerular capillary pressure, and blood pressure, and its dysfunction may reduce renal function and cause glomerular damage.

Computational pulmonary edema: A microvascular model of alveolar capillary and interstitial flow.

We present a microvascular model of fluid transport in the alveolar septa related to pulmonary edema. It consists of a two-dimensional capillary sheet coursing by several alveoli. The alveolar epithelial membrane runs parallel to the capillary endothelial membrane with an interstitial layer in between, making one long septal tract. A coupled system of equations uses lubrication theory for the capillary blood, Darcy flow for the porous media of the interstitium, a passive alveolus, and the Starling equation at both membranes. Case examples include normal physiology, cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), hypoalbuminemia, and effects of PEEP. COVID-19 has dramatically increased ARDS in the world population, raising the urgency for such a model to create an analytical framework. Under normal conditions fluid exits the alveolus, crosses the interstitium, and enters the capillary. For edema, this crossflow is reversed with fluid leaving the capillary and entering the alveolus. Because both the interstitial and capillary pressures decrease downstream, the reversal can occur within a single septal tract, with edema upstream and clearance downstream. Clinically useful solution forms are provided allowing calculation of interstitial fluid pressure, crossflows, and critical capillary pressures. Overall, the interstitial pressures are found to be significantly more positive than values used in the traditional physiological literature. That creates steep gradients near the upstream and downstream end outlets, driving significant flows toward the distant lymphatics. This new physiological flow provides an explanation to the puzzle, noted since 1896, of how pulmonary lymphatics can function so far from the alveoli: the interstitium is self-clearing.

The Molecular Pharmacology and Therapeutics of Angiogenesis

Angiogenesis is the formation of new vasculature on top of the pre-existing ones, which is critical during the species’ lifespan. It is responsible for delivering oxygen and nutrients to metabolically active tissues, therefore playing an essentialrole in physiological conditions, such as wound healing and pathological circumstances, like malignancies. Althoughsharing similar characteristics, the blood vessels in pathological angiogenesis develop irregularly and disorganizedly.Therefore, the leakage of materials from blood vessels is familiar in abnormal angiogenesis, which may result inmuch higher interstitial pressure than internal pressure. Whether the angiogenesis is physiological or pathological,the proliferation of normal dormant endothelial cells is an essential requirement. Additionally, angiogenesis is alsoinitiated by vascular endothelial growth factor A (VEGF-A) interacting with the vascular endothelial growth factorreceptor 2 (VEGFR2) or the co-receptor neuropilin-1 (NRP-1). The Vegfa gene can be spliced in many ways, creatingnumerous VEGF-A isoforms, each with unique interactions with VEGFR2. Several drugs have been approved as thefirst- or second-line of angiogenesis, thereby preventing cancer progression. The widely used is monoclonal antibodies(bevacizumab) and receptor tyrosine kinase inhibitor (sorafenib and axitinib). However, they lack selectivity and, asa result, are less effective and have considerable adverse effects. As a natural drug, Paclitaxel has an anti-angiogeniceffect in addition to its chemotherapeutic effect. However, different doses of paclitaxel have different anti-angiogenicmechanisms and different effects on different species.

The Molecular Pharmacology and Therapeutics of Angiogenesis

Angiogenesis is the formation of new vasculature on top of the pre-existing ones, which is critical during the species’ lifespan. It is responsible for delivering oxygen and nutrients to metabolically active tissues, therefore playing an essentialrole in physiological conditions, such as wound healing and pathological circumstances, like malignancies. Althoughsharing similar characteristics, the blood vessels in pathological angiogenesis develop irregularly and disorganizedly.Therefore, the leakage of materials from blood vessels is familiar in abnormal angiogenesis, which may result inmuch higher interstitial pressure than internal pressure. Whether the angiogenesis is physiological or pathological,the proliferation of normal dormant endothelial cells is an essential requirement. Additionally, angiogenesis is alsoinitiated by vascular endothelial growth factor A (VEGF-A) interacting with the vascular endothelial growth factorreceptor 2 (VEGFR2) or the co-receptor neuropilin-1 (NRP-1). The Vegfa gene can be spliced in many ways, creatingnumerous VEGF-A isoforms, each with unique interactions with VEGFR2. Several drugs have been approved as thefirst- or second-line of angiogenesis, thereby preventing cancer progression. The widely used is monoclonal antibodies(bevacizumab) and receptor tyrosine kinase inhibitor (sorafenib and axitinib). However, they lack selectivity and, asa result, are less effective and have considerable adverse effects. As a natural drug, Paclitaxel has an anti-angiogeniceffect in addition to its chemotherapeutic effect. However, different doses of paclitaxel have different anti-angiogenicmechanisms and different effects on different species.

The Molecular Pharmacology and Therapeutics of Angiogenesis

Angiogenesis is the formation of new vasculature on top of the pre-existing ones, which is critical during the species’ lifespan. It is responsible for delivering oxygen and nutrients to metabolically active tissues, therefore playing an essentialrole in physiological conditions, such as wound healing and pathological circumstances, like malignancies. Althoughsharing similar characteristics, the blood vessels in pathological angiogenesis develop irregularly and disorganizedly.Therefore, the leakage of materials from blood vessels is familiar in abnormal angiogenesis, which may result inmuch higher interstitial pressure than internal pressure. Whether the angiogenesis is physiological or pathological,the proliferation of normal dormant endothelial cells is an essential requirement. Additionally, angiogenesis is alsoinitiated by vascular endothelial growth factor A (VEGF-A) interacting with the vascular endothelial growth factorreceptor 2 (VEGFR2) or the co-receptor neuropilin-1 (NRP-1). The Vegfa gene can be spliced in many ways, creatingnumerous VEGF-A isoforms, each with unique interactions with VEGFR2. Several drugs have been approved as thefirst- or second-line of angiogenesis, thereby preventing cancer progression. The widely used is monoclonal antibodies(bevacizumab) and receptor tyrosine kinase inhibitor (sorafenib and axitinib). However, they lack selectivity and, asa result, are less effective and have considerable adverse effects. As a natural drug, Paclitaxel has an anti-angiogeniceffect in addition to its chemotherapeutic effect. However, different doses of paclitaxel have different anti-angiogenicmechanisms and different effects on different species.

The Revised Starling Hypothesis: Modeling the impact of the glycocalyx on vascular refilling during ultrafiltration in humans

The glycocalyx lines systemic capillaries and influences the distribution of osmotic forces across the capillary between the intravascular and interstitial compartments. By creating a pericapillary space between the capillary and the interstitium with a low osmotic pressure, the predicted and measured water flux at the distal end of systemic capillaries is outward under physiological conditions – contrary to the prediction of the traditional Starling model of capillary fluid transport. This has led to a ‘revised’ Starling model in which the predicted the movement of water from the capillary into the interstitium is consistently outward, and the return of water from the interstitial compartment necessary to maintain intravascular volume occurs nearly exclusively through the lymphatic system. We developed a methematicl model of the revised Starling Hypothesis that is applicable to the whole body in the special circumstance of hemodialysis, where the contributions of renal function to blood volume regulation may be ignored, and the total input and output of water and solutes are controlled and measured as part of the process of hemodialysis. We created a revised, two compartment (vascular+interstitial space), Starling model using the quantitative model of Facchini et al. (Microvasc. Res. 94:52-63, 2014) that describes capillary transport through the glycocalyx (albeit as normalized dimensionless values). We modelled the return of interstitial water to the vascular space through lymphatic flow based on the interstitial pressure (Possenti et al., Micro. Vasc. Res. 122:101-110, 2019), and we estimated the interstitial pressure based upon the formulation of Chapple et al. (Comp. Meth, and Prog. In Biomed. 41: 33-54,1993). We used the two-compartment model (intravascular and extravascular spaces) developed by de los Reyes et al. (J. Theoret. Biol. 390:146-155, 2016) to analyze transcapillary fluxes based on the traditional Starling model, and we embedded the description of fluxes across glycocalyx developed by Facchini et al. to decribe the fluxes of solutes and water across the glycocalyx and peri-glycocalyx/sub-capillary space and added control of lymphatic function within this two-compartment model to create a revised Starling model. The traditional and revised models were evaluated using data from periods of ultrafiltration in which the hematocrit (Crit-line), body weight and measured fluid input or ultrafiltrate removed were measured, and we compared the predicted fluxes of solvent and solutes across the capillary and through the lymphatic system between the traditional and revised Starling models. The two models lead to dramatically different predictions—all of the fluid transported out of the capillary must come back via the lymphatics according to the revised Starling model. This places vital importance upon the lymphatic flow during vascular refilling when blood volume is reduced and must be repleted to maintain stable cardiac function. Partially funded by the Renal Research Institute This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Contrast-enhanced subharmonic aided pressure estimation for assessment of intracranial pressure in vivo.

Intracranial pressure (ICP) monitoring in children currently requires invasive techniques. Subharmonic aided pressure estimation (SHAPE) uses contrast-enhanced ultrasound (CEUS) to measure intravascular and interstitial pressure, but utility in ICP measurements has yet to be explored. The objective of this study was to investigate SHAPE as a novel tool for noninvasive ICP measurements in fetal lambs. Eighteen fetal lambs at 107-139days gestational age (term = 145days) underwent subdural ICP catheter placement. The brain was imaged in the coronal plane in CEUS mode optimized for SHAPE, while infusing an US contrast agent into the fetal circulation. After SHAPE calibration, saline was infused via the subdural catheter to increase ICP. Five-second SHAPE cine clips were obtained at various ICPs. Subharmonic intensity values of the whole brain and thalami were correlated with ICP values using mixed effects linear regression analyses and the strength of the relationship was evaluated by Spearman's rank-order correlation. Forty-nine experiments produced 723 datapoints, including SHAPE intensity values and mean ICP measurements. There was a statistically significant inverse relationship between SHAPE intensity values and ICP measurements in the whole brain and thalami (median rho value - 0.58 and - 0.56, respectively). SHAPE intensity values of the brain demonstrate an inverse and statistically significant correlation with in vivo ICP measurements in an animal model.

Abstract 594: Effects of interstitial pressure on lung cancer cells

Abstract Chronic inflammation is a risk factor for various types of cancer. The pressure in the interstitial tissues has been reported to be elevated in chronic inflammation and cancer. However, little is known about the biological effect of pressure from the basal side on epithelia, and a significance of the elevated interstitial fluid pressure in cancer biology is still poorly understood. In this study, we investigated the effect of hydrostatic pressure on cultured lung cancer cells grown on Transwell permeable filters by changing the height of the surfaces of culture medium in the apical and basal sides. A gradient of the hydrostatic pressure from the basal to the apical side induced stratification of epithelia. The elimination of the hydrostatic pressure gradient restored the stratification of epithelia. Interestingly, cavities were found within the stratified epithelia, and the characteristics of apical cell polarity including microvilli and tight junctions were formed in the surfaces the cavities. The cavities with similar aberrant cell polarity were also observed in human lung cancer tissues. The hydrostatic pressure gradient from the basal side also promoted cell proliferation and suppressed apoptosis. On the other hand, the expression levels of phosphorylated ERK and AKT were not significantly affected by the hydrostatic pressure. These results indicate that the pressure from the basal side to the epithelia promotes cell proliferation, suppresses apoptosis and induces aberrant cell polarity, which results in epithelial stratification. The findings in this study suggest that the elevated interstitial fluid pressure in chronic inflammation and cancer tissues facilitates cancer growth and plays a significant role in cancer biology. Citation Format: Shinsaku Tokuda, Keisuke Onoi, Tadaaki Yamada, Koichi Takayama. Effects of interstitial pressure on lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 594.

Abstract 202: Perfused patient-derived tumor organoid models with autologous immune cells for preclinical drug development

Abstract The paradigm shift towards inclusion of primary patient samples in preclinical drug development bottlenecks at the tissue procurement step due to an on-going lack of ’research-ready’ tumor samples. Organoid technology was developed as a solution to this hurdle. Their ability to expand in culture makes them a renewable resource similar to cell lines while recapitulating key properties of the primary tissue, including tumor heterogeneity, structural organization and drug responses. As preclinical drug development continues to adopt organoid-based screening technology and immune-oncology agents continue to be advanced, there is high demand for more complex organoid-based models capable of more accurately predicting individual patient drug responses. Due to their development process, the vast majority of organoids do not contain immune cells, resulting in the need to utilize allogeneic immune cells for any immune cell involved interrogation of the models. Maintaining the immune cells for incorporation with the organoid model can overcome this hindrance. Additionally, perfused organoid models offer a complex, ex vivo model with the ability to replicate the mechanical forces imparted by blood flow and interstitial pressure. Compared to 2D and static 3D cultures, perfused 3D culture models show enhanced proliferative and migratory capacities and can be sustained as long-term cultures. In our previous studies, DNA methylation signatures in patient-derived breast microtumors grown in Kiyatec’s 3DKUBE™ perfusion bioreactor matched the primary tissues of derivation. Given the need for more complex biology when assessing immune-oncology agents, the physiological relevance in maintaining gene expression ex vivo, and the capability to sustain long-term viability, the impact of autologous immune cells and perfusion on the success of organotypic culture was investigated across a panel of primary patient tumors. Immune cells were profiled for status and activity and imaging and viability assays were used to evaluate static and perfused 3D organoid models for differences in viability and morphology. PCR was used to examine how mechanically transduced forces alter gene expression and DNA methylation signatures. Drug responses were measured using our KIYA-Predict™ platform, comparing organoid drug responses to primary tissue drug responses. Results of this study provide insight on alternative methods of organotypic culture and evidence for the utilization of more complex tissue modeling in preclinical drug development. Citation Format: Melissa Millard, Natalie Dance, Teresa M. DesRochers. Perfused patient-derived tumor organoid models with autologous immune cells for preclinical drug development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 202.

Abstract 4809: A novel microfluidic platform for PDAC organoid culture and drug screening

Abstract Pancreatic Ductal Adenocarcinoma (PDAC), the most common pancreatic cancer type, will become the second leading cause of cancer-related deaths by 2030 with mortality rates of up to 93%. Current standard-of-care for patients with PDAC includes chemotherapeutic regimens and pancreatic cancer surgery. However, only 20% of the patients are eligible for surgery due to late diagnosis. Although chemotherapeutic regimens are the leading treatment to PDAC patients, these are still very limited and the development of resistance to treatment is often observed. PDAC tumors are characterized by high-density stroma and hypovascularization, therefore these present high interstitial pressure and hypoxia. These features potentially interfere with the efficiency of chemotherapeutic drugs and highlight the urgent need for novel PDAC screening platforms. Here, we describe the establishment of PDAC organoid cultures in the MIMETAS OrganoPlate®. The aim of this project was to determine the treatment response of PDAC organoids in mono-, and co-culture with pancreatic stellate cells (PSCs) under hypoxic and normoxic conditions. To recapitulate in-vivo like conditions, the 2-lane OrganoPlate® from MIMETAS was used to study organoid growth and sensitivity to treatment. Several standard of care (chemo-)therapeutics were tested on PDAC organoids embedded within an extracellular matrix in the Organoplate® 2-lane. These were exposed to chemotherapeutic treatments for 72h. PDAC organoids showed an overall better survival when grown in co-culture with PSCs. Interestingly, organoids grown in co-culture showed a higher survival rate under hypoxic conditions. In contrast, when grown in monoculture cell viability was higher or similar under normoxic conditions than in hypoxia for the different chemotherapeutics. The OrganoPlate® 2-lane provides an excellent platform for (co-) cultivation and high-throughput phenotypic drug screening of PDAC organoids, thereby potentially enabling the development of novel in-vivo like model systems for efficient patient stratification and drug discovery. Citation Format: Marlene Geyer, Daniel Schreyer, Lisa-Marie Gaul, Désiréé Goubert, Susanne Pfeffer, Christian Pilarsky, Karla S. Queiroz. A novel microfluidic platform for PDAC organoid culture and drug screening. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4809.

How should we treat acute kidney injury caused by renal congestion?

Decreased kidney function is associated with increased risk of cardiovascular events and mortality, and heart failure (HF) is a well-known risk factor for renal dysfunction. Acute kidney injury (AKI) in patients with HF often is attributed to prerenal factors, such as renal hypoperfusion and ischemia as a result of decreased cardiac output. Another such factor is reduction of absolute or relative circulating blood volume, with the decrease in renal blood flow leading to renal hypoxia followed by a decrease in the glomerular filtration rate. However, renal congestion is increasingly being recognized as a potential cause of AKI in patients with HF. Increased central venous pressure and renal venous pressure lead to increased renal interstitial hydrostatic pressure and a reduction of the glomerular filtration rate. Both decreased kidney function and renal congestion have been shown to be important prognostic factors of HF, and adequate control of congestion is important for improving kidney function. Loop and thiazide diuretics are recommended as standard therapies to reduce volume overload. However, these agents are associated with worsening renal function even though they are effective for improving congestive symptoms. There is growing interest in tolvaptan, which can improve renal congestion by increasing excretion of free water and decreasing the required dose of loop diuretic, thereby improving kidney function. This review summarizes renal hemodynamics, the pathogenesis of AKI due to renal ischemia and renal congestion, and diagnosis and treatment options for renal congestion.

From Localized Mild Hyperthermia to Improved Tumor Oxygenation: Physiological Mechanisms Critically Involved in Oncologic Thermo-Radio-Immunotherapy.

(1) Background: Mild hyperthermia (mHT, 39-42 °C) is a potent cancer treatment modality when delivered in conjunction with radiotherapy. mHT triggers a series of therapeutically relevant biological mechanisms, e.g., it can act as a radiosensitizer by improving tumor oxygenation, the latter generally believed to be the commensurate result of increased blood flow, and it can positively modulate protective anticancer immune responses. However, the extent and kinetics of tumor blood flow (TBF) changes and tumor oxygenation are variable during and after the application of mHT. The interpretation of these spatiotemporal heterogeneities is currently not yet fully clarified. (2) Aim and methods: We have undertaken a systematic literature review and herein provide a comprehensive insight into the potential impact of mHT on the clinical benefits of therapeutic modalities such as radio- and immuno-therapy. (3) Results: mHT-induced increases in TBF are multifactorial and differ both spatially and with time. In the short term, changes are preferentially caused by vasodilation of co-opted vessels and of upstream normal tissue vessels as well as by improved hemorheology. Sustained TBF increases are thought to result from a drastic reduction of interstitial pressure, thus restoring adequate perfusion pressures and/or HIF-1α- and VEGF-mediated activation of angiogenesis. The enhanced oxygenation is not only the result of mHT-increased TBF and, thus, oxygen availability but also of heat-induced higher O2 diffusivities, acidosis- and heat-related enhanced O2 unloading from red blood cells. (4) Conclusions: Enhancement of tumor oxygenation achieved by mHT cannot be fully explained by TBF changes alone. Instead, a series of additional, complexly linked physiological mechanisms are crucial for enhancing tumor oxygenation, almost doubling the initial O2 tensions in tumors.

Pre-treatment of oncolytic reovirus improves tumor accumulation and intratumoral distribution of PEG-liposomes.

PEGylated liposomes (PEG-liposomes) are a promising drug delivery vehicle for tumor targeting because of their efficient tumor disposition profiles via the enhanced permeability and retention (EPR) effect. However, tumor targeting of PEG-liposomes, particularly their delivery inside the tumors, is often disturbed by physical barriers in the tumor, including tumor cells themselves, extracellular matrices, and interstitial pressures. In this study, B16 melanoma tumor-bearing mice were injected intravenously with oncolytic reovirus before administration of PEG-liposomes to enhance PEG-liposomes' tumor disposition. Three days after reovirus administration, significant expression of reovirus sigma 3 protein, elevation of apoptosis-related gene expression, and activation of caspase 3 in the tumors were found. Apoptotic cells were found inside the tumors. These data indicated that reovirus efficiently replicated in the tumors and induced apoptosis of tumor cells. The tumor disposition levels of PEG-liposomes were approximately doubled by reovirus pre-administration, compared with a PBS-pretreated group. PEG-liposomes were widely distributed in the tumors of reovirus-pretreated mice, whereas in the PBS-pretreated group, PEG-liposomes were found mainly around or inside the blood vessels in the tumors. Pre-treatment with reovirus also improved the tumor accumulation of PEG-liposomes in human pancreatic BxPC-3 tumors. 3D imaging analysis of whole BxPC-3 tumors demonstrated that pretreatment with reovirus led to the enhancement of PEG-liposome accumulation inside the tumors. Combination treatment with reovirus and paclitaxel-loaded PEG-liposomes (PTX-PEG-liposomes) significantly suppressed B16 tumor growth. These results provide important information for clinical use of combination therapy of reovirus and nanoparticle-based drug delivery system (DDS).

A microfluidic-based PDAC organoid system reveals the impact of hypoxia in response to treatment

Pancreatic Ductal Adenocarcinoma (PDAC) is estimated to become the second leading cause of cancer-related deaths by 2030 with mortality rates of up to 93%. Standard of care chemotherapeutic treatment only prolongs the survival of patients for a short timeframe. Therefore, it is important to understand events driving treatment failure in PDAC as well as identify potential more effective treatment opportunities. PDAC is characterized by a high-density stroma, high interstitial pressure and very low oxygen tension. The aim of this study was to establish a PDAC platform that supported the understanding of treatment response of PDAC organoids in mono-, and co-culture with pancreatic stellate cells (PSCs) under hypoxic and normoxic conditions. Cultures were exposed to Gemcitabine in combination with molecules targeting relevant molecular programs that could explain treatment specific responses under different oxygen pressure conditions. Two groups of treatment responses were identified, showing either a better effect in monoculture or co-culture. Moreover, treatment response also differed between normoxia and hypoxia. Modulation of response to Gemcitabine was also observed in presence of a Hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) inhibitor and HIF inhibitors. Altogether this highlights the importance of adjusting experimental conditions to include relevant oxygen levels in drug response studies in PDAC.

Cancer-Associated Fibroblasts: Lessons from Pancreatic Cancer

Cancer-associated fibroblasts (CAFs) are present in all malignancies. Arguably, in none are they as prevalent as they are in pancreatic ductal adenocarcinoma (PDAC), where they often outnumber cancer cells. The origin and function of CAFs are still not completely understood, and attempts to target this cell population as a component of combination therapy have so far not succeeded. Our understanding of pancreatic CAFs is in rapid evolution. Heterogeneity of CAFs is the key concept to understand this cell population. We discuss heterogeneity of origin, with recent findings challenging the notion that CAFs uniformly derive from pancreatic stellate cells, and instead suggesting that multiple types of resident fibroblasts contribute to CAF expansion. Heterogeneity in gene expression divides CAFs in different subpopulations. Most importantly, heterogeneity in function underlies the complexity of CAFs. CAFs deposit components of the extracellular matrix, contributing to the high interstitial pressure in pancreatic cancer. CAFs serve as “feeder” cells for cancer cells by providing metabolites, thus mitigating the effect of the low-nutrient environment of PDAC. At the same time, CAFs regulate the function of the immune system, inhibiting antitumor immune responses. Understanding the functional role of different CAF populations and the drivers of each of their functional roles is key to devising new ways to target this cell population in PDAC.

Abstract B007: Remodeling the hyaluronan-rich tumor extracellular matrix using hyaluronidase-expressing genetically engineered MSCs for tumor regression and metastasis prevention in sarcomas

Abstract Sarcomas are a diverse group of rare malignant tumors the develop in the bone and connective tissue and are often aggressive with ~50% of patients developing metastases. Due to their rarity and diversity, there is a great lack of standard therapies resulting in a 65% and 15% 5-year survival rate for regional and metastatic disease, respectively. Tumorigenesis is largely influenced by communication between the tumor microenvironment (TME), cancer cells, and the extracellular matrix (ECM). The ECM promotes cancer initiation and dissemination from the primary tumor and fosters a favorable microenvironment for metastatic colonization of tumor cells. Due to their mesenchymal origin, sarcomas are thought to produce and deposit large quantities of ECM. One component of the tumor-ECM known to promote an aggressive cancer phenotype is hyaluronan (HA). Abundant HA in the TME arises from overactive HA synthases that produce HA or downregulation of hyaluronidases (Hyals) that catalyze HA degradation. HA-rich tumor ECM promote cancer progression by regulating chemokine and cytokine trafficking, increasing hypoxia and interstitial pressure, and limiting delivery of antitumor therapies. In-silico profiling of sarcomas revealed an increase in HA synthase mRNA expression in 50.78% and correlated with 35% decrease in overall patient survival (P = 0.0027), compared to sarcomas with low HA synthase expression. To target this HA-rich tumor ECM, we sought to develop a cell-based approach to locally deliver HA-remodeling enzymes to minimize the drawbacks of systemic therapy and enhance anti-tumor responses. We developed genetically engineered mesenchymal stromal cells (GEMesys) that express Hyal, using mesenchymal stem cells derived from mouse lungs. We hypothesized that the Hyal-GEMesys would home to and degrade the HA-rich ECM preventing cancer progression. The therapeutic efficacy of Hyal-GEMesys was tested in osteosarcoma (F42010) and rhabdomyosarcoma (M-3-9M) syngeneic murine models. Preliminary data demonstrated encouraging efficacy of Hyal-GEMesys in reducing tumor volume in the osteosarcoma (up to 1.4-fold, p=0.0035-0.0172) and rhabdomyosarcoma M-3-9M model (up to 2-fold, P= 0.0428). Further, analysis of osteosarcoma tumors revealed reduced HA (up to 2.3-fold, P=0.0078) and collagen-I content (up to 3-fold, P= 0.0025) indicating our Hyal-GEMesys functionally remodel the ECM in vivo. Changes in ECM in GEMesy treated group were associated with changes in immune infiltration with an increase in CD4+ (P=0.0221) and CD8+ (P=0.0087) T cells and a decrease in IBA1+ (P=0.0144) macrophages. Analysis of rhabdomyosarcoma tumors revealed reduced HA content (up to 2-fold, P-0.00206). Future studies will more deeply explore the mechanisms of ECM-mediated immune changes and impact on metastatic progression. Our cell-based approach to deliver hyaluronidases holds promise of effectively degrading and remodel the HA-rich tumor ECM to enhance anti-tumor responses, prevent metastases and improve clinical outcomes for patients with high-risk sarcoma malignancies. Citation Format: Alice Browne, Miranda Clements, Wei Ju, Daniel Brock, Rosandra Kaplan. Remodeling the hyaluronan-rich tumor extracellular matrix using hyaluronidase-expressing genetically engineered MSCs for tumor regression and metastasis prevention in sarcomas [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B007.

How to interpret serum creatinine increases during decongestion.

During decongestion in acute decompensated heart failure (ADHF), it is common to observe elevations in serum creatinine (sCr) values due to vascular congestion, a mechanism that involves increased central venous pressure that has a negative impact on the nephron, promoting greater absorption of water and sodium, increased interstitial pressure in an encapsulated organ developing "renal tamponade" which is one of main physiopathological mechanism associated with impaired kidney function. For the treatment of this syndrome, it is recommended to use diuretics that generate a high urinary output and natriuresis to decongest the venous system, during this process the sCr values can rise, a phenomenon that may bother some cardiologist and nephrologist, since raise the suspicion of kidney damage that could worsen the prognosis of these patients. It is recommended that increases of up to 0.5 mg/dL from baseline are acceptable, but some patients have higher increases, and we believe that an arbitrary number would be impractical for everyone. These increases in sCr may be related to changes in glomerular hemodynamics and true hypovolemia associated with decongestion, but it is unlikely that they are due to structural injury or truly hypoperfusion and may even have a positive connotation if accompanied by an effective decongestion and be associated with a better prognosis in the medium to long term with fewer major cardiovascular and renal events. In this review, we give a comprehensive point of view on the interpretation of creatinine elevation during decongestion in patients with ADHF.