Understanding how lymphatic system contributes to normal physiology of heart, lung, blood, sleep systems will help also lead to new approaches for treatment of heart, lung, blood, sleep diseases.

Basic understanding of the development and hemodynamics of the lymphatic system and reagents to study the lymphatic function are available.
Lymphatic vasculature is essential for fluid hemostasis in the body, collects and returns the protein- and lipid-rich interstitial fluid to blood circulation, and also involved in immune cell trafficking and inflammation. Given these important physiological roles, function of the lymphatic system is expected to contribute to normal physiology of organs and its dysfunction to major diseases. There is very little or no information how the lymphatic system contribute to health and diseases of the cardiovascular, pulmonary and blood systems, and there are many unanswered questions. Answers to these questions may lead to new approaches for treatment of major HLB diseases. Main challenge is to get heart, lung, blood, sleep investigators interested in studying the contribution of the lymphatic system to heart, lung, blood, sleep health and diseases.

The use of umbilical cord blood or haploidentical donors has proven effective in patients with hematologic malignancies, but in non-malignant disorders outcomes are limited by graft rejection. Overcoming rejection in this context would be applicable to other non-malignant disorders such as thalassemia, sickle cell anemia, and other congenital disorders of hematopoiesis.

It will require a large coordinated network like BMT-CTN to obtain sufficient patients studied in a uniform fashion to provide consistent reproducible data. .

Inherited monogenic hematologic diseases such as hemophilia, beta-thalassemia and sickle cell disease are prime targets for future application of genome editing technology. However, studies are still needed to advance our understanding of the biology of genome editing as well as determine which other disorders are amenable to genome editing correction. Emphasis on preclinical research that focuses on determining the accuracy, safety and efficiency of this technology in order to help minimize off-target mutations and reduce toxicity, is essential for effective translation of this technology into the clinic. Once preclinical efficacy is established, support will be needed for clinical vector production, toxicity testing of the vectors/reagents used, and the performance of clinical trials. The gene correction strategies developed for inherited disorders will also be attractive for other hematologic diseases, and autoimmune disorders like lupus, rheumatoid arthritis, and type I diabetes). There is also a critical need for supporting preclinical validation studies, scale-up and GMP cell manufacturing, all of which could be shared infrastructures across multiple diseases in the NHLBI portfolio.

SCD is the most common genetic disease in the United States affecting 100,000 individuals or 1 in 400 African American births. Pain, stroke, acute chest syndrome and priapism are common morbidities affecting patients with sickle cell disease, which often result in emergency room visits and/or hospitalizations. Despite advances in treatment, sickle cell disease is associated with significant mortality and shortened life expectancy. Defining the optimal role of red blood cell exchange and plasma exchange (which may be used to remove plasma molecules such as inflammatory factors and free hemoglobin) in the management and prevention of the complications of sickle cell disease and may not only prolong the life of these patients but is expected to improve the quality of their lives. In addition, clearly defining the indications for simple verses exchange transfusion therapy has the potential to minimize both alloimmunization to red blood cells (reported to occur in up to 75% of patients with sickle cell disease) and iron overload associated with transfusion.

Transfusion therapy may be efficacious to sickle cell patients by providing increased oxygen delivery to tissues and/or decreasing the amount of sickle hemoglobin present by suppression of erythropoiesis. Understanding the relative contributions of these mechanisms will assist with optimal use of transfusion therapy as well as inform the development of novel alternative therapies

Multi-center trials should be feasible, given the number of patients with sickle cell disease in the US. Participation by larger academic centers which care for sickle cell patients should facilitate trials. Methods for automated red cell exchange and plasma exchange are available and in common use at many centers. Great interest exists among physicians caring for sickle cell patients (as exemplified by the recent NIH consensus document and ASFA sickle cell consensus conference) which is a strength of this proposal. Challenges include agreement on standard treatment protocols across centers and long term follow up of patients. Maintaining vascular access in sickle cell patients is another challenge when performing apheresis procedures on sickle cell patients

i. In patients with pulmonary hypertension, the use of multiple tests to characterize the type and severity has long been recommended by global experts; one commonly used diagnostic algorithm recommends more than ten different tests to accurately define this complex, heterogeneous disease. Despite the algorithm used, to confirm a diagnosis of one specific type of PH, pulmonary arterial hypertension (PAH), one must always directly measure the pressures in the heart and pulmonary artery through a right heart catheterization (RHC). Complications for this procedure are rare, but not non-existent with potentially 1 in every 100 patients having a right heart catheterization experiencing a serious adverse event (Hoeper MM 2006). Patients would significantly benefit from a non-invasive method of quantifying their pulmonary artery pressures and/or disease progression, but to date this has not been possible with echocardiography due to measurement errors (Laver 2014), CT scan due in part to measurement inconsistencies (Alhamad 2011), and cardiac MRI due to lack of standardization and multicenter trials (Peacock 2013). Not only would wider utilization of a non-invasive method of measuring pulmonary artery pressures and disease progression potentially reduce the risk from RHC, depending on the modality it could lead to earlier diagnosis of this progressive disease and/or application in countries where RHC is less common.

Addressing a non-invasive method of measuring pulmonary artery pressures requires investment in both technology and multicenter clinical trials to validate these measures.

The evolution of the anticoagulation recommendation in pulmonary arterial hypertension (PAH) is a relatively logical one at face value. Early in the modern era of PAH management, a “thrombosis” in the small pulmonary arteries was identified and described; studies since then have demonstrated hypercoagulability in patients with severe disease. Together, these observations led to a theory that in-situ thrombosis contributed to the PAH disease progression and a belief that anticoagulation should be beneficial. The empirical evidence currently supporting this recommendation comes mostly from a retrospective cohort study of the European COMPERA PH registry and a systematic review of 7 retrospective cohort studies that are at least 10 years old—2 of which did not suggest a survival benefit—and in a time where only 4 of the widely used PAH-targeted therapies were approved by the FDA. Purely based on observational evidence with a number of potential biases, warfarin (Coumadin) is widely used in PAH management to this day. Warfarin in this patient population is not without its risks, as some subgroups of PAH patients are at increased risk of bleeding complications based on their disease process alone. Assessing the true benefit of this widely used background therapy could allow clinicians and patients to more accurately weigh the risks and burden of anticoagulation with a true understanding of the survival benefit.

Addressing this compelling question is indeed feasible through an NIH-sponsored randomized, double-blind, placebo-controlled trial of anticoagulation in patients with certain types of pulmonary arterial hypertension.

Pulmonary arterial hypertension is a heterogeneous condition generally characterized by high blood pressure in the lungs and increased pulmonary vascular resistance that leads to right heart failure if left untreated. Though some causes of PAH are seen in both adult and pediatric populations, some etiologies are seen exclusively in pediatric populations, including persistent pulmonary hypertension of the newborn, bronchopulmonary dysplasia, lung hypoplasia, and alveolar capillary dysplasia. Despite these differences in disease etiology, and known physiologic differences in pediatric populations, inhaled nitric oxide (iNO) in the acute setting is the only approved medication for PAH treatment in children. A number of issues have decreased pediatric PAH pharmaceutical research, including protection of the pediatric population as vulnerable subjects, principle of scientific necessity, balance of risk and potential benefit, parental consent/child assent, and feasibility of pediatric clinical trial design and implementation. Encouraging clinical trials of existing adult medications and potentially emerging, novel agents specifically for pediatrics—either through direct sponsorship or regulatory incentives—would not only lead to better outcomes for pediatric PAH patients, but potentially to a better and more comprehensive characterization of the developing pulmonary vascular system and right ventricle.

Several challenges exist for addressing this critical challenge. First, there are a number of differences between conducting clinical research in pediatric populations compared to adult populations. This not only includes the broad items referenced above, but items as noted by Rose and colleagues related to clinical trial design and analysis including (1) accepted age-matched normal ranges for laboratory values; (2) requirements for the validation of clinical endpoints for the assessment of efficacy and safety; and (3) standards for long-term safety monitoring and pharmacovigilance (Rose K, et al. NEJM 2005). Sponsorship of this type of clinical research is a second concern, which could either be mitigated by direct support from the National Institutes of Health of pediatric PAH clinical trials or in regulatory changes incentivizing pediatric clinical research in rare diseases.

Understanding of many components of the PAH disease state have evolved significantly in the past thirty years. When initially described by an NIH registry, in a time where pulmonary transplantation was the only treatment for PAH, the average life expectancy of PAH patients was estimated to be 2.8 years. Since then, 12 PAH-targeted therapies have been approved by the FDA; these therapies primarily act by dilating the pulmonary arteries in order to allow blood to flow easier through the pulmonary vascular system. Despite these advances and complex therapies, long-term afterload reduction is not achievable in most PAH patients. Patients continue to die from right ventricular failure, highlighting the important relationship of the pulmonary arterial system and right ventricle. Little is known about how and why the RV progresses from hypertrophy to full RV failure, the diagnostic signs indicating early RV failure, and how best to intervene to support the failing ventricle. Knowledge in this area is critical, however, as the RV is able to recover in many patients with severe PAH after lung transplantation. The relationship between the lung vasculature and cardiac function, and specifically a characterization of RV failure, was included as a research opportunity in the Strategic Plan for Lung Vascular Research in an NHLBI-ORDR Workshop Report (Erzurum S, et al. 2010).

The primary challenge of addressing this CQ on how right ventricular function can be improved in the setting of increased afterload is the comprehensive analysis and support that will need to be provided, spanning from basic to clinical science. To begin, strong support of biologic characterization of the right ventricle needs to be provided. The RV is distinctly different from the more comprehensively studied left ventricle (LV), and subsequently responds differently to changes in pressure, neurotransmitters, hormones, and pharmaceutical therapies to name only a few. However, when identified, these RV biologic distinctions can be further explored to develop a better understanding of RV failure and potential points of intervention.

Since 2006, 12 medical therapies for PAH have been approved by the FDA, which have increased survival of this rare disease from around 2.8 years to approximately 9 years; these therapies primarily act by dilating the pulmonary arteries in order to reduce pulmonary vascular resistance to blood flow. However, patients continue to die from right ventricular failure, highlighting the important relationship of the pulmonary arterial system and right ventricle (RV). Despite patients ultimately dying from RV failure, little is known about the effect of the currently available PAH-targeted therapies on RV functional support. Prostacyclins, PDE5i, and sGC agonists are thought to enhance RV contractility—though the long-term effects remain unknown—while ERAs are thought to reduce it. The direct RV effect of some potential therapies targeting the pseudo-malignancy theory of PAH is a concern, as these therapies seek to reduce the hypertrophy and angiogenesis that may actually be supporting the adapting RV. Further, therapies targeting the ventricle directly have historically been centered on the LV—for example β-adrenergic receptor blockers and RAS inhibition—and either remain controversial or without data in the RV. There remains no identified RV-specific therapy to either provide support through increase contractility or molecularly prevent the progression from RV hypertrophy to ultimate failure.

The primary challenge of addressing this CC on the lack of RV-targeted therapies for the treatment of PAH is the comprehensive analysis and support that will need to be provided, spanning from basic to clinical science. To begin, strong support of biologic characterization of the right ventricle needs to be provided. The RV is distinctly different from the more comprehensively studied left ventricle, and subsequently responds differently to autocrine, paracrine, neuroendocrine, pressure, and pharmaceutical changes to name only a few. However, when identified, these RV biologic distinctions can be translated and tested clinically to more comprehensively and appropriately treat the RV-arterial uncoupling ultimately leading to right heart failure: through both reduction in afterload and an increase in contractility.

In the critically ill, RBC transfusion is indicated to improve O2 delivery. Although RBC transfusion increases hemoglobin concentration (Hb) and thereby blood O2 content, it does not necessarily follow that O2 delivery to tissues is likewise increased. Current approaches to transfusion decision making in critical care settings maintain an ‘adequate’ RBC mass well above a level that may limit tissue O2 delivery. With improved understanding of vascular signaling and gas transport by RBCs and of the array of defects comprising the RBC ‘storage lesion’, we appreciate that this strategy must be balanced by consideration that: (1) donor and recipient RBCs do not exhibit similar physiology and (2) RBC transfusion may cause harm (beyond transfusion reactions and transmission of infection) – and that this harm appears progressive with: transfusion volume, frequency and donor exposure. As such, ‘restrictive’ Hb thresholds for RBC transfusion are appreciated to be at least non-inferior to ‘liberal’ Hb thresholds for a broad array of conditions. A paradigm shift is emerging in approach to the critically ill, with re-consideration of the ‘Hb trigger’ strategy, itself. Ideally, the decision to transfuse should be based upon individual and context-specific consideration of the degree to which anemia contributes to tissue O2 delivery.

We need to identify specific physiologic endpoints linked to outcomes as well as determine the appropriate thresholds for these goals. We must improve current means to assess functionality of the circulating RBC mass and its specific relationship to tissue O2 delivery in both humans and animal models. Approaches to resolve this gap could be conducted in the following areas during the next 3-5 years (studies may be independent or ancillary to clinical transfusion trials). Examples include but are not limited to the following: (1) clinical and translational research studies examining physiologic tolerance of acute and chronic anemia in the critically ill populations; (2) basic and clinical research exploring accuracy, precision and reliability of novel approaches to quantify and monitor O2 consumption and delivery (global/regional). Investigations should also determine the relationship of these measures to clinically relevant patient outcomes, both global (mortality, ventilator dependence, length of stay, etc.) and organ-specific; and (3) studies evaluating the process of transfusion decision making in the setting of critical illness.

Humans exposed to RBC alloantigens, following therapeutic transfusion or in pregnancy following maternal exposure to fetal RBCs, can generate humoral alloantibodies capable of leading to hemolytic transfusion reaction, (HTR), or of leading to HDFN. RBC transfusions can also induce autoantibodies, and can lead to hyperhemolysis. It is poorly understood why some patients mount a detectable alloantibody response (“responders”), whereas others do not (“non-responders”). Within the responder population, alloantibodies may be categorized as “clinically significant” or “clinically insignificant”, based upon whether the resultant specific alloantibodies have been previously reported to cause HTR or HDFN. However, incompatible transfusion will only result in meaningful in vivo hemolysis in some patients, even with antibody specificities classified as clinically significant.

The ability to define responder/non-responder status before initial RBC exposure has the potential to: 1) decrease rates of RBC alloimmunization in responders through the provision of extended matched RBCs for initial and subsequent RBC exposure; 2) conserve valuable antigen negative RBC units for patients who will derive the greatest benefit; 3) conserve transfusion service resources in terms of time spent identifying antibodies and procuring antigen negative RBC units; and 4) decrease rates of HTR and HDFN.

Patients with hemoglobinopathies, especially those with SCD and thalassemia, have high rates of RBC alloimmunization and thus are important target populations for these studies. The impact of methods to reduce RBC antigen exposure or pathogen inactivation on neoantigen development remains unknown. The health impact of addressing the question of RBC alloimmunization is that the discovery of mechanistic underpinnings will provide a rational basis for the development and translation of novel diagnostic and therapeutic approaches, with a goal of increasing transfusion safety.

Though these questions are unlikely to be completely answered within the next 3-10 years, existing and emerging immunohematology and genomics tools, evolving sophistication of animal models, and existing and novel systems for human studies including donor-recipient repositories have the potential to increase the understanding of when and how alloimmunity to RBCs evolves, in what contexts it is clinically significant—even life-threatening—and how this important, but currently challenging and poorly understood condition, might be prevented and/or mitigated.

Cancer patients undergo intensive medical and surgical therapies to treat their underlying disease. Treatment commonly results in anemia requiring RBC and platelet transfusions to support the patient through the hypoproliferative phase of chemotherapy. This is particularly true for those patients requiring hematopoetic stem cell transplantation (HSCT). Following therapy, cancer outpatients commonly receive RBC transfusions for weeks to months to maintain their functional status.

Common causes of death in patients with hematological malignancies and other cancers are infections and bleeding. A meta-analysis of clinical trials suggested that liberal transfusion is associated with greater risk of infection. Conversely, restrictive transfusion could adversely affect quality of life and functional status in oncology populations. In addition, pre-clinical and clinical studies support that concomitant anemia and thrombocytopenia significantly compound bleeding risk, and that hemostasis can be optimized in thrombocytopenia by maintaining a higher hematocrit. Although bleeding risks in relation to platelet transfusion thresholds are well studied in patients with hematological malignancy, optimal hemoglobin levels in thrombocytopenic patients are not known. Despite the significant allocation of blood components to cancer patients as a whole, RBC transfusion practices are not well studied within this group.

Randomized controlled clinical trials and other studies investigating optimal transfusion thresholds and other measures of practice are required to provide health care providers with evidence to guide one of the most common therapies administered in the setting of malignancy. The clinically important end points of well-designed studies could include: 1) quality of life and functional status for both inpatients and outpatients; 2) neurocognitive development in pediatric populations; 3) bleeding events / bleeding scores; 4) impact on immunity including immunomodulation and infection; 5) reconstitution of hematopoiesis; and 6) survival and/or recurrence of disease.. Besides a generalizable study population, certain target populations of interest are those with high risk disease, HSCT patients, patients undergoing radiation therapy, and pediatric patients.

There are >1.6 million new cases of cancer annually in the USA, including >50,000 with leukemia and >6,000 with HSCT. Cancer therapies are rapidly advancing in the era of genomics and immunotherapy. Capitalizing on the tradition of research in cancer, single and multicenter studies of RBC transfusion are feasible using randomized controlled designs in conjunction with clinical trials of chemotherapeutic regimens. The results of these studies will impact a large patient population’s quality of life, and may ultimately impact healthcare cost and blood demand.

Studies on epigenetic mechanisms have extraordinary promise for the development of transformative therapeutic approaches for non-malignant hematologic disorders, however, limited progress has been made in advancing therapies to counteract the often crippling complications of these conditions. In the case of sickle cell disease, an ensemble of proteins has been implicated in mediating the epigenetic repression of gamma-globin expression, raising the possibility that antagonizing the actions of these proteins to increase gamma-globin expression may be a useful treatment strategy. However, in certain cases, some of these proteins are deemed “undruggable,” based on their structural attributes. There is a critical need to identify druggable components of the multi-step epigenetic mechanisms as well as develop better models and assays that will more effectively identify modulators of “undruggable” proteins. Given the rich proteome and improved technologies available today, studies of proteomics, metabolomics, and regulatory RNAs are likely to reveal promising translational avenues. In addition, approaches to modifying the expression of the components of this pathway are underway using developing gene therapy strategies, such as viral vectors and/or gene editing can quickly advance therapy in sickle cell disease and β-thalassmia.

Methods to expand hematopoietic stem cells have continued to be examined extensively because stem cell numbers in the graft are important for clinical outcomes following transplantation. These numbers are particularly relevant in umbilical cord blood (UCB) transplantation, where low numbers of stem cells are directly related to delayed hematopoietic and immune reconstitution. Improved HSC expansion strategies may significantly impact transplantation outcome, enabling broader applications beyond UCB transplantation. Furthermore, these strategies are also needed to realize the full therapeutic potential of genome editing technologies to correct hematopoietic stem cells derived from patients with hematologic disorders. Since efforts to expand HSCs in cytokine-supported liquid cultures have been largely unsuccessful, efficient expansion will require an appropriate context that is provided by the hematopoietic stem cell niche. Future studies must also evaluate how niche signals regulate stem cell function to optimize cell expansion, and proper humanized mouse models must be developed to help predict stem cell function and regulation by the niche.

The reprogramming of adult stem cells has resulted in the generation of induced pluripotent stem cells (iPSCs) that can develop into any tissue of the body. These iPSCs ultimately may be used as a transplantable source of stem cells for a variety of hematologic diseases. Although this technology has enabled the generation of patient-specific or disease-specific stem cells that are also amenable to genetic manipulation, the major scientific hurdle has been the ability to create clinically meaningful functional blood products, including transplantable HSCs from differentiating iPSCs. The production of clinically functional blood products -- i.e. red blood cells derived from autologous iPSCs --could replace allogeneic products in highly immunized patients and the generation of megakaryocytes for patient-specific platelet production from iPSCs could drive significant progress in this area. Furthermore, disease-specific iPSCs could serve as targets for both drug development and drug screening in patients with rare hematologic disorders. In addition, support for scale-up and GMP processes, which are difficult to fund via the R01 mechanism will require specific grant opportunities tailored to infrastructure and process development.