2017 Research Grants
Victor A. McKusick Fellowship Grant:
James Foster, PhD, Johns Hopkins School of Medicine, $100,000 2-year Victor A. McKusick Fellowship Grant entitled “Organ Specific Expression of the Short Isoform of ADAMTS2 and Its Role in Corneal Development.”
The aim of this project is to investigate the organ specific regulation of collagen processing enzymes with the objective of understanding why a disease (Ehlers Danlos syndrome, dermatosparaxis type) that should devastate the highly regulated extra-cellular matrix of the cornea does not occur. This will be achieved by generation of knock-out cell lines of both isoforms of ADAMTS2 in corneal and skin fibroblasts, and enable us to test the hypothesis that the short form of ADAMTS2 has restricted tissue specificity and action.
Findings from this research will give insight into the organ specific regulation of extra-cellular matrix assembly. Whilst the population of patients affected by ADAMTS2 mutations is small, there is a large population of patients with diseases of the cornea where collagen assembly is perturbed. Therefore, understanding the mechanisms of assembly and processing in these patients could lead to treatments of the larger population.
Early Investigator Grants:
Gillian McLellan, BVMS, PhD, DACVO, University of Wisconsin-Madison, $75,000 2-year Early Investigator Grant entitled “Delineating Pathology of the aqueous humor outflow pathways in animals with LTBP2 mutation.”
Eye disease is very common in Marfan syndrome and in related connective tissue disorders, including Weill-Marchesani syndrome. Dislocation of the lens in the eye (ectopia lentis) is the most consistent feature of these diseases and can have a significant negative impact on vision. People with Marfan syndrome and related diseases are also at substantially higher risk of losing vision to glaucoma than the general population. Blindness due to glaucoma is irreversible, as the disease causes loss of nerve cells in the retina and optic nerve of the eye that cannot be repaired. High eye pressure (intraocular pressure or IOP) causes this damage in most cases, but the underlying reasons for high IOP and glaucoma in patients with gene mutations causing Marfan syndrome and similar conditions have not been fully worked out. Although lens dislocation can undoubtedly contribute to glaucoma development, it would appear that at least some patients are born with malformed structures inside their eye that regulate fluid pressure, while others develop damage to these structures later in life. However, the precise reasons for this malformation and for glaucoma development remains unclear, and this gap in our understanding could delay diagnosis and appropriate treatment of glaucoma in affected patients. Our goal in this proposal is to study pathology in the eyes of animals that have a mutation in a gene that causes similar eye problems to those seen in human patients with Marfan syndrome other, related connective tissue disorders. By providing new knowledge and a better understanding of the causes of glaucoma in these diseases, we will aid physicians in screening and treatment of their patients in order to limit vision loss in individuals with this complication.
Francesca Seta, PhD, Boston University School of Medicine, $75,000 2-year Early Investigator Grant entitled “Preclinical Study to test the Efficacy of Sirtuin-1 against the Vascular Complications of Marfan's and Related Disorders.”
Dr. Seta seeks to determine whether sirtuin-1 (SirT1), an evolutionarily conserved enzyme important for a variety of cellular functions, can be beneficial against pathological aortic remodeling and dissection in animal models of Marfan syndrome. SirT1 is known as the longevity gene and is activated by natural compounds found in red wine and plants, called polyphenols, such as resveratrol. The lab will use innovative animal models, developed in their laboratory, in which SirT1 is over-expressed specifically in vascular smooth muscle cells, the major component of the aorta, to test the hypothesis that SirT1 is protective against aortic dissection and death.
Joseph Turek, MD, University of Iowa, $75,000 2-year Early Investigator Grant entitled “A TRPC4-dependent amplification pathway contributes to aortic aneurysm progression in Marfan syndrome.”
Transient receptor potential (TRP) channels have emerged as likely regulators of vascular smooth muscle cell activity. Specifically, TRPC4 channels revealed marked upregulation in Marfan mice when using a new method to induce aneurysms in 2-weeks. Antagonism of the TRPC4 response with a multidrug regimen including losartan halts aneurysmal growth in this animal model. This project will work to define the novel TRPC4-dependent mechanism and how it might work in concert with the already known TFGb to contribute to aneurysm growth. This study has the potential to reveal new unique therapeutic targets to combat the devastating aortic pathology in Marfan syndrome.
Clinical Research Grant
James Hoekel, OD, Washington University, $100,000 2-year Clinical Research Grant entitled “Intraocular Lens Implant and Corneal Laser Surgery in Visually Impaired Children with Marfan Syndrome.”
Impaired vision is common in patients with Marfan Syndrome. More than half of Marfan patients have dislocation of the natural lens of the eye(s) due to weak connective tissue. These Marfan patients become extremely nearsighted and have high astigmatism at an early age, limiting school activities, play, and overall quality of life. The nearsightedness can be corrected surgically by implantation of a plastic lens or by laser surgery on the front surface of the eye (the cornea). The cornea is made of connective tissue. Because Marfan syndrome is a connective tissue disorder, it is important to know the effects of surgery on the cornea. Corneal weakness would make a surgeon opt for intraocular lens surgery rather than corneal laser surgery. However, if corneal integrity was normal, the patient may be a better candidate for laser surgery, eliminating the need for the high‑risk intraocular procedure. The facts generated by our study should answer these questions and help ophthalmologists decide on the safest way to correct blurred vision in Marfan syndrome patients.
Bettina Willie, PhD, McGill University, $100,000 2-year Faculty Grant entitled “Osteocyte Mechanobiology in Marfan Syndrome.”
Fibrillin-1 is one of the proteins present in bone. Abnormalities in the gene for fibrillin-1 cause several heritable disorders which lead to clinical problems in bone, including low bone mass, severe spinal deformities such as scoliosis and kyphosis, and exaggerated or reduced bone length. Marfan syndrome is the most frequent disorder in this group. Osteocytes are bone cells thought to sense mechanical load applied to the skeleton. It is also thought that osteocytes coordinate the actions of other bone cells; they tell the osteoblasts to form bone and the osteoclasts to remove bone.
We have recently discovered that the network of osteocytes in the bones of mice with Marfan syndrome are less organized than those in healthy mice. This disorganized osteocyte structure may impair their ability to sense mechanical load and their communication with other bone cells leading to less bone formation in mice with Marfan.
Based on these findings, we propose to determine if the bones of these Marfan mice respond to mechanical loading similarly to that of healthy mice. We will use a method of applying compressive forces to the lower leg of mice and then measuring how much bone forms in response to the forces. This is a well-established method in our team. We will also explore whether a drug therapy that targets the osteocyte can enhance bone mass in Marfan mice. To accomplish these goals, we will employ a combination of biochemical, cell biological and in vivo methods. This study may lead to results that could be readily translated into beneficial approaches to treat Marfan syndrome patients.
Jonathan Weinsaft, M.D., Weill-Cornell Medical College, $100,000 2-year Faculty grant entitled “Cardiovascular MRI Wall Stress Characterization for Prediction of Adverse Aortic Remodeling Following Surgical Aneurysm Repair”
Aortic graft surgery - a procedure that involves replacement of native aortic tissue with synthetic material - is often used to treat Marfan syndrome patients with enlarged (aneurysmal) or torn (dissected) aortas. Graft surgery can be lifesaving and is known to improve clinical outcomes soon after surgery, but Marfan syndrome patients can again develop aortic enlargement or life-threatening aortic tears years after their initial surgical repair. One possible reason for this may be the manner in which aortic wall stiffness (a known predictor of dissection and aneurysm) is altered in patients with Marfan syndrome. Another reason may be the way in which surgical grafts affect blood flow and stiffness of the aorta.
This research study will comprehensively test the impact of surgical grafts on native aortic tissue. To do so, cardiac magnetic resonance (CMR) imaging – including state of the art methods to measure aortic flow and wall stiffness – will be performed before and after aortic graft surgery among Marfan syndrome patients (as well as matched patients with bicuspid aortic valve [BAV] and sporadic aortic aneurysms) undergoing elective surgical grafting. CMR measurements of aortic wall stiffness will be compared to direct analyses of aortic tissue samples obtained at the time of graft surgery. Samples obtained during surgery will be exposed to stretch (material property) testing to confirm MRI findings. Aim 1 will compare stiffness and elasticity of the native aorta before and after surgical grafting among patients with MFS, BAV, and sporadic aneurysms. Aim 2 will examine aortic stiffness patterns in areas located both adjacent to and far away from surgical grafts. Aim 3 will determine the way in which surgical grafts impact speed and direction of blood flow in non-grafted areas. Our research team has a track record of expertise in CMR, material property testing, and Marfan syndrome clinical research that is well suited to address these important investigative issues.
Knowledge gained from this study will clarify the way in which surgical grafts affect native aortic tissue. In doing so, it will help to determine whether risk for repeat aortic aneurysm or dissection in Marfan syndrome patients is solely due to altered aortic wall tissue properties associated with this diagnosis, or further increased by changes caused by surgical grafts. Results will guide future research that will use CMR and computer based models to test new therapeutic approaches for placement of surgical grafts in areas with mild or no dilation but high wall stiffness, towards the ultimate goal of improving clinical outcomes for Marfan syndrome patients at risk for aortic aneurysm and dissection.
Pascal Bernatchez, Ph.D., University of British Columbia, $100,000 2-year Faculty Grant entitled, “Endothelial Function in Marfan: A Target and Clinical Marker”
Despite numerous studies in Marfan animals and patients, the effect of the drugs typically given to Marfan patients to help stabilize their aorta are still to this day very controversial. This is in great part due to low degree of successful stabilization of aorta (most Marfan (MFS) patients undergo aortic repair surgery anyway) despite chronic side effects (such as tiredness). Although they have clear beneficial effects in other kind of aortic diseases, what is the point for patients of taking medications such as atenolol or losartan without robust evidence of their effect in Marfan syndrome? This is an obvious dichotomy for patients and their family.
We and others have shown that Marfan patients and mice suffer from ‘unhealthy blood vessels’ very early in life; this condition called vascular endothelial dysfunction is synonym with ‘problematic blood vessels’ and show some resemblance to hypertension. Our preliminary data show that making blood vessels healthy again, independently of blood pressure, is a key aspect of successful Marfan patient management. For instance, mice with healthier blood vessels do not exhibit aortic root dilation, whereas mice with bad blood vessels show worsened aortic root widening. Mild aerobic exercise, the ubiquitous approach to increase vessel health, can block MFS aortic root widening in mice. In MFS patients on losartan, those who show improvements in a key marker of blood vessel health, nitric oxide release, show much greater stabilization of their aorta then those who don’t.
Our objective is to confirm the relevance of blood vessel health as a therapeutic target and marker of successful protection during losartan-based management. This new way of thinking for MFS management is leading us to test many clinically-available losartan analogs to determine the superior one at improving MFS vessel health. The specificity of the new losartan analogue will be tested in MFS mice with irreversible blood vessel disease, which should cancel the effect of the new losartan analogue. In the meantime, we will confirm the importance of vessel health by showing in MFS patients that those who show improvements in vessel health will experience aortic root stability, whereas those who don’t will see their aorta enlarge.
Finding new, already available drugs that work better in MFS is very relevant. Determining which patient should stick to losartan or switch to another medication like atenolol is a major step towards greater personalized medicine for MFS management.
Juan Miguel Redondo-Moya, Ph.D., Spanish National Cardiovascular Centre, $100,000 2-year Faculty Grant, entitled “NO Signaling and ADAMTS1 Substrates in the Pathogenesis of Marfan Syndrome”
Aortic aneurysm is the most common and serious problem linked to the genetic disease Marfan syndrome (MFS). In this condition, the enlargement of the aorta—the large artery that carries oxygenated blood from the heart—can lead to death if the artery wall bursts. Drugs such as β- blockers are used to try to slow down the rate of aortic enlargement, but unfortunately do not prevent rupture or dissection of the aorta. There is therefore an urgent need to identify and develop new therapies.
We recently discovered that MFS patients have lower levels of the protein Adamts1 in aortic tissue than are found in tissue from organ transplant donors. In mice, genetic inactivation of Adamts1 resulted features of MFS, including aortic dilation and aneurysm formation. These effects were driven by enhanced production of nitric oxide (NO), shown by the fact that treatment with NO synthesis inhibitors reduced blood vessel size and reversed the clinical signs of aneurysm formation in these MFS mice. We now plan to specifically assess the role of each protein involved in NO production and its relationship to aneurysm formation. NO is produced by three enzymes, called NOS1, NOS2 and NOS3. Using a specific inhibitor of NOS2 (1400W), we recently showed that NOS2 is an important mediator of the aortic pathology in MFS mice. However, the roles of NOS1 and NOS3 proteins in aneurysm development is still unknown. We therefore plan to generate MFS mice that lack either NOS1 or NOS3, which we will analyze for signs of aortic dilation and aneurysm formation (blood vessel size, aortic wall thickening, elastic fiber fragmentation, and proteoglycan deposition). As a complementary strategy, we will treat MFS mice with the specific NOS1 inhibitor Nω-Propyl-L-arginine. Unfortunately, there are no specific inhibitors available against NOS3.