Rare Disease Day Spotlight

 

RARE DISEASE DAY 2021 SPOTLIGHT

I would like to thank two amazing human beings that have helped Vivienne along her journey with Propionic Acidemia. First, I would like to thank Ms. Heather, who is Vivienne’s Nutritionist/Dietician. Since she took on Vivienne’s case, Vivi’s health has improved. She has made such a difference in Vivienne’s life! Now, I know why so many parents emphasized the importance of a great dietician! Ms. Heather has been very caring, very attentive,a great listener and very committed to Vivi’s case!

Second, I would like to thank Dr. Baker! Dr. Baker has been an extraordinary geneticist! His dedication and amazing care has helped Vivi stay away from many hospital stays. I feel so blessed in having both Dr. Baker and Ms.Heather as Vivienne’s care team. They both have gained my confidence. Dr. Baker and Heather truly made a difference in Vivienne’s life!

Thank you from the Lopez Family!

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Nalani has been lucky to have some amazing people in her life helping her along in her journey. She has been attending a weekly social group at Coeur Academy in Missouri for about 6 years now. They get together, talk about their week, plan activities and play games. They cook a “Thanksgiving feast” and exchange gifts on Christmas. They go shopping and go out to eat together. She is the only girl and tells everyone she meets that she has 4 boyfriends. Nalani is extremely social and this program has given her a group of true friends. I am so thankful to them. I don’t know what she would do without Ann, Sarah and her boyfriends at social group! – Angela  (picture of Nalani and her Teacher)

 

PAF Awards Initial Research Grant Houten DeVita

PAF Awards $50,000 New Research Grant

 

PI: Sander Houten, Ph.D., Department of Genetics and Genomic Sciences,

Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, NY, US

 

 

 

Co-PI: Robert J. DeVita, Ph.D., Department of Pharmacological Sciences, Drug Discovery Institute,

Icahn School of Medicine at Mount Sinai, NY, US

 

 

“Substrate reduction as a novel therapeutic strategy for propionic acidemia”

Amino acid metabolism and in particular the degradation of valine and isoleucine are a significant source of propionyl-CoA, the substrate of propionyl-CoA carboxylase. Current treatment of propionic acidemia aims to decrease the degradation of valine and isoleucine through medical diets and avoidance of fasting. Drs Houten and DeVita, the investigators on this project, aim to develop a pharmacological substrate reduction therapy for propionic acidemia that limits the degradation of these amino acids. They propose to inhibit short/branched-chain acyl-CoA dehydrogenase (SBCAD) and isobutyryl-CoA dehydrogenase (ACAD8), which are involved in isoleucine and valine degradation, respectively. Inhibition of these enzymes is thought to be safe because in contrast to propionic acidemia, inherited defects of SBCAD and ACAD8 are thought to be benign conditions. In cell line models, inhibition of SBCAD using a genetic KO or an inhibitor was efficacious and led to a pronounced decrease in the propionyl-CoA carboxylase substrate. The investigators anticipate to find a few hit inhibitors of SBCAD and ACAD8 that can be further optimized and serve as a starting point for a broader translational drug discovery program for treatment of propionic acidemia.

 

PAF Awards $49,953 New Research Grant – Swietach

PAF Awards $49,953 New Research Grant

PI: Pawel Swietach, Professor of Physiology, Department of Physiology, Anatomy & Genetics, University of Oxford, England

“Aberrant protein propionylation and distinct histone marks in propionic acidemia: new disease mechanisms and risk factors for cardiac disease”

The challenge placed on our hearts – to contract and relax in a correct sequence and with adequate strength – is formidable.  The elegant biological solution to this mechanical problem is an organ that pumps millions of liters of blood to support life for many decades.  However, the quality and span of a person’s life is strongly linked to cardiac health.  Thanks to scientific breakthroughs, better treatments are now available for cardiac disease, allowing patients to live longer and happier lives.  Our goal at Oxford University’s British Heart Foundation Centre of Research Excellence is to ensure that scientific progress addresses a wide spectrum of disorders, irrespective of their incidence.

Cardiac problems are common in propionic acidemia (PA).  Sadly, dilated cardiomyopathy and long-QT syndrome are often the cause of childhood death.  In order to treat and prevent these cardiac problems, we must first understand the underlying mechanisms.  Once these processes are described, our aimis to identify targets for drugs or interventions.  We believe that this ambition is achievable thanks to the wealth of knowledge about the heart and the vast repertoire of drugs approved for therapy in various other cardiac conditions.  Many of these drugs could be “repurposed” for PA-associated disorders, giving hope to many families for a timely treatment.

For this PAF-funded project, we have assembled a consortium of scientists who are eager to devote their expertise to studying PA.  My laboratory’s expertise is in cardiac cellular physiology in the context of acid-base disorders. We are joined by Tom Milne who is Associate Professor in Epigenetics at Oxford, Holger Kramer, an expert on proteomics, and Steve Krywawych, principal biochemist at Great Ormond Street Hospital in London. Resources and facilities made available to this project include a mouse model of PA, courtesy of Michael Barry and Lourdes Desviat, methods to characterise cardiac function from the cell to organ level, as well as measurements of changes at the protein and gene level.  This interdisciplinary but focused approach allows us to identify potential targets for PA treatment.  Indeed, our preliminary findings point to one such enzyme, and the aim of this project is to test and validate our hypothesis.

PA is associated with major metabolic changes, and many of these substances are not merely intermediates in a chain of events, but can have strong biological actions that are not always intuitive to predict.  Our project will investigate how the build-up of propionate affects cardiac genes through a chemical reaction that causes DNA scaffolds (called histones) to “open up” genes that should not normally be expressed in a healthy heart.  Many genes will be affected by this, but some are more closely linked to the cardiac disorder.  After identifying these lead genes, we will test the extent to which blocking these could be curative. In parallel, we will investigate if propionate can also react with other targets in the cell, such as proteins underpinning contraction.  Indeed, our work suggests that a promising avenue for research relates to so-called excitation-contraction coupling, a process that converts cardiac electricity to a mechanical response.

We are excited to be part of the PA research family and wish to take this opportunity to invite patients, carers, and supporters to our lab for a visit.

 

PAF Awards Continuation Grant to Guofang Zhang at Duke University

Guofang Zhang, PhD, Duke University

“Propionyl-CoA and propionylcarnitine mediate cardiac complications in patients with propionic acidemia”

Update August 2020

Cardiac disease is one of complications often associated with propionic acidemia (PA). Understanding the pathological mechanism is essential to prevent the development of complication. Our previous research has shown that propionyl-CoA accumulation inhibits the metabolism of fatty acid which is a major fuel for cardiac energy. The loss of fuel switch flexibility could interfere with cardiac energy metabolism and potentially develop cardiac complications particularly under various stresses. Our research was funded by PAF to investigate the pathological mechanism of cardiomyopathy associated with PA in 2019. In the year 1 of PAF award, we started to map out the metabolic source of propionyl-CoA in heart. Surprisingly, the amino acids (isoleucine, threonine, methionine, valine) and protein which are known to be substrates of propionyl-CoA have negligible contribution to propionyl-CoA production in heart. However, our data does not exclude the possibility that these amino acids substantially contribute to propionyl-CoA production in other organs, like liver. Circulating propionate is a major source of cardiac propionyl-CoA. It also fits the observation that heart prefers fatty acids including short-chain fatty acids as energy substrates. More than 99% propionate originating from microbiome is efficiently removed/metabolized at its first pass through liver in healthy rodents. Therefore, circulating propionate maintains at very low level after liver. The deficiency of PCC attenuates hepatic ability of disposing propionate and increases circulating propionate level, which exacerbates propionyl-CoA accumulation in heart. Our results show the “metabolic filtering” role of liver in maintaining efficient cardiac energy metabolism. 

In order to understand the pathological mechanism of cardiac complication associated with PA, a PA-mediated cardiac complication model is essential. In year 2 of PAF award, we will first develop and confirm a mouse model with cardiac complication before pathological mechanism study. With the collaboration with Dr. Michael Barry, we will characterize cardiac function and metabolic phenotype of Pcca-/-(A138T) mouse that is a PA animal model created by Dr. Michael Barry. We will induce cardiac complication with Pcca-/-(A138T) mice by diets or stresses if it is necessary. After that, we will examine how cardiac energy metabolism is disturbed using stable isotope-based metabolic flux and RNA-Seq approaches. Furthermore, we will further investigate how propionylcarnitine expansion in the heart could deplete cardiac acetylcarnitine, acetyl-CoA buffer, and affects cardiac acute energy demanding. The long-term goal of our research is to find a therapeutic target on cardiac propionyl-CoA metabolism to mitigate cardiac complication associated with PA.

PAF Grant Maclean

PAF Awards $50,000 New Research Grant

Ken Maclean, PhD, University of Colorado Denver 

“Chemical Chaperone Treatment to Restore Enzyme Activity in Folding Mutations of Propionyl-Co-A Carboxylase: Towards a Personalized Therapeutic Strategy in Propionic Acidemia (PA)” – In Summer 2020, PAF awarded a $50,000 grant.”  

Propionic acidemia (PA) is a severe life-threatening disease for which there is currently no truly effective treatment. The disease is caused by mutation in one of the two genes that code for the enzyme propionyl-CoA carboxylase (PCC). This enzyme is made up of two different proteins that fold around each other into a complex structure with six of each of these two molecules. This is a very unusual and complex structure for a metabolic enzyme and recent work in our laboratory has found that a number of specific mutations that cause PA cause problems by interfering with the protein folding and/or assembly process leading to a non-functional enzyme and thus the disease. In cells, proteins with complicated folding patterns are often assisted in their folding by other proteins called chaperones. We have observed that a number of mutant forms of PCC can be restored to normal activity if they are helped to fold correctly using these chaperone proteins. In our study, we will examine a number of chemicals that can also function as chaperones and assist with protein folding with a view towards restoring full activity in mutant forms of PCC. This work will initially occur in a bacterial PCC expression system to identify promising compounds and then depending upon progress, move into treating human PCC patient derived cells. These studies have the potential to serve as an initial first step in the rational design of a personalized medicine strategy for patients with specific mutations causing PA.

PAF research summary Elango

PAF Awards $44,253 New Research Grant

Rajavel Elango, PhD, University of British Columbia

“Optimizing amino acids in medical foods to manage propionic acidemia”  

Propionic Acidemia (PA) is primarily caused by an enzymatic defect, propionyl-CoA carboxylase (PCC), in the catabolic pathway of valine, isoleucine and other propiogenic precursors. The dietary management of PA mainly depends on protein restriction from food to reduce supply of propiogenic amino acids, and the use of special medical foods. These medical foods contain all essential amino acids and nutrients, but no propiogenic compounds. Recently, concerns have been raised about their use, due to the imbalanced content of the Branched Chain Amino Acids (BCAA) – high leucine, to minimal or no valine and isoleucine. The imbalanced mixture of BCAA negatively impacts plasma concentrations of valine and isoleucine, and has been proposed to affect growth in pediatric PA patients. 

In an ongoing retrospective natural history study (n=4), patients with PA treated at our center from birth (or diagnosis) to age 18y, we observed that higher intake of medical food (compared to intact protein) results in lower ht-for-age Z scores. Based on these pilot data, we propose that there is an immediate need to determine the optimal amounts of leucine to be present in the medical foods.

Therefore, the specific objectives of the current study are to:

  1. Stable isotope studies
    1. Determine the ideal ratio among BCAA in children using the stable isotope-based indicator amino acid method to optimize protein synthesis in a Proof-of-Principle approach.
    2. Test the ratio among BCAA using the same stable isotope-based method in our cohort of PA patients to determine impact on protein synthesis, and plasma metabolite responses.
  2. Determine the impact of the use of natural (intact) vs formula (medical food) protein on anthropometric, biochemical and clinical outcomes via a retrospective natural history study of PA patients treated at BC Children’s Hospital.

Recent dietary guidelines for PA are discouraging the reliance on medical foods as a sole dietary source. However most individuals with PA are at risk for malnutrition and depend on these medical foods as an easy tolerable source of energy and protein. Thus, determining the optimal ratio of BCAA in PA medical foods is necessary to optimize protein synthesis, promote anabolism, growth and prevent the accumulation of toxic metabolites. 

Our laboratory, equipped with use of novel stable isotope tracers to examine protein and amino acid metabolism, is ideally suited to address the question of the ideal BCAA ratio to be used for dietary management of PA and potentially impact health outcomes.

 

PAF attends 2019 Abbott Nutrition Conference

17th Abbott Metabolic Conference: Advances in Management of Inherited Metabolic Disorders
Memphis, TN May 30-June 1, 2019
By Brittany S Smith, PAF Board Member & Treasurer

PAF had a table at the 2019 ABBOTT Metabolic Conference.

There were several presentations and debates that were relevant to the PA community. The first was Dr. Sufin Yap, MD, from Sheffield, UK, who spoke on Organic Acidemias. She described how she has observed her patients in a metabolic crisis and that their livers can enlarge very rapidly. Dr. Yap also described how she has used Carbaglu within a crisis situation and it has brought the ammonia levels down on her patients. The medication was also shown to improve the quality of life of patients with PA using the medication, this was shown by using the PedsQL, a quality of life survey tool. Carbaglu has been used in Europe for over 15 years.

Three dietitians gave a joint presentation on Emergency Preparedness, detailing the impacts of natural disasters on the clinics and staff and also families serviced by their clinics. Amy Cunningham, RD; Suzanne Hollander, RD; and Heather Saavedra, RD, each detailed natural disasters they have had in their areas of the country, which have included wild fires, hurricanes, flooding, droughts, and earthquakes. They have not only impacted families, but the clinic operations. In some cases the hospital and clinics were closed for months. Families, too, were significantly impacted and in one case, a family utilizing one of the clinics had only 5-10 minutes to flee their home. Overall, they indicated a need for all of the metabolic clinics and newborn screening offices to create Emergency Preparedness plans, as well as, helping affected families to prepare as well.

The last session that I wanted to mention was a debate session in which a team of doctors and dietitians each had to debate one side of a treatment suggestion. One was on liver transplantation and whether to encourage or discourage a metabolic family to investigate liver transplantation. While the debate was interesting, the discussion that followed was poignant; they were open to being corrected if they had misstated facts, one being using the livers from those with PA and UCDs in a “domino” transplant, and the other was that they all recommended encouraging their families to seek out information and go down a treatment route if the parents felt that was what was best.

 

The Propionic Acidemia Nutrition Guidelines are now published

Great News – The “Propionic Acidemia Nutrition Guidelines” Are Now Published!

The Nutrition Guideline Committee is happy to announce that the Organic Acidemia Workgroup has published the “Propionic Acidemia (PROP) Nutrition Guidelines” in the February, 2019 issue of Molecular Genetics and Metabolism. The article is available and can be downloaded at no cost at https://doi.org/10.1016/j.ymgme.2019.02.007.

Publication of the PROP/PA Nutrition Guidelines in Molecular Genetics and Metabolism brings the latest evidence- and consensus-based nutrition management recommendations to the attention of clinicians, researchers, policy makers, insurers, and patients.

The new Nutrition Management Guidelines for PROP/PA provide:

  • New directions including:
    • A greater emphasis on nutritional needs such as nutrient intake, nutritional interventions, supplementation, etc.
    • Less emphasis on  medical management which has been covered in previous publications;
    • Additional topics such as monitoring to ensure nutritional adequacy, nutritional issues with pregnancy and lactation, nutritional management for secondary complications such as pancreatitis, and finally a section addressing liver transplantation and the nutritional management before, during, and after the procedure.

 

Two consumer-oriented pieces, Frequently Asked Questions and a Consumer Summary, provide patients and families with information to use when interacting with their providers. The summary highlights key recommendations and suggests questions that patients and families may want to discuss with the metabolic team.

  • When patients and health care providers (HCPs) have the same information, they can work together as a team to identify the treatment that is best for the patient’s situation.
  • You can access these pieces at the Genetic Metabolic Dietitians International (GMDI) or Southeast Genetics Network websites located at http://www.Southeastgeneticsnetwork.org/ngp  and http://www.GMDI.org
  • The new guidelines should lead to greater consistency of care across centers.
    • There are several important resources included in the guidelines including recommended nutrient intakes, monitoring schedules, and nutritional interventions tables.
    • A web site that provides all the resources and references used to develop the guidelines is available so that health care clinicians and others can readily obtain the background information related to the guidelines at the websites listed above.
    • The guidelines development method utilized evidence from published research, practice-based medical literature and expert consensus processes.

SIMD 2019

PAF at SIMD 2019

Jill Chertow and Maria L. Cotrina represented PAF and the PA Community at the Society for Inherited Metabolic Disorders (SIMD) 41st Annual Meeting on April 6-9, 2019 in Bellevue, Washington.  Propionic Acidemia Foundation (PAF) partners with the National Urea Cycle Disorders Foundation (NUCDF) in sharing an exhbition booth.

Maria L. Cotrina shared her poster on “High Incidence of Autism/ASD in Propionic Acidemia: Data from the Propionic Acidemia and Urea Cycle Disorders Registries.”

 

 

Arianna F. Anzmann, MS was the recipient of  the SIMD Founders Award (Best Oral Presentation by a Trainee).  Her presentation “Multi-Omics Studies in Patient-Derived and CRISPR-Edited Cellular Models of Methylmalonc Acidemia and Propionic Acidemia Reveal Dysregulation fo Serine Metabolism: New Directions for Cellular Pathogenesis in Disorders of Branch Chain Amino Acid Metabolism.”  was a result of a 2017 PAF awarded grant to Hilary Vernon, MD, PhD, Johns Hopkins University for the project “Targeting Serine and Thiol Metabolism in Propionic Acidemia”.

Propionic Acidemia Foundation Research Grant – Richard

PAF Awards $33,082.12  Research Grant in 2019

PAF Awards $30,591  Continuation Grant in 2020

Eva Richard, PhD, Universidad Autonoma de Madrid, Spain

“Cardiomyocytes derived from induced pluripotent stem cells as a new model for therapy development in propionic acidemia”

Understanding the cellular and molecular mechanisms that occur in genetic diseases is essential for the investigation of new strategies for their prevention and treatment. In this context, induced pluripotent stem cells (iPSC) offer unprecedented opportunities for modeling human disease. One of the fundamental powers of iPSC technology lies in the competency of these cells to be directed to become any cell type in the body, thus allowing researchers to examine disease mechanisms and identify and test novel therapeutics in relevant cell types.

The main objective of this project is focused on the generation of human iPSC-derived cardiomyocytes (hiPSC-CMs) from propionic acidemia (PA) patients as a new human cellular model for the disease.In PA, cardiac symptoms, namely cardiac dysfunction and arrhythmias, have been recognized as progressive late-onset complications resulting in one of the major causes of disease mortality. Using hiPSC-CMs we will study cellular processes, such as mitochondrial function and oxidative stress which have been recognized as main contributors for PA pathophysiology. In addition, our aim is to unravel novel altered pathways using high-throughput techniques such as RNAseq and miRNA analysis. We will also examine the potential beneficial effects of an antioxidant and a mitochondrial biogenesis activator in PA cardiomyocytes. The results that derive from this project will be relevant for the disease providing insight into the affected biological processes, and thus providing tools and models for the identification of novel adjuvant treatments for PA.

Update April 2020 – Eva Richard PhD

Thanks to propionic acidemia (PA) foundation, we have developed a new cellular model of PA based on induced pluripotent stem cells (iPSC) with the goal of defining new PA pathomechanisms which could be potential therapeutical targets. Traditionally, disease pathophysiology has been studied in immortalized or human cell lines and in animal models. Unfortunately, immortalized cells often do not respond as primary cells and animal models do not exactly recapitulate patients‘ clinical symptoms. So far, patients-derived fibroblasts have been mainly used as cellular models in PA due to their availability and robustness, but they have important limitations. The ability to reprogram somatic cells to iPSCs has revolutionized the way of modeling human disease. To study rare diseases,
stem cell models carrying patient-specific mutations have become highly important as all cell types can be differentiated from iPSCs.

We have generated and characterized two iPSC lines from patients-derived fibroblasts with defects in the PCCA and PCCB genes; and an isogenic control in which the mutation of the PCCB patient was genetically corrected using CRISPR/Cas9 technology. These iPSC lines have been successfully differentiated into cardiomyocytes,
and their presence was easily established by visual observation of spontaneously contracting regions and by the expression of several cardiac markers. PCCA iPSC-derived cardiomyocytes exhibited reduced oxygen consumption, an accumulation of residual bodies and lipid droplets, and increased ribosomal biogenesis. Furthermore, we found increased protein levels of HERP, GRP78, GRP75, SIG-1R and MFN2 suggesting
endoplasmic reticulum stress and calcium perturbations in these cells. We also analysed a series of heart-enriched miRNAs previously found deregulated in heart tissue of a PA murine model and confirmed their altered expression.

The present study represents the first report of the characterization of cardiomyocytes derived from iPSCs generated by PA patients ́ fibroblasts reprogramming. Our results provide evidence that several pathomechanisms may have a relevant role in cardiac dysfunction, a common complication in PA disease. This new cellular PA model offers a powerful tool to unravel disease mechanism and, potentially, to enable drug
screening/drug testing. Despite improved therapy over the past few decades, the outcome of PA patients is still unsatisfactory, highlighting the requirement to evaluate new therapies aimed at preventing or alleviating the clinical symptoms. Additional research is required to determine the contribution of the mechanisms identified in this work to the cardiac phenotype and how this knowledge can help formulating better personalized therapeutic
strategies in the future.

We sincerely thank the Propionic Acidemia Foundation for supporting our investigation, which has resulted in a truly motivating experience for us, feeling we belong to the PA research family. The funding we received has led to important advances in PA pathophysiology, and our aim is to continue this research in the near future.

Update September 2019 – Eva Richard PhD

There is an unmet clinical need to develop effective therapies for propionic acidemia (PA). Advances in supportive treatment based on dietary restriction and carnitine supplementation have allowed patients to live beyond the neonatal period. However, the overall outcome remains poor in most patients, who suffer from numerous complications related to disease progression, among them cardiac alterations, a major cause of PA morbidity and mortality. In our research, we developed a new cellular model of PA based on induced pluripotent stem cells (iPSC) with the goal of defining new molecular pathways involved in the pathophysiology of PA which would be potential treatment targeting.

Traditionally, disease pathophysiology has been studied in immortalized or human cell lines and in animal models. Unfortunately, immortalizedcells often do not respond as primary cells and animal models do not exactly recapitulate patients‘ symptoms. So far, patients-derived fibroblasts have been mainly usedas cellular models in PAdue to theiravailability and robustness, but they have important limitations.

The ability to reprogram somatic cells to iPSCs has revolutionized the way of modeling human disease. To study rare diseases, stem cell models carrying patient-specific mutations have become highly important as all cell types can be differentiated from iPSCs. We have generated and characterized two iPSC lines from patients-derived fibroblasts with defects in PCCA and PCCB genes. These iPSC lines can be differentiated into cardiomyocytes that mimic the tissue-specific hallmarks of the disease. The presence of PA cardiomyocytes has been easily established by visual observation of spontaneously contracting regions, and the expression of several cardiac markers. We have observed that PCCA-deficient cardiomyocytes present an increase in degradation products and in lipid droplets, and exhibit mitochondrial dysfunction compared to control cells. We further discovered the down-regulation of several miRNAs in PCCA cardiomyocytes compared to control ones, and several miRNAs targets are currently being analyzed in order to investigate underlying cellular pathological mechanisms. Interestingly, we have performed several experiments to analyze the effect of the mitochondrial biogenesis activator, MIN-102 compound (PPAR agonist, derivative of pioglitazone) in cardiomyocytes.

Preliminary results showed an increase in the oxygen consumption rateof PCCA and control cells. In our next steps, we plan to complete the analysis in the PCCA cardiomyocyte line, characterize PCCB cardiomyocytes and to study in depth the therapeutic potential of MitoQ and MIN-102 compounds.

We would like to sincerely thank the Propionic Acidemia Foundation for supporting our research.

Update March 2020

 “Cardiomyocytes derived from induced pluripotent stem cells as a new model for therapy development in propionic acidemia.”

Eva Richard, Associate Professor

There is an unmet clinical need to develop effective therapies for propionic acidemia (PA). Advances in supportive treatment based on dietary restriction and carnitine supplementation have allowed patients to live beyond the neonatal period. However, the overall outcome remains poor in most patients, who suffer from numerous complications related to disease progression, among them cardiac alterations, a major cause of PA morbidity and mortality. In our research, we developed a new cellular model of PA based on induced pluripotent stem cells (iPSC) with the goal of defining new molecular pathways involved in the pathophysiology of PA which could be potential therapeutical targets.

Traditionally, disease pathophysiology has been studied in immortalized or human cell lines and in animal models. Unfortunately, immortalized cells often do not respond as primary cells and animal models do not exactly recapitulate patients‘ symptoms. So far, patients-derived fibroblasts have been mainly used as cellular models in PA due to their availability and robustness, but they have important limitations.

The ability to reprogram somatic cells to iPSCs has revolutionized the way of modeling human disease. To study rare diseases, stem cell models carrying patient-specific mutations have become highly important as all cell types can be differentiated from iPSCs. We have generated and characterized two iPSC lines from patients-derived fibroblasts with defects in the PCCA and PCCB genes. These iPSC lines can be differentiated into cardiomyocytes that mimic the tissue-specific hallmarks of the disease. The presence of cardiomyocytes has been easily established by visual observation of spontaneously contracting regions, and the expression of several cardiac markers. PCCA iPSC-derived cardiomyocytes exhibited an alteration of autophagy process with an accumulation of residual bodies and mitochondrial dysfunction characterized by reduced oxygen consumption and alteration of mitochondrial biogenesis due to a deregulation of PPARGC1A. We also evaluated the expression of heart-enriched miRNAs previously associated with cardiac dysfunction and several miRNAs were found deregulated. Furthermore, we found increased protein levels of Herp, Grp78, Grp75, sigma-1R and Mfn2 suggesting ER stress and calcium perturbations in these cells.

We are planning to analyze PCCB cardiomyocytes to compare the results with PCCA and control data. We are working to obtain mature cardiomyocytes in order to perform electrophysiology studies (K+ currents) using a whole-cell patch clamp method. We are interested in the study of the tissue-specific bioenergetic signature comparing cardiomyocytes derived from control and PA patients´ iPSCs by reverse phase protein microarrays (RPPMA). Future work also includes testing the effect of the mitochondrial biogenesis activator, MIN-102 compound (PPAR agonist, derivative of pioglitazone) and of the mitochondrial targeting antioxidant MitoQ in PA cardiomyocytes.

We would like to sincerely thank the Propionic Acidemia Foundation for supporting our research.