The following projects received 2018 New Ideas Awards from Medicine by Design:
Enabling skeletal muscle repair and functional recovery following denervation-induced injury using ultrasound mediated gene delivery
Dr. Jane Batt, St. Michael’s Hospital
Dr. Howard Leong-Poi, St. Michael’s Hospital
Skeletal muscle is essential for mobility and its health relies upon innervation. Accidental limb trauma with peripheral nerve injury results in immediate loss of muscle function and wasting. This is reversible if re-innervation occurs in a timely manner, due to muscle’s robust capacity for regeneration and self-repair. If re-innervation is delayed however, regeneration/repair is exhausted and muscle fibroses. Peripheral nerves possess the innate ability to regenerate; but the rate is limited to 1 mm/day. Thus, with proximal limb trauma (e.g. above the elbow), by the time the nerve regrows to its target muscles (e.g. hand), muscles restorative potential is lost. Permanent physical disability results, negatively impacting quality of life and inducing significant societal costs (e.g. health care, lost productivity/job retraining, long term disability).
We have no therapies to sustain denervated muscle awaiting re-innervation. We aim to use the novel approach of ultrasound mediated gene delivery (UMGD) to promote the repair and regeneration of denervated muscle and sustain its receptivity to reinnervation. With UMGD, genes in minicircle plasmids coupled to carrier microbubbles are systemically administered, and directed to induce tissue specific transfection and temporary (6-8 week) gene expression by high-power ultrasound mediated microbubble destruction over the target tissue. Using the rodent tibial nerve transection model, we will provide tailored non-invasive, localized, sequential gene therapy to denervated muscle to sustain its reparative capacity thereby enabling complete functional recovery with re-innervation. As therapeutic ultrasound and microbubbles are already in use for clinical sonothrombolysis, this is a project of rapid and highly translatable potential.
Direct reprogramming of astrocytes as a novel therapy for stroke repair
Maryam Faiz, Division of Anatomy, Department of Surgery, U of T
Cindi Morshead, Division of Anatomy, Department of Surgery, U of T
Stroke is the leading cause of adult disability in Canada and the third leading cause of death. Currently, tissue plasminogen activator (TPA) is the only FDA approved treatment for stroke. Unfortunately, it is only administered to a small number of patients due to a very narrow treatment window. As a result, the majority of stroke survivors have long-term functional impairments, for which rehabilitation offers limited improvement. The need for novel therapies to promote plasticity and beneficial functional outcomes, including the regeneration of lost tissue, is clear. Reprogramming, the conversion of one cell type to another, offers one such possibility. Reprogrammed cells would replace those lost to stroke. However, there has been virtually no assessment of functional recovery following reprogramming. We propose to examine astrocyte reprogramming in studies that are particularly relevant to human stroke. We will investigate the effects on cognition, which has been understudied despite the strong association of cognitive stroke with high rates of disability. We will use a clinically relevant mouse model of stroke we recently developed that leads to significant cognitive impairments. Importantly, we will examine differences in the response of males and females to reprogramming, as per international stroke recommendations on designing effective pre-clinical studies. Few studies have investigated sex differences, despite the fact that men and women show disparities in stroke prevalence, incidence, and mortality. We predict that the development of astrocyte-based advanced therapeutics will result in novel treatment options to accelerate stroke recovery and improve the quality of life for stroke survivors.
Development of non-viral, immune-modulatory nanoparticles for systemic delivery of CRISPR/Cas9 as a treatment intervention for Duchenne muscular dystrophy
Paul Santerre, Institute of Biomaterials & Biomedical Engineering and Faculty of Dentistry, U of T
Dr. Ronald Cohn, SickKids
Anthony Gramolini, Department of Physiology, U of T
We will develop non-viral vehicles for the systemic delivery of genome editing machinery with specific emphasis on targeting both mature skeletal muscle and satellite cells associated with Duchenne muscular dystrophy (DMD). Clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9) is a powerful new gene editing tool with the potential to revolutionize regenerative medicine if its delivery can be controlled. The objective of the research focuses on generating novel degradable and biocompatible amino-acid derived nanoparticles (DPNPs) with specific tissue targeting function, using a U of T patented polyurethane platform technology (Santerre) with inherent immune-modulating character and previously established chronic in vivo safety in porcine and rat models. These carrier systems will address limitations with current CRISPR/Cas9 systems, specifically: 1) eliminates the use of immune reactive virus transports; 2) enables co-delivery of guide RNA and Cas9; 3) reduces off-target tissue damage; 4) reduces off-target genetic changes; 5) extends half-life of the therapy in serum. The therapy will be used to edit dystrophin gene mutations, already defined by the Cohn group. Dystrophin is a key protein required for muscle integrity, and various mutations in the encoding gene are linked to DMD. Studies will evaluate the therapeutic nanoparticles in a newly generated DMD mouse model and determine their capacity to correct the underlying mutation, and establishing a technology to enable novel therapies for DMD patients in Canada and abroad. Using innovative mass spectrometry detection tools (Gramolini) we will track Cas9 presence in multiple tissues over time, and determine global protein expression responses.
Impact of pre-transplant inflammation on the host hematopoietic stem cell susceptibility to the transplant preparative regimen
Dr. Donna Wall, SickKids
John Dick, Princess Margaret Cancer Centre, University Health Network
Dr. Rebecca Marsh, Cincinnati Children’s Hospital Medical Center
Hematopoietic stem cell (HSC) transplant is the oldest form of stem cell therapy and is widely used in the replacement of defective hematopoietic systems (aplastic anemia, sickle cell anemia, immunodeficiencies) and the treatment of leukemia and solid tumors. Replacement of autologous HSC with genetically-modified HSC is one of the first successful applications of gene therapy (ADA-deficient SCID and thalassemia). Both therapies require durable replacement of host HSC. Achieving complete replacement of the host hematopoietic system with donor cells is especially challenging in patients who are inflamed in the immediate pre-transplant period (e.g. patients with hemophagocytic lymphohistiocytosis or recent infections). There is evidence that inflammatory cytokines such as tumor necrosis factor alpha (TNFa) and interferon gamma (IFNg), which are present during infection or immune responses, affect HSC fate and function. We propose that there is an immune-mediated quiescence of host HSC that allows escape from pre-transplant/gene therapy preparative chemotherapy and that these quiescent host cells compete with donor HSCs for engraftment and subsequent hematopoiesis – a new mechanism for graft failure. This project will evaluate HSCs from normal and inflamed children to assess immune-mediated changes in HSC fate, function, and vulnerability to chemo/radiation therapy. We will also study a prospective cohort of children undergoing transplant and evaluate engraftment outcomes and how they relate to clinical and laboratory measures of inflammation. This will not only clarify the role inflammation plays in HSC biology but also lead to a change in pre-transplant preparative regimen for inflamed patients and ultimately any patient undergoing HSC therapy.
Using chemogenetics to repair the primary motor cortex in amyotrophic lateral sclerosis
Melanie Woodin, Department of Cell & Systems Biology
Janice Robertson, Department of Laboratory Medicine & Pathobiology and Tanz Centre for Research in Neurodegenerative Disease
Amyotrophic lateral sclerosis (ALS), also commonly known as Lou Gehrig’s disease, is a neurodegenerative disease characterized by loss of neurons responsible for voluntary muscle movement causing paralysis. ALS currently affects 2,500-3000 Canadians, and ~80% of those will die within 2-5 years. There is no cure for ALS, nor are there any effective treatments. An early characteristic of ALS is hyperactivity of the primary motor cortex, which is the region of the brain controlling voluntary movements. Cortical hyperexcitability promotes the degeneration of the neurons that connect through the spinal cord to control muscles. Our team recently discovered that by reversing the hyperactivity in the motor cortex we could delay the onset of ALS in a mouse model of the disease. We reversed the hyperactivity using chemogenetics, which is a revolutionary technique that allows the remote activation of engineered macromolecules to regulate neuronal activity. While our chemogenetic-mediated functional regeneration holds significant therapeutic potential for ALS patients, the clinical translation of this discovery is currently limited by the delivery method of the chemogenetic tools. In the current project we will overcome these limitations by delivering the chemogenetic tool directly to the required cell type using an adeno-associated virus (AAV; containing a pyramidal neuron promoter). This strategy holds significant clinical benefit because viral vectors are in multiple phase I-III clinical trials, and the chemogenetic activator (clozapine) is widely used clinically. To our knowledge this research is the first worldwide to use AAV-directed chemogenetics to promote regeneration in a neurodegenerative disease.