Lipin1 and Micro-Dystrophin Gene Therapies for DMD: Independent and Combined Therapeutic Potential - Project Summary Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disorder caused by loss-of-function mutations in the DMD gene, resulting in the absence of dystrophin and progressive deterioration of skeletal muscle, along with respiratory and cardiac complications. Respiratory failure and cardiomyopathy remain the leading causes of death, with an average life expectancy of ~24 years. While micro-dystrophin gene therapies represent a major advancement, they face key limitations. Due to AAV vector packaging constraints, current constructs are truncated (mini- or micro-dystrophins) and often lack critical functional domains. Additionally, as non-native transgenes, these constructs can elicit cellular immune responses, potentially limiting their efficacy, safety, and long-term durability. These limitations highlight the urgent need for complementary or alternative therapeutic strategies. Lipin1, a phosphatidic acid phosphatase (PAP) and transcriptional co-regulator, is the major lipin isoform in the skeletal muscle and heart and plays key roles in lipid metabolism, membrane integrity and muscle function. We found that lipin1 expression is markedly reduced in muscle tissues of DMD patients and in mdx and D2-mdx mouse models, identifying its upregulation as a promising therapeutic strategy. Our recent studies demonstrate that lipin1 enhances sarcolemmal stability, reduces inflammation, preserves cardiomyocyte architecture, promotes neuronal nitric oxide synthase (nNOS) localization and activity, improves muscle strength, and significantly extends survival in dystrophic mice. Importantly, lipin1 is an endogenous protein with a compact coding sequence (~3 kb), enabling efficient AAV-mediated delivery and potentially reduced immunogenicity compared to dystrophin-based constructs. We hypothesize that lipin1 gene therapy will improve sarcolemmal integrity and enhance skeletal, respiratory, and cardiac function in dystrophic muscle. Moreover, we propose that combining lipin1 with micro-dystrophin gene therapy will produce synergistic therapeutic effects that exceed the benefits of either approach alone. This will be tested through the following Specific Aims: 1) Determine the therapeutic efficacy of lipin1 gene delivery in severe dystrophic D2-mdx mice by evaluating tissue transduction, safety, immunogenicity, histopathology, and functional outcomes; 2) Assess the therapeutic effects of lipin1 monotherapy, micro-dystrophin monotherapy, and their combination in D2-mdx mice to assess whether targeting complementary pathways yields additive or synergistic benefits in skeletal, cardiac, and respiratory function. NIH Mission Relevance: This research will define the therapeutic potential of lipin1 as an effective treatment for DMD, either alone or in combination with current dystrophin-based therapies. By elucidating the complementary and distinct mechanisms of lipin1, these studies aim to establish a novel combinatorial gene therapy strategy to improve both quality of life and survival in DMD. Moreover, insights into lipin1’s molecular functions may inform treatment approaches for other muscle-wasting conditions involving membrane fragility, such as rhabdomyolysis, sarcopenia, and related muscular dystrophies.
