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Abstract Microphysiological systems provide the opportunity to model accelerated changes at the human tissue level in the extreme space environment. Spaceflight-induced muscle atrophy experienced by astronauts shares similar physiological changes to muscle wasting in older adults, known as sarcopenia. These shared attributes provide a rationale for investigating molecular changes in muscle cells exposed to spaceflight that may mimic the underlying pathophysiology of sarcopenia. We report the results from three-dimensional myobundles derived from muscle biopsies from young and older adults, integrated into an autonomous CubeLab™, and flown to the International Space Station (ISS) aboard SpaceX CRS-21 as part of the NIH/NASA funded Tissue Chips in Space program. Global transcriptomic RNA-Seq analyses comparing the myobundles in space and on the ground revealed downregulation of shared transcripts related to myoblast proliferation and muscle differentiation. The analyses also revealed downregulated differentially expressed gene pathways related to muscle metabolism unique to myobundles derived from the older cohort exposed to the space environment compared to ground controls. Gene classes related to inflammatory pathways were downregulated in flight samples cultured from the younger cohort compared to ground controls. Our muscle tissue chip platform provides an approach to studying the cell autonomous effects of spaceflight on muscle cell biology that may not be appreciated on the whole organ or organism level and sets the stage for continued data collection from muscle tissue chip experimentation in microgravity. We also report on the challenges and opportunities for conducting autonomous tissue-on-chip CubeLabTM payloads on the ISS.

OBJECTIVES/GOALS: Our team has developed a high-throughput 3D patient-derived muscle platform to study signaling pathways associated with skeletal muscle disease. This platform will be used to study pathologies of human muscle that arise from genetic mutations and processes of aging along with pharmacologic interventions to improve mass, function, and performance. METHODS/STUDY POPULATION: In the current study, 3D skeletal muscle is formed from young healthy male samples. Samples are treated with urocortin II (UCNII) or vehicle for ten days and evaluated for tissue performance. Functional assessments include real-time contraction magnitudes using digital image correlation (DIC) analysis of video collected during electrical pulse stimulation and end-point measures of initial and repeated tetanic force production. Functional measures provide indices of patient muscle synchronicity, strength, and endurance related to drug efficacy and toxicity which we will correlate to pro-growth protein signaling via Luminex. A subset of these samples will also be analyzed by histology and microscopy to assess muscle fiber density, type, and size, as well as myotube fusion index and sarcomere uniformity. RESULTS/ANTICIPATED RESULTS: We anticipate that healthy muscle treated with UCNII will have increased synchronicity and contraction magnitudes in DIC analysis throughout their seven-day electrical pulse stimulation protocol. We also expect to see sustained contraction magnitudes in DIC analysis at the end of electrical pulse stimulation indicating fatigue resistance in the drug treated group compared to no-drug control. Like our real-time DIC data, we anticipate increases to initial and sustained maximal force production in the drug treated group. We expect that drug treated muscle will present with an increased fiber density, fiber diameter, and fusion index with uniform sarcomeres. Finally, we expect heightened pro-growth signaling pathways in treated vs. controls. DISCUSSION/SIGNIFICANCE: The current study will serve as an initial investigation of the endogenous ligand UCNII for enhancing skeletal muscle mass and performance in human muscle laying the framework for future drug efficacy and toxicity studies. This platform will ultimately enhance the study of muscle diseases and translation of therapeutics to clinical settings.

Diabetes produces a chronic inflammatory state that contributes to the development of vascular disease and impaired wound healing. Despite the known individual and societal impacts of diabetic ulcers, there are limited therapies effective at improving healing. Stromal cell-derived factor 1α (SDF-1α) is a CXC chemokine that functions via activation of the CXC chemokine receptor type 4 (CXCR4) receptor to recruit hematopoietic cells to locations of tissue injury and promote tissue repair. The expression of SDF-1α is reduced in diabetic wounds, suggesting a potential contribution to wound healing impairment and presenting the CXCR4 receptor as a target for therapeutic investigations. We developed a high-throughput β-arrestin recruitment assay and conducted structure–activity relationship (SAR) studies to screen compounds for utility as CXCR4 agonists. We identified CXCR4 agonist UCUF-728 from our studies and further validated its activity in vitro in diabetic fibroblasts. UCUF-728 reduced overexpression of miRNA-15b and miRNA-29a, negative regulators of angiogenesis and type I collagen production, respectively, in diabetic fibroblasts. In vivo, UCUF-728 reduced the wound closure time by 36% and increased the evidence of angiogenesis in diabetic mice. Together, this work demonstrates the clinical potential of small molecule CXCR4 agonists as novel therapies for pathologic wound healing in diabetes.