Publications

Huang, P, Russell, AL, Lefavor, R, et al. Feasibility, Potency, and Safety of Growing Human Mesenchymal Stem Cells in Space for Clinical Application. NPJ Microgravity. 2020;6:16.

Growing stem cells on Earth is very challenging and limited to a few population doublings. The standard two-dimensional (2D) culture environment is an unnatural condition for cell growth. Therefore, culturing stem cells aboard the International Space Station (ISS) under a microgravity environment may provide a more natural three-dimensional environment for stem cell expansion and organ development. In this study, human-derived mesenchymal stem cells (MSCs) grown in space were evaluated to determine their potential use for future clinical applications on Earth and during long-term spaceflight. MSCs were flown in Plate Habitats for transportation to the ISS. The MSCs were imaged every 24–48 h and harvested at 7 and 14 days. Conditioned media samples were frozen at −80 °C and cells were either cryopreserved in 5% dimethyl sulfoxide, RNAprotect, or paraformaldehyde. After return to Earth, MSCs were characterized to establish their identity and cell cycle status. In addition, cell proliferation, differentiation, cytokines, and growth factors’ secretion were assessed. To evaluate the risk of malignant transformation, the space-grown MSCs were subjected to chromosomal, DNA damage, and tumorigenicity assays. We found that microgravity had significant impact on the MSC capacity to secrete cytokines and growth factors. They appeared to be more potent in terms of immunosuppressive capacity compared to their identical ground control. Chromosomal, DNA damage, and tumorigenicity assays showed no evidence of malignant transformation. Therefore, it is feasible and potentially safe to grow MSCs aboard the ISS for potential future clinical applications.

Chakraborty N, Waning DL, Gautam A, Hoke A, Sowe B, Youssef D, Butler S, Savagilo M, Childress P, Kumar R, Moyler C, Dimitrov G, Kacena M, Hammamieh R. Gene-Metabolite Network Linked to Inhibited Bioenergetics in Association With Spaceflight-induced Loss of Male Mouse Quadriceps Muscle. J Bone Miner Res, 2020;35(10):2049-2057.

Prolonged residence of mice in spaceflight is a scientifically robust and ethically ratified model of muscle atrophy caused by continued unloading. Under the Rodent Research Program of NASA, we assayed the large scale mRNA and metabolomic perturbations in the quadriceps of C57BL/6j male mice that lived in spaceflight (FLT) or on the Ground (Control or CTR) for approximately four weeks. The wet weights of the quadriceps were significantly reduced in FLT mice. Next generation sequencing and untargeted mass spectroscopic assays interrogated the gene‐metabolite landscape of the quadriceps. A majority of top ranked differentially suppressed genes in FLT encoded proteins from the myosin or troponin families, suggesting sarcomere alterations in space. Significantly enriched gene‐metabolite networks were found linked to sarcomeric integrity, immune fitness, and oxidative stress response; all inhibited in space as per in silico prediction. A significant loss of mitochondrial DNA copy numbers in FLT mice underlined the energy deprivation associated with spaceflight induced stress. This hypothesis was reinforced by the transcriptomic sequencing‐metabolomics integrative analysis that showed inhibited networks related to protein, lipid and carbohydrate metabolism, and ATP synthesis and hydrolysis. Finally, we discovered important upstream regulators, which could be targeted for next generation therapeutic intervention for chronic disuse of the musculoskeletal system.

Ballerini A, Chua CYX, Rhudy J, Susnjar A, Di Trani N, Jain PR, Laue G, Lubicka D, Shirazi-Fard Y, Ferrari M, Stodieck L, Cadena S, Grattoni A. Counteracting Muscle Atrophy on Earth and in Space via Nanofluidics Delivery of Formoterol [published ahead of print May 10, 2020]. Adv Ther. 2020;3:2000014. doi:10.1002/adtp.202000014

Skeletal muscle atrophy is a critical health problem that affects quality of life and increases morbidity and mortality. At present, exercise training remains the only intervention and pharmaceutical treatments remain elusive. Formoterol (FMT), a β2‐adrenergic receptor agonist, has emerged as a potential therapeutic by triggering skeletal muscle anabolism with daily dosing. Here, the efficacy of sustained FMT release is investigated via a subcutaneously implanted nanofluidic delivery system (nF) to prevent muscle wasting. Pharmacokinetics of nF‐mediated sustained FMT delivery (nF‐FMT) in healthy mice is assessed for 56 days, which demonstrates an anabolic effect on skeletal muscles. Using a hind limb suspension unloading mouse model, it is shown that nF‐FMT treatment attenuates soleus mass loss in comparison to control mice. Further, the very first study of an implantable drug delivery device in microgravity in vivo is launched. The microgravity environment aboard the International Space Station is leveraged to assess the atrophy prevention capability of nF‐FMT in mice for 29 and 55 days. Muscle hypertrophy is observed in both ground control and spaceflight mice treated with nF‐FMT compared to their respective vehicle controls. Overall, the nF system is presented as a viable platform for sustained delivery of FMT for therapeutic intervention of skeletal muscle atrophy.

Xia Y, Steen PH. Dissipation of Oscillatory Contact Lines Using Resonant Mode Scanning. NPJ Microgravity. 2020;6:3.

Moving contact-lines (CLs) dissipate. Sessile droplets, mechanically driven into resonance by plane-normal forcing of the contacting substrate, can exhibit oscillatory CL motions with CL losses dominating bulk dissipation. Conventional practice measures CL dissipation based on the rate of mechanical work of the unbalanced Young’s force at the CL. Typical approaches require measurements local to the CL and assumptions about the “equilibrium” contact angle (CA). This paper demonstrates how to use scanning of forcing frequency to characterize CL dissipation without any dependence on measurements from the vicinity of the CL. The results are of immediate relevance to an International Space Station (ISS) experiment and of longer-term relevance to Earth-based wettability applications. Experiments reported here use various concentrations of a water-glycerol mixture on a low-hysteresis non-wetting substrate.

McMackin PM, Griffin SR, Riley FP, Gulati S, Debono NE, Raghunandan A, Lopez JM, Hirsa AH. Simulated Microgravity in the Ring-sheared Drop. NPJ Microgravity. 2020;6:2.

The ring-sheared drop is a module for the International Space Station to study sheared fluid interfaces and their influence on amyloid fibril formation. A 2.54-cm diameter drop is constrained by a stationary sharp-edged ring at some latitude and sheared by the rotation of another ring in the other hemisphere. Shearing motion is conveyed primarily by the action of surface shear viscosity. Here, we simulate microgravity in the laboratory using a density-matched liquid surrounding the drop. Upon shearing, the drop’s deformation away from spherical is found to be a result of viscous and inertial forces balanced against the capillary force. We also present evidence that the deformation increases with increasing surface shear viscosity.

Di Trani N, Pimpinelli A, Grattoni A. Finite-size Charged Species Diffusion and pH Change in Nanochannels. ACS Appl Mater Interfaces. 2020;12:10.

Molecular transport through nanofluidic structures exhibits properties that are unique at the nanoscale. The high surface-to-volume ratio of nanometer-sized confined spaces renders particle interactions with the surface of central importance. The electrical double layer (EDL) at the solid-liquid interface of charged surfaces, generates an enrichment of counterions and the exclusion of co-ions that lead to a change in their diffusivity. In addition, the diffusive transport is altered by steric and hydrodynamic interactions between fluid molecules and the boundaries. An extensive body of literature investigates molecular transport at the nanoscale. However, most studies account for ionic species as point charges, severely limiting the applicability of results to 'large' nanofluidic systems. Moreover, and even more importantly, the change of pH in the nanoconfined region inside nanochannels has been completely overlooked. Corroborated by experimental data, here we present an all-encompassing analysis of molecular diffusion from the micro- to the ultra-nanoscale. While accounting for finite-size ions, we compute self-consistently the pH inside the channels. Surprisingly, we found that the concentration of ions + can change by more than 2 orders of magnitude compared to the bulk, hugely affecting molecular transport. Further, we found that counterions exhibit both enrichment and exclusion, depending on the size of nanochannels. Achieving a greater understanding of the effective transport properties of fluids at the nanoscale will fill the gap in knowledge that still limits the development of innovative systems for medicine and industrial applications alike.

Choi SY, Saravia-Butler A, Shirazi-Fard Y, Leveson-Gower D, Stodieck L, Cadena S, Beegle J, Solis S, Ronca A, Globus R. Validation of a New Rodent Experimental System to Investigate Consequences of Long Duration Space Habitation. Sci Rep. 2020;10:2336.

Animal models are useful for exploring the health consequences of prolonged spaceflight. Capabilities were developed to perform experiments in low earth orbit with on-board sample recovery, thereby avoiding complications caused by return to Earth. For NASA's Rodent Research-1 mission, female mice (ten 32 wk C57BL/6NTac; ten 16 wk C57BL/6J) were launched on an unmanned vehicle, then resided on the International Space Station for 21/22d or 37d in microgravity. Mice were euthanized on-orbit, livers and spleens dissected, and remaining tissues frozen in situ for later analyses. Mice appeared healthy by daily video health checks and body, adrenal, and spleen weights of 37d-flight (FLT) mice did not differ from ground controls housed in flight hardware (GC), while thymus weights were 35% greater in FLT than GC. Mice exposed to 37d of spaceflight displayed elevated liver mass (33%) and select enzyme activities compared to GC, whereas 21/22d-FLT mice did not. FLT mice appeared more physically active than respective GC while soleus muscle showed expected atrophy. RNA and enzyme activity levels in tissues recovered on-orbit were of acceptable quality. Thus, this system establishes a new capability for conducting long-duration experiments in space, enables sample recovery on-orbit, and avoids triggering standard indices of chronic stress.

Chen X, Wang H, Yu M, Kim JK, Qi H, Ha P, Jiang W, Chen E, Luo X, Needle RB, Baik L, Yang C, Shi J, Kwak JH, Ting K, Zhang X, Soo C. Cumulative inactivation of Nell-1 in Wnt1 expressing cell lineages results in craniofacial skeletal hypoplasia and postnatal hydrocephalus. Cell Death Differ. 2019;27:1415-1430.

Upregulation of Nell-1 has been associated with craniosynostosis (CS) in humans, and validated in a mouse transgenic Nell-1 overexpression model. Global Nell-1 inactivation in mice by N-ethyl-N-nitrosourea (ENU) mutagenesis results in neonatal lethality with skeletal abnormalities including cleidocranial dysplasia (CCD)-like calvarial bone defects. This study further defines the role of Nell-1 in craniofacial skeletogenesis by investigating specific inactivation of Nell-1 in Wnt1 expressing cell lineages due to the importance of cranial neural crest cells (CNCCs) in craniofacial tissue development. Nell-1flox/flox; Wnt1-Cre (Nell-1Wnt1 KO) mice were generated for comprehensive analysis, while the relevant reporter mice were created for CNCC lineage tracing. Nell-1Wnt1 KO mice were born alive, but revealed significant frontonasal and mandibular bone defects with complete penetrance. Immunostaining demonstrated that the affected craniofacial bones exhibited decreased osteogenic and Wnt/β-catenin markers (Osteocalcin and active-β-catenin). Nell-1-deficient CNCCs demonstrated a significant reduction in cell proliferation and osteogenic differentiation. Active-β-catenin levels were significantly low in Nell-1-deficient CNCCs, but were rescued along with osteogenic capacity to a level close to that of wild-type (WT) cells via exogenous Nell-1 protein. Surprisingly, 5.4% of young adult Nell-1Wnt1 KO mice developed hydrocephalus with premature ossification of the intrasphenoidal synchondrosis and widened frontal, sagittal, and coronal sutures. Furthermore, the epithelial cells of the choroid plexus and ependymal cells exhibited degenerative changes with misplaced expression of their respective markers, transthyretin and vimentin, as well as dysregulated Pit-2 expression in hydrocephalic Nell-1Wnt1 KO mice. Nell-1Wnt1 KO embryos at E9.5, 14.5, 17.5, and newborn mice did not exhibit hydrocephalic phenotypes grossly and/or histologically. Collectively, Nell-1 is a pivotal modulator of CNCCs that is essential for normal development and growth of the cranial vault and base, and mandibles partially via activating the Wnt/β-catenin pathway. Nell-1 may also be critically involved in regulating cerebrospinal fluid homeostasis and in the pathogenesis of postnatal hydrocephalus

Chan A. Taking RAS Research to Space. Cancer.gov. 2019, Dec 17.

On December 5, 2018, I watched the Falcon 9 rocket launch from Cape Canaveral, Florida, on SpaceX CRS-16 mission. A flash of fire, followed by an unrelenting rumbling sound that crescendoes to a deafening roar, shaking the ground and the air. As I watched the rocket ascending and gradually disappearing from my vision, I prayed for the safe docking of the capsule to the International Space Station (ISS), not just because I wanted to make sure the six astronauts on the ISS get their supply of food and water, but also because I had experiments in the capsule! In collaboration with the International Space Station National Laboratory, the NCI RAS Initiative launched a panel of RAS proteins in various conditions to promote crystal growth in microgravity on the International Space Station (ISS). Our goal was to solve protein structures by X-ray crystallography that we could not solve with crystals grown under Earth’s gravity.

Beheshti A, Chakravarty K, Fogle H, Fazelinia H, Silveira WAD, Boyko V, Polo SL, Saravia-Butler AM, Hardiman G, Taylor D, Galazka JM, Costes SV. Multi-omics analysis of multiple missions to space reveal a theme of lipid dysregulation in mouse liver. Sci Rep. 2019 Dec 16;9(1):19195.

Spaceflight has several detrimental effects on the physiology of astronauts, many of which are recapitulated in rodent models. Mouse studies performed on the Space Shuttle showed disruption of lipid metabolism in liver. However, given that these animals were not sacrificed on-orbit and instead returned live to earth, it is unclear if these disruptions were solely induced by space stressors (e.g. microgravity, space radiation) or in part explained by the stress of return to Earth. In this work we analyzed three liver datasets from two different strains of mice (C57BL/6 (Jackson) & BALB/c (Taconic)) flown aboard the International Space Station (ISS). Notably, these animals were sacrificed on-orbit and exposed to varying spaceflight durations (i.e. 21, 37, and 42 days vs 13 days for the Shuttle mice). Oil Red O (ORO) staining showed abnormal lipid accumulation in all space-flown mice compared to ground controls regardless of strain or exposure duration. Similarly, transcriptomic analysis by RNA-sequencing revealed several pathways that were affected in both strains related to increased lipid metabolism, fatty acid metabolism, lipid and fatty acid processing, lipid catabolic processing, and lipid localization. In addition, key upstream regulators were predicted to be commonly regulated across all conditions including Glucagon (GCG) and Insulin (INS). Moreover, quantitative proteomic analysis showed that a number of lipid related proteins were changed in the livers during spaceflight. Taken together, these data indicate that activation of lipotoxic pathways are the result of space stressors alone and this activation occurs in various genetic backgrounds during spaceflight exposures of weeks to months. If similar responses occur in humans, a prolonged change of these pathways may result in the development of liver disease and should be investigated further.

Reichert P, Prosise W, Fischmann TO, Scapin G, Narasimhan C, Spinale A, Polniak R, Yang X, Walsh E, Patel D, Benjamin W, Welch J, Simmons D, Strickland C.. Pembrolizumab Microgravity Crystallization Experimentation. NPJ Microgravity. 2019;5:28.

Crystallization processes have been widely used in the pharmaceutical industry for the manufacture, storage, and delivery of small-molecule and small protein therapeutics. However, the identification of crystallization processes for biologics, particularly monoclonal antibodies, has been prohibitive due to the size and the flexibility of their overall structure. There remains a challenge and an opportunity to utilize the benefits of crystallization of biologics. The research laboratories of Merck Sharp & Dome Corp. (MSD) in collaboration with the International Space Station (ISS) National Laboratory performed crystallization experiments with pembrolizumab (Keytruda®) on the SpaceX-Commercial Resupply Services-10 mission to the ISS. By leveraging microgravity effects such as reduced sedimentation and minimal convection currents, conditions producing crystalline suspensions of homogeneous monomodal particle size distribution (39 μm) in high yield were identified. In contrast, the control ground experiments produced crystalline suspensions with a heterogeneous bimodal distribution of 13 and 102 μm particles. In addition, the flight crystalline suspensions were less viscous and sedimented more uniformly than the comparable ground-based crystalline suspensions. These results have been applied to the production of crystalline suspensions on earth, using rotational mixers to reduce sedimentation and temperature gradients to induce and control crystallization. Using these techniques, we have been able to produce uniform crystalline suspensions (1–5 μm) with acceptable viscosity (<12 cP), rheological, and syringeability properties suitable for the preparation of an injectable formulation. The results of these studies may help widen the drug delivery options to improve the safety, adherence, and quality of life for patients and caregivers.

Wnorowski A, Sharma A, Chen H, Wu H, Shao N-Y, Sayed N, Liu C, Countryman S, Stodieck LS, Rubins KH, Wu SM, Lee PHU, Wu JC. Effects of Spaceflight on Human Induced Pluripotent Stem Cell-derived Cardiomyocyte Structure and Function. Stem Cell Rep. 2019;13:960-979.

With extended stays aboard the International Space Station (ISS) becoming commonplace, there is a need to better understand the effects of microgravity on cardiac function. We utilized human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to study the effects of microgravity on cell-level cardiac function and gene expression. The hiPSC-CMs were cultured aboard the ISS for 5.5 weeks and their gene expression, structure, and functions were compared with ground control hiPSC-CMs. Exposure to microgravity on the ISS caused alterations in hiPSC-CM calcium handling. RNA-sequencing analysis demonstrated that 2,635 genes were differentially expressed among flight, post-flight, and ground control samples, including genes involved in mitochondrial metabolism. This study represents the first use of hiPSC technology to model the effects of spaceflight on human cardiomyocyte structure and function.

Low LA, Giulianotti MA. Tissue Chips in Space: Modeling Human Diseases in Microgravity. Pharm Res. 2019 Dec 17;37(1):8.

Microphysiological systems (MPS), also known as "organs-on-chips" or "tissue chips," leverage recent advances in cell biology, tissue engineering, and microfabrication to create in vitro models of human organs and tissues. These systems offer promising solutions for modeling human physiology and disease in vitro and have multiple applications in areas where traditional cell culture and animal models fall short. Recently, the National Center for Advancing Translational Sciences (NCATS) at the National Institutes of Health (NIH) and the International Space Station (ISS) U.S. National Laboratory have coordinated efforts to facilitate the launch and use of these MPS platforms onboard the ISS. Here, we provide an introduction to the NIH Tissue Chips in Space initiative and an overview of the coordinated efforts between NIH and the ISS National Laboratory. We also highlight the current progress in addressing the scientific and technical challenges encountered in the development of these ambitious projects. Finally, we describe the potential impact of the Tissue Chips in Space program for the MPS field as well as the wider biomedical and health research communities.

Giulianotti MA, Low LA. Pharmaceutical Research Enabled through Microgravity: Perspectives on the Use of the International Space Station U.S. National Laboratory. Pharm Res. 2020;37:1.

The International Space Station (ISS) is a marvel of international partnership and engineering. With more than 10 years of assembly led by five space agencies representing 15 countries, the ISS has now been operating and supporting a continuous human presence in space for nearly 20 years, hosting more than 200 people from 18 countries. In addition to serving as a crewed spacecraft and satellite in low Earth orbit (LEO), the ISS is a one-of-a-kind platform for research that takes advantage of the unique space environment to accelerate discovery and explore human limits (1). Research on the ISS helps NASA and international partners reduce the risk of human exploration beyond Earth’s orbit—but it also enables biomedical discovery with direct application to technologies and therapeutics that impact life on Earth. The vision to leverage space for Earth-based benefits was realized when the U.S. Congress designated the ISS as a U.S. National Laboratory in 2005, allowing for increased utilization of the ISS by a broad range of users focused on Earth-based benefits (Fig. 1). In this commentary, we briefly summarize how the ISS and its predecessors paved the way for drug discovery in space, discuss how the ISS National Laboratory is engaged in expanding this research, and provide a perspective on the future industrialization of space to improve medical innovation and drug discovery that benefits life on Earth. We focus on three examples to illustrate the benefits of in-orbit pharmaceutical research: rodent research, tissue chips, and macromolecular crystal growth.

Amselem S. Remote Controlled Autonomous Microgravity Lab Platforms for Drug Research in Space. Pharm Res. 2019, 36:183-198.

Research conducted in microgravity conditions has the potential to yield new therapeutics, as advances can be achieved in the absence of phenomena such as sedimentation, hydrostatic pressure and thermally-induced convection. The outcomes of such studies can significantly contribute to many scientific and technological fields, including drug discovery. This article reviews the existing traditional microgravity platforms as well as emerging ideas for enabling microgravity research focusing on SpacePharma's innovative autonomous remote-controlled microgravity labs that can be launched to space aboard nanosatellites to perform drug research in orbit. The scientific literature is reviewed and examples of life science fields that have benefited from studies in microgravity conditions are given. These include the use of microgravity environment for chemical applications (protein crystallization, drug polymorphism, self-assembly of biomolecules), pharmaceutical studies (microencapsulation, drug delivery systems, behavior and stability of colloidal formulations, antibiotic drug resistance), and biological research, including accelerated models for aging, investigation of bacterial virulence , tissue engineering using organ-on-chips in space, enhanced stem cells proliferation and differentiation.

Robertson MJ, Raghunathan S, Potaman VN, Zhang F, Stewart MD, McConnell BK, Schwartz RJ. CRISPR-Cas9-induced IGF1 Gene Activation as a Tool for Enhancing Muscle Differentiation via Multiple Isoform Expression. FASEB J. 2020;34:555-570.

Muscle wasting, or muscle atrophy, can occur with age, injury, and disease; it affects the quality of life and complicates treatment. Insulin-like growth factor 1 (IGF1) is a key positive regulator of muscle mass. The IGF1/Igf1 gene encodes multiple protein isoforms that differ in tissue expression, potency, and function, particularly in cel-lular proliferation and differentiation, as well as in systemic versus localized signal-ing. Genome engineering is a novel strategy for increasing gene expression and has the potential to recapitulate the diverse biology seen in IGF1 signaling through the overexpression of multiple IGF1 isoforms. Using a CRISPR-Cas9 gene activation approach, we showed that the expression of multiple IGF1 or Igf1 mRNA variants can be increased in human and mouse skeletal muscle myoblast cell lines using a sin-gle-guide RNA (sgRNA). We found increased IGF1 protein levels in the cell culture media and increased cellular phosphorylation of AKT1, the main effector of IGF1 signaling. We also showed that the expression of Class 1 or Class 2 mRNA variants can be selectively increased by changing the sgRNA target location. The expression of multiple IGF1 or Igf1 mRNA transcript variants in human and mouse skeletal muscle myoblasts promoted myotube differentiation and prevented dexamethasone-induced atrophy in myotubes in vitro. Our findings suggest that this novel approach for enhancing IGF1 signaling has potential therapeutic applications for treating skel-etal muscle atrophy.

Tagle, DA. The NIH Microphysiological Systems Program: Developing In Vitro Tools for Safety and Efficacy in Drug Development. Curr Opp Pharmacol. 2019;48:146-154.

Approximately 30% of drugs have failed in human clinical trials due to adverse reactions despite promising pre-clinical studies, and another 60% fail due to lack of efficacy. One of the major causes in the high attrition rate is the poor predictive value of current preclinical models used in drug development despite promising pre-clinical studies in 2-D cell culture and animal models. Microphysiological Systems or Tissue Chips are bioengineered microfluidic cell culture systems seeded with primary or stem cells that mimic the histoarchitecture, mechanics and physiological response of functional units of organs and organ systems. These platforms are useful tools for predictive toxicology and efficacy assessments of candidate therapeutics. Implementation of tissue chips in drug development requires effective partnerships with stakeholders, such as regulatory agencies, pharmaceutical companies, patient groups, and other government agencies. Tissue chips are also finding utility in studies in precision medicine, environmental exposures, reproduction and development, infectious diseases, microbiome and countermeasures agents.

Yeung CK, Koenig P, Countryman S, Thummel KE, Himmelfarb J, Kelly EJ. Tissue Chips in Space—Challenges and Opportunities. Clin Trans Sci. 2019, Sept 16.

The microgravity environment results in a multitude of physiological changes associated with aging and altered organ function. Deployment of microphysiological systems, also known as “tissue chips” to the International Space Station United States National Laboratory, will allow the study of these changes at the cellular/molecular level. The goal of these studies is to expand understanding of age‐related conditions to improve human health on earth.

Vowinckel B, Biegert E, Luzzatto-Fegiz P, Meiburg E. Consolidation of Freshly Deposited Cohesive and Noncohesive Sediment: Particle-resolved Simulations. Phys. Rev. Fluids. 2019, 4;074305.

We analyze the consolidation of freshly deposited cohesive and noncohesive sediment by means of particle-resolved direct Navier-Stokes simulations based on the immersed boundary method. The computational model is parametrized by material properties and does not involve any arbitrary calibrations. We obtain the stress balance of the fluid-particle mixture from first principles and link it to the classical effective stress concept. The detailed data sets obtained from our simulations allow us to evaluate all terms of the derived stress balance. We compare the settling of cohesive sediment to its noncohesive counterpart, which corresponds to the settling of the individual primary particles. The simulation results yield a complete parametrization of the Gibson equation, which has been the method of choice to analyze self-weight consolidation.

Maupin KA, Childress P, Brinker A, Khan F, Abeysekera I, Aguilar IN, Olivos DJ 3rd, Adam G, Savaglio MK, Ganesh V, Gorden R, Mannfeld R, Beckner E, Horan DJ, Robling AG, Chakraborty N, Gautam A, Hammamieh R, Kacena MA. Skeletal Adaptations in Young Male Mice After 4 Weeks Aboard the International Space Station. NPJ Microgravity. 2019, Sep 24;5:21.

Gravity has an important role in both the development and maintenance of bone mass. This is most evident in the rapid and intense bone loss observed in both humans and animals exposed to extended periods of microgravity in spaceflight. Here, cohabitating 9-week-old male C57BL/6 mice resided in spaceflight for ~4 weeks. A skeletal survey of these mice was compared to both habitat matched ground controls to determine the effects of microgravity and baseline samples in order to determine the effects of skeletal maturation on the resulting phenotype. We hypothesized that weight-bearing bones would experience an accelerated loss of bone mass compared to non-weight-bearing bones, and that spaceflight would also inhibit skeletal maturation in male mice. As expected, spaceflight had major negative effects on trabecular bone mass of the following weight-bearing bones: femur, tibia, and vertebrae. Interestingly, as opposed to the bone loss traditionally characterized for most weight-bearing skeletal compartments, the effects of spaceflight on the ribs and sternum resembled a failure to accumulate bone mass. Our study further adds to the insight that gravity has site-specific influences on the skeleton.

Dadwal UC, Maupin KA, Zamarioli A, Tucker A, Harris JS, Fischer JP, Rytlewski JD, Scofield DC, Wininger AE, Bhatti FUR, Alvarez M, Childress PJ, Chakraborty N, Gautam A, Hammamieh R, Kacena MA. The effects of spaceflight and fracture healing on distant skeletal sites. Sci Rep. 2019 Aug 6;9(1):11419. doi: 10.1038/s41598-019-47695-3.

Spaceflight results in reduced mechanical loading of the skeleton, which leads to dramatic bone loss. Low bone mass is associated with increased fracture risk, and this combination may compromise future, long-term, spaceflight missions. Here, we examined the systemic effects of spaceflight and fracture surgery/healing on several non-injured bones within the axial and appendicular skeleton. Forty C57BL/6, male mice were randomized into the following groups: (1) Sham surgery mice housed on the earth (Ground + Sham); (2) Femoral segmental bone defect surgery mice housed on the earth (Ground + Surgery); (3) Sham surgery mice housed in spaceflight (Flight + Sham); and (4) Femoral segmental bone defect surgery mice housed in spaceflight (Flight + Surgery). Mice were 9 weeks old at the time of launch and were euthanized approximately 4 weeks after launch. Micro-computed tomography (μCT) was used to evaluate standard bone parameters in the tibia, humerus, sternebra, vertebrae, ribs, calvarium, mandible, and incisor. One intriguing finding was that both spaceflight and surgery resulted in virtually identical losses in tibial trabecular bone volume fraction, BV/TV (24-28% reduction). Another important finding was that surgery markedly changed tibial cortical bone geometry. Understanding how spaceflight, surgery, and their combination impact non-injured bones will improve treatment strategies for astronauts and terrestrial humans alike.

Williams IM, Wu JC. Generation of Endothelial Cells from Human Pluripotent Stem Cells. Arterioscler Thromb Vascr Biol. 2019, 39(7):1317-1329.

Endothelial cells (ECs) are critical for several aspects of cardiovascular disease therapy, including vascular regeneration, personalized drug development, and tissue engineering. Human pluripotent stem cells (hPSCs) afford us with an unprecedented opportunity to produce virtually unlimited quantities of human ECs. In this review, we highlight key developments and outstanding challenges in our ability to derive ECs de novo from hPSCs. Furthermore, we consider strategies for recapitulating the vessel- and tissue-specific functional heterogeneity of ECs in vitro. Finally, we discuss ongoing attempts to utilize hPSC-derived ECs and their progenitors for various therapeutic applications. Continued progress in generating hPSC-derived ECs will profoundly enhance our ability to discover novel drug targets, revascularize ischemic tissues, and engineer clinically relevant tissue constructs. Visual Overview- An online visual overview is available for this article.

Ronca AE, Moyer EL, Talyansky Y, Lowe M, Padmanabhan S, Choi S, Gong C, Cadena SM, Stodieck, L, Globus RK. Behavior of mice Aboard the International Space Station. Sci Rep. 2019;28;9(1),4717.

Interest in space habitation has grown dramatically with planning underway for the first human transit to Mars. Despite a robust history of domestic and international spaceflight research, understanding behavioral adaptation to the space environment for extended durations is scant. Here we report the first detailed behavioral analysis of mice flown in the NASA Rodent Habitat on the International Space Station (ISS). Following 4-day transit from Earth to ISS, video images were acquired on orbit from 16- and 32-week-old female mice. Spaceflown mice engaged in a full range of species-typical behaviors. Physical activity was greater in younger flight mice as compared to identically-housed ground controls, and followed the circadian cycle. Within 9–11 days after launch, younger (but not older), mice began to exhibit distinctive circling or ‘race-tracking’ behavior that evolved into a coordinated group activity. Organized group circling behavior unique to spaceflight may represent stereotyped motor behavior, rewarding effects of physical exercise, or vestibular sensation produced via self-motion. Affording mice the opportunity to grab and run in the RH resembles physical activities that the crew participate in routinely. Our approach yields a useful analog for better understanding human responses to spaceflight, providing the opportunity to assess how physical movement influences responses to microgravity.

Camberos V, Baio J, Bailey L, Hasaniya N, Lopez LV, Kearns-Jonker M. Effects of Spaceflight and Simulated Microgravity on YAP1 Expression in Cardiovascular Progenitors: Implications for Cell-Based Repair. Int. J. Mol. Sci. 2019;20(11), 2472.

Spaceflight alters many processes of the human body including cardiac function and cardiac progenitor cell behavior. The mechanism behind these changes remains largely unknown; however, simulated microgravity devices are making it easier for researchers to study the effects of microgravity. To study the changes that take place in cardiac progenitor cells in microgravity environments, adult cardiac progenitor cells were cultured aboard the International Space Station (ISS) as well as on a clinostat and examined for changes in Hippo signaling, a pathway known to regulate cardiac development. Cells cultured under microgravity conditions, spaceflight-induced or simulated, displayed upregulation of downstream genes involved in the Hippo pathway such as YAP1 and SOD2. YAP1 is known to play a role in cardiac regeneration which led us to investigate YAP1 expression in a sheep model of cardiovascular repair. Additionally, to mimic the effects of microgravity, drug treatment was used to induce Hippo related genes as well as a regulator of the Hippo pathway, miRNA-302a. These studies provide insight into the changes that occur in space and how the effects of these changes relate to cardiac regeneration studies.

Cadena SM, Zhang Y, Fang J, Brachat S, Kuss P, Giorgetti E, Stodieck LS, Kneissel M, Glass DJ. Skeletal muscle in MuRF1 null mice is not spared in low-gravity conditions, indicating atrophy proceeds by unique mechanisms in space. Sci Rep. 2019;28;9(1), 9397.

Microgravity exposure is associated with loss of muscle mass and strength. The E3 ubiquitin ligase MuRF1 plays an integral role in degrading the contractile apparatus of skeletal muscle; MuRF1 null (KO) mice have shown protection in ground-based models of muscle atrophy. In contrast, MuRF1 KO mice subjected to 21 days of microgravity on the International Space Station (ISS) were not protected from muscle atrophy. In a time course experiment microgravity-induced muscle loss on the ISS showed MuRF1 gene expression was not upregulated. A comparison of the soleus transcriptome profiles between spaceflight and a publicly available data set for hindlimb suspension, a claimed surrogate model of microgravity, showed only marginal commonalities between the models. These findings demonstrate spaceflight induced atrophy is unique, and that understanding of effects of space requires study situated beyond the Earth’s mesosphere.