Simulated microgravity attenuates myogenesis and contractile function of 3D engineered skeletal muscle tissues

While the effects of microgravity on inducing skeletal muscle atrophy have been extensively studied, the impacts of microgravity on myogenesis and its mechanisms remain unclear. In this study, we developed a microphysiological system of engineered muscle tissue (EMT) fabricated using a collagen / Matrigel composite hydrogel and murine skeletal myoblasts. This 3D EMT model allows non-invasive quantitative assessment of contractile function. After applying a 7-day differentiation protocol to induce myotube formation, the EMTs clearly exhibited sarcomerogenesis, myofilament formation, and synchronous twitch and tetanic contractions with electrical stimuli. Using this 3D EMT system, we investigated the effects of simulated microgravity at 10-3 G on myogenesis and contractile function utilizing a random positioning machine. EMTs cultured for 5 days in simulated microgravity exhibited significantly reduced contractile forces, myofiber size, and differential expression of muscle contractile, myogenesis regulatory, and mitochondrial biogenesis-related proteins. These results indicate simulated microgravity attenuates myogenesis, resulting in impaired muscle function.

Biomanufacturing of 3D Tissue Constructs in Microgravity and their Applications in Human Pathophysiological Studies

The growing interest in bioengineering in-vivo-like 3D functional tissues has led to novel approaches to the biomanufacturing process as well as expanded applications for these unique tissue constructs. Microgravity, as seen in spaceflight, is a unique environment that may be beneficial to the tissue-engineering process but cannot be completely replicated on Earth. Additionally, the expense and practical challenges of conducting human and animal research in space make bioengineered microphysiological systems an attractive research model. In this review, published research that exploits real and simulated microgravity to improve the biomanufacturing of a wide range of tissue types as well as those studies that use microphysiological systems, such as organ/tissue chips and multicellular organoids, for modeling human diseases in space are summarized. This review discusses real and simulated microgravity platforms and applications in tissue-engineered microphysiological systems across three topics: 1) application of microgravity to improve the biomanufacturing of tissue constructs, 2) use of tissue constructs fabricated in microgravity as models for human diseases on Earth, and 3) investigating the effects of microgravity on human tissues using biofabricated in vitro models. These current achievements represent important progress in understanding the physiological effects of microgravity and exploiting their advantages for tissue biomanufacturing.

X-linked hydrocephalus genes: Their proximity to telomeres and high a + T content compared to Parkinson's disease

Proximity to telomeres (i) and high adenine and thymine (A + T) content (ii) are two factors associated with high mutation rates in human chromosomes. We have previously shown that >100 human genes when mutated to cause congenital hydrocephalus (CH) meet either factor (i) or (ii) at 91% matching, while two factors are poorly satisfied in human genes associated with familial Parkinson's disease (fPD) at 59%. Using the sets of mouse, rat, and human chromosomes, we found that 7 genes associated with CH were located on the X chromosome of mice, rats, and humans. However, genes associated with fPD were in different autosomes depending on species. While the contribution of proximity to telomeres in the autosome was comparable in CH and fPD, high A + T content played a pivotal contribution in X-linked CH (43% in all three species) than in fPD (6% in rodents or 13% in humans). Low A + T content found in fPD cases suggests that PARK family genes harbor roughly 3 times higher chances of methylations in CpG sites or epigenetic changes than X-linked genes.

Mutability of druggable kinases and pro-inflammatory cytokines by their proximity to telomeres and A+T content

Mutations of protein kinases and cytokines are common and can cause cancer and other diseases. However, our understanding of the mutability in these genes remains rudimentary. Therefore, given previously known factors which are associated with high mutation rates, we analyzed how many genes encoding druggable kinases match (i) proximity to telomeres or (ii) high A+T content. We extracted this genomic information using the National Institute of Health Genome Data Viewer. First, among 129 druggable human kinase genes studied, 106 genes satisfied either factors (i) or (ii), resulting in an 82% match. Moreover, a similar 85% match rate was found in 73 genes encoding pro-inflammatory cytokines of multisystem inflammatory syndrome in children. Based on these promising matching rates, we further compared these two factors utilizing 20 de novo mutations of mice exposed to space-like ionizing radiation, in order to determine if these seemingly random mutations were similarly predictable with this strategy. However, only 10 of these 20 murine genetic loci met (i) or (ii), leading to only a 50% match. When compared with the mechanisms of top-selling FDA approved drugs, this data suggests that matching rate analysis on druggable targets is feasible to systematically prioritize the relative mutability-and therefore therapeutic potential-of the novel candidates.

How businesses are working together to deliver NASA/JPL-designed ventilators to the world in the fight against COVID-19

In response to the COVID-19 pandemic, NASA Jet Propulsion Laboratory (JPL) engineers had embarked on an ambitious project to design a reliable, easy-to-use, and low-cost ventilator that was made of readily available parts to address the unexpected global shortage of these lifesaving devices. After successfully designing and building the VITAL (Ventilator Intervention Technology Accessible Locally) ventilator in record time, FDA Emergency Use Authorization (EUA) was obtained and then the license to manufacture and sell these ventilators was made available to select companies through a competitive process. STARK Industries, LLC (STARK), located in Columbus, OH, USA, was one of only eight U.S. companies to be selected to receive this worldwide license. Motivated by its mission to improve human health and well-being through innovated medical technologies, STARK accepted the challenge of further developing the VITAL technology and manufacturing the ventilators in large quantities and making them available to those in need around the world. To this end, Spiritus Medical, Inc (Spiritus) was spun off from STARK to focus on the ventilator business. Through collaborative efforts with various corporate, academic, governmental, and non-profit partners, Spiritus was able to successfully begin manufacturing and selling its ventilators. Due to its low-cost nature and its straightforward design, this ventilator is ideal for use in developing countries where ventilators are in short supply and affordability is a major consideration. This is a story of how NASA's ingenuity, based on space-based know-how and experience, was used to rapidly design this innovative ventilator. And by forging partnerships with highly qualified and motivated partners such as STARK and Spiritus, NASA has succeeded in translating this work into technology that could potentially save thousands of lives in the fight against the COVID-19 pandemic.

PDMS-PEG Block Copolymer and Pretreatment for Arresting Drug Absorption in Microphysiological Devices

Poly(dimethylsiloxane) (PDMS) is a commonly used polymer in organ-on-a-chip devices and microphysiological systems. However, due to its hydrophobicity and permeability, it absorbs drug compounds, preventing accurate drug screening applications. Here, we developed an effective and facile method to prevent the absorption of drugs by utilizing a PDMS-PEG block copolymer additive and drug pretreatment. First, we incorporated a PDMS-PEG block copolymer into PDMS to address its inherent hydrophobicity. Next, we addressed the permeability of PDMS by eliminating the concentration gradient via pretreatment of the PDMS with the drug prior to experimentally testing drug absorption. The combined use of a PDMS-PEG block copolymer with drug pretreatment resulted in a mean reduction of drug absorption by 91.6% in the optimal condition. Finally, we demonstrated that the proposed method can be applied to prevent drug absorption in a PDMS-based cardiac microphysiological system, enabling more accurate drug studies.

Factors mediating spaceflight-induced skeletal muscle atrophy

Skeletal muscle atrophy is a well-known consequence of spaceflight. Because of the potential significant impact of muscle atrophy and muscle dysfunction on astronauts and to their mission, a thorough understanding of the mechanisms of this atrophy and the development of effective countermeasures is critical. Spaceflight-induced muscle atrophy is similar to atrophy seen in many terrestrial conditions, and therefore our understanding of this form of atrophy may also contribute to the treatment of atrophy in humans on Earth. The unique environmental features humans encounter in space include the weightlessness of microgravity, space radiation, and the distinctive aspects of living in a spacecraft. The disuse and unloading of muscles in microgravity are likely the most significant factors that mediate spaceflight-induced muscle atrophy, and have been extensively studied and reviewed. However, there are numerous other direct and indirect effects on skeletal muscle that may be contributing factors to the muscle atrophy and dysfunction seen as a result of spaceflight. This review offers a novel perspective on the issue of muscle atrophy in space by providing a comprehensive overview of the unique aspects of the spaceflight environment and the various ways in which they can lead to muscle atrophy. We systematically review the potential contributions of these different mechanisms of spaceflight-induced atrophy and include findings from both actual spaceflight and ground-based models of spaceflight in humans, animals, and in vitro studies.

Cardiac effects and clinical applications of MG53

Heart disease remains the leading cause of mortality globally, so further investigation is required to identify its underlying mechanisms and potential targets for treatment and prevention. Mitsugumin 53 (MG53), also known as TRIM72, is a TRIM family protein that was found to be involved in cell membrane repair and primarily found in striated muscle. Its role in skeletal muscle regeneration and myogenesis has been well documented. However, accumulating evidence suggests that MG53 has a potentially protective role in heart tissue, including in ischemia/reperfusion injury of the heart, cardiomyocyte membrane injury repair, and atrial fibrosis. This review summarizes the regulatory role of MG53 in cardiac tissues, current debates regarding MG53 in diabetes and diabetic cardiomyopathy, as well as highlights potential clinical applications of MG53 in treating cardiac pathologies.

Multi-Cellular Functions of MG53 in Muscle Calcium Signaling and Regeneration

Since its identification in 2009, multiple studies have indicated the importance of MG53 in muscle physiology. The protein is produced in striated muscles but has physiologic implications reaching beyond the confines of striated muscles. Roles in muscle regeneration, calcium homeostasis, excitation-contraction coupling, myogenesis, and the mitochondria highlight the protein’s wide-reaching impact. Numerous therapeutic applications could potentially emerge from these physiologic roles. This review summarizes the current literature regarding the role of MG53 in the skeletal muscle. Therapeutic applications are discussed.

Anticoagulation management following left ventricular assist device implantation is similar across all provider strategies

OBJECTIVES

Thromboembolic and bleeding events are potential complications following left ventricular assist device implantation. A tight control of the international normalized ratio (INR) is believed to be crucial in the reduction of postimplant complications. There is significant variability among institutions as to whether a device implanting centre should be managing the INR. In this study, we evaluated the effect of INR management strategies in maintaining a therapeutic INR.

METHODS

A retrospective review was utilized to identify patients implanted with either the HeartMate II or the HeartWare HVAD between January 2011 and February 2016. Patients were stratified into 4 groups based on the post-discharge INR management strategy: outside hospital system anticoagulation clinic, outside hospital primary care provider, implanting centre anticoagulation clinic or implanting centre ventricular assist device office. The INR data were collected and analysed for both the early (discharge, 7, 14, 21 and 30 days) and late (3, 6, 9 and 12 months) postoperative periods.

RESULTS

There were 163 patients identified during the study period who met the study inclusion criteria: 49 (30%) patients were managed by an outside hospital system anticoagulation clinic, 59 (36.2%) patients by an outside hospital physician/primary care provider, 22 (13.5%) patients by the implanting centre anticoagulation clinic and 33 (20.2%) patients by the implanting centre ventricular assist device office. There were no statistically significant differences found between management strategies across all time points.

CONCLUSIONS

There was no statistically significant difference found between the management strategies examined. Regardless of the chosen INR management strategy, patients have similar INR values and postoperative outcomes.

Zinc in Wound Healing Modulation

Wound care is a major healthcare expenditure. Treatment of burns, surgical and trauma wounds, diabetic lower limb ulcers and skin wounds is a major medical challenge with current therapies largely focused on supportive care measures. Successful wound repair requires a series of tightly coordinated steps including coagulation, inflammation, angiogenesis, new tissue formation and extracellular matrix remodelling. Zinc is an essential trace element (micronutrient) which plays important roles in human physiology. Zinc is a cofactor for many metalloenzymes required for cell membrane repair, cell proliferation, growth and immune system function. The pathological effects of zinc deficiency include the occurrence of skin lesions, growth retardation, impaired immune function and compromised would healing. Here, we discuss investigations on the cellular and molecular mechanisms of zinc in modulating the wound healing process. Knowledge gained from this body of research will help to translate these findings into future clinical management of wound healing.

Increased resource use in lung transplant admissions in the lung allocation score era

RATIONALE

In 2005, the lung allocation score (LAS) was implemented to prioritize organ allocation to minimize waiting-list mortality and maximize 1-year survival. It resulted in transplantation of older and sicker patients without changing 1-year survival. Its effect on resource use is unknown.

OBJECTIVES

To determine changes in resource use over time in lung transplant admissions.

METHODS

Solid organ transplant recipients were identified within the Nationwide Inpatient Sample (NIS) data from 2000 to 2011. Joinpoint regression methodology was performed to identify a time point of change in mean total hospital charges among lung transplant and other solid-organ transplant recipients. Two temporal lung transplant recipient cohorts identified by joinpoint regression were compared for baseline characteristics and resource use, including total charges for index hospitalization, charges per day, length of stay, discharge disposition, tracheostomy, and need for extracorporeal membrane oxygenation.

MEASUREMENTS AND MAIN RESULTS

A significant point of increased total hospital charges occurred for lung transplant recipients in 2005, corresponding to LAS implementation, which was not seen in other solid-organ transplant recipients. Total transplant hospital charges increased by 40% in the post-LAS cohort ($569,942 [$53,229] vs. $407,489 [$28,360]) along with an increased median length of stay, daily charges, and discharge disposition other than to home. Post-LAS recipients also had higher post-transplant use of extracorporeal membrane oxygenation (odds ratio, 2.35; 95% confidence interval, 1.56-3.55) and higher incidence of tracheostomy (odds ratio, 1.52; 95% confidence interval, 1.22-1.89).

CONCLUSIONS

LAS implementation is associated with a significant increase in resource use during index hospitalization for lung transplant.

Heart transplantation with or without prior mechanical circulatory support in adults with congenital heart disease

OBJECTIVES

Recent analyses establish that heart transplantation is increasing among adults with congenital heart disease (ACHD), but the effects of pretransplant mechanical circulatory support (MCS) on perioperative and post-transplant outcomes have not been examined in the ACHD population.

METHODS

Scientific Registry of Transplant Recipients data on all adult heart transplants from September 1987 to September 2012 (n = 47 160) were classified based on primary diagnosis codes as CHD or non-CHD and MCS or non-MCS. Demographic, procedural, outcome and survival variables were compared between MCS and non-MCS ACHD patient groups.

RESULTS

MCS was used in 83 (6.8%) ACHD patients compared with 8625 (18.8%) patients without CHD (P < 0.001). MCS as a fraction of ACHD transplants increased over time (P = 0.002). MCS patients spent more time on the wait list, had a higher baseline serum creatinine and were more likely to be male, status 1A, hospitalized, in the ICU and/or on a ventilator prior to transplant. However, MCS patients experienced equivalent short-term survival (30-day mortality = 10.8% in MCS vs 13.5% in non-MCS, P = 0.62) and overall survival by Kaplan-Meier analysis (P = 0.57). MCS patients had a longer post-transplant length of stay and were more likely to be transfused, but otherwise had no significant differences in adverse outcomes.

CONCLUSIONS

MCS is less commonly used in adult CHD patients compared with all patients undergoing heart transplant, but has been increasing over time. Within the ACHD population, patients with MCS have a higher risk profile, but except for increased transfusion rate and longer length of stay, do not experience less favourable post-transplant outcomes.

Skeletal muscle atrophy in bioengineered skeletal muscle: a new model system

Skeletal muscle atrophy has been well characterized in various animal models, and while certain pathways that lead to disuse atrophy and its associated functional deficits have been well studied, available drugs to counteract these deficiencies are limited. An ex vivo tissue-engineered skeletal muscle offers a unique opportunity to study skeletal muscle physiology in a controlled in vitro setting. Primary mouse myoblasts isolated from adult muscle were tissue engineered into bioartificial muscles (BAMs) containing hundreds of aligned postmitotic muscle fibers expressing sarcomeric proteins. When electrically stimulated, BAMs generated measureable active forces within 2-3 days of formation. The maximum isometric tetanic force (Po) increased for ∼3 weeks to 2587±502 μN/BAM and was maintained at this level for greater than 80 days. When BAMs were reduced in length by 25% to 50%, muscle atrophy occurred in as little as 6 days. Length reduction resulted in significant decreases in Po (50.4%), mean myofiber cross-sectional area (21.7%), total protein synthesis rate (22.0%), and noncollagenous protein content (6.9%). No significant changes occurred in either the total metabolic activity or protein degradation rates. This study is the first in vitro demonstration that length reduction alone can induce skeletal muscle atrophy, and establishes a novel in vitro model for the study of skeletal muscle atrophy.

Surgical treatment of an amniotic fluid embolism with cardiopulmonary collapse

Amniotic fluid embolism is a rare but devastating condition associated with a very high rate of morbidity and mortality. The treatment has traditionally been aggressive supportive care. We report a case of a term pregnant woman with complete cardiovascular collapse secondary to a paradoxical amniotic fluid embolism. The embolism was seen on transesophageal echocardiogram during an emergency Cesarean section as a free-floating interatrial clot through a patent foramen ovale. She was subsequently and successfully treated with immediate cardiopulmonary bypass, thromboembolectomy, and closure of the patent foramen ovale.

Effect of sustained-release PDGF and TGF-beta on cyclophosphamide-induced impaired wound healing

BACKGROUND

Proper wound healing is pivotal to successful surgical outcomes. Previous studies have shown that growth factors can be used to enhance tissue repair under impaired healing conditions. However, because of limited delivery methods, the growth factors in these studies were delivered either topically or as a single local administration.

METHODS

Sixty Sprague-Dawley rats were divided equally into five groups and served as untreated normal controls or were implanted subcutaneously with a novel sustained-release drug delivery system through a dorsal incisional wound. This system delivered either transforming growth factor (TGF)-beta alone, platelet-derived growth factor (PDGF) alone, or TGF-beta and PDGF in combination, or served as unloaded sham controls. Wound healing was impaired in all treated rats by the administration of cyclophosphamide on days 1, 3, and 5. Wound tensile breaking strength was determined on days 4, 7, and 14.

RESULTS

Sustained release of either TGF-beta or PDGF alone not only failed to improve the healing of cyclophosphamide-induced impaired wound healing but resulted in a paradoxical decrease in wound tensile breaking strength by day 7. However, the combined delivery of both TGF-beta and PDGF improved wound healing and significantly increased wound tensile breaking strength by day 7.

CONCLUSIONS

Sustained-release delivery of TGF-beta and PDGF in combination, but not separately, by a subcutaneously implanted drug delivery system significantly improves cyclophosphamide-induced impaired wound healing in rats.