The Effects of APOE Alleles, Cognitive Activities, and Social Activities on Cognitive Decline in African Americans.

OBJECTIVE: Older African Americans are among the fastest growing populations, yet are underrepresented in studies examining risk factors related to decline. The present study examines whether biological factors (APOE alleles) interact with behavioral factors including cognitive activities (e.g., reading, playing games) and social activities (e.g., participating in social groups) to predict cognitive decline in African Americans. METHODS: 734 African American adults from the Minority Aging Research Study (MARS), aged 65 and older (with no known dementia at the time of enrollment) underwent annual cognitive testing for up to 10 years. At baseline, APOE status was determined and participants reported their frequency of participation in social and cognitive activities. Structural equation modelling was used to examine the effects of APOE, cognitive activities, and social activities on cognitive decline, and their interaction effects over a ten-year period. RESULTS: The number of APOE alleles had an effect on cognitive decline, such that a greater number of APOE4 alleles was associated with greater cognitive decline, whereas a greater number of APOE2 alleles was associated with less cognitive decline. Cognitive and social activities did not interact with APOE count to predict cognitive decline, however, APOE4 and social activities had additive, independent effects on cognitive decline. DISCUSSION: Results replicate prior findings linking APOE4 to cognitive decline and highlight the importance of APOE2 and social activities in delaying cognitive decline in African Americans.

Advancing Cartilage Tissue Engineering: A Review of 3D Bioprinting Approaches and Bioink Properties.

Articular cartilage is crucial in human physiology, and its degeneration poses a significant public health challenge. While recent advancements in 3D bioprinting and tissue engineering show promise for cartilage regeneration, there remains a gap between research findings and clinical application. This review critically examines the mechanical and biological properties of hyaline cartilage, along with current 3D manufacturing methods and analysis techniques. Moreover, we provide a quantitative synthesis of bioink properties used in cartilage tissue engineering. After screening 181 initial works, 33 studies using extrusion bioprinting were analyzed and synthesized, presenting results that indicate the main materials, cells, and methods utilized for mechanical and biological evaluation. Altogether, this review motivates the standardization of mechanical analyses and biomaterial assessments of 3D bioprinted constructs to clarify their chondrogenic potential.

Novosorb Biodegradable Temporizing Matrix for Reconstruction of Complex Upper-Extremity Wounds.

Purpose: Dermal matrices can be used in management of upper-extremity wounds to create vascularized wound beds in the setting of exposed bone or tendon. Early outcomes of Novosorb biodegradable temporizing matrix (BTM) demonstrated success when used in the treatment of complex wounds. We hypothesize that BTM is effective for reconstruction of upper-extremity wounds. Methods: A retrospective review was performed for patients who underwent reconstruction of upper-extremity wounds with BTM between January 2017 and May 2022. Results: In total, 51 patients (39 males and 12 females) were included. Wound etiology included trauma (n = 30), burn (n = 12), infection (n = 8), and vasopressor-related injury (n = 1). The average size of BTM was 162.5 cm2, and the average time from BTM application to wound closure was 90.1 days. Twenty-seven (52.9%) patients required skin grafting, whereas 20 (39.2%) did not and re-epithelialized spontaneously. Those who did not require skin grafting had significantly smaller wound sizes compared to those who required skin grafting (58.5 cm2 vs 248.6 cm2; P = .002). Complications occurred in 14 patients, including infection (n = 5), fluid collection (n = 5), and template dehiscence (n = 4). Wound closure was successful in 92% of patients. Conclusions: Novosorb BTM is effective for the management of upper-extremity wounds with exposed bone and tendon. Clinical relevance: In the management of complex upper-extremity wounds with exposed bone and tendon, even when devoid of paratenon or periosteum, Novosorb BTM provides a safe and effective alternative to more complex reconstructive options.

Characterization of arteriosclerosis based on computer-aided measurements of intra-arterial thickness.

Purpose: Our purpose is to develop a computer vision approach to quantify intra-arterial thickness on digital pathology images of kidney biopsies as a computational biomarker of arteriosclerosis. Approach: The severity of the arteriosclerosis was scored (0 to 3) in 753 arteries from 33 trichrome-stained whole slide images (WSIs) of kidney biopsies, and the outer contours of the media, intima, and lumen were manually delineated by a renal pathologist. We then developed a multi-class deep learning (DL) framework for segmenting the different intra-arterial compartments (training dataset: 648 arteries from 24 WSIs; testing dataset: 105 arteries from 9 WSIs). Subsequently, we employed radial sampling and made measurements of media and intima thickness as a function of spatially encoded polar coordinates throughout the artery. Pathomic features were extracted from the measurements to collectively describe the arterial wall characteristics. The technique was first validated through numerical analysis of simulated arteries, with systematic deformations applied to study their effect on arterial thickness measurements. We then compared these computationally derived measurements with the pathologists' grading of arteriosclerosis. Results: Numerical validation shows that our measurement technique adeptly captured the decreasing smoothness in the intima and media thickness as the deformation increases in the simulated arteries. Intra-arterial DL segmentations of media, intima, and lumen achieved Dice scores of 0.84, 0.78, and 0.86, respectively. Several significant associations were identified between arteriosclerosis grade and pathomic features using our technique (e.g., intima-media ratio average [ τ = 0.52 , p < 0.0001 ]) through Kendall's tau analysis. Conclusions: We developed a computer vision approach to computationally characterize intra-arterial morphology on digital pathology images and demonstrate its feasibility as a potential computational biomarker of arteriosclerosis.

Cancer-related Fear and Worry in Patients with Low-Risk Thyroid Cancer: A Longitudinal Cohort Study.

CONTEXT: Little is known about how patients' emotions impact the choice between hemi- and total thyroidectomy (TT) for low-risk thyroid cancer (LR-TC) and how these emotions change after treatment. OBJECTIVE: To investigate thyroid cancer-specific fear and worry both before and after treatment of LR-TC with hemi- or TT. METHODS: This prospective cohort study enrolled adults with confirmed or likely LR-TC at 15 institutions. Participants completed measures of thyroid cancer-related fear and worry at the time of their treatment decision and 9-months later. Participants were categorized as having low, medium, or high levels of fear and worry in accordance with the literature. Those choosing hemi-thyroidectomy were compared to those choosing TT. RESULTS: Of 177eligible patients, 125 (70.6%) enrolled and 114 completed both surveys (91.2% retention). Overall, 41 (36.0%) participants chose hemi-thyroidectomy and 73 (64.0%) chose TT. Across all participants, thyroid cancer-related fear and worry both decreased significantly after surgery (fear 25.8±6.4 to 23.1±7.4; worry 8.2±2.4 to 5.4±2.1, p<0.001). The proportion of participants with high fear decreased from 64.9% to 50.9%, while the proportion with high worry decreased from 75.4% to 41.2% (p<0.001 for both). At both time points, no differences existed between those choosing hemi- and TT in levels of worry or fear. CONCLUSION: Patients with LR-TC report lower levels of fear and worry 9-months after surgery regardless of the extent of surgery, suggesting that both surgeries provide an emotional benefit to some patients. Thyroid cancer-related fear and worry do not appear to influence patients' decisions to undergo hemi- or TT.

Integrated multimodal cell atlas of Alzheimer's disease.

Alzheimer's disease (AD) is the leading cause of dementia in older adults. Although AD progression is characterized by stereotyped accumulation of proteinopathies, the affected cellular populations remain understudied. Here we use multiomics, spatial genomics and reference atlases from the BRAIN Initiative to study middle temporal gyrus cell types in 84 donors with varying AD pathologies. This cohort includes 33 male donors and 51 female donors, with an average age at time of death of 88 years. We used quantitative neuropathology to place donors along a disease pseudoprogression score. Pseudoprogression analysis revealed two disease phases: an early phase with a slow increase in pathology, presence of inflammatory microglia, reactive astrocytes, loss of somatostatin+ inhibitory neurons, and a remyelination response by oligodendrocyte precursor cells; and a later phase with exponential increase in pathology, loss of excitatory neurons and Pvalb+ and Vip+ inhibitory neuron subtypes. These findings were replicated in other major AD studies.

Changes in vaginal cytokines concentrations during artificial insemination and natural service in beef heifers.

OBJECTIVE: Heifer development is crucial for the optimization of reproductive efficiency in beef production. Heifer development is largely influenced by nutrition. Nutritional status of these heifers can influence immunological responses that are crucial for reproduction. Commercial Angus heifers (n = 9) were utilized, in a pilot study, to elucidate the effects of sampling time (days 0, 7, 14, 21, 28, and 35), pregnancy status, and type of mating on individual cytokine concentrations and cytokine profiles in the vagina following breeding. RESULTS: Cytokine profiles were analyzed using MetaboAnalyst 5.0 and one-way ANOVAs were performed in R Studio to identify differences in individual cytokines based on sampling time, pregnancy status, and type of mating. Cytokine profiles were different (P = 0.05) 7 days after either mating type. Cytokines, IL-1ß, IL-17a, MCP-1, and TNFα were different based on the mating type and pregnancy status. Multiple cytokines, IL-1α, IL-1ß, IL-6, IL-8, IL-10, IL-17a, VEGFa, and MIP1α, were different between days regardless of pregnancy status. In conclusion, vaginal cytokines differ based on pregnancy status, type of mating, and time which may be indicative of vital pathways that need to be activated for pregnancy.

Regeneration of full thickness common extensor tendon tear after percutaneous microfragmented adipose graft.

Tennis elbow, also commonly known as lateral epicondylitis or common extensor tendinosis, is a common musculoskeletal injury in the adult population. Currently, the standard treatment regimen prescribed for this injury involves a combination of rest, physical therapy, bracing and anti-inflammatory medications. If refractory to these conservative measures, platelet-rich plasma has been shown effective. However, in the case of full thickness tears, surgery has remained the only treatment option until now. We present a case report of a 56-year-old man with a diagnosis of a left large full thickness tear and rupture with retraction of his common extensor tendon (CET) following a corticosteroid injection. The patient was treated with microfragmented adipose transfer. He was re-evaluated around 7 weeks and again at 15 weeks post-treatment and demonstrated ultrasound evidence of complete bridging and remodeling of his prior full thickness CET tear and resolution of retraction. This case presents a promising option for patients with full thickness CET tears who would like to refrain from or are unable to have surgery. Further research and possible randomized controlled trials are needed to further assess the full efficacy of microfragmented adipose transfer in the treatment of full thickness CET tears.

Adipose cells from a patient's own body fat are one of the best sources of mesenchymal stem cells (MSC) and growth factors that contribute to the generation of collagen protein fibers. MSC's are versatile cells that can differentiate into a variety of cell types, while collagen is an important component of muscles and tendons, as it provides structure. MSC's can be harvested from one's own fat and then used to help supplement the body's natural repair process of a variety of injured tissues. This case presents a patient with a history of persistent elbow pain caused by a large full-thickness tear and rupture of the common extensor tendon (CET) of the elbow. Full thickness tears are large deep tears that extend across the entirety of the tendon. Generally, partial CET tears of varying severities are some of the most common tendon injuries seen in the elbow and are injuries that historically, are treated with conservative management, such as pain medication, cortisone injection, physical therapy, platelet-rich plasma or surgery once/if conservative interventions fail. Full thickness tears, however, usually require surgery for patients to feel better. In this case, the patient underwent a novel regenerative treatment alternative to surgery, known as microfragmented adipose transfer (MFAT), to repair the torn CET. Fat was harvested from his flanks, was washed and cleaned, then injected into the CET tear of the elbow. He experienced significant improvements in function and pain and tendon healing was documented using ultrasound and MRI imaging. This case supports using MFAT for lateral elbow pain caused by full-thickness CET tears as a novel and significantly less invasive method than surgery. Our case illustrates the need for more research and possible clinical trials evaluating MFAT as a treatment option for common musculoskeletal pathologies.

Splenic Torsion From a Wandering Spleen.

Wandering spleen is a unique condition defined as a hypermobile spleen with a sole attachment to its vascular pedicle. The most common complication is torsion of the spleen, resulting in a surgical emergency. Early diagnosis and prevention of splenic infarction are the mainstays of treatment to help preserve immunologic function. We report a case of torsion of the wandering spleen in a 23-year-old active-duty male with a prior childhood history of duodenal atresia. His abdominal examination demonstrated a palpable midline mass, which was confirmed by CT abdomen and pelvis to be a wandering spleen with twisting of the vascular pedicle. The patient was taken for an exploratory laparotomy, where an infarcted spleen was identified with associated twisting of the splenic hilum, and a splenectomy was performed. Post-operatively, the patient is healthy and symptom-free at the three-month follow-up and has returned to active duty.

"Trust Women": Characteristics of and learnings from patients of a Shield Law medication abortion practice in the United States.

INTRODUCTION: The 2022 Massachusetts Shield Law protects telemedicine providers who care for abortion seekers in other states from criminal, civil, and licensure penalties. In this article we explore the characteristics of patients of The Massachusetts Medication Abortion Access Project (The MAP). METHODS: The MAP is an asynchronous telemedicine service that offers mifepristone/misoprostol to abortion seekers in all 50 states who are at or under 11 weeks pregnancy gestation on initial intake. The MAP charges USD250 using a pay-what-you-can model. We analyzed medical questionnaires and payments submitted by patients who received care from The MAP during its first 6 months of operations using descriptive statistics and for content and themes. RESULTS: From October 1, 2023-March 31, 2024, 1994 patients accessed care through The MAP. Almost all (n = 1973, 99%) identified as women/girls and about half (n = 984, 49%) were aged 20-29. The MAP cared for patients in 45 states; 84% (n = 1672) of these patients received pills in abortion ban or restricted southern states. Patients paid USD134.50 on average; 29% (n = 577) paid USD25 or less. Nearly two-thirds (n = 1293, 65%) received subsidized care; financial hardship featured prominently in patient comments. DISCUSSION: Considerable demand exists for medication abortion care from Shield Law providers. The MAP demonstrates that providers can trust women and other pregnancy capable people to decide for themselves whether to obtain medication abortion pills by mail and to pay what they can afford without being required to justify their need. Identifying ways to support Shield Law provision and further subsidize abortion care are needed.

Anatomic variations of the supinator nerve for transfer to the posterior interosseous nerve in tetraplegia.

The anatomy of the supinator nerve was evaluated in 20 fresh-frozen cadavers. Variations in branching patterns, number of motor branches and distance of the branch points from the radial nerve relative to the radiocapitellar joint are described.

Advancing Protein Analysis: A Low-Pressure Drift Tube Orbitrap Mass Spectrometer for Ultraviolet Photodissociation-Based Structural Characterization.

Owing to its ability to generate extensive fragmentation of proteins, ultraviolet photodissociation (UVPD) mass spectrometry (MS) has emerged as a versatile ion activation technique for the structural characterization of native proteins and protein complexes. Interpreting these fragmentation patterns provides insight into the secondary and tertiary structures of protein ions. However, the inherent complexity and diversity of proteins often pose challenges in resolving their numerous conformations. To address this limitation, we combined UVPD-MS with drift tube ion mobility, offering potential to acquire conformationally selective MS/MS information. A low-pressure drift tube (LPDT) Orbitrap mass spectrometer equipped with 193 nm UVPD capabilities enables the analysis of protein conformers through the analysis of arrival time distributions (ATDs) of individual fragment ions. ATDs of fragment ions are compared for different backbone cleavage sites of the protein or different precursor charge states to give information about regions of potential folding or elongation. This integrated platform offers promise for advancing our understanding of protein structures in the gas phase.

Association of complicated appendicitis with geographic and socioeconomic measures in children.

BACKGROUND: Complicated appendicitis, considered a marker of delay in accessing surgical care among children, has been inconsistently associated with race, socioeconomic status, insurance type, rurality, and distance to care. This statewide assessment measured factors associated with complicated appendicitis while overcoming limitations of prior work, namely, selection bias and use of inexact socioeconomic status measures. METHODS: Children (<18 years) undergoing appendectomy for appendicitis in Wisconsin from 2018 to 2021 were identified in the Wisconsin Hospital Association database. Patient residence and hospital locations were used to determine rurality, travel distances, and socioeconomic status as measured by Area Deprivation Index, Child Opportunity Index, Community Need Index, and county-level poverty rates. Multivariable logistic regression was used to assess factors associated with complicated appendicitis. RESULTS: Among 5,881 children undergoing appendectomy, 1,375 (23.4%) had complicated appendicitis. Adjusting for other variables, complicated appendicitis was associated with younger age (adjusted odds ratio 0.90 per year increase); Hispanic White race/ethnicity (adjusted odds ratio 1.40-1.63); distance to the hospital where surgery was performed (adjusted odds ratio 1.16-1.17 per 10-mile increase); and very low Child Opportunity Index (adjusted odds ratio 1.29), Community Need Index (adjusted odds ratio 1.20 per 1-score increase), and county-level poverty (adjusted odds ratio 1.02 per 1% increase). Insurance type, rurality, and Area Deprivation Index were not associated with complicated appendicitis. Residential county-level complicated appendicitis rates (0.0%-50.0%) had moderate correlation to pediatric county-level poverty rates (rs=0.43). CONCLUSION: Complicated appendicitis was associated with Child Opportunity Index, Community Need Index, and county-level poverty but not insurance type, rurality, or Area Deprivation Index. There was geographic variability in complicated appendicitis rates, with modest correlation to county-level poverty. Targeted interventions among Hispanic populations and those with travel- and socioeconomic status-related barriers to care may be beneficial in preventing complicated appendicitis among children.

Does Resurfacing the Patella Increase the Risk of Extensor Mechanism Injury within the First 2 Years after Total Knee Arthroplasty?

Extensor mechanism injury (EMI) following total knee arthroplasty (TKA) is a potentially catastrophic complication and may lead to significant morbidity or need for revision reconstructive procedures. Patellar resurfacing (PR), while commonly performed during TKA, reduces overall patella bone stock and may increase the risk of EMI after TKA. The purpose of this study was to assess if PR in elderly patients raises the risk for subsequent EMI.The American Joint Replacement Registry (AJRR) was queried to identify Medicare patients ≥65 years old undergoing primary elective TKA for osteoarthritis between January 2012 and March 2020. Patient age, sex, and Charlson Comorbidity Index (CCI) were collected. Records were subsequently merged with Medicare claims records and evaluated for the occurrence of patella fracture, quadriceps tendon rupture, or patellar tendon rupture based on International Classification of Diseases 9 and 10 (ICD 9/10) diagnosis codes within 2 years of TKA. Patients were stratified based on whether PR occurred or not (NR). Logistic regression was used to determine the association between PR and EMI.A total of 453,828 TKA were eligible for inclusion and 428,644 (94.45%) underwent PR. The incidence of PR decreased from 96.06% in 2012 to 92.35% in 2022 (p < 0.001). Patients undergoing PR were more often female (60.93 vs. 58.50%, p < 0.001) and had a lower mean CCI (3.09 [1.10] vs. 3.16 [1.20], p < 0.001). Odds for EMI did not differ based on whether PR was performed (odds ratio [OR]: 0.85, 95% confidence interval [CI]: 0.65-1.11, p = 0.2246). Increasing age (OR: 1.06, 95% CI: 1.05-1.07, p < 0.0001]) and CCI (OR: 1.06, 95% CI: 0.95-1.19, p = 0.0009) were associated with EMI.PR is commonly performed during TKA in the United States and was not found to increase odds for EMI within 2 years of TKA in patients ≥65 years old. Increased age and medical comorbidity were associated with higher odds for subsequent EMI.

Single-cell analysis of human airway epithelium identifies cell type-specific responses to Aspergillus and Coccidioides.

Respiratory fungal infections pose a significant threat to human health. Animal models do not fully recapitulate human disease, necessitating advanced models to study human-fungal pathogen interactions. In this study, we utilized primary human airway epithelial cells (hAECs) to recapitulate the lung environment in vitro and investigate cellular responses to two diverse, clinically significant fungal pathogens, Aspergillus fumigatus and Coccidioides posadasii. To understand the mechanisms of early pathogenesis for both fungi, we performed single-cell RNA sequencing of infected hAECs. Analysis revealed that both fungi induced cellular stress and cytokine production. However, the cell subtypes affected and specific pathways differed between fungi, with A. fumigatus and C. posadasii triggering protein-folding-related stress in ciliated cells and hypoxia responses in secretory cells, respectively. This study represents one of the first reports of single-cell transcriptional analysis of hAECs infected with either A. fumigatus or C. posadasii, providing a vital dataset to dissect the mechanism of disease and potentially identify targetable pathways.

Insights into the Main Protease of SARS-CoV-2: Thermodynamic Analysis, Structural Characterization, and the Impact of Inhibitors.

The main protease (Mpro) of SARS-CoV-2 is an essential enzyme for coronaviral maturation and is the target of Paxlovid, which is currently the standard-of-care treatment for COVID-19. There remains a need to identify new inhibitors of Mpro as viral resistance to Paxlovid emerges. Here, we report the use of native mass spectrometry coupled with 193 nm ultraviolet photodissociation (UVPD) and integrated with other biophysical tools to structurally characterize Mpro and its interactions with potential covalent inhibitors. The overall energy landscape was obtained using variable temperature nanoelectrospray ionization (vT-nESI), thus providing quantitative evaluation of inhibitor binding on the stability of Mpro. Thermodynamic parameters extracted from van't Hoff plots revealed that the dimeric complexes containing each inhibitor showed enhanced stability through increased melting temperatures as well as overall lower average charge states, giving insight into the basis for inhibition mechanisms.

Tools for genetic engineering and gene expression control in Novosphingobium aromaticivorans and Rhodobacter sphaeroides.

Alphaproteobacteria have a variety of cellular and metabolic features that provide important insights into biological systems and enable biotechnologies. For example, some species are capable of converting plant biomass into valuable biofuels and bioproducts that have the potential to contribute to the sustainable bioeconomy. Among the Alphaproteobacteria, Novosphingobium aromaticivorans, Rhodobacter sphaeroides, and Zymomonas mobilis show promise as organisms that can be engineered to convert extracted plant lignin or sugars into bioproducts and biofuels. Genetic manipulation of these bacteria is needed to introduce engineered pathways and modulate expression of native genes with the goal of enhancing bioproduct output. Although recent work has expanded the genetic toolkit for Z. mobilis, N. aromaticivorans and R. sphaeroides still need facile, reliable approaches to deliver genetic payloads to the genome and to control gene expression. Here, we expand the platform of genetic tools for N. aromaticivorans and R. sphaeroides to address these issues. We demonstrate that Tn7 transposition is an effective approach for introducing engineered DNA into the chromosome of N. aromaticivorans and R. sphaeroides. We screen a synthetic promoter library to identify isopropyl ß-D-1-thiogalactopyranoside-inducible promoters with regulated activity in both organisms (up to ~15-fold induction in N. aromaticivorans and ~5-fold induction in R. sphaeroides). Combining Tn7 integration with promoters from our library, we establish CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) interference systems for N. aromaticivorans and R. sphaeroides (up to ~10-fold knockdown in N. aromaticivorans and R. sphaeroides) that can target essential genes and modulate engineered pathways. We anticipate that these systems will greatly facilitate both genetic engineering and gene function discovery efforts in these species and other Alphaproteobacteria.IMPORTANCEIt is important to increase our understanding of the microbial world to improve health, agriculture, the environment, and biotechnology. For example, building a sustainable bioeconomy depends on the efficient conversion of plant material to valuable biofuels and bioproducts by microbes. One limitation in this conversion process is that microbes with otherwise promising properties for conversion are challenging to genetically engineer. Here we report genetic tools for Novosphingobium aromaticivorans and Rhodobacter sphaeroides that add to the burgeoning set of tools available for genome engineering and gene expression in Alphaproteobacteria. Our approaches allow straightforward insertion of engineered pathways into the N. aromaticivorans or R. sphaeroides genome and control of gene expression by inducing genes with synthetic promoters or repressing genes using CRISPR interference. These tools can be used in future work to gain additional insight into these and other Alphaproteobacteria and to aid in optimizing yield of biofuels and bioproducts.

Dissecting contributions of pulmonary arterial remodeling to right ventricular afterload in pulmonary hypertension.

Pulmonary hypertension (PH) is defined as an elevation in the right ventricle (RV) afterload, characterized by increased hemodynamic pressure in the main pulmonary artery (PA). Elevations in RV afterload increase RV wall stress, resulting in RV remodeling and potentially RV failure. From a biomechanical standpoint, the primary drivers for RV afterload elevations include increases in pulmonary vascular resistance (PVR) in the distal vasculature and decreases in vessel compliance in the proximal PA. However, the individual contributions of the various vascular remodeling events toward the progression of PA pressure elevations and altered vascular hemodynamics remain elusive. In this study, we used a subject-specific one-dimensional (1D) fluid-structure interaction (FSI) model to investigate the alteration of pulmonary hemodynamics in PH and to quantify the contributions of vascular stiffening and increased resistance towards increased main pulmonary artery (MPA) pressure. We used a combination of subject-specific hemodynamic measurements, ex-vivo mechanical testing of arterial tissue specimens, and ex-vivo X-ray micro-tomography imaging to develop the 1D-FSI model and dissect the contribution of PA remodeling events towards alterations in the MPA pressure waveform. Both the amplitude and pulsatility of the MPA pressure waveform were analyzed. Our results indicated that increased distal resistance has the greatest effect on the increase in maximum MPA pressure, while increased stiffness caused significant elevations in the characteristic impedance. The method presented in this study will serve as an essential step toward understanding the complex interplay between PA remodeling events that leads to the most severe adverse effect on RV dysfunction.

Rapidly Degrading Hydrogels to Support Biofabrication and 3D Bioprinting Using Cartilage Microtissues.

In recent years, there has been increased interest in the use of cellular spheroids, microtissues, and organoids as biological building blocks to engineer functional tissues and organs. Such microtissues are typically formed by the self-assembly of cellular aggregates and the subsequent deposition of a tissue-specific extracellular matrix (ECM). Biofabrication and 3D bioprinting strategies using microtissues may require the development of supporting hydrogels and bioinks to spatially localize such biological building blocks in 3D space and hence enable the engineering of geometrically defined tissues. Therefore, the aim of this work was to engineer scaled-up, geometrically defined cartilage grafts by combining multiple cartilage microtissues within a rapidly degrading oxidized alginate (OA) supporting hydrogel and maintaining these constructs in dynamic culture conditions. To this end, cartilage microtissues were first independently matured for either 2 or 4 days and then combined in the presence or absence of a supporting OA hydrogel. Over 6 weeks in static culture, constructs engineered using microtissues that were matured independently for 2 days generated higher amounts of glycosaminoglycans (GAGs) compared to those matured for 4 days. Histological analysis revealed intense staining for GAGs and negative staining for calcium deposits in constructs generated by using the supporting OA hydrogel. Less physical contraction was also observed in constructs generated in the presence of the supporting gel; however, the remnants of individual microtissues were more observable, suggesting that even the presence of a rapidly degrading hydrogel may delay the fusion and/or the remodeling of the individual microtissues. Dynamic culture conditions were found to modulate ECM synthesis following the OA hydrogel encapsulation. We also assessed the feasibility of 3D bioprinting of cartilage microtissues within OA based bioinks. It was observed that the microtissues remained viable after extrusion-based bioprinting and were able to fuse after 48 h, particularly when high microtissue densities were used, ultimately generating a cartilage tissue that was rich in GAGs and negative for calcium deposits. Therefore, this work supports the use of OA as a supporting hydrogel/bioink when using microtissues as biological building blocks in diverse biofabrication and 3D bioprinting platforms.