3D-cultured blastoids model human embryogenesis from pre-implantation to early gastrulation stages.

Naive human pluripotent stem cells have the remarkable ability to self-organize into blastocyst-like structures ("blastoids") that model lineage segregation in the pre-implantation embryo. However, the extent to which blastoids can recapitulate the defining features of human post-implantation development remains unexplored. Here, we report that blastoids cultured on thick three-dimensional (3D) extracellular matrices capture hallmarks of early post-implantation development, including epiblast lumenogenesis, rapid expansion and diversification of trophoblast lineages, and robust invasion of extravillous trophoblast cells by day 14. Extended blastoid culture results in the localized activation of primitive streak marker TBXT and the emergence of embryonic germ layers by day 21. We also show that the modulation of WNT signaling alters the balance between epiblast and trophoblast fates in post-implantation blastoids. This work demonstrates that 3D-cultured blastoids offer a continuous and integrated in vitro model system of human embryonic and extraembryonic development from pre-implantation to early gastrulation stages.

Stem-cell-derived trophoblast organoids model human placental development and susceptibility to emerging pathogens.

Trophoblast organoids derived from placental villi provide a 3D model system of human placental development, but access to first-trimester tissues is limited. Here, we report that trophoblast stem cells isolated from naive human pluripotent stem cells (hPSCs) can efficiently self-organize into 3D stem-cell-derived trophoblast organoids (SC-TOs) with a villous architecture similar to primary trophoblast organoids. Single-cell transcriptome analysis reveals the presence of distinct cytotrophoblast and syncytiotrophoblast clusters and a small cluster of extravillous trophoblasts, which closely correspond to trophoblast identities in the post-implantation embryo. These organoid cultures display clonal X chromosome inactivation patterns previously described in the human placenta. We further demonstrate that SC-TOs exhibit selective vulnerability to emerging pathogens (SARS-CoV-2 and Zika virus), which correlates with expression levels of their respective entry factors. The generation of trophoblast organoids from naive hPSCs provides an accessible 3D model system of the developing placenta and its susceptibility to emerging pathogens.

Effects of the Anterolateral Ligament and Anterior Cruciate Ligament on Knee Joint Mechanics: A Biomechanical Study Using Computational Modeling.

Background: Recent studies on lateral knee anatomy have reported the presence of a true ligament structure, the anterolateral ligament (ALL), in the anterolateral region of the knee joint. However, its biomechanical effects have not been fully elucidated. Purpose: To investigate, by using computer simulation, the association between the ALL and anterior cruciate ligament (ACL) under dynamic loading conditions. Study Design: Descriptive laboratory study; Level of evidence, 5. Methods: The authors combined medical imaging from 5 healthy participants with motion capture to create participant-specific knee models that simulated the entire 12 degrees of freedom of tibiofemoral (TF) and patellofemoral (PF) joint behaviors. These dynamic computational models were validated using electromyographic data, muscle activation data, and data from previous experimental studies. Forces exerted on the ALL with ACL deficiency and on the ACL with ALL deficiency, as well as TF and PF contact forces with deficiencies of the ACL, ALL, and the entire ligament structure, were evaluated under gait and squat loading. A single gait cycle and squat cycle were divided into 11 time points (periods 0.0-1.0). Simulated ligament forces and contact forces were compared using nonparametric repeated-measures Friedman tests. Results: Force exerted on the ALL significantly increased with ACL deficiency under both gait- and squat-loading conditions. With ACL deficiency, the mean force on the ALL increased by 129.7% under gait loading in the 0.4 period (P < .05) and increased by 189% under high flexion during the entire cycle of squat loading (P < .05). A similar trend of significantly increased force on the ACL was observed with ALL deficiency. Contact forces on the TF and PF joints with deficiencies of the ACL, ALL, and entire ligament structure showed a complicated pattern. However, contact force exerted on TF and PF joints with respect to deficiencies of ACL and ALL significantly increased under both gait- and squat-loading conditions. Conclusion: The results of this computer simulation study indicate that the ACL and the ALL of the lateral knee joint act as secondary stabilizers to each other under dynamic load conditions.

OCT4 cooperates with distinct ATP-dependent chromatin remodelers in naïve and primed pluripotent states in human.

Understanding the molecular underpinnings of pluripotency is a prerequisite for optimal maintenance and application of embryonic stem cells (ESCs). While the protein-protein interactions of core pluripotency factors have been identified in mouse ESCs, their interactome in human ESCs (hESCs) has not to date been explored. Here we mapped the OCT4 interactomes in naïve and primed hESCs, revealing extensive connections to mammalian ATP-dependent nucleosome remodeling complexes. In naïve hESCs, OCT4 is associated with both BRG1 and BRM, the two paralog ATPases of the BAF complex. Genome-wide location analyses and genetic studies reveal that these two enzymes cooperate in a functionally redundant manner in the transcriptional regulation of blastocyst-specific genes. In contrast, in primed hESCs, OCT4 cooperates with BRG1 and SOX2 to promote chromatin accessibility at ectodermal genes. This work reveals how a common transcription factor utilizes differential BAF complexes to control distinct transcriptional programs in naïve and primed hESCs.

Probing the signaling requirements for naive human pluripotency by high-throughput chemical screening.

Naive human embryonic stem cells (hESCs) have been isolated that more closely resemble the pre-implantation epiblast compared to conventional "primed" hESCs, but the signaling principles underlying these discrete stem cell states remain incompletely understood. Here, we describe the results from a high-throughput screen using ∼3,000 well-annotated compounds to identify essential signaling requirements for naive human pluripotency. We report that MEK1/2 inhibitors can be replaced during maintenance of naive human pluripotency by inhibitors targeting either upstream (FGFR, RAF) or downstream (ERK1/2) kinases. Naive hESCs maintained under these alternative conditions display elevated levels of ERK phosphorylation but retain genome-wide DNA hypomethylation and a transcriptional identity of the pre-implantation epiblast. In contrast, dual inhibition of MEK and ERK promotes efficient primed-to-naive resetting in combination with PKC, ROCK, and TNKS inhibitors and activin A. This work demonstrates that induction and maintenance of naive human pluripotency are governed by distinct signaling requirements.

Diversification in Functions and Expressions of Soybean FLOWERING LOCUS T Genes Fine-Tunes Seasonal Flowering.

The proper timing of flowering in response to environmental changes is critical for ensuring crop yields. FLOWERING LOCUS T (FT) homologs of the phosphatidylethanolamine-binding protein family play important roles as floral integrators in many crops. In soybean, we identified 17 genes of this family, and characterized biological functions in flowering for ten FT homologs. Overexpression of GmFT homologs in Arabidopsis revealed that a set of GmFT homologs, including GmFT2a/2b, GmFT3a/3b, and GmFT5a/5b, promoted flowering similar to FT; in contrast, GmFT1a/1b, GmFT4, and GmFT6 delayed flowering. Consistently, expressions of GmFT2a, GmFT2b, and GmFT5a were induced in soybean leaves in response to floral inductive short days, whereas expressions of GmFT1a and GmFT4 were induced in response to long days. Exon swapping analysis between floral activator GmFT2a and floral repressor GmFT4 revealed that the segment B region in the fourth exon is critical for their antagonistic functions. Finally, expression analysis of GmFT2a, GmFT5a, and GmFT4 in soybean accessions exhibiting various flowering times indicated that the mRNA levels of GmFT2a and GmFT5a were higher in early flowering accessions than in late-flowering accessions, while GmFT4 showed the opposite pattern. Moreover, the relative mRNA levels between GmFT2a/GmFT5a and GmFT4 was important in determining day length-dependent flowering in soybean accessions. Taken together, our results suggest that the functions of GmFT homologs have diversified into floral activators and floral repressors during soybean evolution, and the timing of flowering in response to changing day length is determined by modulating the activities of antagonistic GmFT homologs.

Finite element analysis of the influence of the posterior tibial slope on mobile-bearing unicompartmental knee arthroplasty.

BACKGROUND: The most common modes of failure reported in unicompartmental knee arthroplasty (UKA) in its first two decades were wear on the polyethylene (PE) insert, component loosening, and progressive osteoarthritis in the other compartment. The rates of implant failure due to poor component positioning in patients who have undergone UKA have been reported. However, the effect of the posterior tibial slope on the biomechanical behavior of mobile-bearing Oxford medial UKA remains unknown. METHODS: We applied finite element (FE) analysis to evaluate the effects of the posterior tibial slope in mobile-bearing UKA on the contact stresses in the superior and inferior surfaces of PE inserts and articular cartilage as well as the forces exerted on the anterior cruciate ligament (ACL). Seven FE models for posterior tibial slopes of -1°, 1°, 3°, 5°, 7°, 9°, and 11° were developed and analyzed under normal-level walking conditions based on this approach. RESULTS: The maximum contact stresses on both the superior and inferior surfaces of the PE insert decreased as the posterior tibial slope increased. However, the maximum contact stress on the lateral articular cartilage and the force exerted on the ACL increased as the posterior tibial slope increased. CONCLUSIONS: Increasing the tibial slope led to a reduction in the contact stress on the PE insert. However, a high contact stress on the other compartment and increased ACL force can cause progressive osteoarthritis in the other compartment and failure of the ACL.

Finite Element Study on the Preservation of Normal Knee Kinematics with Respect to the Prosthetic Design in Patient-Specific Medial Unicompartmental Knee Arthroplasty.

Alterations in native knee kinematics in medial unicompartmental knee arthroplasty (UKA) are caused by the nonanatomic articular surface of conventional implants. Technology for an anatomy mimetic patient-specific (PS) UKA has been introduced. However, there have been no studies on evaluating the preservation of native knee kinematics with respect to different prosthetic designs in PS UKA. The purpose of this study was to evaluate the preservation of native knee kinematics with respect to different UKA designs using a computational simulation. We evaluated three different UKA designs: a nonconforming design, an anatomy mimetic design, and a conforming design for use under gait and squat loading conditions. The results show that the anatomy mimetic UKA design achieves closer kinematics to those of a native knee compared to the other two UKA designs under such conditions. The anatomy memetic UKA design exhibited a 0.39 mm and 0.36° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, under the gait and squat loading conditions, the conforming UKA design shows limited kinematics compared to the nonconforming UKA design. Our results show that the conformity of each component in PS UKA is an important factor in knee joint kinematics; however, the anatomy mimetic UKA design cannot restore perfect native kinematics.

Derivation of trophoblast stem cells from naïve human pluripotent stem cells.

Naïve human pluripotent stem cells (hPSCs) provide a unique experimental platform of cell fate decisions during pre-implantation development, but their lineage potential remains incompletely characterized. As naïve hPSCs share transcriptional and epigenomic signatures with trophoblast cells, it has been proposed that the naïve state may have enhanced predisposition for differentiation along this extraembryonic lineage. Here we examined the trophoblast potential of isogenic naïve and primed hPSCs. We found that naïve hPSCs can directly give rise to human trophoblast stem cells (hTSCs) and undergo further differentiation into both extravillous and syncytiotrophoblast. In contrast, primed hPSCs do not support hTSC derivation, but give rise to non-self-renewing cytotrophoblasts in response to BMP4. Global transcriptome and chromatin accessibility analyses indicate that hTSCs derived from naïve hPSCs are similar to blastocyst-derived hTSCs and acquire features of post-implantation trophectoderm. The derivation of hTSCs from naïve hPSCs will enable elucidation of early mechanisms that govern normal human trophoblast development and associated pathologies.

The placenta is one of the most important human organs, but it is perhaps the least understood. The first decision the earliest human cells have to make, shortly after the egg is fertilized by a sperm, is whether to become part of the embryo or part of the placenta. This choice happens before a pregnancy even implants into the uterus. The cells that commit to becoming the embryo transform into 'naïve pluripotent' cells, capable of becoming any cell in the body. Those that commit to becoming the placenta transform into 'trophectoderm' cells, capable of becoming the two types of cell in the placenta. Placental cells either invade into the uterus to anchor the placenta or produce hormones to support the pregnancy. Once a pregnancy implants into the uterus, the naïve pluripotent cells in the embryo become 'primed'. This prevents them from becoming cells of the placenta, and it poses a problem for placental research. In 2018, scientists in Japan reported conditions for growing trophectoderm cells in the laboratory, where they are known as "trophoblast stem cells". These cells were capable of transforming into specialized placental cells, but needed first to be isolated from the human embryo or placenta itself. Dong et al. now show how to reprogram other pluripotent cells grown in the laboratory to produce trophoblast stem cells. The first step was to reset primed pluripotent cells to put them back into a naïve state. Then, Dong et al. exposed the cells to the same concoction of nutrients and chemicals used in the 2018 study. This fluid triggered a transformation in the naïve pluripotent cells; they started to look like trophoblast stem cells, and they switched on genes normally active in trophectoderm cells. To test whether these cells had the same properties as trophoblast stem cells, Dong et al. gave them chemical signals to see if they could mature into placental cells. The stem cells were able to transform into both types of placental cell, either invading through a three-dimensional gel that mimics the wall of the uterus or making pregnancy hormones. There is a real need for a renewable supply of placental cells in pregnancy research. Animal placentas are not the same as human ones, so it is not possible to learn everything about human pregnancy from animal models. A renewable supply of trophoblast stem cells could aid in studying how the placenta forms and why this process sometimes goes wrong. This could help researchers to better understand miscarriage, pre-eclampsia and other conditions that affect the growth of an unborn baby. In the future, it may even be possible to make custom trophoblast stem cells to study the specific fertility issues of an individual.

Prediction of wear performance in femoral and tibial conformity in patient-specific cruciate-retaining total knee arthroplasty.

BACKGROUND: Articular surface curvature design is important in tibiofemoral kinematics and the contact mechanics of total knee arthroplasty (TKA). Thus far, the effects of articular surface curvature have not been adequately discussed with respect to conforming, nonconforming, and medial pivot designs in patient-specific TKA. Therefore, this study evaluates the underlying relationship between the articular surface curvature geometry and the wear performance in patient-specific TKA. METHODS: We compare the wear performances between conventional and patient-specific TKA under gait loading conditions using a computational simulation. Patient-specific TKAs investigated in the study are categorized into patient-specific TKA with conforming articular surfaces, medial pivot patient-specific TKA, and bio-mimetic patient-specific TKA with a patient's own tibial and femoral anatomy. The geometries of the femoral components in patient-specific TKAs are identical. RESULTS: The anterior-posterior and internal-external kinematics change with respect to different TKA designs. Moreover, the contact pressure and area did not directly affect the wear performance. In particular, conforming patient-specific TKAs exhibit the highest volumetric wear and wear rate. The volumetric wear in a conforming patient-specific TKA is 29% greater than that in a medial pivot patient-specific TKA. CONCLUSION: The findings in this study highlight that conformity changes in the femoral and tibial inserts influence the wear performance in patient-specific TKA. Kinematics and contact parameters should be considered to improve wear performance in patient-specific TKA. The conformity modification in the tibiofemoral joint changes the kinematics and contact parameters, and this affects wear performance.

The anterolateral ligament is a secondary stabilizer in the knee joint: A validated computational model of the biomechanical effects of a deficient anterior cruciate ligament and anterolateral ligament on knee joint kinematics.

OBJECTIVES: The aim of this study was to investigate the biomechanical effect of the anterolateral ligament (ALL), anterior cruciate ligament (ACL), or both ALL and ACL on kinematics under dynamic loading conditions using dynamic simulation subject-specific knee models. METHODS: Five subject-specific musculoskeletal models were validated with computationally predicted muscle activation, electromyography data, and previous experimental data to analyze effects of the ALL and ACL on knee kinematics under gait and squat loading conditions. RESULTS: Anterior translation (AT) significantly increased with deficiency of the ACL, ALL, or both structures under gait cycle loading. Internal rotation (IR) significantly increased with deficiency of both the ACL and ALL under gait and squat loading conditions. However, the deficiency of ALL was not significant in the increase of AT, but it was significant in the increase of IR under the squat loading condition. CONCLUSION: The results of this study confirm that the ALL is an important lateral knee structure for knee joint stability. The ALL is a secondary stabilizer relative to the ACL under simulated gait and squat loading conditions.Cite this article: Bone Joint Res 2019;8:509-517.

Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty.

Recent advances in imaging technology and additive manufacturing have led to the introduction of customized unicompartmental knee arthroplasty (UKA) that can potentially improve functional performance due to customized geometries, including customized sagittal and coronal curvature and enhanced bone preservation. The purpose of this study involved evaluating the biomechanical effect of the tibial insert design on the customized medial UKA using computer simulations. We developed sagittal and coronal curvatures in a native knee mimetic femoral component design. We utilized three types of tibial insert design: flat, anatomy mimetic, and conforming design. We evaluated contact stress on the tibial insert and other compartments, including the lateral meniscus and articular cartilage, under gait and squat loading conditions. For the conforming UKA design, the tibial insert and lateral meniscus exhibited the lowest contact stress under stance phase gait cycle. However, for the conforming UKA design, the tibial insert and lateral meniscus exhibited the highest contact stress under swing phase gait cycle. For the flat UKA design, the articular cartilage exhibited the lowest contact stress under gait and squat loading conditions. The anatomy mimetic UKA design exhibited the most normal-like contact stress on the other compartments under gait and squat loading conditions. The results reveal the importance of conformity between the femoral component and the tibial insert in the customized UKA. Based on the results on the femoral component as well as the tibial insert in the customized UKA, the anatomy mimetic design preserves normal knee joint biomechanics and thus may prevent progressive osteoarthritis of the other knee compartments.

The biomechanical effect of tibiofemoral conformity design for patient-specific cruciate retainging total knee arthroplasty using computational simulation.

BACKGROUND: Alterations to normal knee kinematics performed during conventional total knee arthroplasty (TKA) focus on the nonanatomic articular surface. Patient-specific TKA was introduced to provide better normal knee kinematics than conventional TKA. However, no study on tibiofemoral conformity has been performed after patient-specific TKA. The purpose of this study was to compare the biomechanical effect of cruciate-retaining (CR) implants after patient-specific TKA and conventional TKA under gait and deep-knee-bend conditions. METHODS: The examples of patient-specific TKA were categorized into conforming patient-specific TKA, medial pivot patient-specific TKA and anatomy mimetic articular surface patient-specific TKA. We investigated kinematics and quadriceps force of three patient-specific TKA and conventional TKA using validated computational model. The femoral component designs in patient specific TKA were all identical. RESULTS: The anatomy mimetic articular surface patient-specific TKA provided knee kinematics that was closer to normal than the others under the gait and deep-knee-bend conditions. However, the other two patient-specific TKA designs could not preserve the normal knee kinematics. In addition, the closest normal quadriceps force was found for the anatomic articular surface patient-specific TKA. CONCLUSIONS: Our results showed that the anatomy mimetic articular surface patient-specific TKA provided close-to-normal knee mechanics. Other clinical and biomechanical studies are required to determine whether anatomy mimetic articular surface patient-specific TKA restores more normal knee mechanics and provides improved patient satisfaction.

Total knee arthroplasty application of polyetheretherketone and carbon-fiber-reinforced polyetheretherketone: A review.

Polyetheretherketone (PEEK) and carbon-fiber-reinforced PEEK (CFR-PEEK) have been successfully used in the field of orthopedic implants. The polymers PEEK and CFR-PEEK are resistant to fatigue strain and radiologically transparent. These have mechanical properties and are therefore suitable for a range of orthopedic applications. Polymer composites have been proposed for orthopedic applications with the potential of reducing stress-shielding, weight of the implants, wear, and risk of osteolysis. They prevent the release of metal ions by replacing the metal articulating components. The purpose of this review was to investigate the biomechanical effects, technical data, and safety of PEEK and CFR-PEEK biomaterials and evaluate their potential for new innovations in the design of total knee arthroplasty (TKA). This review paper provides an overview with schematics and descriptions, specifically aimed at the development of PEEK and CFR-PEEK for TKA. The appropriate applications for femoral, tibial, and bearing components are highlighted for the optimal design of TKA composite, showing successful biomechanical effects.

Biomechanical analysis of a changed posterior condylar offset under deep knee bend loading in cruciate-retaining total knee arthroplasty.

BACKGROUND: The conservation of the joint anatomy is an important factor in total knee arthroplasty (TKA). The restoration of the femoral posterior condylar offset (PCO) has been well known to influence the clinical outcome after TKA. OBJECTIVE: The purpose of this study was to determine the mechanism of PCO in finite element models with conservation of subject anatomy and different PCO of ±1, ±2, ±3 mm in posterior direction using posterior cruciate ligament-retaining TKA. METHODS: Using a computational simulation, we investigated the influence of the changes in PCO on the contact stress in the polyethylene (PE) insert and patellar button, on the forces on the collateral and posterior cruciate ligament, and on the quadriceps muscle and patellar tendon forces. The computational simulation loading condition was deep knee bend. RESULTS: The contact stresses on the PE insert increased, whereas those on the patellar button decreased as posterior condylar offset translated to the posterior direction. The forces exerted on the posterior cruciate ligament and collateral ligaments increased as PCO translated to the posterior direction. The translation of PCO in the anterior direction, in an equivalent flexion angle, required a greater quadriceps muscle force. CONCLUSIONS: Translations of the PCO in the posterior and anterior directions resulted in negative effects in the PE insert and ligament, and the quadriceps muscle force, respectively. Our findings suggest that orthopaedic surgeons should be careful with regard to the intraoperative conservation of PCO, because an excessive change in PCO may lead to quadriceps weakness and an increase in posterior cruciate ligament tension.

Biomechanical effect with respect to the sagittal positioning of the femoral component in unicompartmental knee arthroplasty.

BACKGROUND: Component malalignment in unicompartmental knee arthroplasty (UKA) has been related to the concentration in tibiofemoral joint of contact stress and to poor post-operative outcomes. Few studies investigated a biomechanical effect of femur component position in sagittal plane. The purpose of this study was to evaluate the biomechanical effect of the femoral components on the sagittal alignment under flexion and extension conditions using computational simulations. METHODS: The flexion and extension conditions of the femoral component were analyzed from 10° extension to 10° flexion in 1° increments. We considered the contact stresses in the polyethylene (PE) inserts and articular cartilage, and the force on the collateral ligament, under gait cycle conditions. RESULTS: The contact stress on the PE insert increased as flexion of the femoral component increased, but there was not a remarkable difference in the amount of increased contact stress upon extension. There was no difference in the contact stress on the articular cartilage upon extension of the femoral component, but it increased in flexion during stance and double support periods. The forces on the medial collateral ligaments increased with the extension and decreased with the flexion of the femoral component, whereas the forces on the lateral collateral ligaments showed opposite trends. CONCLUSIONS: Surgeons should be concerned with femoral component position on UKA not only in frontal plane but also in the sagittal plane, because flexion or extension of the femoral component may impact the PE or opposite compartment along with the surrounding ligaments around knee joint.

A carvedilol-responsive microRNA, miR-125b-5p protects the heart from acute myocardial infarction by repressing pro-apoptotic bak1 and klf13 in cardiomyocytes.

BACKGROUND: Cardiac injury is accompanied by dynamic changes in the expression of microRNAs (miRs), small non-coding RNAs that post-transcriptionally regulate target genes. MiR-125b-5p is downregulated in patients with end-stage dilated and ischemic cardiomyopathy, and has been proposed as a biomarker of heart failure. We previously reported that the ß-blocker carvedilol promotes cardioprotection via ß-arrestin-biased agonism of ß1-adrenergic receptor while stimulating miR-125b-5p processing in the mouse heart. We hypothesize that ß1-adrenergic receptor/ß-arrestin1-responsive miR-125b-5p confers the improvement of cardiac function and structure after acute myocardial infarction. METHODS AND RESULTS: Using cultured cardiomyocyte (CM) and in vivo approaches, we show that miR-125b-5p is an ischemic stress-responsive protector against CM apoptosis. CMs lacking miR-125b-5p exhibit increased susceptibility to stress-induced apoptosis, while CMs overexpressing miR-125b-5p have increased phospho-AKT pro-survival signaling. Moreover, we demonstrate that loss-of-function of miR-125b-5p in the mouse heart causes abnormalities in cardiac structure and function after acute myocardial infarction. Mechanistically, the improvement of cardiac function and structure elicited by miR-125b-5p is in part attributed to repression of the pro-apoptotic genes Bak1 and Klf13 in CMs. CONCLUSIONS: In conclusion, these findings reveal a pivotal role for miR-125b-5p in regulating CM survival during acute myocardial infarction.

Near-infrared angiography for critical limb ischemia in a diabetic murine model.

Peripheral arterial disease (PAD) is a highly prevalent disease process that afflicts more than 20% of individuals with diabetes. Progression of PAD in the setting of diabetes can lead to critical limb ischemia (CLI), which is associated with increased risk of wounds, gangrene, and limb loss. Prompt noninvasive evaluation of limbs affected by PAD progression and CLI is currently limited. Here, we evaluate the utility of a custom-designed multispectral imaging system for fluorescence-based near-infrared angiography and compare it to the existing gold standard of laser-scanning Doppler perfusion assessments. Due to its higher resolution and fluorescence sensitivity, near-infrared angiography demonstrates a greater capacity to characterize altered dynamic arterial perfusion in a clinically relevant diabetic murine model for CLI. Furthermore, we demonstrate that our imaging system can accurately track arterial perfusion recovery over time following induced ischemia, and reveal unique phenotypic differences in the setting of diabetes.

N-Acetylcysteine accelerates amputation stump healing in the setting of diabetes.

Over 60% of lower extremity amputations are performed in patients with diabetes and peripheral arterial disease, and at least 25% require subsequent reamputation due to poor surgical site healing. The mechanisms underlying poor amputation stump healing in the setting of diabetes are not understood. N-acetylcysteine (NAC) is known to promote endothelial cell function and angiogenesis and may have therapeutic benefits in the setting of diabetes. We tested the hypothesis that NAC alters the vascular milieu to improve healing of amputation stumps in diabetes using a novel in vivo murine hindlimb ischemia-amputation model. Amputation stump tissue perfusion and healing were evaluated in C57BL/6J adult mice with streptozotocin-induced diabetes. Compared with controls, mice treated with daily NAC demonstrated improved postamputation stump healing, perfusion, adductor muscle neovascularization, and decreased muscle fiber damage. Additionally, NAC stimulated HUVEC migration and proliferation in a phospholipase C ß-dependent fashion and decreased Gαq palmitoylation. Similarly, NAC treatment also decreased Gαq palmitoylation in ischemic and nonischemic hindlimbs in vivo In summary, we demonstrate that NAC accelerates healing of amputation stumps in the setting of diabetes and ischemia. The underlying mechanism appears to involve a previously unrecognized effect of NAC on Gαq palmitoylation and phospholipase C ß-mediated signaling in endothelial cells.-Zayed, M. A., Wei, X., Park, K., Belaygorod, L., Naim, U., Harvey, J., Yin, L., Blumer, K., Semenkovich, C. F. N-acetylcysteine accelerates amputation stump healing in the setting of diabetes.

Effects of measurement methods for tibial rotation axis on the morphometry in Korean populations by gender.

BACKGROUND: There have been arguments for methodology in tibial rotation axis measurement, which accordingly determines the morphometry of the proximal tibia in total knee arthroplasty. The morphometry of the proximal tibia for the Korean population is determined by gender, based on the anatomical tibial axis and reliable rotational orientation in knee replacements, to evaluate the size suitability of the currently available prostheses in Korea. METHODS: This study reconstructed the MRI images in three-dimensions for identification and measurement of the mediolateral (ML) and anteroposterior (AP) lengths of the proximal tibia and the tibial aspect ratio (ML/AP) using proximal tibial anthropometric data for 700 osteoarthritic knees (587 females and 113 males). The ML and AP lengths were measured using tibial rotation axis techniques based on the medial one-third tibial tubercle and Cobb's method. RESULTS: Significant differences (P<0.05) in ML, medial anteroposterior (MAP), lateral anteroposterior (LAP) lengths, and aspect ratio (ML/LAP) were observed for males and females with respect to different measurement techniques for the tibial rotation axis. However, the measured aspect ratio (ML/MAP) of tibiae for the Korean population did not show significance. The measured aspect ratio (ML/AP) ratio of tibiae for the Korean population was higher than that of currently available tibial components. CONCLUSIONS: Results from this study can guide development of gender-specific tibial prosthesis designs with different ML and AP aspect ratios based on the tibial anatomical rotation axis for the Korean population.