Donor Groups Research Articles

Solvent-Directed Social Chiral Self-Sorting in Pd2L4 Coordination Cages.

A family of Pd2L4 cages prepared from ligands based on an axially chiral diamino-[1,1'-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative ("social") chiral self-sorting, exclusively yielding the meso-trans product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form. The experimental (solvent-dependent NMR, single-crystal X-ray diffraction) observations of this cooperative interaction could be explained by computational analyses only when explicit solvation was considered. Furthermore, we prepared a larger chiral ligand with isoquinoline donors, which, unlike the first one, does not undergo social self-sorting from its racemic mixture, further highlighting the importance of solvents bridging short distances between the amino groups. Homochiral cages formed from this larger ligand, however, furnish a cavity that can bind anionic and neutral metal complexes such as [Pt(CN)6]2- and Cr(CO)6 and discriminate between the two enantiomers of chiral guest camphor sulfonate.

Succinyl-coenzyme A: a key metabolite and succinyl group donor in erythropoiesis.

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Tunable Isometric Donor‐Acceptor Wurster‐Type Covalent Organic Framework Photocathodes

AbstractCovalent organic frameworks (COFs) offer remarkable versatility, combining ordered structures, high porosity, and tailorable functionalities in nanoscale reaction spaces. Herein, we report the synthesis of a series of isostructural, photoactive Wurster‐type COFs achieved by manipulating the chemical and electronic nature of the Wurster aromatic amine building blocks. A series of donor‐acceptor‐donor (D‐A‐D) Wurster building block molecules was synthesized by incorporating heteroaromatic acceptors with varying strengths between triphenylamine donor groups. These tailored building blocks were integrated into a 2D COF scaffold, resulting in highly crystalline structures and similar morphologies across all COFs. Remarkably, this structural uniformity was also achieved in the synthesis of homogeneous and oriented thin films. Steady‐state photoluminescence revealed a tunable red‐shift in film emission exceeding 100 nm, demonstrating effective manipulation of their optical properties. Furthermore, photoelectrochemical (PEC) water splitting studies exhibited a doubled current density (8.1 μA cm−2 at 0.2 VRHE) for the COF with the strongest acceptor unit. These findings highlight the potential of Wurster D‐A‐D COFs in photoelectrochemical water splitting devices and pave the way for further exploration of chemical functionality‐reactivity‐property relationships in this promising class of photoactive materials.

Synthetic Strategies Towards the Generation of Penicillin-Containing Hybrids in the Search for Anticancer Activity.

An extended library of hybrids that combined a penicillin derivative with a peptoid moiety was designed and synthetized using either a solid-phase or a mixed solid-phase/solution-phase strategy. The library was further evaluated for antiproliferative activity. While none of the different synthesized compounds showed significant cytotoxicity against a normal cell line, tumor cell results drew several conclusions, when comparing with our reference, the highly active triazolylpeptidyl penicillin derivative, TAF7f. Thus, when the 1,2,3-triazole group was exchanged by its "retro-inverse" analogue, no change was noted in the activity of the hybrids; however, better performance was generally obtained if the triazole is replaced by a glycine moiety. Additionally, the absence of hydrogen bond donor groups decreased the compounds activity, which could explain that, in general, this set of derivatives were less active than their peptide-containing analogues. From this study, is indisputable that, regardless of the type of chain (peptide, peptoid or mixture) attached to penicillin, an isobutyl side chain placed in the position closest to penicillin and a benzyl in the next position are determinant for the activity.

CCR8/CCL1 and CXCR3/CXCL10 axis mediated memory T cell activations in recalcitrant drug-induced hypersensitivity patients.

As a drug-induced hypersensitivity syndrome, drug reaction with eosinophilia and systemic symptoms (DRESS) is potentially fatal. Most patients with DRESS recover within a few weeks; however, some patients may suffer from a prolonged disease course and develop autoimmune sequelae. We investigated the immune mechanism and therapeutic targets of patients with recalcitrant DRESS with a prolonged disease course. A total of 32 patients with recalcitrant DRESS with a prolonged treatment course ≥8 weeks, 28 patients with short-duration DRESS with a treatment course <2 weeks, and 26 healthy individuals were enrolled in the study for analysis. Bulk transcriptome results demonstrated that mRNA expression levels of CCR8 and CXCR3 were significantly increased in the blood samples from patients in the acute stage of prolonged DRESS (adjusted p-values: CCR8=1.50×10-9 and CXCR3=2.60×10-4, respectively, for comparison of patients with prolonged DRESS to the healthy donor group). Serum and skin lesional concentrations of CCL1 and CXCL10, as the ligands of CCR8 and CXCR3, respectively, were significantly elevated in patients with prolonged DRESS as compared to those patients with short-duration DRESS. The results from high-parameter flow cytometry and autoantibody screening also identified significant escalations of CD8+ GNLY+CXCR3+effector memory T cells, CD8+central memory T cells, CD4+CCR8+Th2 cells, and IgG-anti-HES6 autoantibodies in patients with prolonged DRESS. Furthermore, in vitro blocking assays revealed that JAK inhibitors (mainly tofacitinib and upadacitinib) significantly decreased the release of CCL1 and CXCL10, and some patients with prolonged DRESS were successfully treated with JAK inhibitors. JAK inhibitors (tofacitinib and upadacitinib) were associated with decreased concentrations of CCL1 and CXCL10, suggesting that they may attenuate CCR8/CCL1- and CXCR3/CXCL10-axis-mediated memory T cell activation, which contribute to disease pathogenesis for patients with recalcitrant DRESS and a long-term treatment course.

Reproduction of experimental data for stacked caffeine dimers using various computational methods

Reliable description of stacking interaction of aromatic molecules is important for the understanding structure, stability, and functions of biopolymers. The caffeine molecule is an ideal object for this study as the stacking interactions are the preferential ones for self-associations of this hydrophobic molecule without H-bond donor groups. The analysis of anhydrous caffeine crystal structures revealed five types of caffeine stacking dimers. Geometry optimization of these dimers was performed using two molecular mechanics force fields, ab-initio method Møller Plesset of the second order (MP2), and density functional theory (DFT) with different functionals. The comparison of geometric parameters of the caffeine dimers obtained using different theoretical methods with those in crystals enables us to suggest the methods providing the most reliable stacking characteristics. These methods are: the MP2 with Basis Set Superposition Error correction (MP2/CP), Poltev force field, along with PBE0-DH, SCAN and PBE-D3 functionals of DFT. For the methods, which give the dimer interaction energy close to that obtained by MP2/CP method, the evaluated sublimation enthalpy values are shown to be close to the experimental data. Additionally, MP2/CP, Poltev FF and PBE0-DH functional showed to be the methods that describe well both the energy and geometry of the caffeine stacking dimer.

Male fertility is preserved following ixekizumab treatment-a real life pilot study.

Preserving fertility is crucial when managing male patients with spondyloarthritis (SpA) and/or psoriasis (PsO), especially in young men. Chronic inflammation, hormonal dysregulation, and immunosuppressive therapies can negatively impact male fertility. Over the past decades, positive data have emerged regarding the reproductive safety of various therapies in men. Ixekizumab (IXE), a high-affinity monoclonal antibody targeting IL-17A, has shown a safe profile for male fertility in small studies. This pilot study assesses the impact of IXE treatment on sperm parameters in SpA and/or PsO patients in a real-world setting. Consecutive adult male SpA and/or PsO patients eligible for or undergoing IXE treatment were prospectively enrolled. Demographic data, disease characteristics, laboratory assessments, comorbidities, and previous treatments were recorded. Sperm analysis was conducted after a minimum of 6 months of IXE treatment, and also before treatment inititation in a subgroup of patients. Parallel sperm evaluations were performed in a control group of healthy donors. Ten patients were enrolled: 8 with SpA and 2 with PsO. After 6 months of IXE treatment, all patients had normal sperm parameters. One SpA and PsO patient with baseline oligozoospermia showed normal parameters at follow-up and achieved a successful pregnancy post-treatment. Compared with controls, IXE-treated patients had lower sperm concentrations but higher vitality. In our limited size pilot study on SpA and PsO patients, Ixekizumab exposure did not impair male fertility. Sperm parameters remained within normal ranges after a minimum of 6 months of treatment. Early Ixekizumab treatment may preserve or potentially reverse fertility impairment.

Heterogeneously Catalyzed Reductive Depolymerization of Lignin to Value-Added Chemicals.

Lignin is an abundant renewable source of aromatics, but its complex heterogeneous structure poses challenges for its depolymerization and valorization. Heterogeneously catalyzed reductive depolymerization (HCRD) has emerged as a promising approach, utilizing heterogeneous catalysts to facilitate selective bond cleavage in lignin and hydrogen transfer to stabilize the products under mild conditions. This review provides a comprehensive understanding of the hydrogen transfer mechanisms in HCRD, involving different hydrogen sources, including molecular hydrogen, alcohols, formic acid, etc., and the native hydrogen donor groups in lignin. The interaction between hydrogen sources and catalyst design is explored, emphasizing how catalyst characteristics must align with specific hydrogen transfer pathways to optimize efficiency and selectivity. Precious metal-based and non-precious metal-based catalysts are examined, highlighting advances that enhance hydrogen activation and transfer. Comparative analyses of hydrogen sources reveal distinct advantages and limitations. The significance of HCRD in lignin valorization and the development of integrated biorefineries is underscored, emphasizing its potential to contribute to a sustainable bioeconomy through improved process integration and economic viability.

Exploring characteristic features for effective HCN1 channel inhibition using integrated analytical approaches: 3D QSAR, molecular docking, homology modelling, ADME and molecular dynamics.

Neuropathic pain (NP) is characterized by hyperalgesia, allodynia, and spontaneous pain. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channel involved in neuronal hyperexcitability, has emerged as an important target for the drug development of NP. HCN channels exist in four different isoforms, where HCN1 is majorly expressed in dorsal root ganglion having an imperative role in NP pathophysiology. A specific HCN1 channel inhibitor will hold the better potential to treat NP without disturbing the physiological roles of other HCN isoforms. The main objective is to identify and analyze the chemical properties of scaffolds with higher HCN1 channel specificity. The 3D-QSAR studies highlight the hydrophobic & hydrogen bond donor groups enhance specificity towards the HCN1 channel. Further, the molecular interaction of the scaffolds with the HCN1 pore was studied by generating an open-pore model of the HCN1 channel using homology modelling and then docking the molecules with it. In addition, the important residues involved in the interaction between HCN1 pore and scaffolds were also identified. Moreover, ADME predictions revealed that compounds had good oral bioavailability and solubility characteristics. Subsequently, molecular dynamics simulation studies revealed the better stability of the lead molecules A7 and A9 during interactions and ascertained them as potential drug candidates. Cumulative studies provided the important structural features for enhancing HCN1 channel-specific inhibition, paving the way to design and develop novel specific HCN1 channel inhibitors.

Cosensitization of a Tetraethylene Glycol‐Substituted Unsymmetrical Zinc Phthalocyanine Sensitized Solar Cells with D131 Auxiliary Dye Exhibited Enhanced Efficiency

AbstractAn asymmetric zinc phthalocyanine dye (ZnPcT3C), bearing three tetraethylene glycol donor groups and one carboxylic acid anchoring group, was synthesized as a photosensitizer dye for dye‐sensitized solar cells (DSSCs). The tetraethylene glycol (TEG), consisting of four ethoxy units, works as an amphiphilic long‐chain donor group that greatly helped in reducing the molecular aggregation. Carboxylic acid group, on the other hand, an acceptor, together with TEG in ZnPcT3C functions as a ‘push–pullʼ system suitable for DSSCs. Absorption spectra of ZnPcT3C in DMSO showed a strong sharp Q band in the infrared region 600–700 nm with (λmax = 682 nm) and a less intense soret band appeared in the region 300–400 nm with λmax = 340 nm. The zinc phthalocyanine (ZnPcT3C) exhibited molar extinction coefficient (ε) of 72,727 L mol−1cm−1. The emission was observed at λem = 695 nm upon excitation at 650 nm and exhibited a fluorescence decay of 2.82 ns. The ZnPcT3C dye sensitised solar cell (c = 1 mM) exhibited the power conversion efficiency (η) of 3.52% in chloroform in I−/I3 electrolyte under simulated 100% brightness. Cosensitization of ZnPcT3C with another auxiliary dye D131 in 1:1 ratio in a cocktail‐type DSSC attained the power conversion efficiency of twice as high as η = 6.27% in an identical condition. A mixture of D131 (λmax = 470 nm) dye with the ZnPcT3C phthalocyanine harvests sunlight across the visible spectra, enabling DSSCs to attain a large photocurrent and photovoltage, enhancing power conversion efficiency.

The Antigen-Specific Response of NK Cells to SARS-CoV-2 Correlates With KIR2DS4 Expression.

Natural killer (NK) cells play a pivotal role in the immune response against viral infections, including SARS-CoV-2. However, our understanding of memory NK cell responses in the context of SARS-CoV-2 remains limited. To address this, we investigated the memory-like response of NK cells to SARS-CoV-2 peptides, presented by autologous cells. Blood samples from 45 donors underwent analysis for SARS-CoV-2 IgG antibodies, categorizing them into four groups based on the antibody kind and level. NK cells from SARS-CoV-2-experienced donors demonstrated enhanced degranulation and activation levels, IFNγ production and proliferative potential in response to SARS-CoV-2 peptides. Investigation of highly proliferating NK cells demonstrated the formation of distinct clusters depending on the SARS-CoV-2 peptide supplementation and the donor group. RNA sequencing revealed differential gene expression patterns, highlighting metabolism, protein transport, and immune response genes. Notably, KIR2DS4 expression correlated with enhanced IFNγ production, degranulation and proliferation levels, suggesting a role in SARS-CoV-2 recognition. Collectively, these findings provide detailed insights into antigen-specific NK cell responses to SARS-CoV-2 peptides, indicating potential mechanisms underlying NK cell activation in antiviral immunity.

Stratification risk computation of primary graft gysfunction in heart transplant recipients on a smartphone application

Abstract Introduction There are no standardized guidelines for helping graft allocation in heart transplant (HTx) and accepting transplants from marginal donors and donors after circulatory arrest make decision making even more complex and time consuming than ever. The organ allocation process should include a risk analysis for primary graft dysfunction (PGD) that represents the most dreadful complication of HTx. There are 3 score systems validated to predict PGD but none has clear superior predictive capability compared to the others and the complexity of score computation potentially discourage their clinical use. A score integrating all the variables presented in a user-friendly format should improve efficacy and safeness of the organ allocation process. Methods Severe PGD defined as need for temporary mechanical circulatory support (ECMO) in the first 24 hours following HTx was considered the end-point for risk stratification computation. As a derivation cohort we used meta-analytic approach for identifying variables that are independently associated to severe PGD. The overall prevalence of each variable was determined to define the absolute risk increase value in presence of each factor. We then created a scoring system applying multivariate logistic regression model. As a validation cohort we studied the performance of the score in a retospective series of HTx performed at our institution from 2013 to 2022. We used C statistic equivalent to the area under a receiver-operating characteristic curve for dichotomous outcomes. Values above 0.7 were considered acceptable. We eventually developed an application for smartphone for risk computation. Results On 64 papers screened, 5 studies were considered eligible for the derivation cohort definition. Cumulative number of patients considered was 10’175 with an incidence of severe PGD of 7.1% (CI 5.3 - 10.4) and a 30-day mortality of 41%. 13 variables were identified (table 1). The ROC curve predicted the use of ECMO with the specificity and the sensitivity of 0,81 and 0,92 respectively. We have included in the validation cohort 128 out of 150 transplanted patients, excluding pediatric and double organs transplants. The mean donor age was 45 +/- 12,4 years, 72 (54%) were men. The mean recipient age was 57 +/- 9,3; 92 were men; 32 recipients (25%) needed ECMO support within 24 hours post-transplant; 75% of the donors in the ECMO group were &amp;gt; 40 y.o.; 30 days mortality was 3.1% and 6,2% in the non-ECMO and ECMO group respectively. We validated the model on our cohort defying a binary outcome (ECMO yes/no). Conclusion Clinicians fill donor, recipient and surgical parameters in user-friendly smartphone application identifying patients that are most likely to need ECMO support post HTx. The decision-making process during organ allocation evolves from what was once little more than personal experience and intuition to a reliable evidence-based method based on personalized risk prediction.Table 1

Corrolato(oxo)antimony(V) Dimer with Hydrogen-Bond Donor Groups in Secondary Coordination Sphere as a Catalyst for Hydrogen Evolution Reaction.

The focus is on developing alternative molecular catalysts using main-group elements and implementing strategic improvements for sustainable hydrogen production. For this purpose, a FB corrole with a (2-(2-((4-methylphenyl)sulfonamido)ethoxy)phenyl) group inserted into the meso position (C-10) of the corrole, along with its high-valent (corrolato)(oxo)antimony(V) dimer, was synthesized. In the crystal structure analysis of the FB corrole and the (corrolato)(oxo)antimony(V) dimer complex, it was noted that the sulfonamido group in the ligand periphery sits atop the corrole ring. The electrochemical hydrogen evolution reaction (HER) of the (corrolato)(oxo)antimony(V) dimer was studied and compared with a previously reported (corrolato)(oxo)antimony(V) complex, which lacks hydrogen-bond donor groups in the secondary coordination sphere. The newly designed molecules, featuring hydrogen-bond donor groups in the secondary coordination sphere, demonstrated clear superiority in the electrochemical HER. Controlled potential electrolysis was employed to evaluate the charge accumulation associated with hydrogen generation in a homogeneous three-electrode system in the presence of 50 mM TFA. The produced hydrogen exhibits a Faradaic efficiency of approximately 80.96%, a turnover frequency (TOF) of 0.44 h-1, and a production rate of 52.83 μL h-1, highlighting the effective catalytic activity of the (corrolato)(oxo)antimony(V) dimer in hydrogen evolution.

INCLUSION OF AZULENE STRUCTURAL UNITS IN THE BASIS OF CONJUGATED POLYMERS: IMPROVEMENT OF PROTON SENSITIVITY AND FLUORESCENCE

The growing interest in aromatic polymer compounds with an extended π-electron coupling system is explained by their importance as functional materials for organic optoelectronics. At present, much attention is paid to arylated, as well as substituted by electron acceptor and/or electron donor groups, aromatic and heteroaromatic compounds. One of the advantages of such conjugated aromatic systems is that they can fine-tune the electronic structure of materials in order to optimize their performance and morphology. In this regard, the structural isomer of naphthalene - azulene is of considerable interest. The nonalternant aromatic hydrocarbon azulene has unique electronic and spectral properties, including a polarized structure with a dipole moment of the order of 1,08 D and abnormal Anti-Kasha fluorescence S2→S0. The article discusses the synthesis of two fluorene-azulene π-conjugated copolymers using the modern methodology of organic synthesis as the Suzuki − Miyaura -cross−coupling reaction. It was shown that the interaction of 1,3-dibromazulene, as well as 2,7-Bis(3-bromoazulen-1-yl)-9,9-dioctyl-fluorene with 2,2'-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(1,3,2-dioxaborinane) under Suzuki − Miyaura cross-coupling conditions, azulene conjugate copolymers were synthesized: poly[2,7-(9,9-dioctylfluorenyl)-alt-(1ꞌ,3ꞌ - azulenyl)] and poly[1,3-bis(9ꞌ,9ꞌ-dioctylfluoren-2ꞌ-yl)azulenyl]-alt-[1ꞌꞌ,3ꞌꞌ - azulenyl]. It is revealed that neutral solutions of the obtained copolymers are nonfluorescent, but they become luminescent upon addition of trifluoroacetic acid. The «launching» of fluorescence occurs as a result of the formation of a 6 π-electron azulenyl cation, which rearranges the general electronic character of polymers, in particular, HOMO-LUMO levels and band gap. The obtained results demonstrate that the introduction of azulene units into a conjugated polymer framework has great potential for application as new protic functional materials.

Au···I coinage bonds: Boosting photoluminescence efficiency and solid‐state molecular motion

AbstractCoinage bonds, a type of noncovalent interaction, occur between group 11 elements (Au, Ag, and Cu) with electron donor groups. Despite theoretical validation, empirical evidence remains limited. In this study, an aggregation‐induced emission (AIE)‐active Au(I) complex, ITCPAu, which exhibits Au···I coinage bonds, was revealed based on the single‐crystal X‐ray diffraction and theoretical calculations. Further examination of the luminescence properties of the ITCPAu revealed multiswitchable behavior, including mechanochromism and thermochromism. Nearly pure white‐light emission was achieved with Commission Internationale de L'Eclairage (CIE) 1931 chromaticity coordinates of (0.30, 0.31) by grinding the green‐emissive ITCPAu monomer crystals. Moreover, visualization and manipulation of solid‐state molecular motion (SSMM) in the yellow‐emissive ITCPAu dimer crystals, driven by the robust Au···I coinage bonds, were revealed through a combination of crystal engineering and luminescent properties. Furthermore, to support the robust Au···I coinage bonds, a versatile carrier for small solvent molecules in crystal lattices was developed for uptake and release. Our findings provide experimental and theoretical evidence for Au···I coinage bonds, highlighting their ability to boost photoluminescence quantum yield (PLQY) and trigger SSMM, emphasizing their potential in developing smart materials with stimuli‐responsive properties.

Association of regular plasmapheresis donation with serum protein and electrolyte levels: a multicentre cross-sectional study in China

BackgroundChina’s plasmapheresis donation policy differs from that of Western countries. The association between regular plasmapheresis donation and donor health in China is still unknown.ObjectivesTo investigate the association of regular plasmapheresis...

Cationic or Neutral: Dependence of Photophysical Properties of Bis-Alkynylphosphonium Pt(II) Complexes on Ancillary Ligand.

A series of D-π-A alkynylphosphonium salts with different linker between donor and acceptor groups was used to synthesize two series of trans-bis-alkynylphosphonium Pt(II) complexes with different ancillary ligands (triphenylphosphine, P series, and cyanide, CN series). The nature of the ancillary ligand manages the overall charge and emission properties of the complexes obtained. In addition, the variation of the linker in alkynylphosphonium ligands allows fine-tuning the luminescence wavelength. Dicationic series P is unstable in solution under UV excitation, whereas in the solid state, these complexes are the first example of phosphorescent trans-phosphine-bis-alkynyl Pt(II) compounds. Neutral series CN demonstrates bright emission in solution, including dual emission for 2CN complex with biphenyl linker in alkynylphosphonium ligand. However, in the solid state for the CN series drastic decrease in the emission quantum yield compared to the P series was observed. DFT calculations reveal the complicated emission nature for the both P and CN series with various contributions of 3ILCT, 3LLCT and 3MLCT states. However, in the naphthyl-containing derivatives 3P and 3CN, the dominating 3LC character with some admixture of CT states is postulated.

AI-FEED: Prototyping an AI-Powered Platform for the Food Charity Ecosystem

This paper presents the development and functionalities of the AI-FEED web-based platform (ai-feed.ai), designed to address food and nutrition insecurity challenges within the food charity ecosystem. AI-FEED leverages advancements in artificial intelligence (AI) and blockchain technology to facilitate improved access to nutritious food and efficient resource allocation, aiming to reduce food waste and bolster community health. The initial phase involved comprehensive interviews with various stakeholders to gather insights into the ecosystem’s unique challenges and requirements. This informed the design of four distinct modules in the AI-FEED platform, each targeting the needs of one of four stakeholder groups (food charities, donors, clients, and community leaders). Prototyping and iterative feedback processes were integral to refining these modules. The food charity module assists charities in generating educational content and predicting client needs through AI-driven tools. Based on blockchain technology, the food donor module streamlines donation processes, enhances donor engagement, and provides donor recognition. The client module provides real-time information on food charity services and offers a centralized repository for nutritional information. The platform includes a comprehensive mapping and proposal system for community leaders to strategically address local food insecurity issues. AI-FEED’s integrated platform approach allows data sharing across modules, enhancing overall functionality and impact. The paper also discusses ethical considerations, potential biases in AI systems, and the transformation of AI-FEED from a research project to a sustainable entity. The AI-FEED platform exemplifies the potential of interdisciplinary collaboration and technological innovation in addressing societal challenges, particularly in improving food security and community health.

Stress fracture of bone under physiological multiaxial cyclic loading: Activity-based predictive models

While it is known that excessive accumulation of fatigue damage from daily activities contributes to fracture, a model of bone failure under physiologically relevant multiaxial cyclic loading needs to be developed in order to develop effective management strategies for stress or fatigue fractures. The role of strain-induced damage from repetitive loading is a strong candidate for such a model, as cycles of mechanical loading leading to failure can be measured directly. However, this approach has been limited by the restrictions of uniaxial loading models, which often overestimates the fatigue life of bone and suggests that bone will only break well beyond the realistic limits of exercise. To address this gap and develop a physiologically relevant model, our study leverages the power of four commonly used engineering failure criteria as a model for multiaxial loading using a cohort of human tibiae from cadaveric donors (age range 21–85 years old). Four failure criteria (Von Mises, Tsai-Wu, Findley critical plane, and maximum shear strain) were found to be effective in vitro models of tibial fracture when age groups of donors were combined (r2 > 0.84) and stratified (younger: 21–52-years-old versus older: 57–85-years-old) (r2 > 0.83) (p < 0.001). Each failure criterion displayed distinctly lower fatigue curves for the older age group. The maximum shear strain model was used to determine the efficacy of this approach to predict fatigue fractures in humans using published in vivo data from human volunteers. Consistent with in vivo observations in general population, the model demonstrated failure at 5000 to 200,000 loading cycles depending on activities such as jumping, sprinting, and walking, with a 3-fold reduction of fatigue life in older donors. These findings dramatically improve estimates of fatigue life under repetitive loading and demonstrate how age-related changes in bone significantly increase its propensity for fatigue-induced fractures.

Does old-to-young kidney transplantation rejuvenate old donor kidneys?

The number of older organ donors is increasing due to the aging population. Aged kidneys often face problems such as delayed graft function but previous murine experiments suggested the possibilities of rejuvenation, for example, in a parabiosis setting between old and young mice. To investigate kidney-graft rejuvenation, we compared an old-to-young (O-Y) patient transplantation group and a transplantation group with donors/recipients of approx. the same age (SA) with the renal senescence marker p16 in kidney biopsy samples at baseline and one year post-transplantation. We retrospectively analyzed our hospital's 32 cases of living-donor ABO-compatible transplants performed between 2013-2020. Both the baseline and one-year biopsy (n=9) or only the baseline biopsy (n=32) were analyzed. We divided the nine cases into an O-Y group (donors' median age 68 yrs, recipients 41, difference -27) and an SA group (donors' median age 53 yrs, recipients 51.5, difference -3.5). p16 was stained with the clones JC8 and E6H4 to determine the precise p16-positive rate. The 32 baseline biopsies' p16-positive rate was weakly related to donor age, suggesting that the p16-positive rate can help evaluate kidney senescence. The (n=5) O-Y group's p16-positive rates were at baseline 0.08 and one year 0.12; the (n=4) SA group's rate was 0.03 at both baseline and one year. No kidney rejuvenation was observed, even when old donor kidneys went to young recipients.