Deep generative design of porous organic cages via a variational autoencoder

Porous organic cages (POCs) are a class of porous molecular materials characterised by their tunable, intrinsic porosity; this functional property makes them candidates for applications including guest storage and separation. Typically formed via dynamic covalent chemistry reactions from multifunctionalised molecular precursors, there is an enormous potential chemical space for POCs due to the fact they can be formed by combining two relatively small organic molecules, which themselves have an enormous chemical space. However, identifying suitable molecular precursors for POC formation is challenging, as POCs often lack shape persistence (the cage collapses upon solvent removal with loss of its cavity), thus losing a key functional property (porosity). Generative machine learning models have potential for targeted computational design of large functional molecular systems such as POCs. Here, we present a deep-learning-enabled generative model, Cage-VAE, for the targeted generation of shape-persistent POCs. We demonstrate the capacity of Cage-VAE to propose novel, shape-persistent POCs, via integration with multiple efficient sampling methods, including Bayesian optimisation and spherical linear interpolation.

Porous liquids - the future is looking emptier

The development of microporosity in the liquid state is leading to an inherent change in the way we approach applications of functional porosity, potentially allowing access to new processes by exploiting the fluidity of these new materials. By engineering permanent porosity into a liquid, over the transient intermolecular porosity in all liquids, it is possible to design and form a porous liquid. Since the concept was proposed in 2007, and the first examples realised in 2015, the field has seen rapid advances among the types and numbers of porous liquids developed, our understanding of the structure and properties, as well as improvements in gas uptake and molecular separations. However, despite these recent advances, the field is still young, and with only a few applications reported to date, the potential that porous liquids have to transform the field of microporous materials remains largely untapped. In this review, we will explore the theory and conception of porous liquids and cover major advances in the area, key experimental characterisation techniques and computational approaches that have been employed to understand these systems, and summarise the investigated applications of porous liquids that have been presented to date. We also outline an emerging discovery workflow with recommendations for the characterisation required at each stage to both confirm permanent porosity and fully understand the physical properties of the porous liquid.

Detection rate of serrated polyps and serrated polyposis syndrome in colorectal cancer screening cohorts: a European overview

OBJECTIVE

The role of serrated polyps (SPs) as colorectal cancer precursor is increasingly recognised. However, the true prevalence SPs is largely unknown. We aimed to evaluate the detection rate of SPs subtypes as well as serrated polyposis syndrome (SPS) among European screening cohorts.

METHODS

Prospectively collected screening cohorts of ≥1000 individuals were eligible for inclusion. Colonoscopies performed before 2009 and/or in individuals aged below 50 were excluded. Rate of SPs was assessed, categorised for histology, location and size. Age-sex-standardised number needed to screen (NNS) to detect SPs were calculated. Rate of SPS was assessed in cohorts with known colonoscopy follow-up data. Clinically relevant SPs (regarded as a separate entity) were defined as SPs ≥10 mm and/or SPs >5 mm in the proximal colon.

RESULTS

Three faecal occult blood test (FOBT) screening cohorts and two primary colonoscopy screening cohorts (range 1.426-205.949 individuals) were included. Rate of SPs ranged between 15.1% and 27.2% (median 19.5%), of sessile serrated polyps between 2.2% and 4.8% (median 3.3%) and of clinically relevant SPs between 2.1% and 7.8% (median 4.6%). Rate of SPs was similar in FOBT-based cohorts as in colonoscopy screening cohorts. No apparent association between the rate of SP and gender or age was shown. Rate of SPS ranged from 0% to 0.5%, which increased to 0.4% to 0.8% after follow-up colonoscopy.

CONCLUSIONS

The detection rate of SPs is variable among screening cohorts, and standards for reporting, detection and histopathological assessment should be established. The median rate, as found in this study, may contribute to define uniform minimum standards for males and females between 50 and 75 years of age.

C4d Complement Split Product in Diagnosis of Immunological Activity of Chronic Allograft Nephropathy

INTRODUCTION

Activation of the humoral branch of the immunological response is currently believed to play an important role in pathogenesis of chronic allograft nephropathy. The impact of humoral alloreactivity, indicated by the presence of C4d deposits in peritubular capillaries of a renal allograft, on the development of chronic allograft nephropathy is a significant problem in transplantation. The aim of the study was to assess and correlate C4d expression in patients with chronic allograft nephropathy, with clinical and morphological variables, as well as to assess the impact of a change in immunosuppression regimen on posttransplant course and renal allograft morphology.

PATIENTS AND METHODS

Twenty-six patients with chronic allograft nephropathy underwent biopsies to correlate C4d expression with clinical parameters and morphological findings. In all patients azathioprine was replaced with mycophenolate mofetil with additional CsA dose reduction in 12 patients. After 1 year, 14 protocol biopsies were performed.

RESULTS

The frequency of C4d peritubular capillary deposition among patients with chronic allograft nephropathy was 30%. C4d expression appeared later after transplantation, was correlated with chronic allograft glomerulopathy and proteinuria but not other clinical or histological variables. C4d deposits displayed no independent impact on serum creatinine level. Proteinuria was significantly more reduced in the C4d(+) group. Progression of chronic morphological changes was significantly accelerated in the C4d(+) group.

CONCLUSION

C4d peritubular capillary expression did not differentiate patients after immunosuppression enhancement, but it predisposed to progression of chronic morphological findings during 1-year observation.

Serum TGF-beta1 correlates with chronic histopathological lesions in protocol biopsies of kidney allograft recipients

INTRODUCTION

Transforming growth factor-beta (TGF-beta) is a well-known profibrotic factor playing a role in chronic kidney allograft nephropathy. Cyclosporine (CsA)-sparing immunosuppressive regimens may improve long-term graft function. Our aim was to study the influence of immunosuppressive treatment with versus without calcineurin inhibitors on serum TGF-beta levels and histological changes in protocol biopsies of kidney allograft recipients.

PATIENTS AND METHODS

In this prospective, randomized study of 42 low-rejection risk patients we randomized two groups: group A: mycophenolate mofetil (MMF), prednisone, daclizumab, and reduced CsA dose for 7 months (5 mg per kg per day) followed by complete withdrawal (n = 21); and group B: normal CsA dose (10 mg per kg per day adjusted according to C2 levels), MMF, prednisone, and no daclizumab (n = 21).

METHODS

In both groups we performed histological assessments (Banff 97) and measured serum TFG-beta levels before as well as, at 3 and 12 months after transplantation.

RESULTS

We found a relationship between immunosuppressive regimen and the TGF-beta concentration over 1 year of observation. Before transplant the TGF-beta1 levels did not differ between the groups (P = .29); at 3 months they were 33 +/- 9 vs 49 +/- 15 pg per mL, respectively, in groups A and B (P = .08), and at 12 months they were 39.5 +/- 4 versus 55.5 +/- 11 pg per mL, respectively, in groups A and B (P = .03). Protocol biopsies at 12 months in group B showed chronic tubular lesions more pronounced than in group A. TGF-beta1 concentrations were significantly higher among group B than A. We conclude that TGF-beta1 concentration may predict the development of kidney graft fibrosis; early CsA withdrawal may achieve a reduction in chronic tubular and interstitial injury of cadaveric kidney allografts.

The role of the protocol biopsies in renal allograft recipients

Subclinical rejection and long-term cyclosporine nephrotoxicity are well-known risk factors of chronic allograft nephropathy. In a prospective study 32 low-risk patients were randomized to either a reduced CsA dose (5 mg/kg/d) and daclizumab (group A, n = 16) for 7 months posttransplant with subsequent CsA tapering/withdrawal, or to a normal CsA dose (10 mg/kg/day) without daclizumab (group B, n = 16). Both groups received MMF and prednisone. Protocol biopsies were obtained at engraftment and 3 and 12 months after Tx. The number of rejection episodes was the primary endpoint. The secondary endpoints were: renal function, histological parameters related to CsA, and serum levels of TGF-beta and PDGF-BB. A low incidence of clinically suspected rejection episodes was observed (19% in group A and 12.4% in group B; P = NS). Although protocol biopsies showed 12 subclinical rejection episodes (six in group A, six in group B), serum creatinine levels were not different between the examined groups at 3 months. However, at 12 months, there was a statistically improved mean creatinine level in group A patients (1.2 mg/dL +/- 0.5 in group A vs 1.54 mg/dL in group B; P <.05). Chronic histopathologic changes were significant for biopsies at 3 and 12 months in both groups compared to the baseline findings for protocol biopsies (with no differences between groups, or between 3 and 12 months in both groups). Serum TGF-beta and PDGF-BB did not differ between the groups. Protocol biopsies may be useful to monitor safety and efficiency of new immunosuppressive protocols. Immunosuppressive regimens with low CsA doses followed by the drug's complete withdrawal seem to be efficient and safe in low-risk kidney allograft recipients.