Aged Tendons Exhibit Altered Mechanisms of Strain-Dependent Extracellular Matrix Remodeling

Aging is a primary risk factor for degenerative tendon injuries, yet the etiology and progression of this degeneration are poorly understood. While aged tendons have innate cellular differences that support a reduced ability to maintain mechanical tissue homeostasis, the response of aged tendons to altered levels of mechanical loading has not yet been studied. To address this question, we subjected young and aged murine flexor tendon explants to various levels of in vitro tensile strain. We first compared the effect of static and cyclic strain on matrix remodeling in young tendons, finding that cyclic strain is optimal for studying remodeling in vitro. We then investigated the remodeling response of young and aged tendon explants after 7 days of varied mechanical stimulus (stress deprivation, 1%, 3%, 5%, or 7% cyclic strain) via assessment of tissue composition, biosynthetic capacity, and degradation profiles. We hypothesized that aged tendons would show muted adaptive responses to changes in tensile strain and exhibit a shifted mechanical setpoint, at which the remodeling balance is optimal. Interestingly, we found that 1% cyclic strain best maintains native physiology while promoting extracellular matrix (ECM) turnover for both age groups. However, aged tendons display fewer strain-dependent changes, suggesting a reduced ability to adapt to altered levels of mechanical loading. This work has a significant impact on understanding the regulation of tissue homeostasis in aged tendons, which can inform clinical rehabilitation strategies for treating elderly patients.

3D human tissue models and microphysiological systems for HIV and related comorbidities

Three-dimensional (3D) human tissue models/microphysiological systems (e.g., organs-on-chips, organoids, and tissue explants) model HIV and related comorbidities and have potential to address critical questions, including characterization of viral reservoirs, insufficient innate and adaptive immune responses, biomarker discovery and evaluation, medical complexity with comorbidities (e.g., tuberculosis and SARS-CoV-2), and protection and transmission during pregnancy and birth. Composed of multiple primary or stem cell-derived cell types organized in a dedicated 3D space, these systems hold unique promise for better reproducing human physiology, advancing therapeutic development, and bridging the human-animal model translational gap. Here, we discuss the promises and achievements with 3D human tissue models in HIV and comorbidity research, along with remaining barriers with respect to cell biology, virology, immunology, and regulatory issues.

Functional human skin explants as tools for assessing mast cell activation and inhibition

Mast cells are activated through a variety of different receptors to release preformed granules and mediators synthesized de novo. However, the physiology and function of mast cells are not fully understood. Traditional studies of mast cell activation in humans have utilized cultures of tissue-derived mast cells including CD34+ progenitor cells or well-characterized commercially available cell lines. One limitation of these methods is that mast cells are no longer in a natural state. Therefore, their applicability to human skin disorders may be limited. Human skin explant models have been utilized to investigate the short-term effects of cell mediators, drugs, and irritants on skin while avoiding the ethical concerns surrounding in vivo stimulation studies with non-approved agents. Nonetheless, few studies have utilized intact human tissue to study mast cell degranulation. This "Methods" paper describes the development and application of an intact skin explant model to study human mast cell activation. In this manuscript, we share our protocol for setting up ex vivo human skin explants and describe the results of stimulation experiments and techniques to minimize trauma-induced histamine release. Skin explants were generated using de-identified, full-thickness, non-diseased skin specimens from plastic and reconstructive surgeries. Results were reproducible and demonstrated FcɛRI- and MRGPRX2-induced mediator release which was inhibited with the use of a BTK inhibitor and QWF, respectively. Thus, this explant model provides a quick and accessible method of assessing human skin mast cell activation and inhibition.

An Efficient Agrobacterium-Mediated Genetic Transformation System for Gene Editing in Strawberry (Fragaria × ananassa)

The octoploid-cultivated strawberry variety Benihope (Fragaria × ananassa Duch cv. Benihope) is an important commercial plant. It is highly susceptible to different diseases, which ultimately leads to a reduction in yield. Gene-editing methods, such as CRISPR/Cas9, demonstrate potential for improving disease resistance in the strawberry cv. Benihope. Establishing a plant regeneration system suitable for CRISPR/Cas9 gene editing is crucial for obtaining transgenic plants on a large scale. This research established a callus induction and plant regeneration system for Agrobacterium-mediated CRISPR/Cas9 gene editing in strawberry cv. Benihope by evaluating multiple types of explants and various plant growth regulators throughout the entire tissue culture process. The results showed that the efficiency of callus induction is strongly influenced by the type of explant and is highly sensitive to the combination of plant growth regulators. Among the different plant growth regulators employed, thidiazuron (TDZ), in combination with 2,4-dichlorophenoxyacetic acid (2,4-D), effectively induced callus formation and plant regeneration from explants derived from nutrient tissues such as runner tips and crowns. In addition, the regeneration experiment demonstrated that the addition of polyvinylpyrrolidone (PVPP) to the shoot regeneration medium could inhibit tissue browning. The gene-edited plants in which some or all of the Fvb7-1, Fvb7-2, Fvb7-3, and Fvb7-4 genes in the MLO (Mildew resistance Locus O) gene family were knocked out by CRISPR/Cas9 system were obtained by applying the plant regeneration system developed in this study.

California sea lion (Zalophus californianus) lymph-node explant reveals involvement and possible transcriptional regulation of SLAM and nectin-4 during phocine distemper virus infection

Phocine distemper virus (PDV) is a significant cause of mortality for phocid seals; however, the susceptibility of otariids to this virus is poorly understood. The authors used a lymph-node explant culture system from California sea lions (Zalophus californianus, CSL) to investigate: (1) the role of signaling lymphocyte activation molecule (SLAM) and nectin-4 in PDV infection and their cellular expression patterns, (2) if PDV induces transcriptional regulation of cell-entry receptors, and (3) the involvement of apoptosis in PDV infection. PDV replicated in the lymph-node explants with peak replication 3 days post-infection (dpi), but the replication was not sustained 4 to 5 dpi. The PDV+ cells co-localized SLAM and nectin-4. These cells expressed IBA1, indicating a histiocytic lineage. Comparison of receptor expression between infected and mock-infected lymph nodes suggested transcriptional downregulation of both receptors during the initial stage of infection and upregulation during the late stage of infection, but the values lack of statistical significance. Cleaved caspase-3+ cells were slightly increased in the infected lymph nodes compared with the mock-infected lymph node from 1 to 4 dpi, but without statistical significance, and a few apoptotic cells co-expressed PDV. The results suggest that lymph-node explants might be an important model to study PDV pathogenesis. CSLs have the potential to be infected with PDV, as they express both cell-entry receptors in histiocytes. The lack of statistical significance in the PDV replication, transcriptional regulation of viral receptors, and changes in apoptosis suggest that although CSL might be infected by PDV, they might be less susceptible than phocid species.

Studies on Improving the Efficiency of Somatic Embryogenesis in Grapevine (Vitis vinifera L.) and Optimising Ethyl Methanesulfonate Treatment for Mutation Induction

Somatic embryogenesis (SE) has many applications in grapevine biotechnology including micropropagation, eradicating viral infections from infected cultivars, mass production of hypocotyl explants for micrografting, as a continuous source for haploid and doubled haploid plants, and for germplasm conservation. It is so far the only pathway for the genetic modification of grapevines through transformation. The single-cell origin of somatic embryos makes them an ideal explant for mutation breeding as the resulting mutants will be chimera-free. In the present research, two combinations of plant growth regulators and different explants from flower buds at two stages of maturity were tested in regard to the efficiency of callusing and embryo formation from the callus produced in three white grape cultivars. Also, the treatment of somatic embryos with the chemical mutagen ethyl methanesulfonate (EMS) was optimised. Medium 2339 supplemented with β-naphthoxyacetic acid (5 μM) and 6-benzylaminopurine (BAP-9.0 μM) produced significantly more calluses than medium 2337 supplemented with 2,4-dichlorophenoxyacetic acid (4.5 µM) and BAP (8.9 µM) in all explants. The calluses produced on medium 2337 were harder and more granular and produced more SEs. Although the stage of the maturity of floral bud did not have a significant effect on the callusing of the explants, calluses produced from immature floral bud explants in the premeiotic stage produced significantly more SEs than those from more mature floral buds. Overall, immature ovaries and cut floral buds exposing the cut ends of filaments, style, etc., tested for the first time in grapevine SE, produced the highest percentage of embryogenic calluses. It is much more efficient to cut the floral bud and culture than previously reported explants such as anthers, ovaries, stigmas and styles during the short flowering period when the immature flower buds are available. When the somatic embryos of the three cultivars were incubated for one hour with 0.1% EMS, their germination was reduced by 50%; an ideal treatment considered to obtain a high frequency of mutations for screening. Our research findings will facilitate more efficient SE induction in grapevines and inducing mutations for improving individual traits without altering the genetic background of the cultivar.

Multicenter Comparative Analysis of Late Open Conversion in Patients With Adherence and Nonadherence to Instructions for Use Endovascular Aneurysm Repair

PURPOSE

The widespread adoption of endovascular aneurysm repair (EVAR) as preferred treatment modality for abdominal aortic aneurysm (AAA) has enlarged the number of patients needing open surgical conversion (OSC). The relationship between adherence to Instructions For Use (IFU) and EVAR long-term outcomes remains controversial. The aim of this study is to compare preoperative differences and postoperative outcomes between EVAR patients not adjusted to IFU and adjusted to IFU who underwent OSC.

METHODS

This multicenter retrospective study reviewed 33 explanted EVARs between January 2003 and December 2019 at 14 Vascular Units. Patients were included if OSC occurred >30 days after implantation and excluded if explantation was performed to treat an endograft infection, aortic dissection, or traumatic transections. Variables analyzed included baseline characteristics, adherence to IFU, implant and explant procedural details, secondary reinterventions, and postoperative outcomes.

RESULTS

Fifteen explanted patients (15/33, 45.5%) were identified not accomplished to IFU (out-IFU) at initial EVAR vs 18 explanted patients adjusted (in-IFU). During follow-up, a mean of 1.73±1.2 secondary reinterventions were performed, with more type I endoleaks treated in the subgroup out-IFU: 16.7% vs 6.3% in-IFU patients and more type III endoleaks (8.3% vs 0%). Patients out-IFU had shorter mean interval from implant to explant: 47.60±28.8 months vs 71.17±48. Type II endoleak was the most frequent indication for explantation. Low-flow endoleaks (types II, IV, V) account for 44% of indications for OSC in subgroup of patients in-IFU, compared with 13.3% in patients out-IFU and high-flow endoleaks (types I and III) were the main indication for patients out-IFU (33.3% vs 16.7% in-IFU). Total endograft explantation was performed in 57.5% of cases (19/33) and more suprarenal clamping was required in the subgroup out-IFU. Overall, 30-day mortality rate was 12.1% (4/33): 20% for patients out-IFU and 5.6% in-IFU.

CONCLUSIONS

In our experience, type II endoleak is the most common indication for conversion and differences have been found between patients treated outside IFU with explantation taking place earlier during follow-up, mainly due to high-flow endoleaks and with higher mortality in comparison with patients adjusted to IFU. Ongoing research is required to delve into these differences.

LVAD therapy as a catalyst to heart failure remission and myocardial recovery

The management of chronic heart failure over the past decade has witnessed tremendous strides in medical optimization and device therapy including the use of left ventricular assist devices (LVAD). What we once thought of as irreversible damage to the myocardium is now demonstrating signs of reverse remodeling and recovery. Myocardial recovery on the structural, molecular, and hemodynamic level is necessary for sufficient recovery to withstand explant and achieve sustained recovery post-LVAD. Guideline-directed medical therapy and unloading have been shown to aid in recovery with the potential to successfully explant the LVAD. This review will summarize medical optimization, assessment for recovery, explant methodologies and outcomes post-recovery with explant of durable LVAD.

Combination of Genomic Landsscape and 3D Culture Functional Assays Bridges Sarcoma Phenotype to Target and Immunotherapy

Genomic-based precision medicine has not only improved tumour therapy but has also shown its weaknesses. Genomic profiling and mutation analysis have identified alterations that play a major role in sarcoma pathogenesis and evolution. However, they have not been sufficient in predicting tumour vulnerability and advancing treatment. The relative rarity of sarcomas and the genetic heterogeneity between subtypes also stand in the way of gaining statistically significant results from clinical trials. Personalized three-dimensional tumour models that reflect the specific histologic subtype are emerging as functional assays to test anticancer drugs, complementing genomic screening. Here, we provide an overview of current target therapy for sarcomas and discuss functional assays based on 3D models that, by recapitulating the molecular pathways and tumour microenvironment, may predict patient response to treatments. This approach opens new avenues to improve precision medicine when genomic and pathway alterations are not sufficient to guide the choice of the most promising treatment. Furthermore, we discuss the aspects of the 3D culture assays that need to be improved, such as the standardisation of growth conditions and the definition of in vitro responses that can be used as a cut-off for clinical implementation.

The Burden of Revision Total Ankle Replacement Has Increased From 2010 to 2020

Background

Total ankle replacement (TAR) surgery has increased in recent decades. The aim of this study was to investigate the evolving burden of revision surgery and risk factors and timing of revision or explant.

Methods

Using the 2010 to 2020 PearlDiver M151Ortho data set, this retrospective cohort study identified primary TAR, TAR revision, and TAR explant patients via Current Procedural Terminology (CPT) and International Classification of Disease Procedural (ICD-P) codes. This database contains billing claims information across all payers and sites of care in the United States. Patient factors investigated included age, sex, and Elixhauser Comorbidity Index (ECI). Annual incidence for primary TAR was normalized per 100 000 covered lives in the data set for each year of study and recorded. Annual incidence of revision TAR and explant were normalized per 100 TARs performed for each year of study. Multivariate logistic regression analyses were performed to determine independent risk factors for revision TAR or explant. For explants, the eventual intervention by 2 years was analyzed. Ten-year timing and survival to revision or explant surgery following unilateral TAR were characterized.

Results

A total of 10 531 primary, 1218 revision, and 1735 explant TARs were identified. After normalization, TAR utilization increased by 284% from 2010 to 2020, annual TAR revisions rose 28%, and annual TAR explants decreased 65%. Independent predictors of revision TAR were younger age (odds ratio [OR] 1.29 per decade decrease) and higher ECI (OR 1.23 per 2-point increase). Independent predictors of explant included younger age (OR 1.80 per decade decrease), female sex (OR 1.17), and higher ECI (OR 1.35 per 2-point increase). The 10-year implant survival rate was 91.8%, of which 73% of revisions and 83% of explants occurred in the first 3 years following index TAR.

Conclusion

TAR utilization has grown substantially over the past decade, with minimal increases in the annual rate of revision surgery with respect to index procedures performed.

Level of Evidence

Level III, retrospective cohort study.

Nodal coordinates the anterior-posterior patterning of germ layers and induces head formation in zebrafish explants

Much progress has been made toward generating analogs of early embryos, such as gastruloids and embryoids, in vitro. However, methods for how to fully mimic the cell movements of gastrulation and coordinate germ-layer patterning to induce head formation are still lacking. Here, we show that a regional Nodal gradient applied to zebrafish animal pole explant can generate a structure that recapitulates the key cell movements of gastrulation. Using single-cell transcriptome and in situ hybridization analysis, we assess the dynamics of the cell fates and patterning of this structure. The mesendoderm differentiates into the anterior endoderm, prechordal plate, notochord, and tailbud-like cells along an anterior-posterior axis, and an anterior-posterior-patterned head-like structure (HLS) progressively forms during late gastrulation. Among 105 immediate Nodal targets, 14 genes contain axis-induction ability, and 5 of them induce a complete or partial head structure when overexpressed in the ventral side of zebrafish embryos.

Development and characterization of ferret ex vivo tracheal injury and cell engraftment model

The field of airway biology research relies primarily on in vitro and in vivo models of disease and injury. The use of ex vivo models to study airway injury and cell-based therapies remains largely unexplored although such models have the potential to overcome certain limitations of working with live animals and may more closely replicate in vivo processes than in vitro models can. Here, we characterized a ferret ex vivo tracheal injury and cell engraftment model. We describe a protocol for whole-mount staining of cleared tracheal explants, and showed that it provides a more comprehensive structural overview of the surface airway epithelium (SAE) and submucosal glands (SMGs) than 2D sections, revealing previously underappreciated structural anatomy of tracheal innervation and vascularization. Using an ex vivo model of tracheal injury, we evaluated the injury responses in the SAE and SMGs that turned out to be consistent with published in vivo work. We used this model to assess factors that influence engraftment of transgenic cells, providing a system for optimizing cell-based therapies. Finally, we developed a novel 3D-printed reusable culture chamber that enables live imaging of tracheal explants and differentiation of engrafted cells at an air-liquid interface. These approaches promise to be useful for modeling pulmonary diseases and testing therapies. Graphical abstract1,2. We describe here a method for differential mechanical injury of ferret tracheal explants that can be used to evaluate airway injury responses ex vivo. 3. Injured explants can be cultured at ALI (using the novel tissue-transwell device on the right) and submerged long-term to evaluate tissue-autonomous regeneration responses. 4. Tracheal explants can also be used for low throughput screens of compounds to improve cell engraftment efficiency or can be seeded with particular cells to model a disease phenotype. 5. Lastly, we demonstrate that ex vivo-cultured tracheal explants can be evaluated by various molecular assays and by immunofluorescent imaging that can be performed live using our custom-designed tissue-transwell.

Low Morbidity Anatomical Revascularisation for an Infected Aorto-Bifemoral Graft Using a Staged Hybrid Procedure

A 66-year-old woman presented with a right femoral false aneurysm following an aortobifemoral bypass for lifestyle-limiting claudication. A computed tomography (CT) angiogram revealed features of complete aortobifemoral graft infection. A two-stage procedure was performed. The first hybrid stage involved the excision of only the femoral components and covered stenting of the aortic stump, along with recanalization of bilateral native iliac systems. The second stage, six weeks later, involved aortic stent and graft explant via midline laparotomy with aortic bovine pericardium patch repair (LeMaitre Vascular Inc, Burlington, Massachusetts). Follow-up imaging demonstrated no residual infection, and the patient remained without complication at the 12-month follow-up. This novel approach utilizes hybrid surgical techniques and modern bioprosthetic material to safely manage an infected aortobifemoral bypass graft.

Isolation and characterization of feline dental pulp stem cells

OBJECTIVES

The aim of this study was to isolate feline dental pulp stem cells (fDPSCs) and characterize their clonogenic and proliferative abilities, as well as their multipotency, immunophenotype and cytogenetic stability.

METHODS

Dental pulp was isolated by explant culture from two cats <1 year old at post mortem. Their clonogenicity was characterized using a colony-forming unit fibroblast assay, and their proliferative ability was quantified with a doubling time assay in passages 2, 4 and 6 (P₂, P₄ and P₆, respectively). Multipotency was characterized with an in vitro trilineage differentiation assay in P₂, and cells were immunophenotyped in P₄ by flow cytometry. Chromosomic stability was evaluated by cytogenetic analysis in P₂, P₄ and P₆.

RESULTS

The fDPSCs displayed spindle and epithelial-like morphologies. Isolated cells showed a marked clonogenic capacity and doubling time was maintained from P₂ to P₆. Trilineage differentiation was obtained in one sample, while the other showed osteogenic and chondrogenic differentiation. Immunophenotypic analysis showed fDPSCs were CD45^-, CD90⁺ and CD44⁺. Structural and numerical cytogenetic aberrations were observed in P₂-P₄.

CONCLUSIONS AND RELEVANCE

In this study, fDPSCs from two cats were isolated by explant culture and immunophenotyped. Cells displayed clonogenic and proliferative ability, and multipotency in vitro, and signs of chromosomic instability were observed. Although a larger study is needed to confirm these results, this is the first report of fDPSC isolation and in vitro characterization.

Thermogelling hydrogel charge and lower critical solution temperature influence cellular infiltration and tissue integration in an ex vivo cartilage explant model

Thermogelling hydrogels based on poly(N-isopropyl acrylamide) (p[NiPAAm]) and crosslinked with a peptide-bearing macromer poly(glycolic acid)-poly(ethylene glycol)-poly(glycolic acid)-di(but-2-yne-1,4-dithiol) (PdBT) were fabricated to assess the role of hydrogel charge and lower critical solution temperature (LCST) over time in influencing cellular infiltration and tissue integration in an ex vivo cartilage explant model over 21 days. The p(NiPAAm)-based thermogelling polymer was synthesized to possess 0, 5, and 10 mol% dimethyl-γ-butyrolactone acrylate (DBA) to raise the LCST over time as the lactone rings hydrolyzed. Further, three peptides were designed to impart charge into the hydrogels via conjugation to the PdBT crosslinker. The positively, neutrally, and negatively charged peptides K4 (+), zwitterionic K2E2 (0), and E4 (-), respectively, were conjugated to the modular PdBT crosslinker and the hydrogels were evaluated for their thermogelation behavior in vitro before injection into the cartilage explant models. Samples were collected at days 0 and 21, and tissue integration and cellular infiltration were assessed via mechanical pushout testing and histology. Negatively charged hydrogels whose LCST changed over time (10 mol% DBA) were demonstrated to promote the greatest tissue integration when compared to the positive and neutral gels of the same thermogelling polymer formulation due to increased transport and diffusion across the hydrogel-tissue interface. Indeed, the negatively charged thermogelling polymer groups containing 5 and 10 mol% DBA demonstrated cellular infiltration and cartilage-like matrix deposition via histology. This study demonstrates the important role that material physicochemical properties play in dictating cell and tissue behavior and can inform future cartilage tissue engineering strategies.

Lumbar Spine Osteomyelitis After Permanent Spinal Cord Stimulator Implantation: A Case Report

A spinal cord stimulator (SCS) is an intervention that has become increasingly popular due to its efficacy in treating pain. With the increasing number of SCSs implanted annually, there has been an equal increase in complications, which include infections. We present a patient who underwent an uncomplicated permanent placement of SCS and later developed worsening back pain, weakness, and fever after a mechanical fall and was subsequently found to have vertebral osteomyelitis without an identifiable infection source. While no source or definitive pathogen was discovered, if there is a concern for osteomyelitis radiographically, even in an uncommon situation when medical workup returns inconclusive, explant of the SCS is warranted.

Culturing explants for Cutibacterium at revision shoulder arthroplasty: an analysis of explant and tissue samples at corresponding anatomic sites

BACKGROUND

Culturing of deep tissues obtained at revision arthroplasty for Cutibacterium is a key component of diagnosing a periprosthetic infection. The value of culturing explanted components has not been well described. This study sought to answer the following questions: (1) How does the culture positivity of explant cultures compare with that of deep tissue cultures? (2) How often are explant cultures positive when tissue cultures are not, and vice versa? (3) How does the bacterial density in explant cultures compare with that in tissue cultures?

METHODS

A total of 106 anatomic arthroplasties revised over a 7-year period were included. Explant (humeral head, humeral stem, and glenoid) and tissue (collar membrane, humeral canal tissue, and periglenoid tissue) specimens were sent for semiquantitative Cutibacterium culture. We compared culture positivity and bacterial density when cultures of an explant and tissue adjacent to the implant were both available.

RESULTS

Explants had positive cultures at a higher rate than adjacent tissue specimens for most anatomic sites. Of the shoulders that had Cutibacterium growth, a higher proportion of explants were culture positive when tissue samples were negative (23%-43%) than vice versa (0%-21%). The Cutibacterium density was higher in explants than in tissues. Considering only the results of tissue samples, 16% of the shoulders met our threshold for infection treatment (≥2 positive cultures); however, with the inclusion of the results for explant cultures, additional 14% of cases-a total of 30%-met the criteria for infection treatment.

CONCLUSIONS

In this group of patients, culturing explants in addition to tissue cultures increased the sensitivity for detecting Cutibacterium in revision shoulder arthroplasty.

Biology of myocardial recovery in advanced heart failure with long-term mechanical support

Cardiac remodeling is an adaptive, compensatory biological process following an initial insult to the myocardium that gradually becomes maladaptive and causes clinical deterioration and chronic heart failure (HF). This biological process involves several pathophysiological adaptations at the genetic, molecular, cellular, and tissue levels. A growing body of clinical and translational investigations demonstrated that cardiac remodeling and chronic HF does not invariably result in a static, end-stage phenotype but can be at least partially reversed. One of the paradigms which shed some additional light on the breadth and limits of myocardial elasticity and plasticity is long term mechanical circulatory support (MCS) in advanced HF pediatric and adult patients. MCS by providing (a) ventricular mechanical unloading and (b) effective hemodynamic support to the periphery results in functional, structural, cellular and molecular changes, known as cardiac reverse remodeling. Herein, we analyze and synthesize the advances in our understanding of the biology of MCS-mediated reverse remodeling and myocardial recovery. The MCS investigational setting offers access to human tissue, providing an unparalleled opportunity in cardiovascular medicine to perform in-depth characterizations of myocardial biology and the associated molecular, cellular, and structural recovery signatures. These human tissue findings have triggered and effectively fueled a "bedside to bench and back" approach through a variety of knockout, inhibition or overexpression mechanistic investigations in vitro and in vivo using small animal models. These follow-up translational and basic science studies leveraging human tissue findings have unveiled mechanistic myocardial recovery pathways which are currently undergoing further testing for potential therapeutic drug development. Essentially, the field is advancing by extending the lessons learned from the MCS cardiac recovery investigational setting to develop therapies applicable to the greater, not end-stage, HF population. This review article focuses on the biological aspects of the MCS-mediated myocardial recovery and together with its companion review article, focused on the clinical aspects, they aim to provide a useful framework for clinicians and investigators.

Urocortin-1 Is Chondroprotective in Response to Acute Cartilage Injury via Modulation of Piezo1

Post-traumatic OA (PTOA) is often triggered by injurious, high-impact loading events which result in rapid, excessive chondrocyte cell death and a phenotypic shift in residual cells toward a more catabolic state. As such, the identification of a disease-modifying OA drug (DMOAD) that can protect chondrocytes from death following impact injury, and thereby prevent cartilage degradation and progression to PTOA, would offer a novel intervention. We have previously shown that urocortin-1 (Ucn) is an essential endogenous pro-survival factor that protects chondrocytes from OA-associated pro-apoptotic stimuli. Here, using a drop tower PTOA-induction model, we demonstrate the extent of Ucn's chondroprotective role in cartilage explants exposed to excessive impact load. Using pathway-specific agonists and antagonists, we show that Ucn acts to block load-induced intracellular calcium accumulation through blockade of the non-selective cation channel Piezo1 rather than TRPV4. This protective effect is mediated primarily through the Ucn receptor CRF-R1 rather than CRF-R2. Crucially, we demonstrate that the chondroprotective effect of Ucn is maintained whether it is applied pre-impact or post-impact, highlighting the potential of Ucn as a novel DMOAD for the prevention of injurious impact overload-induced PTOA.

Single-cell landscapes of primary glioblastomas and matched explants and cell lines show variable retention of inter- and intratumor heterogeneity

Glioblastomas (GBMs) are aggressive brain tumors characterized by extensive inter- and intratumor heterogeneity. Patient-derived models, such as organoids and explants, have recently emerged as useful models to study such heterogeneity, although the extent to which they can recapitulate GBM genomic features remains unclear. Here, we analyze bulk exome and single-cell genome and transcriptome profiles of 12 IDH wild-type GBMs, including two recurrent tumors, and of patient-derived explants (PDEs) and gliomasphere (GS) lines derived from these tumors. We find that PDEs are genetically similar to, and variably retain gene expression characteristics of, their parent tumors. Notably, PDEs appear to exhibit similar levels of transcriptional heterogeneity compared with their parent tumors, whereas GS lines tend to be enriched for cells in a more uniform transcriptional state. The approaches and datasets introduced here will provide a valuable resource to help guide experiments using GBM-derived models, especially in the context of studying cellular heterogeneity.

Hypoglossal Nerve Stimulator Explantation: A Case Series

Hypoglossal nerve stimulation (HGNS) has emerged as a successful surgical treatment strategy for moderate to severe obstructive sleep apnea in patients failing first-line positive airway pressure therapy. HGNS explantation due to adverse events such as pain and infection is rare and has yet to be well described. Here, our correspondence describes the first case series of patients who have undergone explantation of the Inspire HGNS system. Five patients were identified who underwent HGNS explantation. Three patients underwent explantation due to magnetic resonance imaging (MRI) incompatibility. One patient underwent explantation due to poor cosmesis. One patient underwent explantation due to surgical site infection. Average operative explant time was 163 minutes. MRI incompatibility, poor cosmesis, and device-related infection are reasons for HGNS explantation. Future need for MRI or chest wall surgery should be considered in patients being evaluated for HGNS implants.

Infectious Complications Following Cochlear Implant: Risk Factors, Natural History, and Management Patterns

OBJECTIVE

To describe the natural history, detail the treatment patterns, and identify the risk factors for cochlear implant (CI) infections in a large US cohort.

STUDY DESIGN

Retrospective study based on insurance claims.

SETTING

Optum Data Mart database: 6101 patients who received CIs from 2003 to 2019.

METHODS

Infections, treatments patterns, and timelines were described. A multivariable logistic regression model was used to assess the association between postoperative oral antibiotics and CI infection.

RESULTS

The cohort includes 4736 (77.6%) adults and 1365 (22.4%) children. Between adult and pediatric patients, rates of CI infection (5.1% vs 4.5%, P = .18) and explantation (1.2% vs 0.8%, P = .11) were not significantly different. Infections typically occurred within 5 months of surgery. Children were diagnosed with CI infection earlier than adults (median difference, -1.5 months; P = .001). Postoperative oral antibiotic supply was not associated with lower risk of CI infection in either children or adults. However, among adults, otitis media was associated with higher odds of CI infection (odds ratio, 1.41; P < .001), while higher income was associated with lower odds of CI infection (odds ratio, 0.71; P = .03).

CONCLUSIONS

Postoperative oral antibiotics were not associated with lower risk of infection or interventions. Otitis media episodes and lower income were associated with increased risk of infection among adults as well as intervention overall. Infection typically presented within the first 6 months after surgery, with children presenting earlier than adults. Overall, our findings serve as a resource for providers to consider in their care of patients with CIs.

Aortic graft explants - A single institution analysis of incidence and outcomes

OBJECTIVES

Explantation of both endovascular endovascular aneurysm repair and open aortic grafts is a procedure associated with high peri-operative risk, and the current study sought to determine the outcomes and trends over time in these patients.

METHODS

This study examined data from all patients undergoing explant of an aortic graft (both open and endovascular) between January 2004 and December 2020 at a single centre. Variables analysed included comorbidities, duration to and indication for explantation, type of revascularization, in-hospital complications and mortality, duration of hospital and ICU stay, and out-patient mortality.

RESULTS

Of 688 open and 1352 EVARs performed, 46 patients underwent 48 explants. Five were open grafts and 43 were endografts, equating to an explant rate of 0.73% of open and 3.18% EVARs. Average time to explant was 70 months, with patients presenting electively having a significantly longer duration to representation than those presenting emergently (51 vs 44 months, p=0.003). Indication for explant was endoleak in 70%, infection in 23%, and occlusion in 6%. Of the endoleaks, 61% of were Type 1, 22% Type II, 11% Type IV, and 6% Type V. On representation, 17 patients (35%) were symptomatic. Overall mortality rate was 8.3%, with a trend for higher mortality in emergent than elective presentations (11.8 vs 6.5%, p=0.55). There was no change in explant rate over time.

CONCLUSIONS

Elective aortic graft explantation is associated with low mortality, despite its complexity and patient comorbidities. Patients presenting with symptoms suffered higher mortality and a longer post-operative course, suggesting that aortic graft explantation should be considered sooner rather than later, rather than persisting with repeated endovascular management.

Evaluating Initial Integration of Cell-Based Chondrogenic Constructs in Human Osteochondral Explants

Integration of an implant with the surrounding tissue is a major challenge in cartilage regeneration. It is usually assessed with in vivo animal studies at the end-stage of implant development. To reduce animal experimentation and at the same time increase screening throughput and speed up implant development, this study examined whether integration of allogeneic cell-based implants with the surrounding native cartilage could be demonstrated in an ex vivo human osteochondral culture model. Chondrocytes were isolated from smooth cartilage tissue of fresh human tibial plateaus and condyles. They were expanded for 12 days either in three-dimensional spinner flask cultures to generate organoids, or in two-dimensional culture flasks for standard cell expansion. Three implant groups were created (fibrin+organoids, fibrin+cells, and fibrin only) and used to fill a Ø 6 mm full-depth chondral defect created in human osteochondral explants (Ø 10 mm, bone length cut to 4 mm) harvested from a second set of fresh human tibial plateaus. Explants were cultured for 1 or 28 days in a double-chamber culture platform. Histology showed that after 28 days the organoids on the interface of the defect remodeled and merged, and cells migrated through the fibrin glue bridging the space between the organoids and between the organoids and the native cartilage. For both conditions, newly formed tissue rich in proteoglycans and collagen type II was present mainly on the edges and in the corners of the defect. In these matrix-rich areas, cells resided in lacunae and the newly formed tissue integrated with the surrounding native cartilage. Biochemical analysis revealed a statistically significant effect of culture time on glycosaminoglycan (GAG) content, and showed a higher hydroxyproline (HYP) content for organoid-filled implants compared with cell-filled implants at both timepoints. This ex vivo human osteochondral culture system provides possibilities for exploration and identification of promising implant strategies based on evaluation of integration and matrix production under more controlled experimental conditions than possible in vivo.

A positive experience in applying the biolistic approach to potato varieties Aksor and Nevskiy

The method of biological ballistics (biolistic transformation, genetic bombardment) of plants is one of the most modern methods used for direct gene transfer into plant cells. The main advantages of this method include the ability to simultaneously incorporate several target genes into the plant genome, carry out transfer without unnecessary agrobacterial parts and plasmid DNA sequences, and the short time needed to produce transgenic cells. For different plant objects, the efficiency of obtaining transgenic plants by the ballistic method varies from 1 to 3 %. For potato plants, the transformation efficiency is quite low at the moment and the selection of optimal conditions for biolistics is one of the pressing issues of practical biotechnology. This article presents a successful experience of introducing two genes of interest into two potato varieties using the biolistic approach. The results of biolistic transformation experiments are presented for two types of explants: potato internodes and calli of the varieties Aksor and Nevskiy. Of the 862 explants used for transformation, 56 regenerated plants were obtained. PCR screening of transformants revealed one plant with the insertion of the chitinase gene, one with the insertion of the endo-β-1,3-glucanase gene, and co-transformation by both genes was confirmed in four regenerants. The average transformation efficiency for potato explants was 0.7 %. A high number of regenerants (56) as opposed to a low number of transformants (6) reflects an attempt to increase the number of regenerants by using a lower concentration of the selective agent (kanamycin). Although this approach requires more effort, it can be used to produce potato lines with integrated genes of interest for further use in crop breeding. The lines of potato obtained in the current study by introducing two genes associated with the plant response to fungal pathogens will be further assessed for their resistance to fungal diseases and, if successful, will be used in potato crop breeding.

The entry inhibitor DS003 (BMS-599793): a BMS-806 analogue, provides superior activity as a pre-exposure prophylaxis candidate

OBJECTIVE

Small molecule inhibitors able to bind to gp120 and prevent CD4+-induced HIV-1 envelope conformational change provide an important class of inhibitors. Currently, only Fostemsavir is approved for HAART, which makes this class of inhibitors attractive candidates for prevention. We assessed the activity of DS003 (BMS-599793), an analogue of BMS-378806, in different mucosal tissues and elucidated its mechanism of action.

DESIGN

Preclinical analysis was performed with human mucosal tissue models as surrogates of in-vivo activity.

METHODS

Antiviral efficacy of DS003 was assessed in mucosal tissue explants (ecto-cervical, penile and colorectal) and in trans-infection models (co-cultures of dendritic or mucosal migratory cells with CD4+ T cells) with several dosing times (2, 24 h and sustained) and in combination with a fusion inhibitor. Binding of DS003 to gp120 was assessed by flow cytometry and bio-layer interferometry and further probed in competitive studies using soluble CD4+ (sCD4+) and an anti-CD4+ induced antibody, 17b.

RESULTS

In all models, the inhibitory activity of DS003 was increased with longer periods of exposure and by combination with a fusion inhibitor. Pre-exposure to sCD4+ impeded DS003 binding to viral envelope. In contrast, DS003 did not impact subsequent binding of sCD4+. Furthermore, sCD4+-induced epitope exposure as assessed by 17b binding was significantly reduced in the presence of DS003.

CONCLUSION

DS003 inhibits HIV-1 infection by binding to or near the CD4+ binding site of gp120, preventing CD4+-induced conformational change essential for viral fusion. These data highlight the potential of DS003 for development as a pre-exposure prophylaxis candidate.

Impact of symptom-guided, progressive cardiac rehabilitation after left ventricular assist device implantation

A 29-year-old woman with a left ventricular assist device (LVAD) completed a progressive, symptom-limited cardiac rehabilitation program consisting of boxing, weight-lifting, and aerobic exercise, where she improved her exercise capacity by 2.7 metabolic equivalents (P < 0.001) and demonstrated significant myocardial recovery, allowing for successful LVAD explant 9 months after implantation.

A Pragmatic Approach to Weaning Temporary Mechanical Circulatory Support: A State-of-the-Art Review

Temporary mechanical circulatory support (TMCS) provides short-term support to patients with or at risk of refractory cardiogenic shock. Although indications, contraindications, and complications of TMCS may guide device selection, optimal strategies for device weaning and explant remain poorly defined. Under the revised adult heart allocation policy implemented by the United Nations for Organ Sharing in October 2018, rejustification of heart transplant listing status includes demonstrating TMCS dependency with attempted device wean trials. However, standardized device-specific weaning and explant protocols have not been proposed or evaluated. This review highlights when to use percutaneous TMCS in cardiogenic shock, with a focus on weaning and explant considerations. Terminology for important concepts that guide device escalation, de-escalation, and explantation have been defined. Clinical, hemodynamic, metabolic, and imaging features have been defined, which can guide a tailored approach to TMCS weaning and explant based on the approach used at the Cleveland Clinic. A narrative review of published studies that have reported TMCS weaning protocols and survey results of member centers from CS-MCS working group centers is also provided. Future research is needed to better understand optimal timing and implementation of standardized protocols to achieve successful TMCS weaning and explant.

Evaluation of tissue integration of injectable, cell-laden hydrogels of cocultures of mesenchymal stem cells and articular chondrocytes with an ex vivo cartilage explant model

This study investigated the chondrogenic activity of encapsulated mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) and its impact on the mechanical properties of injectable poly(N-isopropylacrylamide)-based dual-network hydrogels loaded with poly( l -lysine) (PLL). To this effect, an ex vivo study model was employed to assess the behavior of the injected hydrogels-specifically, their surface stiffness and integration strength with the surrounding cartilage. The highest chondrogenic activity was observed from AC-encapsulated hydrogels, while the effect of PLL on MSC chondrogenesis was not apparent from biochemical analyses. Mechanical testing showed that there were no significant differences in either surface stiffness or integration strength among the different study groups. Altogether, the results suggest that the ex vivo model can allow further understanding of the relationship between biochemical changes within the hydrogel and their impact on the hydrogel's mechanical properties.

Respiratory Tract Explant Infection Dynamics of Influenza A Virus in California Sea Lions, Northern Elephant Seals, and Rhesus Macaques

To understand susceptibility of wild California sea lions and Northern elephant seals to influenza A virus (IAV), we developed an ex vivo respiratory explant model and used it to compare infection kinetics for multiple IAV subtypes. We first established the approach using explants from colonized rhesus macaques, a model for human IAV. Trachea, bronchi, and lungs from 11 California sea lions, 2 Northern elephant seals, and 10 rhesus macaques were inoculated within 24 h postmortem with 6 strains representing 4 IAV subtypes. Explants from the 3 species showed similar IAV infection kinetics, with peak viral titers 48 to 72 h post-inoculation that increased by 2 to 4 log₁₀ PFU/explant relative to the inoculum. Immunohistochemistry localized IAV infection to apical epithelial cells. These results demonstrate that respiratory tissue explants from wild marine mammals support IAV infection. In the absence of the ability to perform experimental infections of marine mammals, this ex vivo culture of respiratory tissues mirrors the in vivo environment and serves as a tool to study IAV susceptibility, host range, and tissue tropism.

IMPORTANCE Although influenza A virus can infect marine mammals, a dearth of marine mammal cell lines and ethical and logistical challenges prohibiting experimental infections of living marine mammals mean that little is known about IAV infection kinetics in these species. We circumvented these limitations by adapting a respiratory tract explant model first to establish the approach with rhesus macaques and then for use with explants from wild marine mammals euthanized for nonrespiratory medical conditions. We observed that multiple strains representing 4 IAV subtypes infected trachea, bronchi, and lungs of macaques and marine mammals with variable peak titers and kinetics. This ex vivo model can define infection dynamics for IAV in marine mammals. Further, use of explants from animals euthanized for other reasons reduces use of animals in research.

Characterization of an Ex Vivo Equine Endometrial Tissue Culture Model Using Next-Generation RNA-Sequencing Technology

Simple Summary

Notwithstanding extensive research into fertility problems in mares, pregnancy rates have remained low mainly because of endometrial inflammation (endometritis). In the field of equine research, endometrial explants have been used to carry out in vitro studies of the mare’s endometrium. However, there has been no wide-ranging assessment of relative stability of this model over time. The aim of this study was to perform an in-depth transcriptomic assessment of endometrial explants over a culture period of 72 h and assess if they are representative of the whole mare. Explants at 24 h demonstrated significant changes when compared to biopsies at 0 h as expected. Even though gene expression changes were seen between 24 and 48 h of culture, prior to this window changes were dominated by the effects of explanting and culture and subsequently, transcription was generally compromised. Our results, therefore have defined the optimal period when explants can be used to study equine endometritis and how the endometrium is modulated during inflammation. It highlights the use of abattoir derived samples to understand the physiology and pathophysiology of the equine endometrium, negating the need to collect repeated uterine biopsies from living mares.

Abstract

Persistent mating-induced endometritis is a major cause of poor fertility rates in the mare. Endometritis can be investigated using an ex vivo equine endometrial explant system which measures uterine inflammation using prostaglandin F_2α as a biomarker. However, this model has yet to undergo a wide-ranging assessment through transcriptomics. In this study, we assessed the transcriptomes of cultured endometrial explants and the optimal temporal window for their use. Endometrium harvested immediately post-mortem from native pony mares (n = 8) were sampled (0 h) and tissue explants were cultured for 24, 48 and 72 h. Tissues were stored in RNALater, total RNA was extracted and sequenced. Differentially expressed genes (DEGs) were defined using DESeq2 (R/Bioconductor). Principal component analysis indicated that the greatest changes in expression occurred in the first 24 h of culture when compared to autologous biopsies at 0 h. Fewer DEGs were seen between 24 and 48 h of culture suggesting the system was more stable than during the first 24 h. No genes were differentially expressed between 48 and 72 h but the low number of background gene expression suggested that explant viability was compromised after 48 h. ESR1, MMP9, PTGS2, PMAIP1, TNF, GADD45B and SELE genes were used as biomarkers of endometrial function, cell death and inflammation across tissue culture timepoints. STRING assessments of gene ontology suggested that DEGs between 24 and 48 h were linked to inflammation, immune system, cellular processes, environmental information processing and signal transduction, with an upregulation of most biomarker genes at 24 h. Taken together our observations indicated that 24–48 h is the optimal temporal window when the explant model can be used, as explants restore microcirculation, perform wound healing and tackle inflammation during this period. This key observation will facilitate the appropriate use of this as a model for further research into the equine endometrium and potentially the progression of mating-induced endometritis to persistent inflammation between 24 and 48 h.

Explant Modeling of the Immune Environment of Head and Neck Cancer

Patients exhibit distinct responses to immunotherapies that are thought to be linked to their tumor immune environment. However, wide variations in outcomes are also observed in patients with matched baseline tumor environments, indicating that the biological response to treatment is not currently predictable using a snapshot analysis. To investigate the relationship between the immune environment of tumors and the biological response to immunotherapies, we characterized four murine head and neck squamous cell carcinoma (HNSCC) models on two genetic backgrounds. Using tumor explants from those models, we identified correlations between the composition of infiltrating immune cells and baseline cytokine profiles prior to treatment. Following treatment with PD-1 blockade, CTLA-4 blockade, or OX40 stimulation, we observed inter-individual variability in the response to therapy between genetically identical animals bearing the same tumor. These distinct biological responses to treatment were not linked to the initial tumor immune environment, meaning that outcome would not be predictable from a baseline analysis of the tumor infiltrates. We similarly performed the explant assay on patient HNSCC tumors and found significant variability between the baseline environment of the tumors and their response to therapy. We propose that tumor explants provide a rapid biological assay to assess response to candidate immunotherapies that may allow matching therapies to individual patient tumors. Further development of explant approaches may allow screening and monitoring of treatment responses in HNSCC.

Exploring potential of copper and silver nano particles to establish efficient callogenesis and regeneration system for wheat (Triticum aestivum L.)

In vitro recalcitrance of wheat to regeneration is the major bottleneck for its improvement through callus-based genetic transformation. Nanotechnology is one of the most dynamic areas of research, which can transform agriculture and biotechnology to ensure food security on sustainable basis. Present study was designed to investigate effects of CuSO₄, AgNO₃ and their nanoparticles on tissue culture responses of mature embryo culture of wheat genotypes (AS-2002 and Wafaq-2001). Initially, MS-based callus induction and regeneration medium were optimized for both genotypes using various concentrations of auxin (2,4-D, IAA) and cytokinins (BAP, kinetin). The genotypes differed for embryogenic callus induction and regeneration potential. Genotype AS-2002 yielded maximum embryogenic calli in response to 3.0 mg/l 2,4-D, whereas Wafaq-2001 offered the highest embryogenic calli against 3.5 mg/l 2,4-D supplemented in the induction medium. Genotype AS-2002 showed maximum regeneration (59.33%) in response to regeneration protocol comprising 0.5 mg/l IAA, 0.3 mg/l BAP and 1.0 mg/l Kin, while Wafaq-2001 performed best in response to 0.5 mg/l IAA, 0.3 mg/l BAP and 1.5 mg/l Kin with 55.33% regeneration efficiency. The same optimized basal induction and regeneration medium for both genotypes were further used to study effects of CuSO₄, AgNO₃ and their nano-particles employing independent experiments. The optimized induction medium fortified with various concentrations of CuSO₄ or CuNPs confirmed significant effects on frequency of embryogenic callus. Addition of either 0.020 mg/l or 0.025 mg/l CuSO₄, or 0.015 mg/l CNPs showed comparable results for embryogenic callus induction and were statistically at par with embryogenic callus induction of 74.00%, 75.67% and 76.83%, respectively. Significantly higher regeneration was achieved from MS-based regeneration medium supplemented with 0.015 mg/l or 0.020 mg/l CuNPs than standard 0.025 mg/l CuSO₄. In another study, the basal induction and regeneration medium were fortified with AgNO₃ or AgNPs ranging from 1 to 7 mg/l along with basal regeneration media devoid of AgNO₃ or AgNPs (control). The maximum embryogenic calli were witnessed from medium fortified with 3.0 mg/l or 4.0 mg/l AgNPs compared with control and rest of the treatments. The standardized regeneration medium fortified with 5.0 mg/l AgNO₃ or 3.0 mg/l AgNPs showed pronounced effect on regeneration of wheat genotypes and offered maximum regeneration compared with control. The individual and combined effect of Cu and Ag nanoparticles along with control (basal regeneration media of each genotype) was also tested. Surprisingly, co-application of metallic NPs showed a significant increase in embryogenic callus formation of genotypes. Induction medium supplemented with 0.015 mg/l CuNPs + 4.0 mg/l AgNPs or 0.020 mg/l CuNPs + 2.0 mg/l AgNPs showed splendid results compared to control and other combination of Cu and Ag nanoparticles. The maximum regeneration was achieved by co-application of 0.015 mg/l CuNP and 4.0 mg/l AgNPs with 21% increment of regeneration over control. It is revealed that CuNPs and AgNPs are potential candidate to augment somatic embryogenesis and regeneration of mature embryo explants of wheat.

Abbreviations: 2,4-D (2,4-dichlorophenoxyacetic acid), BAP (6-benzylaminopurine), IAA (Indole-3-acetic acid), AgNPs (silver nanoparticles), CuNPs (copper nanoparticles)

Setd1a Plays Pivotal Roles for the Survival and Proliferation of Retinal Progenitors via Histone Modifications of Uhrf1

Purpose

The trimethylation of histone H3 at lysine 4 (H3K4me3) facilitates transcriptional gene activation, and Setd1a is the methyltransferase specific to H3K4. H3K4me3 has been reported to regulate rod photoreceptor differentiation; however, the roles H3K4me3 plays in retinal progenitor cell (RPC) proliferation and differentiation during early retinal development remain unclear.

Methods

Using an in vitro retinal explant culture system, we suppressed the expression of Setd1a by introducing shSetd1a. We examined the expression level and H3K4me3 level of genes by RNA Sequencing and ChIP assay, respectively.

Results

We found that Setd1a depletion resulted in increased apoptosis and proliferation failure in late RPCs. Expression of wild-type SETD1A, but not SETD1A that lacked the catalytic SET domain, reversed the shSetd1a-induced phenotype. RNA Sequencing revealed that proliferation-related genes were downregulated upon shSetd1a expression. Based on publicly available H3K4me3-ChIP sequencing data of retinal development, we identified Uhrf1 as a candidate target gene of Setd1a. The expression of shSetd1a led to a decrease in Uhrf1 transcript levels and reduced H3K4me3 levels at the Uhrf1 locus. Increased apoptosis and the suppression of proliferation in late RPCs were observed in retinal explants expressing shUhrf1, similar to the outcomes observed in shSetd1a-expressing retinas. The overexpression of UHRF1 did not rescue shSetd1a-induced apoptosis, but reversed the suppression of proliferation.

Conclusions

These results indicate that Setd1a contributes to the survival and proliferation of retinal cells by regulating histone methylation, Setd1a regulates Uhrf1 expression, and these two molecules cooperate to regulate RPC survival and proliferation.

An ex vivo human osteochondral culture model

To reduce animal experimentation and to overcome translational issues in cartilage tissue engineering, there is a need to develop an ex vivo human tissue-based approach. This study aims to demonstrate that a human osteochondral explant at different stages of osteoarthritis (OA) can be kept in long-term culture while preserving its viability and composition. Osteochondral explants with either a smooth or fibrillated cartilage surface, representing different OA stages, were harvested from fresh human tibial plateaus. Explants were cultured for 2 or 4 weeks in a double-chamber culture platform. The biochemical content of the cartilage of cultured explants did not significantly change over a period of 4 weeks and these findings were supported by histology. Chondrocytes mostly preserved their metabolic activity during culture and active bone and marrow were found in the periphery of the explants, while metabolic activity was decreased in the bone core in cultured explants compared to fresh explants. In fibrillated explants, chondrocyte viability decreased in the periphery of the sample in cultured groups compared to fresh explants (fresh, 94 ± 6%; cultured, 64% ± 17%, 2 weeks, and 69% ± 17%, 4 weeks; P < .05). Although biochemical and histological results did not show changes within the cartilage tissue, the viability of the explants should be carefully controlled for each specific use. This system provides an alternative to explore drug treatment and implant performance under more controlled experimental conditions than possible in vivo, in combination with clinically relevant human osteochondral tissue.

The Last Half Century of Fish Explant and Organ Culture

Explants are three-dimensional tissue fragments maintained outside the organism. The goals of this article are to review the history of fish explant culture and discuss applications of this technique that may assist the modern zebrafish laboratory. Because most zebrafish workers do not have a background in tissue culture, the key variables of this method are deliberately explained in a general way. This is followed by a review of fish-specific explantation approaches, including presurgical husbandry, aseptic dissection technique, choice of media and additives, incubation conditions, viability assays, and imaging studies. Relevant articles since 1970 are organized in a table grouped by organ system. From these, I highlight several recent studies using explant culture to study physiological and embryological processes in teleosts, including circadian rhythms, hormonal regulation, and cardiac development.

Risk Factors and Center-Level Variation in Hepatocellular Carcinoma Under-Staging for Liver Transplantation

Liver transplantation (LT) is curative for most patients with hepatocellular carcinoma (HCC). However, 10%-15% of patients experience HCC recurrence. Patients who are reported as within Milan criteria by imaging are frequently found to be outside the criteria on explant. This under-staging of HCC worsens post-LT outcomes. However, risk factors for under-staging have not been elucidated. Furthermore, it is not known if there is regional or center-level variation in under-staging. We conducted a retrospective analysis of adult patients transplanted for HCC in the United Network for Organ Sharing (UNOS) database between 2012 and 2016. Under-staging was determined on the basis of comparing pre-LT imaging to explant findings. Kaplan-Meier methods and Cox regression were used to evaluate the impact of under-staging on HCC recurrence and post-LT survival. Mixed effects logistic regression was used to identify risk factors for under-staging and to study regional and center-level variation in adjusted analyses. A total of 5424 patients were included in the cohort, of whom 24.9% (n = 1353) were under-staged. Post-LT HCC recurrence and death were significantly associated with under-staging (each P < 0.001). In adjusted analyses, independent predictors of under-staging included age (odds ratio [OR], 1.13 per 10 years; 95% confidence interval [CI], 1.03-1.25), male sex (OR, 1.61; 95% CI, 1.36-1.89), down-staging (OR, 4.03; 95% CI, 2.65-6.11), and pre-LT alpha-fetoprotein (P < 0.001). There was also significant variation in under-staging between UNOS regions and among transplant centers, ranging from 14.8% to 38.1%. We report novel risk factors for HCC under-staging, which worsens post-LT outcomes. Significant center-level and regional variation in under-staging highlights the need for standards that achieve greater uniformity in staging.

Comparison of umbilical cord tissue-derived mesenchymal stromal cells isolated from cryopreserved material and extracted by explantation and digestion methods utilizing a split manufacturing model

BACKGROUND AIMS

Umbilical cord (UC) tissue is recognized as an advantageous source of mesenchymal stromal cells (MSCs), whose therapeutic properties are being actively evaluated in pre-clinical and clinical trials. In recognition of its potential value, storage of UC tissue or cells from UC tissue in newborn stem cell banks is now commonplace; however, strategies for isolating UC-derived MSCs (UCMSCs) from UC tissue have not been standardized. The majority of newborn stem cell banks take one of two approaches to cord tissue processing and cryopreservation: enzymatic digestion of the fresh tissue with cryopreservation of the subsequent cell suspension or cryopreservation of the tissue as a composite whole with later, post-thaw isolation of cells by explantation. Evaluation of UCMSCs derived by these two principal preparation and cryopreservation strategies is important to understanding whether the methods currently employed by newborn stem cell banks retain the desirable clinical attributes of UC cells.

METHODS

UCMSCs were isolated from 10 UC tissue samples by both explantation and enzymatic digestion methods to allow for comparison of cells from the same donor. Cell isolates from both methods were compared pre- and post-cryopreservation as well as after serial passaging. Cell viability, morphology, growth kinetics, immunophenotype, cytokine secretion and differentiation capacity were evaluated.

RESULTS

UCMSCs could be derived from fresh UC tissue by both explantation and digestion methods and from thawed UC tissue by explantation. Initial cell populations isolated by digestion were heterogeneous and took longer to enrich for UCMSCs in culture than populations obtained by explantation. However, once isolated and enriched, UCMSCs obtained by either method showed no significant difference in viability, morphology, rate of proliferation, surface marker expression, levels of cytokine secretion or differentiation capacity.

CONCLUSIONS

Derivation of UCMSCs by explantation after thawing UC cryopreserved as a composite tissue may be favorable in terms of initial purity and number of cells achievable by a specific passage. However, we observed no evidence of functional difference between UCMSCs derived by explanation or digestion, suggesting that cells isolated from cryopreserved material obtained by either method maintain their therapeutic properties.

Complete Pathological Response Noted in Explanted Liver After Y90-SIR-Spheres Therapy for Hepatocellular Carcinoma

In the treatment of hepatocellular carcinoma, achieving complete pathological response (CPR) in explanted liver specimens following any locoregional treatments is associated with reduced recurrence rates and better posttransplant survival compared to the incomplete response. Here, we present the imaging findings of a patient who achieved CPR in the explanted liver following Y-90 SIR-Spheres® therapy.

Axis Specification in Zebrafish Is Robust to Cell Mixing and Reveals a Regulation of Pattern Formation by Morphogenesis

A fundamental question in developmental biology is how the early embryo establishes the spatial coordinate system that is later important for the organization of the embryonic body plan. Although we know a lot about the signaling and gene-regulatory networks required for this process, much less is understood about how these can operate to pattern tissues in the context of the extensive cell movements that drive gastrulation. In zebrafish, germ layer specification depends on the inheritance of maternal mRNAs [1, 2, 3], cortical rotation to generate a dorsal pole of β-catenin activity [4, 5, 6, 7, 8], and the release of Nodal signals from the yolk syncytial layer (YSL) [9, 10, 11, 12]. To determine whether germ layer specification is robust to altered cell-to-cell positioning, we separated embryonic cells from the yolk and allowed them to develop as spherical aggregates. These aggregates break symmetry autonomously to form elongated structures with an anterior-posterior pattern. Both forced reaggregation and endogenous cell mixing reveals how robust early axis specification is to spatial disruption of maternal pre-patterning. During these movements, a pole of Nodal signaling emerges that is required for explant elongation via the planar cell polarity (PCP) pathway. Blocking of PCP-dependent elongation disrupts the shaping of opposing poles of BMP and Wnt/TCF activity and the anterior-posterior patterning of neural tissue. These results lead us to suggest that embryo elongation plays a causal role in timing the exposure of cells to changes in BMP and Wnt signal activity during zebrafish gastrulation.

Video Abstract

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Whole-zebrafish 256-cell stage embryo explants elongate

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Patterned germ layers are established

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Mesoderm formation is robust to extensive cell mixing

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Inhibition of morphogenesis blocks formation of signaling gradients

Treatment of keloids with a single dose of low-energy superficial X-ray radiation to prevent recurrence after surgical excision: An in vitro and in vivo study

BACKGROUND

Although keloids have been empirically treated with steroids and radiation, evidence-based radiation parameters for keloid therapy are lacking.

OBJECTIVE

To determine evidence-based radiation parameters for blocking keloid fibroblast proliferation in vitro and apply them to patients.

METHODS

The effects of various radiation parameters and steroids on cell proliferation, cell death, and collagen production in keloid explants and fibroblasts were evaluated with standard assays. Effective radiation parameters were then tested on patients.

RESULTS

No differences were observed between the effects of 50 and 320 kV radiation or between single and fractionated radiation doses on keloid fibroblasts. A 3 Gy, 50 kV dose inhibited keloid fibroblast proliferation in culture, whereas 9 Gy completely blocked their outgrowth from explants by inducing multiple cell death pathways and reducing collagen levels. Thirteen of 14 keloids treated with a single 8 Gy, 50 kV dose of radiation did not recur, although 4 patients with 6 keloids were lost to follow-up.

LIMITATIONS

Seventy-five percent of patients received steroids for pruritus, whereas approximately 25% of patients were lost to follow-up.

CONCLUSIONS

A single 8 Gy dose of superficial 50 kV radiation delivered an average of 34 days after keloid excision maybe sufficient to minimize recurrence, including in individuals resistant to steroids. Higher radiation energies, doses, or fractions may be unnecessary for keloid therapy.

Fibroblast Growth Factor 2 Enhances Zika Virus Infection in Human Fetal Brain

Zika virus (ZIKV) is an emerging pathogen that can cause microcephaly and other neurological defects in developing fetuses. The cellular response to ZIKV in the fetal brain is not well understood. Here, we show that ZIKV infection of human fetal astrocytes (HFAs), the most abundant cell type in the brain, results in elevated expression and secretion of fibroblast growth factor 2 (FGF2). This cytokine was shown to enhance replication and spread of ZIKV in HFAs and human fetal brain explants. The proviral effect of FGF2 is likely mediated in part by suppression of the interferon response, which would represent a novel mechanism by which viruses antagonize host antiviral defenses. We posit that FGF2-enhanced virus replication in the fetal brain contributes to the neurodevelopmental disorders associated with in utero ZIKV infection. As such, targeting FGF2-dependent signaling should be explored further as a strategy to limit replication of ZIKV.

Replication of Influenza D Viruses of Bovine and Swine Origin in Ovine Respiratory Explants and Their Attachment to the Respiratory Tract of Bovine, Sheep, Goat, Horse, and Swine

Bovine is considered the main reservoir of influenza D virus (IDV), however, low levels of seropositivity in other farmed species suggest a wide range of potential hosts. Nevertheless, it is not clear whether this scenario is the result of rare spillover events upon contact with bovines, or a lack of adaptation of IDV to these hosts. Among these species, sheep represents a crucial component of the rural economy in many developing countries, but little is known about its role in the ecology of the disease. To evaluate the susceptibility of sheep to IDV viruses of different origin, we used ovine respiratory tissues as an ex vivo model and investigated the infective phenotype of two IDV strains isolated from either bovine (IDV-BOV) or swine (IDV-SW). For translatability purposes, we included a parainfluenza type 3 virus, as positive control, given its known respiratory tropism in sheep. We performed a timed evaluation of the viral infectivity, cell tropism and the associated histopathology, by means of tissue culture infectious dose assays on supernatants and histological/immunohistochemical analyses on explanted tissues, respectively. To further investigate differences in the phenotype of these two strains and to identify the potential targets of replication in the most commonly land-based farmed mammalian species, we carried out virus binding assays on histological sections of the respiratory tract of bovine, caprine, ovine, horse and swine. Our results demonstrated that IDV successfully replicates in nasal, tracheal and lung ovine tissues, suggesting a moderate susceptibility of this species to IDV infection. Interestingly, despite the high genetic identity of these strains, IDV- BOV consistently replicated to higher titers than IDV-SW in all respiratory tracts, suggesting IDV viruses might display considerable levels of variability in their phenotype when crossing the species barrier. Virus binding assays confirmed a superior affinity of the IDV viruses for the bovine upper respiratory tract, and a preference for the pharyngeal epithelium of small ruminants, indicating possible targets to improve the sensitivity of virological sampling for diagnostic and post-mortem purposes. Further pathogenesis and cross-species transmission studies will be necessary to elucidate the ecology of IDV and eventually allow the design of cost-effective surveillance strategies.

Three-Dimensional Explant Platform for Studies on Choroid Plexus Epithelium

The choroid plexus (CP) plays a major role in controlling the entry of substances and immune cells into the brain as it forms the blood-cerebrospinal fluid barrier (BCSFB) in the brain ventricles. Dysregulated immune cell trafficking through the epithelial cell (EC) layer of CP is central for the pathogenesis of infectious diseases in the brain and many neurodegenerative disorders. In vitro studies elucidating the function of the CP have so far been limited to the monolayer culture of CP ECs. To mimic immune cell migration across the CP barrier, a three-dimensional model would be advantageous. Here, we present an in vitro platform for studies of the immune cell trafficking based on CP explants/organoids. The explants were generated from fragments of mouse CPs in Matrigel, where the cells formed luminal spaces and could be maintained in culture for at least 8 weeks. We demonstrate expression of the major CP markers in the explants, including transthyretin and aquaporin 1 as well as ZO1 and ICAM-1, indicating a capacity for secretion of cerebrospinal fluid (CSF) and presence of tight junctions. CP explants displayed CP-like cell polarization and formed an intact EC barrier. We also show that the expression of transthyretin, transferrin, occludin and other genes associated with various functions of CP was maintained in the explants at similar levels as in native CP. By using dendritic cells and neutrophils, we show that the migration activity of immune cells and their interactions with CP epithelium can be monitored by microscopy. Thereby, the three-dimensional CP explant model can be used to study the cellular and molecular mechanisms mediating immune cell migration through CP epithelium and other functions of choroid EC. We propose this platform can potentially be used in the search for therapeutic targets and intervention strategies to improve control of (drug) substances and (immune) cell entry into the central nervous system.

Interferon tau-dependent and independent effects of the bovine conceptus on the endometrial transcriptome†

This study investigated bovine conceptus-induced modifications to the endometrial transcriptome related to effects of interferon tau (IFNT), conceptus origin (in vivo vs. in vitro), and conceptus sex. In vitro (IVF) or in vivo (superovulation and artificial insemination, AI) produced blastocysts were transferred into recipient heifers on day 7 of the estrous cycle. On day 15, IVF- or AI-derived conceptuses were obtained by uterine flushing and individually placed on endometrial explants in media for 6 h. Explants were also cultured with media alone as a control or media containing 100 ng/mL IFNT. Total explant RNA was analyzed by RNA-Seq. Incubation of endometrium with IFNT or IVF- or AI-derived conceptuses changed (P ≤ 0.001) expression of 491, 498, and 576 transcripts, respectively, compared to the control. Further, 369 differentially expressed genes (DEGs) were common between explants exposed to IFNT or a conceptus. A total of 240 DEGs were uniquely altered by conceptuses (IVF- and AI-derived) but not IFNT. Of these transcripts, 46 were shared between the IVF and AI groups, while 61 and 133 were specific to IVF and AI conceptuses, respectively. Five genes [melanophilin (MLPH), prominin-2 (PROM2), myeloid associated differentiation marker (MYADM), vomeronasal 1 receptor 4 like (VN1R4L) and 5-hydroxytryptamine receptor 1A (HTR1A)] were more abundant in endometrium exposed to female compared to male conceptuses (P < 0.001). A single gene [ADP-ribosylation factor like GTPase 4C (ARL4C)] was more abundant in response to male conceptuses (P < 0.001) than female conceptuses. These data support the hypothesis that conceptus regulation of gene expression in the endometrium is complex and involves factors other than IFNT that may have a biological role in pregnancy establishment.

Endemic Plant Species Conservation: Biotechnological Approaches

Endemic plant species are usually more vulnerable to anthropogenic threats and natural changes and, therefore, hold a higher extinction risk. The preservation of these species is a major concern on a worldwide context and in situ protection alone will not guarantee their conservation. Ex situ conservation measures must be undertaken to support the conservation of these species, and seed banking is the more efficient and cost-effective method. However, when seed banking is not an option, alternative approaches should be considered. Biotechnological tools provide new and complementary options for plant conservation including short-, medium-, and long-term strategies, and their application for plant species conservation has increased considerably in the last years. This review provides information about the status of the use biotechnology-based techniques for the conservation of endemic plant species. Particular attention is given to cryopreservation, since is the only long-term ex situ conservation strategy that can complement and support the other conservation measures. The cryopreservation of plant genetic resources is, however, more focused on crop or economically important species and few studies are available for endemic plant species. The plant material used, the cryopreservation methods employed, and the assessment of cryogenic effects are reviewed. The reasons to explain the difficulties in cryopreserving these species are discussed and new strategies are proposed to facilitate and increase the interest on this matter. We expect that further studies on the conservation of endemic plant species will increase in a near future, thus contributing to maintain these valuable genetic resources.

Carbamate derivatives of colchicine show potent activity towards primary acute lymphoblastic leukemia and primary breast cancer cells-in vitro and ex vivo study

Colchicine (COL) shows strong anticancer activity but due to its toxicity towards normal cells its wider application is limited. To address this issue, a library of 17 novel COL derivatives, namely N-carbamates of N-deacetyl-4-(bromo/chloro/iodo)thiocolchicine, has been tested against two types of primary cancer cells. These included acute lymphoblastic leukemia (ALL) and human breast cancer (BC) derived from two different tumor subtypes, ER+ invasive ductal carcinoma grade III (IDCG3) and metastatic carcinoma (MC). Four novel COL derivatives showed higher anti-proliferative activity than COL (IC₅₀  = 8.6 nM) towards primary ALL cells in cell viability assays (IC₅₀ range of 1.1-6.4 nM), and several were more potent towards primary IDCG3 (IC₅₀ range of 0.1 to 10.3 nM) or MC (IC₅₀ range of 2.3-9.1 nM) compared to COL (IC₅₀ of 11.1 and 11.7 nM, respectively). In addition, several derivatives were selectively active toward primary breast cancer cells compared to normal breast epithelial cells. The most promising derivatives were subsequently tested against the NCI panel of 60 human cancer cell lines and seven derivatives were more potent than COL against leukemia, non-small-cell lung, colon, CNS and prostate cancers. Finally, COL and two of the most active derivatives were shown to be effective in killing BC cells when tested ex vivo using fresh human breast tumor explants. The present findings indicate that the select COL derivatives constitute promising lead compounds targeting specific types of cancer.

Evidence that reduction in volume protects in situ articular chondrocytes from mechanical impact

Chondrocytes, the resident cells in articular cartilage, carry the burden of producing and maintaining the extracellular matrix (ECM). However, as these cells have a low proliferative capacity and are not readily replaced, chondrocyte death due to extreme forces may contribute to the pathogenesis of osteoarthritis (OA) after injury or may inhibit healing after osteochondral transplantation, a restorative procedure for damaged cartilage that requires a series of mechanical impacts to insert the graft. Consequently, there is a need to understand what factors influence the vulnerability of in situ chondrocytes to mechanical trauma. To this end, the objective of this study was to investigate how altering cell volume by different means (hydrostatic pressure, uniaxial load, and osmotic challenge with and without inhibition of regulatory volume decrease) affects the vulnerability of in situ chondrocytes to extreme mechanical forces. Using a custom experimental platform enabling testing of viable and intact murine cartilage-on-bone explants, we established a strong correlation between chondrocyte volume and vulnerability to impact injury wherein reduced volume was protective. Moreover, we found that the volume-perturbing interventions did not affect cartilage ECM mechanical properties, suggesting that their effects on chondrocyte vulnerability occurred at the cellular level. The findings of this study offer new avenues for novel strategies aimed at preventing chondrocyte loss during osteochondral grafting or to halting the progression of cell death after a joint destabilizing injury.

Mechanosensitive Ca2+ signaling and coordination is diminished in osteocytes of aged mice during ex vivo tibial loading

Purpose: The osteocyte is considered the major mechanosensor in bone, capable of detecting forces at a cellular level to coordinate bone formation and resorption. The pathology of age-related bone loss, a hallmark of osteoporosis, is attributed in part to impaired osteocyte mechanosensing. However, real-time evidence of the effect of aging on osteocyte responses to mechanical load is lacking. Intracellular calcium (Ca²⁺) oscillations have been characterized as an early mechanosensitive response in osteocytes in systems of multiple scales and thus can serve as a real-time measure of osteocyte mechanosensitivity. Our objective was to utilize an ex vivo model to investigate potentially altered mechanosensing in the osteocyte network with aging.Methods: Tibiae were explanted from young-adult (5 mo) and aged (22 mo) female mice and incubated with Fluo-8 AM to visualize osteocyte intracellular Ca²⁺. Whole tibiae were cyclically loaded while in situ osteocyte Ca²⁺ dynamics were simultaneously imaged with confocal microscopy. Responsive osteocyte percentage and Ca²⁺ peak characteristics were quantified, as well as signaling synchrony between paired cells in the field of view.Results: Fewer osteocytes responded to mechanical loading in aged mice compared to young-adult and did so in a delayed manner. Osteocytes from aged mice also lacked the well-correlated relationship between Ca²⁺ signaling synchrony and cell-cell distance exhibited by young-adult osteocytes.Conclusions: We have demonstrated, for the first time, real-time evidence of the diminished mechanosensing and lack of signaling coordination in aged osteocyte networks in tibial explants, which may contribute to pathology of age-induced bone loss.