CD68+ macrophages as crucial components of the foreign body reaction demonstrate an unconventional pattern of functional markers quantified by analysis with double fluorescence staining

A Novel Minimally Invasive Surgically Induced Skeletal Muscle Injury Model in Sheep

Sports-related muscle injuries account for 10-55% of all injuries, which is a growing concern, especially given the aging world population. To evaluate the process of skeletal muscle injury and compare it with muscle lesions observed in humans, we developed a novel in vivo model in sheep. In this model, muscle injury was induced by an ultrasound-guided transverse biopsy at the myotendinous junction of the medial gastrocnemius muscle. Twelve male sheep were examined at 3, 7, 14, and 28 days post-injury. Histological, immunofluorescence, and MRI analyses indicate that our sheep model could resemble key human clinicopathological features. Statistically significant differences (p < 0.05) were observed in collagen I, dMHC, α-SMA, and CD68 immunohistochemical detection when comparing injured and healthy muscles. The injured gastrocnemius muscle exhibited elevated levels of type I collagen, infiltration of CD68(+) macrophages, angiogenesis, and the emergence of newly regenerated dMHC(+) myofibers, which persisted for up to 4 weeks post-injury. Similarly, the progression of muscle injury in the sheep model was assessed using advanced clinical 3 T MRI and compared with MRI scans from human patients. The data indicate that the sheep muscle injury model presents features similar to those observed in human skeletal muscle injuries. This makes it a valuable large animal model for studying muscle injuries and developing novel therapeutic strategies.

Impact of Probiotic Lactiplantibacillus plantarum ATCC 14917 on atherosclerotic plaque and its mechanism

Atherosclerosis is viewed as not just as a problem of lipid build-up in blood vessels, but also as a chronic inflammatory disease involving both innate and acquired immunity. In atherosclerosis, the inflammation of the arterial walls is the key characteristic that significantly contributes to both the instability of plaque and the occlusion of arteries by blood clots. These events ultimately lead to stroke and acute coronary syndrome. Probiotics are living microorganisms that, when consumed in the right quantities, offer advantages for one's health. The primary objective of this study was to investigate the influence of Lactiplantibacillus plantarum ATCC 14917 (ATCC 14917) on the development of atherosclerotic plaques and its underlying mechanism in Apo lipoprotein E-knockout (Apoe-/- mice). In this study, Apoe-/- mice at approximately 8 weeks of age were randomly assigned to three groups: a Normal group that received a normal chow diet, a high fat diet group that received a gavage of PBS, and a Lactiplantibacillus plantarum ATCC 14917 group that received a high fat diet and a gavage of 0.2 ml ATCC 14917 (2 × 109 CFU/mL) per day for a duration of 12 weeks. Our strain effectively reduced the size of plaques in Apoe-/- mice by regulating the expression of inflammatory markers, immune cell markers, chemokines/chemokine receptors, and tight junction proteins (TJPs). Specifically, it decreased the levels of inflammatory markers (ICAM-1, CD-60 MCP-1, F4/80, ICAM-1, and VCAM-1) in the thoracic aorta, (Ccr7, cd11c, cd4, cd80, IL-1β, TNF-α) in the colon, and increased the activity of ROS-scavenging enzymes (SOD-1 and SOD-2). It also influenced the expression of TJPs (occludin, ZO-1, claudin-3, and MUC-3). In addition, the treatment of ATCC 14917 significantly reduced the level of lipopolysaccharide in the mesenteric adipose tissue. The findings of our study demonstrated that our strain effectively decreased the size of atherosclerotic plaques by modulating inflammation, oxidative stress, intestinal integrity, and intestinal immunity.

A Novel Tendon Injury Model, Induced by Collagenase Administration Combined with a Thermo-Responsive Hydrogel in Rats, Reproduces the Pathogenesis of Human Degenerative Tendinopathy

Patellar tendinopathy is a common clinical problem, but its underlying pathophysiology remains poorly understood, primarily due to the absence of a representative experimental model. The most widely used method to generate such a model is collagenase injection, although this method possesses limitations. We developed an optimized rat model of patellar tendinopathy via the ultrasound-guided injection of collagenase mixed with a thermo-responsive Pluronic hydrogel into the patellar tendon of sixty male Wistar rats. All analyses were carried out at 3, 7, 14, 30, and 60 days post-injury. We confirmed that our rat model reproduced the pathophysiology observed in human patients through analyses of ultrasonography, histology, immunofluorescence, and biomechanical parameters. Tendons that were injured by the injection of the collagenase-Pluronic mixture exhibited a significant increase in the cross-sectional area (p < 0.01), a high degree of tissue disorganization and hypercellularity, significantly strong neovascularization (p < 0.01), important changes in the levels of types I and III collagen expression, and the organization and presence of intra-tendinous calcifications. Decreases in the maximum rupture force and stiffness were also observed. These results demonstrate that our model replicates the key features observed in human patellar tendinopathy. Collagenase is evenly distributed, as the Pluronic hydrogel prevents its leakage and thus, damage to surrounding tissues. Therefore, this model is valuable for testing new treatments for patellar tendinopathy.

Xuelian injection ameliorates complete Freund's adjuvant-induced acute arthritis in rats via inhibiting TLR4 signaling

Background

Xuelian injection (XI), a classic preparation extracted from Saussureae Involucratae Herba, has been clinically used to manage rheumatoid arthritis (RA) for nearly twenty years in China. However, the underlying anti-RA mechanism of XI remains unclear. In this study, complete Freund's adjuvant (CFA)-induced acute arthritic model was used to examine the anti-RA effects of XI in vivo. The molecular mechanisms of this action were further investigated using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages.

Methods

XI and XI freeze dried powder were characterized by UPLC analysis. CD68 and TLR4 expression in the ankle joints was measured by immunohistochemistry. The secretion of inflammatory mediators was detected by ELISA. The expression levels of TLR4 involved components were measured by Western blotting. The localization of transcription factors was measured by immunofluorescence assay.

Results

XI treatment ameliorated arthritic symptoms induced by CFA in the ankle joints of rats. The serum levels of inflammatory mediators, including TNF-α, MCP-1, and Rantes were decreased by XI treatment. The elevation of CD68 and TLR4 levels in ankle joints caused by CFA was suppressed by XI treatment. Moreover, XI treatment inhibited the secretion of nitric oxide and prostaglandin E2 in LPS-treated RAW264.7 macrophages. The expression of their enzymes iNOS and COX-2 was also decreased after XI treatment. The production of inflammatory mediators, including TNF-α, IL-6, IL-1β, MCP-1, MIP-1α, and Rantes was reduced by XI treatment in LPS-stimulated RAW264.7 cells. The phosphorylation of p38, JNK, ERK, TBK1, IKKα/β, IκB, p65, c-Jun, and IRF3 was reduced after XI treatment. Additionally, the expression levels of nuclear proteins of p65, c-Jun, and IRF3 were inhibited by XI treatment.

Conclusions

Taken together, XI possesses potential anti-RA effect and the underlying mechanism may be closely associated with the inhibition of TLR4 signaling. Our findings provide further pharmacological justifications for the clinical use of XI in RA treatment.

Epimorphic regeneration in the mammalian tympanic membrane

Adult mammals are generally believed to have limited ability to regenerate complex tissues and instead, repair wounds by forming scars. In humans and across mammalian species, the tympanic membrane (TM) rapidly repairs perforations without intervention. Using mouse models, we demonstrate that the TM repairs itself through a process that bears many hallmarks of epimorphic regeneration rather than typical wound healing. Following injury, the TM forms a wound epidermis characterized by EGFR ligand expression and signaling. After the expansion of the wound epidermis that emerges from known stem cell regions of the TM, a multi-lineage blastema-like cellular mass is recruited. After two weeks, the tissue architecture of the TM is largely restored, but with disorganized collagen. In the months that follow, the organized and patterned collagen framework of the TM is restored resulting in scar-free repair. Finally, we demonstrate that deletion of Egfr in the epidermis results in failure to expand the wound epidermis, recruit the blastema-like cells, and regenerate normal TM structure. This work establishes the TM as a model of mammalian complex tissue regeneration.

A comparison of rat models that best mimic immune-driven preeclampsia in humans

Preeclampsia (PE), a hypertensive pregnancy disorder, can originate from varied etiology. Placenta malperfusion has long been considered the primary cause of PE. However, we and others have showed that this disorder can also result from heightened inflammation at the maternal-fetal interface. To advance our understanding of this understudied PE subtype, it is important to establish validated rodent models to study the pathophysiology and test therapies. We evaluated three previously described approaches to induce inflammation-mediated PE-like features in pregnant rats: 1) Tumor necrosis factor-α (TNF-α) infusion via osmotic pump from gestational day (GD) 14-19 at 50ng/day/animal; 2) Polyinosinic:polycytidylic acid (Poly I:C) intraperitoneal (IP) injections from GD 10-18 (alternate days) at 10mg/kg/day/animal; and, 3) Lipopolysaccharide (LPS) IP injections from GD 13-18 at 20ug-70ug/kg/day per animal. Maternal blood pressure was measured by tail-cuff. Upon sacrifice, fetal and placenta weights were recorded. Placenta histomorphology was assessed using H&E sections. Placenta inflammation was determined by quantifying TNF-α levels and inflammatory gene expression. Placenta metabolic and mitochondrial health were determined by measuring mitochondrial respiration rates and placenta NAD+/NADH content. Of the three rodent models tested, we found that Poly I:C and LPS decreased both fetal weight and survival; and correlated with a reduction in region specific placenta growth. As the least effective model characterized, TNF-α treatment resulted in a subtle decrease in fetal/placenta weight and placenta mitochondrial respiration. Only the LPS model was able to induce maternal hypertension and exhibited pronounced placenta metabolic and mitochondrial dysfunction, common features of PE. Thus, the rat LPS model was most effective for recapitulating features observed in cases of human inflammatory PE. Future mechanistic and/or therapeutic intervention studies focuses on this distinct PE patient population may benefit from the employment of this rodent model of PE.

Choice of Polymer, but Not Mesh Structure Variation, Reduces the Risk of Bacterial Infection with Staphylococcus aureus In Vivo

BACKGROUND

Synthetic mesh material is of great importance for surgical incisional hernia repair. The physical and biochemical characteristics of the mesh influence mechanical stability and the foreign body tissue reaction. The influence on bacterial infections, however, remains ill-defined. The aim of the present study was to evaluate the influence of a modified mesh structure with variation in filament linking on the occurrence of bacterial infection that is indicated by the occurrence of CD68⁺, CD4⁺, and CD8⁺ cells in two different materials.

METHODS

A total of 56 male Sprague Dawley rats received a surgical mesh implant in a subcutaneous abdominal position. The mesh of two different polymers (polypropylene (PP) and polyvinylidenfluoride (PVDF)) and two different structures (standard structure and bold structure with higher filament linking) were compared. During the implantation, the meshes were infected with Staphylococcus (S.) aureus. After 7 and 21 days, meshes were explanted, and the early and late tissue responses to infection were histologically evaluated.

RESULTS

Overall, the inflammatory tissue response was higher at 7 days when compared to 21 days. At 7 days, PP meshes of the standard structure (PP-S) showed the strongest inflammatory tissue response in comparison to all the other groups. At 21 days, no statistically significant difference between different meshes was detected. CD8⁺ cytotoxic T cells showed a significant difference at 21 days but not at 7 days. PP meshes of both structures showed a higher infiltration of CD8⁺ T cells than PVDF meshes. CD4⁺ T helper cells differed at 7 days but not at 21 days, and PVDF meshes in a bold structure showed the highest CD4⁺ T cell count. The number of CD68⁺ macrophages was also significantly higher in PP meshes in a standard structure when compared to PVDF meshes at 21 days.

CONCLUSION

The inflammatory tissue response to S. aureus infection appears to be highest during the early period after mesh implantation. PP meshes showed a higher inflammatory response than PVDF meshes. The mesh material appears to be more important for the risk of infection than the variation in filament linking.

A comparative in vitro and in vivo study of porcine- and bovine-derived non-cross-linked collagen membranes

The porcine-derived non-cross-linked collagen membrane Bio-gide® (BG) and the bovine-derived non-cross-linked collagen membrane Heal-all® (HA) were compared to better understand their in vitro biophysical characteristics and in vivo degradation patterns as a reference for clinical applications. It was showed that the porosity, specific surface area, pore volume and pore diameter of BG were larger than those of HA (64.5 ± 5.2% vs. 48.6 ± 6.1%; 18.6 ± 2.8 m² /g vs. 2.3 ± 0.6 m² /g; 0.114 ± 0.002 cm³ /g vs. 0.003 ± 0.001 cm³ /g; 24.4 ± 3.5 nm vs. 7.3 ± 1.7 nm, respectively); the average swelling ratio of BG was higher than that of HA (412.6 ± 41.2% vs. 270.0 ± 2.7%); the tensile strength of both dry and wet HA was higher than those of BG (18.26 ± 3.27 MPa vs. 4.02 ± 1.35 MPa; 2.24 ± 0.21 MPa vs. 0.16 ± 0.02 MPa, respectively); 73% of HA remained after 72 h in collagenase solution, whereas only 8.2% of BG remained. A subcutaneous rat implantation model revealed that, at 3, 7, 14, 28, and 56 days postmembrane implantation, there were more total inflammatory cells, especially more M1 and M2 polarized macrophages and higher M2/M1 ratio in BG than in HA; in addition, the fibrous capsule around BG was also thicker than that around HA. Moreover, concentrations of dozens of cytokines including interleukin-2(IL-2), IL-7, IL-10 and so forth. in BG were higher than those in HA. It is suggested that BG and HA might be suitable for different clinical applications according to their different characteristics.

A multiplex inhalation platform to model in situ like aerosol delivery in a breathing lung-on-chip

Prolonged exposure to environmental respirable toxicants can lead to the development and worsening of severe respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD) and fibrosis. The limited number of FDA-approved inhaled drugs for these serious lung conditions has led to a shift from in vivo towards the use of alternative in vitro human-relevant models to better predict the toxicity of inhaled particles in preclinical research. While there are several inhalation exposure models for the upper airways, the fragile and dynamic nature of the alveolar microenvironment has limited the development of reproducible exposure models for the distal lung. Here, we present a mechanistic approach using a new generation of exposure systems, the Cloud α AX12. This novel in vitro inhalation tool consists of a cloud-based exposure chamber (VITROCELL) that integrates the breathing ^AXLung-on-chip system (AlveoliX). The ultrathin and porous membrane of the AX12 plate was used to create a complex multicellular model that enables key physiological culture conditions: the air-liquid interface (ALI) and the three-dimensional cyclic stretch (CS). Human-relevant cellular models were established for a) the distal alveolar-capillary interface using primary cell-derived immortalized alveolar epithelial cells (^AXiAECs), macrophages (THP-1) and endothelial (HLMVEC) cells, and b) the upper-airways using Calu3 cells. Primary human alveolar epithelial cells (^AXhAEpCs) were used to validate the toxicity results obtained from the immortalized cell lines. To mimic in vivo relevant aerosol exposures with the Cloud α AX12, three different models were established using: a) titanium dioxide (TiO2) and zinc oxide nanoparticles b) polyhexamethylene guanidine a toxic chemical and c) an anti-inflammatory inhaled corticosteroid, fluticasone propionate (FL). Our results suggest an important synergistic effect on the air-blood barrier sensitivity, cytotoxicity and inflammation, when air-liquid interface and cyclic stretch culture conditions are combined. To the best of our knowledge, this is the first time that an in vitro inhalation exposure system for the distal lung has been described with a breathing lung-on-chip technology. The Cloud α AX12 model thus represents a state-of-the-art pre-clinical tool to study inhalation toxicity risks, drug safety and efficacy.

Immune response differences in degradable and non-degradable alloy implants

Alloy based implants have made a great impact in the clinic and in preclinical research. Immune responses are one of the major causes of failure of these implants in the clinic. Although the immune responses toward non-degradable alloy implants are well documented, there is a poor understanding of the immune responses against degradable alloy implants. Recently, there have been several reports suggesting that degradable implants may develop substantial immune responses. This phenomenon needs to be further studied in detail to make the case for the degradable implants to be utilized in clinics. Herein, we review these new recent reports suggesting the role of innate and potentially adaptive immune cells in inducing immune responses against degradable implants. First, we discussed immune responses to allergen components of non-degradable implants to give a better overview on differences in the immune response between non-degradable and degradable implants. Furthermore, we also provide potential areas of research that can be undertaken that may shed light on the local and global immune responses that are generated in response to degradable implants.

Ventricular opening and cerebrospinal fluid circulation accelerate the biodegradation process of carmustine wafers suggesting their immunomodulation potential in the human brain

PURPOSE

Opening the ventricular system during glioblastoma surgery is often necessary, but the consequent effect on the tumor microenvironment of glioblastoma remains unknown. Implantation of carmustine wafer enables direct drug delivery to the tumor site; however, the exact mechanism of the wafer's biodegradation process is unclear, and the available data is limited to in vivo non-human mammalian studies. We hypothesized that the ventricular opening affects the degradation process of the wafer and the glioblastoma tumor microenvironment.

METHODS

This study included 30 glioblastoma patients. 21 patients underwent carmustine wafer implantation during initial surgery. All patients underwent repeated surgical resection upon recurrence, allowing for pathological comparison of changes associated with wafer implantation. Immunohistochemical analyses were performed using CD68, TMEM119, CD163, IBA1, BIN1, and CD31 antibodies to highlight microglia, macrophages, and tumor vascularity, and the quantitative scoring results were correlated with clinical, molecular, and surgical variables, including the effect of the ventricular opening.

RESULTS

The carmustine wafer implanted group presented significantly less TMEM119-positive microglia within the tumor (P = 0.0002). Simple and multiple regression analyses revealed that the decrease in TMEM119-positive microglia was correlated with longer intervals between surgeries and opened ventricular systems. No correlation was observed between age, methylated O6-methylguanine DNA methyltransferase promoter expression, and the extent of surgical resection.

CONCLUSIONS

Our study findings strongly suggest that biomaterials may possess immunomodulation capacity, which is significantly impacted by the ventricular opening procedure. Furthermore, our data highlights the pathophysiological effects of the ventricular opening within the surrounding human brain, especially after the wafer implantation.

The Alteration of T-Cell Heterogeneity and PD-L1 Colocalization During dMMR Colorectal Cancer Progression Defined by Multiplex Immunohistochemistry

Background

Immune checkpoint inhibitors (ICIs) are quickly becoming key instruments in the treatment of mismatch repair-deficient (dMMR) colorectal cancers (CRCs). Despite their clinical value, ICIs have several limitations associated with their use. Only approximately 15% of all CRCs have a dMMR status, and the overall response rate of ICIs is approximately 40%. The mechanism of ICI resistance is not clear, and its study is limited by the lack of information available on the characterization of the immune microenvironment during the progression from early- to advanced-stage dMMR CRC.

Methods

We used multiplex immunohistochemistry (mIHC) with two panels, each containing five markers, to simultaneously analyze the proportions of immune microenvironment constituents in 59 patients with advanced-stage dMMR CRC and 24 patients with early-stage dMMR CRC. We detected immune cell–associated signatures in the epithelial and stromal regions and evaluated the predictive value of these immune molecules. Student’s t-tests, Mann–Whitney U tests, Cox proportional hazards regression modeling, univariate Cox modeling, and Kaplan–Meier estimation were used to analyze immune cell proportions and survival data.

Results

We observed significantly higher proportions of CD8+ cytotoxic T cells (CD8+) (p = 0.001), CD8+ memory T cells (CD8+CD45RO+) (p = 0.032), and CD4+ regulatory T cells (CD4+FOXP3+) (p = 0.011) in the advanced-stage dMMR CRCs than in the early-stage dMMR CRCs. Furthermore, CD3+ T cells with PD-L1 colocalization (CD3+PD-L1+) (p = 0.043) and CD8+ T cells with PD-L1 colocalization (CD8+PD-L1+) (p = 0.005) were consistently more numerous in patients in the advanced stage than those in the early stage. Our analyses revealed that a high proportion of CD3+PD-1+ T cells was an independent prognostic factor of overall survival (OS) [hazard ratios (HR) = 9.6, p < 0.001] and disease-free survival (DFS) (HR = 3.7, p = 0.010) in patients in the advanced stage.

Conclusion

High numbers of CD8+ cytotoxic T cells and CD8+ memory T cells, which usually represent a cytotoxic function of the adaptive immune system and possibly enhanced inhibition factors, such as CD4+ regulatory T cells and PD-L1 colocalized T cells, were associated with the transformation of the immune microenvironment from the early stage to the advanced stage in dMMR CRCs. Furthermore, CD3+PD-1+ T cells are a prognostic factor for patients with dMMR.

Albiflorin ameliorates inflammation and oxidative stress by regulating the NF-κB/NLRP3 pathway in Methotrexate-induced enteritis

Methotrexate (MTX) treats various diseases but also damages intestinal barrier and leads to enteritis. Albiflorin (ALB) has a variety of pharmacological effects, including antioxidant, anti-inflammation and anti-apoptosis. In the present study, we evaluated the therapeutic effect of ALB on MTX-induced enteritis and investigated the possible mechanisms involved. Male SD rats were intraperitoneally injected with 7 mg/kg MTX for three consecutive days to establish the enteritis model. ALB (20 or 40 mg/kg/day) was intragastrically administrated since two days prior MTX treatment and lasted for six days. We found that ALB treatment increased body weight and intestinal weight of rats with MTX injection. The disease activity index (DAI) score was also decreased after ALB administration. In histological examination, ALB treatment attenuated inflammatory cells infiltration and promoted survival of goblet cells. In detection of inflammatory-associated factors, ALB treatment decreased CD68⁺ cells infiltration, inhibited myeloperoxidase activity, and suppressed intercellular cell adhesion molecule-1 and cyclooxygenase-2 expression. Additionally, ALB reduced malondialdehyde, glutathione levels, inhibited superoxide dismutase activity and suppressed reactive oxygen species production. Moreover, ALB treatment effectively inhibited NLRP3, as well as caspase 1 p20 and interleukin (IL)-1β and 18 expression. Finally, nuclear factor-κB (NF-κB) p65 phosphorylation and nuclear translocation were also demonstrated to be blocked upon ALB treatment. In conclusion, our findings indicated that ALB alleviated MTX-induced enteritis via inhibiting the NF-κB/NLRP3 pathway.

Quantitative Characterization of Macrophage, Lymphocyte, and Neutrophil Subtypes Within the Foreign Body Granuloma of Human Mesh Explants by 5-Marker Multiplex Fluorescence Microscopy

Foreign bodies such as fibers of a surgical mesh induce a typical reaction with an inflammatory infiltrate that forms a surrounding granuloma. This infiltrate is dominated by macrophages, lymphocytes, and neutrophils, whereas its extent of collaboration is widely unknown. In this study, we analyzed 12 samples of surgical meshes explanted from humans by multiplex analyses with three different 5-marker panels – 1. macrophage panel: CD68, CD86, CD105, CD163, and CD206; 2. lymphocyte panel: CD3, CD4, CD8, CD20, and CD68; and 3. neutrophil panel: CD15, histone, MPO, NE, and CD68. Measurement of fluorescence intensity within nuclear masks resulting from DAPI nuclear staining allows exact quantification of cells considered “positive” at a user-defined mean intensity threshold of > 100. Obviously, however, there is no natural threshold as a biological criterion for an intensity that separates “positive” stained cells from unstained cells (“negative”). Multiplex staining of 5 markers always reveals a high rate of coexpression for almost all of the 2⁵ possible marker combinations (= 32 combinations, when using 5 markers simultaneously). The present staining results demonstrate that various morphological and functional subtypes of macrophages, lymphocytes, and neutrophils are abundant in the foreign body granuloma (FBG), which were investigated by regions of interest (ROI) with an area of 1 mm². The widespread coexpression of two or more markers underscores the complex collaboration network of the inflammatory infiltrate. The ability to combine spatial distribution with exact numerical analysis may offer new perspectives for our understanding of the complex interactions in this multidimensional process.

Quantitative assessment of inflammatory infiltrates in kidney transplant biopsies using multiplex tyramide signal amplification and deep learning

Delayed graft function (DGF) is a strong risk factor for development of interstitial fibrosis and tubular atrophy (IFTA) in kidney transplants. Quantitative assessment of inflammatory infiltrates in kidney biopsies of DGF patients can reveal predictive markers for IFTA development. In this study, we combined multiplex tyramide signal amplification (mTSA) and convolutional neural networks (CNNs) to assess the inflammatory microenvironment in kidney biopsies of DGF patients (n = 22) taken at 6 weeks post-transplantation. Patients were stratified for IFTA development (<10% versus ≥10%) from 6 weeks to 6 months post-transplantation, based on histopathological assessment by three kidney pathologists. One mTSA panel was developed for visualization of capillaries, T- and B-lymphocytes and macrophages and a second mTSA panel for T-helper cell and macrophage subsets. The slides were multi spectrally imaged and custom-made python scripts enabled conversion to artificial brightfield whole-slide images (WSI). We used an existing CNN for the detection of lymphocytes with cytoplasmatic staining patterns in immunohistochemistry and developed two new CNNs for the detection of macrophages and nuclear-stained lymphocytes. F1-scores were 0.77 (nuclear-stained lymphocytes), 0.81 (cytoplasmatic-stained lymphocytes), and 0.82 (macrophages) on a test set of artificial brightfield WSI. The CNNs were used to detect inflammatory cells, after which we assessed the peritubular capillary extent, cell density, cell ratios, and cell distance in the two patient groups. In this cohort, distance of macrophages to other immune cells and peritubular capillary extent did not vary significantly at 6 weeks post-transplantation between patient groups. CD163+ cell density was higher in patients with ≥10% IFTA development 6 months post-transplantation (p < 0.05). CD3+CD8-/CD3+CD8+ ratios were higher in patients with <10% IFTA development (p < 0.05). We observed a high correlation between CD163+ and CD4+GATA3+ cell density (R = 0.74, p < 0.001). Our study demonstrates that CNNs can be used to leverage reliable, quantitative results from mTSA-stained, multi spectrally imaged slides of kidney transplant biopsies.

Functionalized Strategies and Mechanisms of the Emerging Mesh for Abdominal Wall Repair and Regeneration

Meshes have been the overwhelmingly popular choice for the repair of abdominal wall defects to retrieve the bodily integrity of musculofascial layer. Broadly, they are classified into synthetic, biological and composite mesh based on their mechanical and biocompatible features. With the development of anatomical repair techniques and the increasing requirements of constructive remodeling, however, none of these options satisfactorily manages the conditional repair. In both preclinical and clinical studies, materials/agents equipped with distinct functions have been characterized and applied to improve mesh-aided repair, with the importance of mesh functionalization being highlighted. However, limited information exists on systemic comparisons of the underlying mechanisms with respect to functionalized strategies, which are fundamental throughout repair and regeneration. Herein, we address this topic and summarize the current literature by subdividing common functions of the mesh into biomechanics-matched, macrophage-mediated, integration-enhanced, anti-infective and antiadhesive characteristics for a comprehensive overview. In particular, we elaborate their effects separately with respect to host response and integration and discuss their respective advances, challenges and future directions toward a clinical alternative. From the vastly different approaches, we provide insight into the mechanisms involved and offer suggestions for personalized modifications of these emerging meshes.

Characterization of innate and adaptive immune cells involved in the foreign body reaction to polypropylene meshes in the human abdomen

Background

Polypropylene (PP) mesh is widely used to reinforce tissues. The foreign body reaction (FBR) to the implant is dominated by innate immune cells, especially macrophages. However, considerable numbers of adaptive immune cells, namely T cells, have also been regularly observed, which appear to play a crucial role in the long-term host response.

Methods

This study investigated the FBR to seven human PP meshes, which were removed from the abdomen for recurrence after a median of one year. Using immunofluorescence microscopy, the FBR was examined for various innate (CD11b⁺ myeloid, CD68⁺ macrophages, CD56⁺ NK) and adaptive immune cells (CD3⁺ T, CD4⁺ T-helper, CD8⁺ cytotoxic, FoxP3⁺ T-regulatory, CD20⁺ B) as well as “conventional” immune cells (defined as cells expressing their specific immune cell marker without co-expressing CD68).

Results

T-helper cells (19%) and regulatory T-cells (25%) were present at comparable rates to macrophages, and clustered significantly toward the mesh fibers. For all cell types the lowest proportions of “conventional” cells (< 60%) were observed at the mesh–tissue interface, but increased considerably at about 50–100 µm, indicating reduced stimulation with rising distance to the mesh fibers.

Conclusion

Both innate and adaptive immune cells participate in the chronic FBR to PP meshes with T cells and macrophages being the predominant cell types, respectively. In concordance with the previous data, many cells presented a “hybrid” pattern near the mesh fibers. The complexity of the immune reaction seen within the foreign body granuloma may explain why approaches focusing on specific cell types have not been very successful in reducing the chronic FBR.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10029-021-02396-7.

Tissue remodeling macrophages morphologically dominate at the interface of polypropylene surgical meshes in the human abdomen

Background

Mesh implants are widely used to reinforce the abdominal wall, although the inevitable inflammatory foreign body reaction (FBR) at the interface leads to complications. Macrophages are suspected to regulate the subsequent scar formation, but it is still unclear whether adequate fibrous scar formation with collagen deposition depends mainly on the presence of M1 or M2 macrophages.

Methods

This study investigated the FBR to seven human polypropylene meshes, which were removed after a median incorporation time of 1 year due to the primary complaint of recurrence. Using immunofluorescence, the FBR was examined in six regional zones with increasing distance from the mesh fibers up to 350 µm, based on the cell densities, macrophage M1 (CD86) and M2 (CD163, CD206) phenotypes, deposition of collagen-I and -III, and expression of matrix metalloproteinase-2 (MMP-2) and -8 as indicator of collagen degradation.

Results

All mesh–tissue complexes demonstrated a decrease in cell density and macrophages with distance to the mesh fibers. Overall, about 60% of the macrophages presented an M2 phenotype, whereas only 6% an M1 phenotype. Over 70% of macrophages showed co-expression with collagen-I or -III and over 50% with MMP-2.

Conclusions

The chronic FBR to polypropylene meshes is associated with an M2 macrophage response, which is accompanied by collagen deposition and MMP-2 expression. These findings challenge the idea that mainly M1 macrophages are related to inflammation and highlights that iatrogenic attempts to polarize these cells towards the M2 phenotype may not be a solution to ameliorate the long-term foreign body reaction.

Electronic supplementary material

The online version of this article (10.1007/s10029-020-02315-2) contains supplementary material, which is available to authorized users.