Macrophage Serum-Based Adhesion to Plasma-Processed Surface Chemistry is Distinct from That Exhibited by Fibroblasts

Correlation between Surface Properties of Polystyrene and Polylactide Materials and Fibroblast and Osteoblast Cell Line Behavior: A Critical Overview of the Literature

Bone reconstruction remains an important challenge today in several clinical situations, notably regarding the control of the competition occurring during proliferation of osteoblasts and fibroblasts. Polystyrene and polylactide are reference materials in the biomedical field. Therefore, it could be expected from the literature that clear correlations have been already established between the behavior of fibroblasts or osteoblasts and the surface characteristics of these materials. After an extensive analysis of the literature, although general trends could be established, our critical review has highlighted the need to develop a more in-depth analysis of the surface properties of these materials. Moreover, the large variation noticed in the experimental conditions used for in vitro animal cell studies impairs comparison between studies. From our comprehensive review on this topic, we have suggested several parameters that would be valuable to standardize to integrate the data from the literature and improve our knowledge on the cell-material interactions.

Characterisation of multipotent stem cells from human peripheral blood using an improved protocol

Background

A promising approach of bone repair is to use stem cells, such as mesenchymal stem cells (MSCs). Seeking available source of MSCs still remains a great challenge in tissue engineering and cell therapy. Peripheral blood (PB) emerges as an alternative source of MSCs which can be easily acquired with minimal invasiveness. This study was undertaken to evaluate the multipotency of PB-MSCs and effects of human PB-MSCs transplantation on ectopic bone regeneration in nude mice.

Methods

Human venous blood collected was mixed with heparin and then red blood cells were removed using red blood cell lysis buffer. Cell suspension was cultured in normoxia-culture and hypoxia-culture conditions, respectively. The non-adherent cells were removed by half changing culture media every three days. Cells were selected due to plastic adherence. The adherent cells were then passaged and subjected to multi-differentiation induction assays in vitro and in vivo ectopic bone formation assay.

Results

Characterization assays indicated that cells cultured under hypoxia possessed potent multi-lineage differentiation capacity and expressed Nanog and Lgr5, as well as a series of MSC surface antigens (including CD29, CD90, CD105, and CD73). Additionally, regenerated bone tissues by transplantation of human PB-MSCs in vivo were confirmed by histological examinations of ectopic osteogenesis assay. A purified population of MSCs can be obtained within a short period of time using this protocol with a successful rate of 60%.

Conclusion

We reported an effective and reliable method to harvest highly purified MSCs with potent multi-differentiation potential from human peripheral blood. Lgr5 may be a potential biomarker for identification of a subpopulation of PB-MSCs.

The translational potential of this article

PB-MSCs is an alternative cell source for cell therapy, which may be harvested, culture expanded and PB-MSCs loaded with β-tricalcium phosphate (β-TCP) may be used to promote bone repair.

Factors Associated with Ventriculoperitoneal Shunt Failures in the First 30 Postoperative Days in Pediatric Patients

OBJECTIVE

Placing of a ventriculoperitoneal shunt (VPS) is one of the most common procedures performed by neurosurgeons. Surgical revision of VPS is a significant cause of patient morbidity and mortality. This study was aimed to provide an analysis of factors related to VPS failures in the first 30 postoperative days in a pediatric cohort.

METHODS

This was a retrospective cohort study of 83 pediatric patients (<18 years old), shunted for the first time at a referral care center, between January 2012 and December 2016. Univariate analysis was used to detect potential predictors of VPS failures within the first 30 postoperative days and in the first 6 months of follow-up. Kaplan-Meier survival curves were used to examine the occurrence of VPS failures over time.

RESULTS

During the first 30 postoperative days, VPS failures occurred in 21 patients (25.3%). Intraventricular hemorrhage (IVH) (odds ratio [OR], 4.41; 95% confidence interval [CI], 1.44-13.48), cerebrospinal fluid (CSF) alterations (OR, 5.11; 95% CI, 1.37-19.1), and previous external ventricular drain (EVD) (OR, 7.05; 95% CI, 1.18-41.8) were significantly associated with shunt failure during the first postoperative month. Kaplan-Meier survival analysis showed decreased shunt survival for patients with IVH, both during the first 30 days after surgery (P = 0.005, log-rank), and during the 6 months after surgery (P = 0.005, log-rank).

CONCLUSIONS

In this study, we found that in pediatric patients, IVH was associated with VPS failure within the first 30 postoperative days and decreased shunt survival over time. Further larger prospective randomized studies are needed to better understand these results.

Fabrication of micropatterns on polypropylene films via plasma pretreatment combined with UV-initiated graft polymerization

In this study, micropatterns on polypropylene films were fabricated via plasma pretreatment and UV-initiated graft polymerization. Firstly, radio-frequency plasma, which does not significantly influence bulk attributes of substrates due to limited penetration depth, was utilized to activate polypropylene films. Then, different sizes of micropatterns of poly(hydroxyethyl methacrylate) (PHEMA) were fabricated on the polypropylene films via UV-initiated graft polymerization of hydroxyethyl methacrylate by using photo-masks. Scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle (CA) were employed to characterize changes of pristine polypropylene films and modified ones in surface morphology, roughness, hydrophilicity, free energy and the surface chemical composition. All of these confirmed the successful grafting of different sizes of PHEMA micropatterns on the polypropylene surface. Furthermore, the influence of PHEMA micropatterns on cell proliferation and cytotoxicity was evaluated in vitro. Analysis of cell behaviour indicated that PHEMA micropatterns of the appropriate size can promote cellular adhesion and proliferation, and the PHEMA-micropatterned polypropylene films had good biocompatibility. The approach presented here provides an alternative to synthesize on the surface of polypropylene films' micropatterns with the aim of using them in a diverse array of applications.

Harvesting pre-polarized macrophages using thermo-responsive substrates

In the cell culture environment macrophages are highly adherent cells. Currently used methods to harvest macrophages have the disadvantage of reducing cell viability and their ability to re-attach after seeding. Although thermo-responsive surfaces have been employed to harvest cell sheets no reports are available to use these to harvest (pre-polarized) macrophages. We show that this method significantly improves the yield of living macrophages and percentage of subsequent cell reattachment, whilst having a minimal effect on the cell phenotype.

Extended culture of macrophages from different sources and maturation results in a common M2 phenotype

Inflammatory responses to biomaterials heavily influence the environment surrounding implanted devices, often producing foreign-body reactions. The macrophage is a key immunomodulatory cell type consistently associated with implanted biomaterials and routinely used in short-term in vitro cell studies of biomaterials aiming to reproduce host responses. Inconsistencies within these studies, including differently sourced cells, different durations of culture, and assessment of different activation markers, lead to many conflicting results in vitro that confound consistency and conclusions. We hypothesize that different experimentally popular monocyte-macrophage cell types have intrinsic in vitro culture-specific differences that yield conflicting results. Recent studies demonstrate changes in cultured macrophage cytokine expression over time, leading to the hypothesis that changes in macrophage phenotype also occur in response to extended culture. Here, macrophage cells of different transformed and primary-derived origins were cultured for 21 days on model polymer biomaterials. Cell type-based differences in morphology and cytokine/chemokine expression as well as changes in cell surface biomarkers associated with differentiation stage, activation state, and adhesion were compared. Results reflect consistent macrophage development toward an M2 phenotype via up-regulation of the macrophage mannose receptor for all cell types following 21-day extended culture. Significantly, implanted biomaterials experiencing the foreign-body response and encapsulation in vivo often elicit a shift toward an analogous M2 macrophage phenotype. In vitro "default" of macrophage cultures, regardless of lineage, to this M2 state in the presence of biomaterials at long culture periods is not recognized, but has important implications to in vitro modeling of in vivo host response.

Conformal encapsulation of three-dimensional, bioresorbable polymeric scaffolds using plasma-enhanced chemical vapor deposition

Bioresorbable polymers such as poly(ε-caprolactone) (PCL) have a multitude of potential biomaterial applications such as controlled-release drug delivery and regenerative tissue engineering. For such biological applications, the fabrication of porous three-dimensional bioresorbable materials with tunable surface chemistry is critical to maximize their surface-to-volume ratio, mimic the extracellular matrix, and increase drug-loading capacity. Here, two different fluorocarbon (FC) precursors (octofluoropropane (C3F8) and hexafluoropropylene oxide (HFPO)) were used to deposit FC films on PCL scaffolds using plasma-enhanced chemical vapor deposition (PECVD). These two coating systems were chosen with the intent of modifying the scaffold surfaces to be bio-nonreactive while maintaining desirable bulk properties of the scaffold. X-ray photoelectron spectroscopy showed high-CF2 content films were deposited on both the exterior and interior of PCL scaffolds and that deposition behavior is PECVD system specific. Scanning electron microscopy data confirmed that FC film deposition yielded conformal rather than blanket coatings as the porous scaffold structure was maintained after plasma treatment. Treated scaffolds seeded with human dermal fibroblasts (HDF) demonstrate that the cells do not attach after 72 h and that the scaffolds are noncytotoxic to HDF. This work demonstrates conformal FC coatings can be deposited on 3D polymeric scaffolds using PECVD to fabricate 3D bio-nonreactive materials.

Intercellular communication through contacts between continuous pseudopodial extensions in a macrophage-like cell line

Cell-to-cell information exchange mediated by membrane protrusions in tunneling nanotubes (TNTs) has been widely described in distinct cell lines. Here, we describe a new form of direct intercellular communication in a murine macrophage-like cell line that is mediated by pseudopodial fusions that form over scraped plastic tissue culture surfaces along scratch lines. These structures are capable of forming intercellular, tunnel-like channels (inter-pseudopodial axis connections) that can be differentiated from TNTs based on length, thickness, tandem arrangement along an axis, pseudopodial origin and permanency. These channels were able to exchange membrane lipids and contain particles 0.5 μm or lesser in diameter between cells and might represent an additional biological function of pseudopodia.

Challenges in the characterization of plasma-processed three-dimensional polymeric scaffolds for biomedical applications

Low-temperature plasmas offer a versatile method for delivering tailored functionality to a range of materials. Despite the vast array of choices offered by plasma processing techniques, there remain a significant number of hurdles that must be overcome to allow this methodology to realize its full potential in the area of biocompatible materials. Challenges include issues associated with analytical characterization, material structure, plasma processing, and uniform composition following treatment. Specific examples and solutions are presented utilizing results from analyses of three-dimensional (3D) poly(ε-caprolactone) scaffolds treated with different plasma surface modification strategies that illustrate these challenges well. Notably, many of these strategies result in 3D scaffolds that are extremely hydrophilic and that enhance human Saos-2 osteoblast cell growth and proliferation, which are promising results for applications including tissue engineering and advanced biomedical devices.

Cultured primary macrophage activation by lipopolysaccharide depends on adsorbed protein composition and substrate surface chemistry

Recent efforts show that significantly reducing implant-adsorbed proteins does not avoid the foreign body response. Fluorinated surfaces are commonly used to passivate cell-mediated inflammatory responses to implanted materials but adsorb host proteins and facilitate the attachment and proliferation of macrophages. This study considers in vitro macrophage activation to fluorinated TeflonAF(®) compared to tissue-culture polystyrene using pre-adsorbed proteins (fibrinogen, BSA, collagen and elastin). Primary macrophage cultures adhere on all pre-adsorbed protein surfaces in a protein concentration-dependent manner and activate to the same extent after 72 h, regardless of surface chemistry. However, macrophages alter their cultured adherent morphology depending on which protein is pre-adsorbed to these surfaces. Macrophages cultured on TeflonAF(®) on all pre-adsorbed proteins produced overall higher levels of the pro-inflammatory cytokines - TNF-α, IL-6, IL-1β or MCP-1 - than those cultured on tissue-culture polystyrene and those cultured in serum-free media. However, at 72 h, macrophages adherent on BSA or fibrinogen pre-adsorbed surfaces failed to exhibit increased amounts of TNF-a, IL-6 or IL-1/S on either TeflonAF(®) or TCPS, as well as MCP-1 on TCPS, in the presence of activating lipopolysaccharide. Different cell responses to pre-adsorbed proteins reflect substrate-specific regulation of macrophage cytokine secretion, indicative of LPS tolerance distinct from secondary macrophage cultures, and also distinct from macrophages adherent to surfaces in the absence of proteins. This result has bearing on connecting macrophage adhesion via adsorbed proteins on (fluorinated) biomaterials, and their resulting chronic activation that yields the FBR and possibly reduces effective macrophage clearance of microbes around implanted materials.

What We Should Know About the Cellular and Tissue Response Causing Catheter Obstruction in the Treatment of Hydrocephalus

The treatment of hydrocephalus by cerebrospinal fluid shunting is plagued by ventricular catheter obstruction. Shunts can become obstructed by cells originating from tissue normal to the brain or by pathological cells in the cerebrospinal fluid for a variety of reasons. In this review, the authors examine ventricular catheter obstruction and identify some of the modifications to the ventricular catheter that may alter the mechanical and chemical cues involved in obstruction, including alterations to the surgical strategy, modifications to the chemical surface of the catheter, and changes to the catheter architecture. It is likely a combination of catheter modifications that will improve the treatment of hydrocephalus by prolonging the life of ventricular catheters to improve patient outcome.

Effect of electrospun fiber diameter and alignment on macrophage activation and secretion of proinflammatory cytokines and chemokines

Macrophage activation can be modulated by biomaterial topography according to the biological scale (micrometric and nanometric range). In this study, we investigated the effect of fiber diameter and fiber alignment of electrospun poly(L-lactic) (PLLA) scaffolds on macrophage RAW 264.7 activation and secretion of proinflammatory cytokines and chemokines at 24 h and 7 days. Macrophages were cultured on four different types of fibrous PLLA scaffold (aligned microfibers, aligned nanofibers, random microfibers, and random nanofibers) and on PLLA film (used as a reference). Substrate topography was found to influence the immune response activated by macrophages, especially in the early inflammation stage. Secretion of proinflammatory molecules by macrophage cells was chiefly dependent on fiber diameter. In particular, nanofibrous PLLA scaffolds minimized the inflammatory response when compared with films and microfibrous scaffolds. The histological evaluation demonstrated a higher number of foreign body giant cells on the PLLA film than on the micro- and nanofibrous scaffolds. In summary, our results indicate that the diameter of electrospun PLLA fibers, rather than fiber alignment, plays a relevant role in influencing in vitro macrophage activation and secretion of proinflammatory molecules.

Fabrication and Characterization of Thermoresponsive Films Deposited by an RF Plasma Reactor

Poly(N-isopropyl acrylamide) (pNIPAM) undergoes a sharp property change in response to a moderate thermal stimulus at physiological temperatures. In this work, we constructed a radio frequency (RF) plasma reactor for the plasma polymerization of pNIPAM. RF deposition is a method that coats surfaces of any geometry producing surfaces that are sterile and uniform, making this technique useful for forming biocompatible films. The films generated are characterized using X-ray photoelectron spectroscopy (XPS), contact angles, cell culture, and interferometry. We find that a plasma with a decreasing series of power settings (i.e., from 100W to 1W) at a pressure of 140 millitorr yields the most favorable results.

Cell-cell signaling in co-cultures of macrophages and fibroblasts

The foreign body response (FBR) comprises a general, ubiquitous host tissue-based reaction to implanted materials. In vitro cell-based models are frequently employed to study FBR mechanisms involving cell signaling responses to materials. However, these models often study only one cell type, identify only limited signals, and cannot accurately represent the complexity of in vivo inflammatory signaling. To address this issue, a cell co-culture system involving two primary effector cells of the FBR, macrophages and fibroblasts, was employed. Cell-cell signaling systems were monitored between these cell types, including long-term 1) culture of one cell type in conditioned media from the other cell type, 2) non-contacting cell co-cultures (paracrine signaling), and 3) contact co-cultures (juxtacrine signaling) of primary- and secondary-derived cells. Cell culture media and cell images were collected on Days 1, 2, 3, 7, 14, and 21 and changes in soluble protein secretion, cellular behavior, and morphology were assessed. Primary- and secondary-derived cells responded uniquely during each signaling scenario and to one another. In general higher in vitro fidelity to FBR-like responses was found in primary cell co-cultures compared to their mono-cultures and all secondary cell cultures.

Rewritable glycochips

We describe microarraying of carbohydrates for protein screening using either disulfide bridge or Schiff base imine immobilization chemistries on plasmachemical deposited functional nanolayers. The commonly observed issue of nonspecific background binding of proteins is overcome by spotting carbohydrates through a protein-resistant overlayer yielding spatially localized interaction with a reactive functional underlayer.

Adsorbed serum albumin is permissive to macrophage attachment to perfluorocarbon polymer surfaces in culture

Monocyte/macrophage adhesion to biomaterials, correlated with foreign body response, occurs through protein-mediated surface interactions. Albumin-selective perfluorocarbon (FC) biomaterials are generally poorly cell-conducive because of insufficient receptor-mediated surface interactions, but macrophages bind to albumin-coated substrates and also preferentially to highly hydrophobic fluorinated surfaces. Bone marrow macrophages (BMMO) and IC-21, RAW 264.7, and J774A.1 monocyte/macrophage cells were cultured on FC surfaces. Protein deposition onto two distinct FC surfaces from complex and single-component solutions was tracked using fluorescence and time-of-flight secondary ion mass spectrometry (ToF-SIMS) methods. Cell adhesion and growth on protein pretreated substrates were compared by light microscopy. Flow cytometry and integrin-directed antibody receptor blocking were used to assess integrins critical for monocyte/macrophage adhesion in vitro. Albumin predominantly adsorbs onto both FC surfaces from 10% serum. In cultures preadsorbed with albumin or serum-dilutions, BMMO responded similar to IC-21 at early time points. Compared with Teflon AF, plasma-polymerized FC was less permissive to extended cell proliferation. The beta(2) integrins play major roles in macrophage adhesion to FC surfaces: antibody blocking significantly disrupted cell adhesion. Albumin-mediated cell adhesion mechanisms to FC surfaces could not be clarified. Primary BMMO and secondary IC-21 macrophages behave similarly on FC surfaces, regardless of preadsorbed protein biasing, with respect to adhesion, cell morphology, motility, and proliferation.

Subsurface oxidation for micropatterning silicon (SOMS)

Here we present a straightforward patterning technique for silicon: subsurface oxidation for micropatterning silicon (SOMS). In this method, a stencil mask is placed above a silicon surface. Radio-frequency plasma oxidation of the substrate creates a pattern of thicker oxide in the exposed regions. Etching with HF or KOH produces very shallow or much higher aspect ratio features on silicon, respectively, where patterning is confirmed by atomic force microscopy, scanning electron microscopy, and optical microscopy. The oxidation process itself is studied under a variety of reaction conditions, including higher and lower oxygen pressures (2 and 0.5 Torr), a variety of powers (50-400 W), different times and as a function of reagent purity (99.5 or 99.994% oxygen). SOMS can be easily executed in any normal chemistry laboratory with a plasma generator. Because of its simplicity, it may have industrial viability.

Antimicrobial efficacy and ocular cell toxicity from silver nanoparticles

Silver in various forms has long been recognized for antimicrobial properties, both in biomedical devices and in eyes. However, soluble drugs used on the ocular surface are rapidly cleared through tear ducts and eventually ingested, resulting in decreased efficacy of the drug on its target tissue and potential concern for systemic side effects. Silver nanoparticles were studied as a source of anti-microbial silver for possible controlled-release contact lens controlled delivery formulations. Silver ion release over a period of several weeks from nanoparticle sources of various sizes and doses in vitro was evaluated in vitro against Pseudomonas aeruginosa strain PA01. Mammalian cell viability and cytokine expression in response to silver nanoparticle exposure is evaluated using corneal epithelial cells and eye-associated macrophages cultured in vitro in serum-free media. Minimal microcidal and cell toxic effects were observed for several silver nanoparticle suspensions and aqueous extraction times for bulk total silver concentrations commensurate with comparative silver ion (e.g., Ag(+) ((aq))) toxicity. This indicates that (1) silver particles themselves are not microcidal under conditions tested, and (2) insufficient silver ion is generated from these particles at these loadings to produce observable biological effects in these in vitro assays. If dosing allows substantially increased silver particle loading in the lens, the bactericidal efficacy of silver nanoparticles in vitro is one possible approach to limiting bacterial colonization problems associated with extended-wear contact lenses.