Differences in protein binding and cytokine release from monocytes on commercially sourced tissue culture polystyrene

Compatibility and function of human induced pluripotent stem cell derived cardiomyocytes on an electrospun nanofibrous scaffold, generated from an ionomeric polyurethane composite

Synthetic scaffolds are needed for generating organized neo-myocardium constructs to promote functional tissue repair. This study investigated the biocompatibility of an elastomeric electrospun degradable polar/hydrophobic/ionic polyurethane (D-PHI) composite scaffold with human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The composite material was electrospun to generate scaffolds, with nanofibres oriented in aligned or random directions. These features enabled the authors to evaluate the effect of characteristic elements which mimic that of the native extracellular matrix (alignment, chemical heterogeneity, and fiber topography) on hiPSC-CMs activity. The functional nature of the hiPSC-CM cultured on gelatin and Matrigel-coated scaffolds were assessed, investigating the influence of protein interactions with the synthetic substrate on subsequent cell phenotype. After 7 days of culture, high hiPSC-CM viability was observed on the scaffolds. The cells on the aligned scaffold were elongated and demonstrated aligned sarcomeres that oriented parallel to the direction of the fibers, while the cells on random scaffolds and a tissue culture polystyrene (TCPS) control did not exhibit such an organized morphology. The hiPSC-CMs cultured on the scaffolds and TCPS expressed similar levels of cardiac troponin-T, but there was a higher expression of ventricular myosin light chain-2 on the D-PHI composite scaffolds versus TCPS, indicating a higher proportion of hiPSC-CM exhibiting a ventricular cardiomyocyte like phenotype. Within 7 days, the hiPSC-CMs on aligned scaffolds and TCPS beat synchronously and had similar conductive velocities. These preliminary results show that aligned D-PHI elastomeric scaffolds allow hiPSC-CMs to demonstrate important cardiomyocytes characteristics, critical to enabling their future potential use for cardiac tissue regeneration.

Cell membrane rupture: a novel test reveals significant variations among different brands of tissue culture flasks

Objectives

Loss of cytoplasmic molecules including protein controls, due to cell membrane rupture can cause errors and irreproducibility in research data. Previous results have shown that during the washing of a monolayer of cells with a balanced salt solution, the fluid force causes cell membrane rupture on some areas of the flasks/dishes. This fact shows the non-uniformity of the polystyrene surface in terms of cell culture. There is at present no simple test to monitor that surface. This paper presents a novel biologically based assay to determine the degree of heterogeneity of flasks supplied by various manufacturers.

Results

This paper shows that significant variation exists in polystyrene surface heterogeneity among several brands of tissue culture flasks, varying from 4 to 20% of the flask surface. There is also large variability within the production lot of a manufacturer. The assay method involves loading the cells with a cytoplasmic fluorescent marker that is released upon cell membrane rupture. Cell membrane rupture also causes the loss of marker proteins such as GAPDH used in Westernblots. This novel assay method can be used to monitor the batch consistency and the manufacturing process of flasks/dishes. It may also be used to test new biomaterials.

Proteome analysis of secretions from human monocyte-derived macrophages post-exposure to biomaterials and the effect of secretions on cardiac fibroblast fibrotic character

The use of exogenous biomolecules (BM) for the purpose of repairing and regenerating damaged cardiac tissue can yield serious side effects if used for prolonged periods. As well, such strategies can be cost prohibitive depending on the regiment and period of time applied. Alternatively, autologous monocytes/monocyte-derived macrophages (MDM) can provide a viable path towards generating an endogenous source of stimulatory BM. Biomaterials are often considered as delivery vehicles to generate unique profiles of such BM in tissues or to deliver autologous cells, that can influence the nature of BM produced by the cells. MDM cultured on a degradable polar hydrophobic ionic (D-PHI) polyurethane has previously demonstrated a propensity to increase select anti-inflammatory cytokines, and therefore there is good rationale to further investigate a broader spectrum of the cells' BM in order to provide a more complete proteomic analysis of human MDM secretions induced by D-PHI. Further, it is of interest to assess the potential of such BM to influence cells involved in the reparative state of vital tissues such as those that affect cardiac cell function. Hence, this current study examines the proteomic profile of MDM secretions using mass spectrometry for the first time, along with ELISA, following their culture on D-PHI, and compares them to two important reference materials, poly(lactic-co-glycolic acid) (PLGA) and tissue culture polystyrene (TCPS). Secretions collected from D-PHI cultured MDM led to higher levels of regenerative BM, AGRN, TGFBI and ANXA5, but lower levels of pro-fibrotic BM, MMP7, IL-1β, IL-6 and TNFα,  when compared to MDM secretions collected from PLGA and TCPS. In the application to cardiac cell function, the secretion collected from D-PHI cultured MDM led to more human cardiac fibroblast (HCFs) migration. A lower collagen gel contraction induced by MDM secretions collected from D-PHI was supported by gene array analysis for human fibrosis-related genes. The implication of these findings is that more tailored biomaterials such as D-PHI, may lead to a lower pro-inflammatory phenotype of macrophages when used in cardiac tissue constructs, thereby enabling the development of vehicles for the delivery of interventional therapies, or be applied as coatings for sensor implants in cardiac tissue that minimize fibrosis. The general approach of using synthetic biomaterials in order to induce MDM secretions in a manner that will guide favorable regeneration will be critical in making the choice of biomaterials for tissue regeneration work in the future. STATEMENT OF SIGNIFICANCE: Immune modulation strategies currently applied in cardiac tissue repair are mainly based on the delivery of defined exogenous biomolecules. However, the use of such biomolecules may pose wide ranging systemic effects, thereby rendering them clinically less practical. The chemistry of biomaterials (used as a potential targeted delivery modality to circumvent the broad systemic effects of biomolecules) can not only affect acute and chronic toxicity but also alters the timeframe of the wound healing cascade. In this context, monocytes/monocyte-derive macrophages (MDM) can be harnessed as an immune modulating strategy to promote wound healing by an appropriate choice of the biomaterial. However, there are limited reports on the complete proteome analysis of MDM and their reaction of biomaterial related interventions on cardiac tissues and cells. No studies to date have demonstrated the complete proteome of MDM secretions when these cells were cultured on a non-traditional immune modulatory ionomeric polyurethane D-PHI film. This study demonstrated that MDM cultured on D-PHI expressed significantly higher levels of AGRN, TGFBI and ANXA5 but lower levels of MMP7, IL-1β, IL-6 and TNFα when compared to MDM cultured on a well-established degradable biomaterials in the medical field, e.g. PLGA and TCPS, which are often used as the relative standards for cell culture work in the biomaterials field. The implications of these findings have relevance to the repair of cardiac tissues. In another aspect of the work, human cardiac fibroblasts showed significantly lower contractility (low collagen gel contraction and low levels of ACTA2) when cultured in the presence of MDM secretions collected after culturing them on D-PHI compared to PLGA and TCPS. The findings place emphasis on the importance of making the choice of biomaterials for tissue engineering and regenerative medicine applied to their use in cardiac tissue repair.

In Vitro Research Reproducibility: Keeping Up High Standards

Concern regarding the reproducibility of observations in life science research has emerged in recent years, particularly in view of unfavorable experiences with preclinical in vivo research. The use of cell-based systems has increasingly replaced in vivo research and the application of in vitro models enjoys an ever-growing popularity. To avoid repeating past mistakes, high standards of reproducibility and reliability must be established and maintained in the field of in vitro biomedical research. Detailed guidance documenting the appropriate handling of cells has been authored, but was received with quite disparate perception by different branches in biomedical research. In that regard, we intend to raise awareness of the reproducibility issue among scientists in all branches of contemporary life science research and their individual responsibility in this matter. We have herein compiled a selection of the most susceptible steps of everyday in vitro cell culture routines that have the potential to influence cell quality and recommend practices to minimize the likelihood of poor cell quality impairing reproducibility with modest investment of time and resources.

Bags versus flasks: a comparison of cell culture systems for the production of dendritic cell-based immunotherapies

In recent years, cell-based therapies targeting the immune system have emerged as promising strategies for cancer treatment. This review summarizes manufacturing challenges related to production of antigen presenting cells as a patient-tailored cancer therapy. Understanding cell-material interactions is essential because in vitro cell culture manipulations to obtain mature antigen-producing cells can significantly alter their in vivo performance. Traditional antigen-producing cell culture protocols often rely on cell adhesion to surface-treated hydrophilic polystyrene flasks. More recent commercial and investigational cancer immunotherapy products were manufactured using suspension cell culture in closed hydrophobic fluoropolymer bags. The shift to closed cell culture systems can decrease risks of contamination by individual operators, as well as facilitate scale-up and automation. Selecting closed cell culture bags over traditional open culture systems entails different handling procedures and processing controls, which can affect product quality. Changes in culture vessels also entail changes in vessel materials and geometry, which may alter the cell microenvironment and resulting cell fate decisions. Strategically designed culture systems will pave the way for the generation of more sophisticated and highly potent cell-based cancer vaccines. As an increasing number of cell-based therapies enter the clinic, the selection of appropriate cell culture vessels and materials becomes a critical consideration that can impact the therapeutic efficacy of the product, and hence clinical outcomes and patient quality of life.

Serum proteins are extracted along with monolayer cells in plasticware and interfere with protein analysis

Washing and lysing monolayer cells directly from cell culture plasticware is a commonly used method for protein extraction. We found that multiple protein bands were enriched in samples with low cell numbers from the 6-well plate cultures. These proteins contributed to the overestimation of cell proteins and led to the uneven protein loading in Western blotting analysis. In Coomassie blue stained SDS-PAGE gels, the main enriched protein band is about 69 kDa and it makes up 13.6% of total protein from 10⁴ U251n cells. Analyzed by mass spectrometry, we identified two of the enriched proteins: bovine serum albumin and bovine serum transferrin. We further observed that serum proteins could be extracted from other cell culture plates, dishes and flasks even after washing the cells 3 times with PBS. A total of 2.3 mg of protein was collected from a single well of the 6-well plate. A trace amount of the protein band was still visible after washing the cells 5 times with PBS. Thus, serum proteins should be considered if extracting proteins from plasticware, especially for samples with low cell numbers.

Synthesis and characterization of biodegradable lysine-based waterborne polyurethane for soft tissue engineering applications

Light-crosslinking waterborne polyurethanes (LWPUs) based on lysine possess appropriate elasticity for soft tissue repair, and can induce macrophages into a wound healing phenotype.

Interaction of a block-co-polymeric biomaterial with immunoglobulin G modulates human monocytes towards a non-inflammatory phenotype

Monocyte interactions with implanted biomaterials can contribute significantly to the ability of a biomaterial to support tissue integration and wound healing, as opposed to a chronic pro-inflammatory foreign body reaction, provided the materials are designed to do so. However, there are few biomaterials available designed to regulate immune cell response with the intention of reducing the pro-inflammatory activation state. Material chemistry is a powerful tool for regulating protein and cell interactions that can be incorporated into surfaces while maintaining desired mechanical properties. The aspects of material chemistry that can support monocyte activation away from a pro-inflammatory state are still poorly understood. Protein adsorption is a key initial event that transforms the surface of a biomedical device into a biological substrate that will govern subsequent cellular interactions. In this study, the chemistry of degradable block polyurethanes, termed degradable polar hydrophobic ionic (D-PHI) polyurethanes, were studied for their unique interactions with bound immunoglobulin G (IgG), a pro-inflammatory protein that supports monocyte-biomaterial interactions. The specific immunological active sites of the polyurethane-adsorbed protein were compared with IgG's adsorbed state on a homopolymeric material with surface chemistry conducive to cell interactions, e.g. tissue culture polystyrene (TCPS). IgG-coated TCPS supported sustained monocyte adhesion and enhanced monocyte spreading, effects not observed with IgG-coated PU. The degradable PU was subsequently shown to reduce the number of exposed IgG-Fab sites following pre-adsorption vs. IgG adsorbed to TCPS, with antibody inhibition experiments demonstrating that Fab-site exposure appears to dominate monocyte-biomaterial interactions. Minor changes in chemical segments within the PU molecular chains were subsequently investigated for their influence on directing IgG interactions towards reducing pro-inflammatory activity. A reduction in chemical heterogeneity within the PU, without significant differences in other material properties known to regulate monocyte response, was shown to increase Fab exposure and subsequently led to monocyte interactions similar to those observed for IgG-coated TCPS. These results infer that reduced IgG-Fab site exposure can be directed by material chemistry to attenuate pro-inflammatory monocyte interactions with biomaterial surfaces, and identify the chemical features of polymeric biomaterial design responsible for this process.

STATEMENT OF SIGNIFICANCE

There is currently limited understanding of material design features that can regulate protein-material interactions in order to prevent adverse inflammatory responses to implanted biomaterials. In this paper, monocyte interactions with biomaterials (specifically a block co-polymeric degradable polyurethane [D-PHI] and tissue culture polystyrene [TCPS]) were investigated as a function of their interactions with adsorbed immunoglobulin G (IgG). D-PHI was shown to attenuate IgG-induced monocyte retention and spreading by reducing IgG-Fab site exposure upon adsorption relative to TCPS. Aspects of D-PHI chemistry important in regulating Fab site exposure were determined. This study thus identifies features of biomaterials, using D-PHI as a case study, which can contribute to the development of new immunomodulatory biomaterial design.

Characterization of a degradable polar hydrophobic ionic polyurethane with circulating angiogenic cells in vitro

This study investigated the interaction of human circulating angiogenic cells (CACs) with a degradable polar hydrophobic ionic polyurethane (D-PHI) which has been previously shown to exhibit anti-inflammatory character and favorable interactions with human endothelial cells (ECs). Given the implication of the CACs in microvessel development it was of intrinsic interest to expand our knowledge of D-PHI biocompatibility with this relevant primary cell involved in angiogenesis. The findings will be compared to a well-established benchmark substrate for CACs, fibronectin-coated tissue culture polystyrene (TCPS). Immunoblotting analysis showed that CACs were a heterogeneous population of cells composed mostly of monocytic cells expressing the CD14 marker. Assessment of the cytokine release profile, using ELISA, showed that D-PHI supported a higher concentration of interleukin-10 (IL-10) when compared to the concentration of tumor necrosis factor alpha, which is indicative of an anti-inflammatory phenotype, and was different from the response with TCPS. It was found that the CACs were attached to D-PHI and remained viable and functional (nitric oxide production) during the seven days of culture. However, there did not appear to be any significant proliferation on D-PHI, contrary to the CAC growth on fibronectin-coated TCPS. It was concluded that D-PHI displayed some of the qualities suitable to enable the retention of CACs onto this substrate, as well as maintaining an anti-inflammatory phenotype, characteristics which have been reported to be important for angiogenesis in vivo.

Biomaterials in co-culture systems: towards optimizing tissue integration and cell signaling within scaffolds

Most natural tissues consist of multi-cellular systems made up of two or more cell types. However, some of these tissues may not regenerate themselves following tissue injury or disease without some form of intervention, such as from the use of tissue engineered constructs. Recent studies have increasingly used co-cultures in tissue engineering applications as these systems better model the natural tissues, both physically and biologically. This review aims to identify the challenges of using co-culture systems and to highlight different approaches with respect to the use of biomaterials in the use of such systems. The application of co-culture systems to stimulate a desired biological response and examples of studies within particular tissue engineering disciplines are summarized. A description of different analytical co-culture systems is also discussed and the role of biomaterials in the future of co-culture research are elaborated on. Understanding the complex cell-cell and cell-biomaterial interactions involved in co-culture systems will ultimately lead the field towards biomaterial concepts and designs with specific biochemical, electrical, and mechanical characteristics that are tailored towards the needs of distinct co-culture systems.

A polymer-based functional pattern on one-dimensional photonic crystals for photon sorting of fluorescence radiation

In this work we introduce the use of a patterned polymer-based surface functionalization of a one-dimensional photonic crystal (1DPC) for controlling the emission direction of fluorescent proteins (ptA) via coupling to a set of two Bloch Surface Waves (BSW). Each BSW dispersion branch relates to a micrometric region on the patterned 1DPC, characterized by a well defined chemical characteristic. We report on the enhanced and spatially selective excitation of fluorescent ptA, and on the spatially-resolved detection of polarized emitted radiation coupled to specific BSW modes. As a result, we provide an optical multiplexing technique for the angular separation of fluorescence radiated from micrometric regions having different surface properties, even in the case the emitting labels are spectrally identical. This working principle can be advantageously extended to a multi-step nanometric relief structure for self-referencing biosensing or frequency-multiplexed fluorescence detection.