Synthesis and fate of immunological surface receptors on cultured Burkitt lymphoma cells

A stable protocol for the fabrication of transplantable human oral mucosal epithelial cell sheets for clinical application

Introduction

Cultured stratified epithelial cell sheets have been clinically utilized as transplantable grafts for the regeneration of epithelial tissues, such as the esophagus, cornea, skin, and intraoral cavity. These cell sheets are expected to gain widespread use as regenerative medicine products and save many patients. For this purpose, establishing and disseminating the stale protocol of fabricating the cell sheet is crucial. The fabrication of cultured stratified epithelial cell sheets consists of many important steps, and since the patients' epithelial cell conditions vary widely and are sometimes unstable, the qualities of the epithelial cell grafts are likewise potentially unstable. Therefore, in this paper, we report the stable protocol for fabrication of the transplantable cell sheet particularly from patient-derived oral mucosal tissues.

Methods

Serum extracted from blood and buccal mucosal tissue were collected in Nagasaki University and transported to Tokyo Women's Medical University. Oral mucosal epithelial cells were collected by minimum trypsin method, and this treatment was studied whether to be a critical procedure. After 14 days cultivation, cultured cells were examined whether to be transplantable as cell sheets.

Results

We successfully transported buccal mucosal tissue and serum without damage and contamination. Oral mucosal epithelial cells were collected with high viability by minimum trypsin method. Finally, we succeeded to stably fabricate oral mucosal epithelial cell sheets in all 10 patients.

Conclusions

We established a stable protocol for the fabrication of human oral mucosal epithelial cell sheets and their transportation in clinical settings in this study. These methodologies could also be basis for transplantation therapy using cultured cell sheets of various types other than oral mucosal epithelial cell and will contribute largely to the future development of regenerative medicine.

Simple Inkjet Process To Fabricate Microstructures of Chitinous Nanocrystals for Cell Patterning

Structural polysaccharide nanocrystals (NCs) including cellulose nanocrystal have attracted attention. In order to broaden the range of application of the NCs, we can take advantage of their original characteristics by establishing simple and reasonable processing methods. We here demonstrate a micropatterning of animal cellular adhesion by inkjet printing of aqueous dispersions of cytocompatible chitinous NCs onto cellophane films. We display how to regulate the deposition form and two-dimensional shape of the chitinous NC micromoldings using a research inkjet printer. Adhesive capability of mouse fibroblasts onto the chitinous substrates was greatly improved by alkali deacetylation. The deacetylated products remained rod-like nanostructures, but the original chitin crystal form changed to that of chitosan by an intensive deacetylation. The adhered cells could be recovered glycolytically. The chitinous micropatterning substrates can be utilized for biomedical applications such as controlling of cellular shapes, precise monitoring molecular events in biochemistry, and drug screening.

Recent development of temperature-responsive surfaces and their application for cell sheet engineering

Cell sheet engineering, which fabricates sheet-like tissues without biodegradable scaffolds, has been proposed as a novel approach for tissue engineering. Cells have been cultured and proliferate to confluence on a temperature-responsive cell culture surface at 37°C. By decreasing temperature to 20°C, an intact cell sheet can be harvested from the culture surface without enzymatic treatment. This new approach enables cells to keep their cell–cell junction, cell surface proteins and extracellular matrix. Therefore, recovered cell sheet can be easily not only transplanted to host tissue, but also constructed a three-dimensional (3D) tissue by layering cell sheets. Moreover, cell sheet manipulation technology and bioreactor have been combined with the cell sheet technology to fabricate a complex and functional 3D tissue in vitro. So far, cell sheet technology has been applied in regenerative medicine for several tissues, and a number of clinical studies have been performed. In this review, recent advances in the preparation of temperature-responsive cell culture surface, the fabrication of organ-like tissue and the clinical application of cell sheet engineering are summarized and discussed.

Cellular cancer vaccines: an update on the development of vaccines generated from cell surface antigens

A recent advance in anti-cancer therapies has been the use of cancer cells to develop vaccines. However, immunization with cancer cell-based vaccines has not resulted in significant long-term therapeutic benefits. A possible reason for this is that while cancer cells provide surface antigens that are targets for a desired immune response, they also contain a high abundance of housekeeping proteins, carbohydrates, nucleic acids, lipids, and other intracellular contents that are ubiquitous in all mammalian cells. These ubiquitous molecules are not the intended targets of this therapy approach, and thus, the immune response generated is not sufficient to eliminate the cancer cells present. In this review, a discussion of the cell surface of cancer cells is presented in relation to the goals of improving antigen composition of cancer cell-based vaccines. Strategies to enrich vaccines for cancer-specific antigens are also discussed.

Cell attachment to PET films coated with a thermo-sensitive block co-polymer with different chemical composition

This objective of this study is to characterize the surface of poly(ethylene terephthalate) (PET) films coated with the thermo-sensitive di-block co-polymers of 2-ethoxyethyl vinyl ether and 2-phenoxyethyl vinyl ether segments (EOVE-b-PhOVE) with a high polydispersity and evaluate the behavior of cell attachment on them at different temperatures. The EOVE segment possessed a low critical solution temperature at 20 degrees C while the hydrophobic PhOVE segment functioned as the site to allow the co-polymer to adsorb onto the PET films. X-ray photoelectron spectroscopy and contact angle measurements revealed that the PET film was coated with the EOVE-b-PhOVE co-polymers. The density of co-polymers coated increased with the concentration of co-polymers used for coating. Irrespective of the co-polymer type, 3T3L1 cells attached on the surface of coated films at 37 degrees C, while the cells showed a spread shape, which is similar to that of cells attached on the original non-coated film. However, when the temperature decreased from 37 to 4 degrees C, the cell shape changed to be round, in contrast to that of the original PET film. The percent increase of round cells depended on the coating density and the polymerization degree of EOVE segment.

Cell growth and detachment from protein-coated PNIPAAm-based copolymers

The cultivation of cells requires the use of unfavorable proteolytic enzymes, which cause cell-surface modification and also need considerable optimization. Recently, with the development of smart polymers, research has looked to using thermoresponsive polymers as cell culture substrates. These novel surfaces allow the cultivation of cells without using enzymes by utilizing the thermoresponsive phase transition property of poly(N-isopropylacrylamide) (PNIPAAm). Copolymers of PNIPAAm and N-tert-butyl-acrylamide (NtBAm) with varying ratios were synthesized and solvent cast. The copolymer films are coated with cell adhesion promoters such as collagen, poly-L-lysine, and laminin to increase their cell adhesion and growth properties. Cell activity measured by the alamarBlue and PicoGreen assays is similar for coated copolymer films and standard tissue culture plastic controls. Deposition of cell adhesion promoters onto the copolymer films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Cell detachment from the copolymer films is dependent on copolymer composition and is not affected by the surface coatings of extracellular matrix (ECM) proteins. The results demonstrate a versatile method for the cultivation of cells while eliminating the need for the use of digestive enzymes such as trypsin.

Maintenance of retinoid metabolism in human retinal pigment epithelium cell culture

If transplantation of cultured retinal pigment epithelium (RPE) or iris pigment epithelium (IPE) is to be successful in the treatment of ocular disease, it is imperative to demonstrate that these cells can perform all of their necessary metabolic functions. Unfortunately, a critical function of the RPE, retinoid metabolism, is often lost rapidly in culture. We have examined whether or not nonspecific proteolytic enzymes commonly used in cell isolation and serial passaging may be responsible for this loss of function, and we have investigated novel isolation and passaging techniques which can alleviate this loss of retinoid metabolism.RPE cells were obtained from human donor eyes by enzymatic and nonenzymatic methods. Cells were cultured either on control tissue culture inserts or on inserts coated with a layer of thermally responsive poly(N -isopropylacrylamide-co-cinnamoylcarbamidemethylstyrene). Upon confluence, cells were detached either by trypsinization or by lowering dish temperature. Retinoid metabolism of cells was assessed after isolation and culture by incubating membrane fractions with3H-all- trans -retinol. Retinoid metabolism was also measured in freshly isolated IPE, corneal endothelium (CE), an RPE cell line (D407), and two hepatocyte cell lines (Hepa 6 and HepG2). Membrane fractions from cells isolated nonenzymatically or using collagenase/hyaluronidase formed 11- cis -retinol, retinal isomers and retinyl esters. Retinoid metabolism of RPE cells freshly isolated by trypsinization showed no 11- cis -retinal and little 11- cis -retinol formation. Nondamaged cells cultured on thermally responsive surfaces detached in sheets upon temperature change. They showed metabolism similar to that of cells freshly isolated by nonenzymatic means. After trypsinization, confluent cultures dissociated into individual cells, but these cells showed poor retinoid metabolism, including no detectable retinyl esters or 11- cis -retinoid isomers. IPE, CE and Hepa 6 did not show any retinoid metabolism. D407 and HepG2 produced retinals, but not the 11- cis isomer.RPE cells isolated using trypsin lose the ability to form critical intermediates in the visual cycle. Collagenase/hyaluronidase or nonenzymatic cell isolation techniques enable these functions to be maintained. After cell culture, thermally responsive surfaces allow nonenzymatic cell detachment and excellent maintenance of retinoid metabolism.

Growth factor and matrix molecules preserve cell function on thermally responsive culture surfaces

Thermally-responsive culture surfaces were designed using copolymers of N-isopropylacrylamide, 4-(aminomethyl)styrene, and acrylic acid. These surfaces contained functional amine and carboxyl groups, which allowed biomolecules to be grafted by amide formation. Epidermal growth factor (EGF), and extracellular matrix (ECM) molecules (collagen type IV, and chondroitin sulfate) were investigated, as surface-grafted biomolecules, for their ability to stimulate cell attachment, proliferation, and function by signaling only from the basal side of cultured cells. Surface analysis of biomolecule-grafted porous inserts showed covalent binding of biomolecules to either amine or carboxyl groups. Multiple attachment to amine and/or carboxyl groups served as cross-linking points that made the polymer hydrogel permanently adherent to the culture surface. Immunofluorescence microscopy techniques gave positive identification of grafted biomolecules. Grafting of EGF improved cell proliferation versus that on nongrafted controls, or controls grafted only with ECM molecules. ECM grafting induced cell attachment on attachment-resistant surfaces. Analysis of trans-epithelial resistance, fluid transport, and polarized g-glutamyl transpeptidase activity indicated that simultaneous grafting of both EGF and ECM produced better polarized cell function than nongrafted controls, or controls grafted with only one type of biomolecule. Covalent grafting of biomolecules did not interfere with cells ability to detach from thermally responsive surfaces upon temperature decrease.

Retinal pigmented epithelium cultures on thermally responsive polymer porous substrates

A cross-linkable co-polymer of UV-sensitive 4-(N-cinnamoylcarbamide)methylstyrene (CCMS) and N-isopropylacrylamide (NIPAAm), was applied to porous tissue culture inserts. Surface chemical analyses of the inserts show an introduction of a thermally responsive polymer comparable to that on similarly incorporated non-porous polystyrene surfaces. Contact angle measurements as well as atomic force microscopy show a surface change in response to changing temperature in an aqueous environment, from hydrophilic, extended polymer chains below 32 degrees C to a dense hydrophobic film above 32 degrees C. Cell growth on porous inserts allowed measurement of cell expression, such as transepithelial resistance and fluid transport, which are not observable on cells from non-porous surfaces. Cultures of retinal pigmented epithelium (RPE) were able to restore an environment similar to in vivo by forming a tight junction barrier membrane upon confluence at 37 degrees C, as observed by changes in morphology, transepithelial resistance, and directionally-specific fluid transport. In addition, cells cultured on these surfaces detached as an oriented polarized sheet when the inserts were brought to 20 degrees C. This cell sheet was transplanted to other tissue culture surface without polymer detachment or dissolution, or cell damage caused by traditional detachment methods using proteolytic enzymes.

Growth factor release from thermally reversible tissue culture substrates

Thermally reversible poly(N-isopropylacrylamide) (PIPAAm) was covalently grafted onto tissue culture dishes to allow detachment of cultured cells upon temperature change from physiological to room temperature. In addition the grafted polymer matrix was used to entrap biomolecules such as growth factors either to be released by diffusion early in cell cultures, or remain entrapped and be reversibly exposed to cell receptors. Experiments with model proteins trypsin and insulin show that amount loaded and released depends upon the PIPAAm grafting density. Dishes grafted with 2.5 microgram/cm2 PIPAAm released approximately four times more model protein over 4 h than dishes grafted with 1.8 microgram/cm2. This in vitro drug delivery system can be used to deliver factors to the basal side of cells early in cell culture by providing high local concentrations without high bulk concentration. Cultures of human retinal pigmented epithelium showed higher growth rate on insulin loaded dishes than on controls containing a similar bulk solution concentration. These cultures retained the ability to detach singly or as confluent sheets from the loaded surfaces.

Novel thermally reversible hydrogel as detachable cell culture substrate

A novel UV crosslinkable co-polymer of 4-(N-cinnamoylcarbamide)methylstyrene (CCMS) and N-isopropylacrylamide (IPAAm) was partially entrapped in traditional tissue-culture-treated polystyrene and crosslinked by UV light irradiation. Dishes modified by this method showed a change in contact angle with respect to temperature as compared to tissue culture polystyrene controls. Surface chemical analysis indicated that the crosslinked hydrogel does not detach from the surface after successive rinsing in ethanol and water, keeping the cells or cell construct free of unwanted soluble polymer after detachment. Cultures of both bovine endothelium and human retinal pigmented epithelium were confirmed to be able to attach and grow on the polymer-modified surfaces morphologically identical to that on control tissue culture polystyrene surfaces. Corresponding to a change in temperature, these cultures would detach and could be transplanted to another culture surface without functional and structural changes. These results show that the new, photo-crosslinkable hydrogel system can utilize the hydrophobic/hydrophilic change of the surface for cell culture detachment while being permanently applicable to any tissue culture geometry.

A novel recovery system for cultured cells using plasma-treated polystyrene dishes grafted with poly(N-isopropylacrylamide)

Poly(N-isopropyl acrylamide) (PIPAAm) demonstrated a fully expanded chain conformation below 32 degrees C and a collapsed, compact conformation at high temperatures. This unique temperature responsive polymer was grafted onto surfaces of commercial polystyrene dishes and used as temperature switches for creating hydrophilic surfaces below 32 degrees C and hydrophobic surfaces above 32 degrees C. Cell attachment and the growth of bovine endothelial cells and rat hepatocytes on PIPAAm-grafted surfaces at 37 degrees C demonstrated similar behavior to the commercialized culture dishes. Both cell types were observed to detach from the PIPAAm-grafted surface simply by reducing the temperature below the polymer transition temperature (collapse). Cells recovered by this method maintained substrate adhesivity, growth, and secretion activities nearly identical to those found in primary cultured cells in contrast to the compromised function found in cultured cells damaged by trypsinization. These results provide strong evidence that PIPAAm-grafted surfaces, as thermal switches are very effective for reversing cell attachment and detachment without cell damage. Properties of cell culture surfaces can be readily transformed by this technique reversibly into hydrophilic and hydrophobic coatings of PIPAAm-grafted polymers.

Behavior of primary bone cells on characterized polystyrene surfaces

Primary bone cells, isolated from the periosteally stripped calvariae of neonate rats, were cultured on 60Co gamma-irradiation-sterilized bacteriologic-grade polystyrene that had been either surface treated with concentrated sulfuric acid or received further gamma-irradiation treatments facilitated cell colonization of the polystyrene compared to those surfaces not treated in the laboratory. x-Ray photoelectron spectroscopy (XPS) showed that the two treatments introduced different chemical groups onto the polymer surface and that cell adhesion was related to gamma-irradiation in a dose-dependent manner. These results show that simple biologic assays, such as cell colonization, are not able to distinguish between differences in surface chemistry demonstrated by such a routinely employed surface analysis technique. Thus, there is a need to develop more sensitive biologic assays that provide functional information of a precision that can be correlated with subtle changes in substratum surface chemistry. Further, we argue that because cells isolated by tissue digestion using proteolytic enzymes respond more readily to changes in the surface chemistry of the substratum they colonize, compared to explanted cells; biologic assays designed for biomaterials testing must take into account changes effected in cell adhesion behavior by isolation procedures.

Preliminary report on cell culture on a thermally reversible copolymer

Anchorage-dependent cells (NRK 49F) were grown at 37 degrees C in serum containing medium on glass coated with a N-isopropyl acrylamide/N-t-butyl acrylamide copolymer (NIPAaM/NTBAM) with a lower critical solution temperature (LCST) of 8 degrees C. After incubating the dishes and adherent cells at 4 degrees C for 1 h, the cells had started to detach in 'sheets', without the use of trypsin; by 2 h the cells had fully detached and formed aggregates. We presume that at 4 degrees C, below the LCST of the coating, the polymer swelled and eventually dissolved, leaving the cells unattached to the solid substrate. We speculate that the 'sheet' morphology of the detaching cells implies that the extracellular matrix produced by the cells during culture was left intact, which may then alter the nature of their subsequent behaviour. The polymer was not optimum for cell attachment and optimization would be needed to realize the potential of this novel mode of cell culture and recovery.

Enzymatic modification of lymphocyte receptors for antigen. III. Resistance of receptors to trypsin at the peak of the immune response

Using sheep erythrocytes (SRBC) as the antigen, two subpopulations of spleen antigen-binding lymphocytes could be distinguished by a marked difference in the susceptibility of their receptors to trypsin. In unimmunized animals, 30% of the antigen-binding cells were trypsin-resistant, whereas at 5 days after immunization, 80-90% were trypsin-resistant, indicating an increase of about 50-fold in trypsin-resistant antigen-binding cells per spleen. In contrast, trypsin-sensitive cells per spleen were only 4-fold higher on day 5 than before immunization. The rise in % trypsin sensitivity preceded the increase in rosettes per spleen, implying that immunization produced a preferential increase in trypsin-resistant antigen binding cells partly by converting sensitive cells to resistant cells. After the 5th day, the trypsin sensitivity of antigen-binding cells slowly returned toward the unimmunized level, but a booster injection of SRBC restored trypsin resistance. Trypsin resistance was not lost in the presence of sodium azide or protein synthesis inhibitors. But a slightly increased trypsin susceptibility was conferred by 2-deoxyglucose, implying that glycolysis or the glycosylation of protein may be involved in maintaining trypsin resistance.

Inhibition of human lymphoma cell-line colony formation by lymphocytes from patients with lymphoma and cancer hospital employees

Inhibition of human lymphoma cell-line colony formation (ICF) was induced by peripheral blood lymphocytes (PBL) from patients with lymphoma and apparently healthy cancer hospital personnel. PBL from patients with non-lymphoma neoplasms and from normal blood bank donors did not elicit ICF. ICF was most marked when PBL were cocultivated for 24 hours in a ratio of 1000:I with target lymphoma cells that had been cultured for 24 hours before exposure. No significant ICF was observed when target cells consisted of human neurogenic sarcoma, melanoma, colon adenocarcinoma, or Chinese hamster cells. It is possible that ICF is elicited by PBL sensitized to a cross-reacting antigen present on the membrane of cultured lymphoma cells. This antigen may be synthesized by a transmissible etiologic factor.