Interactions of acinar cells on biomaterials with various surface properties

Sustainable Release of Propranolol Hydrochloride Laden with Biconjugated-Ufasomes Chitosan Hydrogel Attenuates Cisplatin-Induced Sciatic Nerve Damage in In Vitro/In Vivo Evaluation

Peripheral nerve injuries significantly impact patients' quality of life and poor functional recovery. Chitosan-ufasomes (CTS-UFAs) exhibit biomimetic features, making them a viable choice for developing novel transdermal delivery for neural repair. This study aimed to investigate the role of CTS-UFAs loaded with the propranolol HCl (PRO) as a model drug in enhancing sciatica in cisplatin-induced sciatic nerve damage in rats. Hence, PRO-UFAs were primed, embedding either span 20 or 60 together with oleic acid and cholesterol using a thin-film hydration process based on full factorial design (24). The influence of formulation factors on UFAs' physicochemical characteristics and the optimum formulation selection were investigated using Design-Expert® software. Based on the optimal UFA formulation, PRO-CTS-UFAs were constructed and characterized using transmission electron microscopy, stability studies, and ex vivo permeation. In vivo trials on rats with a sciatic nerve injury tested the efficacy of PRO-CTS-UFA and PRO-UFA transdermal hydrogels, PRO solution, compared to normal rats. Additionally, oxidative stress and specific apoptotic biomarkers were assessed, supported by a sciatic nerve histopathological study. PRO-UFAs and PRO-CTS-UFAs disclosed entrapment efficiency of 82.72 ± 2.33% and 85.32 ± 2.65%, a particle size of 317.22 ± 6.43 and 336.12 ± 4.9 nm, ζ potential of -62.06 ± 0.07 and 65.24 ± 0.10 mV, and accumulatively released 70.95 ± 8.14% and 64.03 ± 1.9% PRO within 6 h, respectively. Moreover, PRO-CTS-UFAs significantly restored sciatic nerve structure, inhibited the cisplatin-dependent increase in peripheral myelin 22 gene expression and MDA levels, and further re-established sciatic nerve GSH and CAT content. Furthermore, they elicited MBP re-expression, BCL-2 mild expression, and inhibited TNF-α expression. Briefly, our findings proposed that CTS-UFAs are promising to enhance PRO transdermal delivery to manage sciatic nerve damage.

Physically-cross-linked poly(vinyl alcohol) cell culture plate coatings facilitate preservation of cell-cell interactions, spheroid formation, and stemness

We employed aqueous solutions of highly-hydrolyzed (>99+%) poly(vinyl alcohol), PVA, to coat plastic dishes as a method to efficiently induce three-dimensional (3D) culturing of cells. The coatings were prepared by simple evaporation of 3 wt/vol% solutions of PVA in water and require no additional processing steps after air drying under sterile conditions. The coating allows spheroids to form in solution. Spheroid formation is usually preferable to two-dimensional (2D) culturing as it creates a more realistic ex vivo model of some human tissues and tumors. Using PVA-coated cell culture plates, we demonstrated that we can grow reproducibly sized spheroids using several human glioma cell lines, including LN229, U87 MG, and Gli36, and the embryonic kidney cell line, 293T. Spheroids formed on PVA-coated plates grow as well as on other commercially-available, low-attachment plates, and have excellent optical imaging properties. As spheroids, LN229 cells express markers of cancer stem cells. Finally, we confirmed that spheroids generated on PVA-coated plates are sensitive to molecular perturbations, as increased expression of the cell adhesion molecule PTPμ significantly increased the size of spheroids. The PVA hydrogel layer is an effective tool for creating a more realistic ex vivo culture system than traditional 2D culture and can be used to generate cell spheroids for potential application in drug screening and personalized medicine for diseases such as cancer.

Functional spheroid organization of human salivary gland cells cultured on hydrogel-micropatterned nanofibrous microwells

Development of a tissue-engineered, salivary bio-gland will benefit patients suffering from xerostomia due to loss of fluid-secreting acinar cells. This study was conducted to develop a bioengineering system to induce self-assembly of human parotid epithelial cells (hPECs) cultured on poly ethylene glycol (PEG) hydrogel-micropatterned polycaprolactone (PCL) nanofibrous microwells. Microwells were fabricated by photopatterning of PEG hydrogel in the presence of an electrospun PCL nanofibrous scaffold. hPECs were plated on plastic dishes, Matrigel, PCL nanofibers, or PCL nanofibrous microwells. When the cells were plated onto plastic, they did not form spheres, but aggregated to form 3D acinar-like spheroids when cultured on Matrigel, PCL, and PCL microwells, with the greatest aggregating potency being observed on the PCL microwells. The 3D-assembled spheroids in the PCL microwells expressed higher levels of salivary epithelial markers (α-amylase and AQP5), tight junction proteins (ZO-1 and occludin), adherence protein (E-cadherin), and cytoskeletal protein (F-actin) than those on the Matrigel and PCL. Furthermore, the 3D-assembled spheroids in the PCL microwells showed higher levels of α-amylase secretion and intracellular calcium concentration ([Ca²⁺]_i) than those on the Matrigel and PCL nanofibers, suggesting more functional organization of hPECs. We established a bioengineering 3D culture system to promote robust and functional acinar-like organoids from hPECs. PCL nanofibrous microwells can be applied in the future for bioengineering of an artificial bio-salivary gland for restoration of salivary function.

STATEMENT OF SIGNIFICANCE

Three dimensional (3D) cultures of salivary glandular epithelial cells using nanofibrous bottom facilitate the formation of acinar-like organoids. In this study, we adapted a PEG hydrogel-micropatterned PCL nanofibrous microwell for the efficient bioengineering of human salivary gland organoids, in which we could easily produce uniform size of 3D organoids. This 3D culture system supports spherical organization, gene and protein expression of acinar markers, TJ proteins, adherence, and cytoskeletal proteins, as well as to promote epithelial structural integrity and acinar secretory functions, and results showed superior efficiency relative to Matrigel and nanofibrous scaffold culture. This 3D culture system has benefits in terms of inert, non-animal and serum-free culture conditions, as well as controllable spheroid size and scalable production of functional SG organoids and is applicable to bioengineering approaches for an artificial bio-gland, as well as to investigations of salivary gland physiology and regeneration.

Biomaterials-based strategies for salivary gland tissue regeneration

The salivary gland is a complex, secretory tissue that produces saliva and maintains oral homeostasis. Radiation induced salivary gland atrophy, manifested as "dry mouth" or xerostomia, poses a significant clinical challenge. Tissue engineering recently has emerged as an alternative, long-term treatment strategy for xerostomia. In this review, we summarize recent efforts towards the development of functional and implantable salivary glands utilizing designed polymeric substrates or synthetic matrices/scaffolds. Although the in vitro engineering of a complex implantable salivary gland is technically challenging, opportunities exist for multidisciplinary teams to assemble implantable and secretory tissue modules by combining stem/progenitor cells found in the adult glands with biomimetic and cell-instructive materials.

Effects of biomaterial-derived fibroblast conditioned medium on the α-amylase expression of parotid gland acinar cells

Salivary gland cells are surrounded by a complex stromal environment, in which fibroblasts are the main cells in proximity to the gland cells. In this study, the interaction between parotid gland acinar cells (PGACs), fibroblasts, and biomaterials was investigated. We prepared different biomaterials, including chitosan, polyvinyl alcohol (PVA), poly (ethylene-co-vinyl alcohol) (EVAL), polyvinylidene fluoride (PVDF), and tissue culture polystyrene (TCPS) to culture fibroblasts and then collect their conditioned media to culture PGACs. We observed no difference in AQP3, AQP5, and E-cadherin expression among different fibroblast conditioned medium treatments. Interestingly, α-amylase expression was obviously enhanced in PGACs cultured in the presence of conditioned medium from fibroblasts cultured on PVDF. Higher neurotrophin-4 (NT-4) expression was observed in PVDF-derived fibroblast conditioned medium using a growth factor protein array assay. In addition, directly adding NT-4 into the culture medium significantly promoted α-amylase expression by PGACs. Finally, nestin and βIII-tubulin expression by fibroblasts cultured on PVDF was also enhanced. Together, these results suggest that PVDF could promote α-amylase expression by PGACs via the NT-4 produced by fibroblasts.

STATEMENT OF SIGNIFICANCE

To date, there is no effective therapy for patients with dry mouth with persistent salivary hypofunction. The study made use of different biomaterials to culture fibroblasts and then collect their conditioned media to culture PGACs. It was found that the effect of fibroblast conditioned medium from PVDF on the α-amylase expression of PGACs was obviously enhanced and higher neurotrophin-4 (NT-4) expression was found in PVDF-derived fibroblast conditioned medium. In addition, directly adding NT-4 into the culture medium significantly promoted the expression of α-amylase by PGACs and the expression of nestin and βIII-tubulin of fibroblasts after being cultured on PVDF was enhanced. Therefore, the present study represents the first description of the role of NT-4 in the expression of α-amylase of PGACs and the role of PVDF in the reprogramming fibroblasts into neural progenitor-like cells, indicating that PVDF could promote the expression of α-amylase by PGACs via the NT-4 produced by fibroblasts.

Development of poly(ethylene glycol) hydrogels for salivary gland tissue engineering applications

More than 40,000 patients are diagnosed with head and neck cancers annually in the United States with the vast majority receiving radiation therapy. Salivary glands are irreparably damaged by radiation therapy resulting in xerostomia, which severely affects patient quality of life. Cell-based therapies have shown some promise in mouse models of radiation-induced xerostomia, but they suffer from insufficient and inconsistent gland regeneration and accompanying secretory function. To aid in the development of regenerative therapies, poly(ethylene glycol) hydrogels were investigated for the encapsulation of primary submandibular gland (SMG) cells for tissue engineering applications. Different methods of hydrogel formation and cell preparation were examined to identify cytocompatible encapsulation conditions for SMG cells. Cell viability was much higher after thiol-ene polymerizations compared with conventional methacrylate polymerizations due to reduced membrane peroxidation and intracellular reactive oxygen species formation. In addition, the formation of multicellular microspheres before encapsulation maximized cell-cell contacts and increased viability of SMG cells over 14-day culture periods. Thiol-ene hydrogel-encapsulated microspheres also promoted SMG proliferation. Lineage tracing was employed to determine the cellular composition of hydrogel-encapsulated microspheres using markers for acinar (Mist1) and duct (Keratin5) cells. Our findings indicate that both acinar and duct cell phenotypes are present throughout the 14 day culture period. However, the acinar:duct cell ratios are reduced over time, likely due to duct cell proliferation. Altogether, permissive encapsulation methods for primary SMG cells have been identified that promote cell viability, proliferation, and maintenance of differentiated salivary gland cell phenotypes, which allows for translation of this approach for salivary gland tissue engineering applications.

Functional recoveries of sciatic nerve regeneration by combining chitosan-coated conduit and neurosphere cells induced from adipose-derived stem cells

Suboptimal repair occurs in a peripheral nerve gap, which can be partially restored by bridging the gap with various biosynthetic conduits or cell-based therapy. In this study, we developed a combination of chitosan coating approach to induce neurosphere cells from human adipose-derived stem cells (ASCs) on chitosan-coated plate and then applied these cells to the interior of a chitosan-coated silicone tube to bridge a 10-mm gap in a rat sciatic nerve. Myelin sheath degeneration and glial scar formation were discovered in the nerve bridged by the silicone conduit. By using a single treatment of chitosan-coated conduit or neurosphere cell therapy, the nerve gap was partially recovered after 6 weeks of surgery. Substantial improvements in nerve regeneration were achieved by combining neurosphere cells and chitosan-coated conduit based on the increase of myelinated axons density and myelin thickness, gastrocnemius muscle weight and muscle fiber diameter, and step and stride lengths from gait analysis. High expressions of interleukin-1β and leukotriene B4 receptor 1 in the intra-neural scarring caused by using silicone conduits revealed that the inflammatory mechanism can be inhibited when the conduit is coated with chitosan. This study demonstrated that the chitosan-coated surface performs multiple functions that can be used to induce neurosphere cells from ASCs and to facilitate nerve regeneration in combination with a cells-assisted coated conduit.

Selective functionalization of nanofiber scaffolds to regulate salivary gland epithelial cell proliferation and polarity

Epithelial cell types typically lose apicobasal polarity when cultured on 2D substrates, but apicobasal polarity is required for directional secretion by secretory cells, such as salivary gland acinar cells. We cultured salivary gland epithelial cells on poly(lactic-co-glycolic acid) (PLGA) nanofiber scaffolds that mimic the basement membrane, a specialized extracellular matrix, and examined cell proliferation and apicobasal polarization. Although cells proliferated on nanofibers, chitosan-coated nanofiber scaffolds stimulated proliferation of salivary gland epithelial cells. Although apicobasal cell polarity was promoted by the nanofiber scaffolds relative to flat surfaces, as determined by the apical localization of ZO-1, it was antagonized by the presence of chitosan. Neither salivary gland acinar nor ductal cells fully polarized on the nanofiber scaffolds, as determined by the homogenous membrane distribution of the mature tight junction marker, occludin. However, nanofiber scaffolds chemically functionalized with the basement membrane protein, laminin-111, promoted more mature tight junctions, as determined by apical localization of occludin, but did not affect cell proliferation. To emulate the multifunctional capabilities of the basement membrane, bifunctional PLGA nanofibers were generated. Both acinar and ductal cell lines responded to signals provided by bifunctional scaffolds coupled to chitosan and laminin-111, demonstrating the applicability of such scaffolds for epithelial cell types.

Spheroid formation and neural induction in human adipose-derived stem cells on a chitosan-coated surface

The application of stem cells appears to have great therapeutic potential to facilitate nerve regeneration in patients with neurodegenerative disease or spinal cord injury. Human adipose-derived stem cells (hADSCs), a subset of multipotent mesenchymal stem cells, possess the great advantages of an abundant amount of cells, less ethical conflict and minimal invasive surgical procedures to obtain the cells. Chitosan, a naturally derived polysaccharide from chitin, has been widely studied to facilitate and guide the direction of nerve regeneration as a biomaterial for the neural tube. Chitosan also serves as a three-dimensional culture substrate to facilitate cellular sphere formation among various cells but is as yet unexplored in hADSCs. In this study, the ability of hADSCs to transdifferentiate from the mesenchymal into the neural lineage by seeding hADSCs on a chitosan-coated surface to form therapeutic cell spheres was investigated. The optimal seeding density (2 × 10(4) cells/cm(2)) and harvesting time (72 h) to obtain sphere formation were determined by cell viability on a chitosan-coated surface. Expression of neural lineage markers was observed by immunofluorescent staining of nestin, neurofilament heavy chain and glial fibrillary acidic protein. The neural induction potentials were also provoked by replating spheres from primary to tertiary passages. The effect of neural induction in hADSCs on a chitosan-coated surface may help to provide cell sources for facilitating nerve regeneration in future clinical applications.

Cell Therapy for Salivary Gland Regeneration

There are still no effective therapies for hyposalivation caused by irradiation. In our previous study, bone marrow stem cells can be transdifferentiated into acinar-like cells in vitro. Therefore, we hypothesized that transplantation with bone marrow stem cells or acinar-like cells may help functional regeneration of salivary glands. Bone marrow stem cells were labeled with nanoparticles and directly co-cultured with acinar cells to obtain labeled acinar-like cells. In total, 140 severely combined immune-deficiency mice were divided into 4 groups for cell therapy experiments: (1) normal mice, (2) mice receiving irradiation around their head-and-neck areas; (3) mice receiving irradiation and intra-gland transplantation with labeled stem cells; and (4) mice receiving irradiation and intra-gland transplantation with labeled acinar-like cells. Our results showed that salivary glands damaged due to irradiation can be rescued by cell therapy with either bone marrow stem cells or acinar-like cells for recovery of saliva production, body weight, and gland weight. Transdifferentiation of bone marrow stem cells into acinar-like cells in vivo was also noted. This study demonstrated that cell therapy with bone marrow stem cells or acinar-like cells can help functional regeneration of salivary glands, and that acinar-like cells showed better therapeutic potentials than those of bone marrow stem cells.

Formation of keratocyte spheroids on chitosan-coated surface can maintain keratocyte phenotypes

Corneal keratocytes have been reported to be able to form spheroids that can preserve their phenotypes after being seeded back onto tissue culture plate in specific culture media. In this study, we found that keratocytes could also form spheroids on a bioengineered material, chitosan-coated surface, with 10% horse serum and Dulbecco's modified Eagle's medium. Under scanning electron microscopy observation, the cells in the spheroids were found to adhere each other tightly, and the cellular boundary could not be distinguished. They could return to a dendritic (keratocyte) morphology and proliferate after they were seeded back onto tissue culture plate. Immunocytochemistry was used to characterize these cells. Reverse transcription-polymerase chain reaction revealed that keratocytes in the spheroids were not from the PAX-6-positive progenitor cells. Further, the results of the seeding density and the number of spheroids formation, cell viability (MTT) assays, negative staining of Ki-67, and Live/Dead assay suggested that the spheroids were from cell aggregation instead of cell proliferation. Cells in the spheroids maintained phenotypes and functions characteristic of keratocytes, as seen by reverse transcription-polymerase chain reaction, collagen gel contraction assay, and challenges of keratocytes with transforming growth factor-beta1. Our results showed that corneal keratocytes could form spheroids on a chitosan-coated surface and maintain a keratocyte phenotype. However, such keratocyte spheroids do not proliferate and cannot withstand transforming growth factor-beta from myofibroblast differentiation.

Vascular cell viability on polyvinyl alcohol hydrogels modified with water-soluble and -insoluble chitosan

Polyvinyl alcohol (PVA) hydrogels blended with chitosan or other biological macromolecules have shown promise for cell culture and tissue engineering. This study investigates the attachment and growth of bovine aortic endothelial (BAEC) and smooth muscle cells (BASMC) on the PVA hydrogels modified with water soluble and water insoluble chitosan. Cell adhesion on the surface of the membranes was examined by phase contrast microscopy while cell morphologies were studied using immunocytochemistry staining with EC and SMC specific biomarkers (F-actin and alpha actin respectively). Cells cultured on 6% PVA, 0.4% chitosan (water soluble and insoluble) hydrogel membranes displayed excellent adhesion and spreading characteristics, in addition to negligible cell structural morphological changes in comparison to a polystyrene control. Similar vascular cell adhesion features were apparent on PVA membranes blended with water-soluble and -insoluble chitosan. Fluorescent activated cell sorter (FACS) analysis was used to determine BAEC and BASMC proliferation and cell viability. Apoptotic levels in BAEC after 7 days were 12.8% +/- 2.5% on the PVA- chitosan WS-1 membrane and 10.1% +/- 1.5% on the control well (n = 3) while comparable results were also noted for BASMC. Equivalent proliferative activity was apparent for BAEC on the control and PVA-chitosan membrane after 7 days, while BASMC showed increased proliferative activity on the membranes. These results indicate that the PVA-chitosan blended hydrogel membranes show promise for cell culture and tissue engineering applications.

Cell-surface interactions of rat tooth germ cells on various biomaterials

This is the first study to explore the effect of biomaterial on tooth germ cell adhesion and proliferation in vitro. The purpose of this study is to evaluate the effects of cell-surface interactions of tooth germ cells on biomaterials with various surface hydrophilicities. The biomaterials used in this study included polyvinyl alcohol (PVA), poly(lactic-co-glycolic acid) (PLGA), poly(ethylene-co-vinyl alcohol; EVAL), and polyvinylidene fluoride (PVDF). Cell morphology was observed by photomicroscopy. Cell growth was assayed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction activity and the characteristic expression of amelogenin and collagen type I in tooth germ cells was investigated using immunocytochemistry. The results indicated that adhesion and proliferation of tooth germ cells to biomaterials with moderate hydrophilicity/hydrophobicity was superior compared to most hydrophobic material PVDF or mosthydrophilic material PVA in this study. Cellular adhesion and proliferation was evident on all tested biomaterials except PVA. The cell spheroids on PVA appeared not to be proliferated and remained as well as reattachable to tissue culture plates. In conclusion, biomaterials with moderate hydrophilicity are suitable for adhesion and proliferation of tooth germ cells. The material PVA may be a good biomaterial for maintaining tooth germ cells in three-dimensional biological restoration.

The alteration of cell membrane charge after cultured on polymer membranes

In this work, cell electrophoresis, measuring the electrophoretic mobility of cells, was used to investigate the variation of surface charge property of cells after cultured on different polymer membranes. HepG2 cell line, derived from a well-differentiated, human hepatoma, was used as a model cell. The polymer biomaterials used in this study included polyvinyl alcohol (PVA), poly(ethylene-co-vinyl alcohol) (EVAL), and polyvinylidene fluoride (PVDF). For cells cultured in the presence of serum, cell mobility after being cultured on PVA substrates was considerably higher than that on EVAL or PVDF substrates. This effect was completely suppressed by cycloheximide (CHX) in the serum-free medium. Taken together, the cell surface charge property can be altered after cells cultured on different polymer substrates. The precise mechanism by which the variation of electrophoretic mobility of cultured cells is unknown, but it is reasonable to assume that the polymer substrates could influence the absorption of serum proteins on cell membrane surface to change cell electrophoretic mobility and, simultaneously, to regulate adhesion, growth and function of cultured cells.