Optimized growth medium for primary culture of human oral keratinocytes

The Hypothalamic-Pituitary-Thyroid Axis Equivalent in Normal and Cancerous Oral Tissues: A Scoping Review

The hypothalamic-pituitary-thyroid (HPT) axis is crucial in regulating thyroid hormone levels that contribute to the development and homeostasis of the human body. Current literature supports the presence of a local HPT axis equivalent within keratinocytes of the skin, with thyroid hormones playing a potential role in cancer progression. However, this remains to be seen within oral tissue cells. An electronic search of Scopus and PubMed/Medline databases was conducted to identify all original publications that reported data on the production or effects of HPT axis components in normal or malignant cells of the oral cavity. The search identified 221 studies, of which 14 were eligible. Eight studies were retrospective analyses of clinical samples, one study involved both in vivo and in vitro experiments, and the remaining five studies were conducted in vitro using cell lines. The search identified evidence of effects of HPT components on oral cancer cells. However, there were limited data for the production of HPT axis components by oral tissues. We conclude that a possible role of the local HPT axis equivalent in the oral mucosa may not be established at present. The gaps in knowledge identified in this scoping review, particularly regarding the production of HPT components by oral tissues, warrant further investigation.

ROCK inhibitor combined with Ca2+ controls the myosin II activation and optimizes human nasal epithelial cell sheets

The proliferation and differentiation of cultured epithelial cells may be modified by Rho-associated kinase (ROCK) inhibition and extracellular Ca²⁺ concentration. However, it was not known whether a combination would influence the behavior of cultured epithelial cells through changes in the phosphorylation of non-muscle myosin light chain II (MLC). Here we show that the combination of ROCK inhibition with Ca²⁺ elevation regulated the phosphorylation of MLC and improved both cell expansion and cell–cell adhesion during the culture of human nasal mucosal epithelial cell sheets. During explant culture, Ca²⁺ enhanced the adhesion of nasal mucosal tissue, while ROCK inhibition downregulated MLC phosphorylation and promoted cell proliferation. During cell sheet culture, an elevation of extracellular Ca²⁺ promoted MLC phosphorylation and formation of cell–cell junctions, allowing the harvesting of cell sheets without collapse. Moreover, an in vitro grafting assay revealed that ROCK inhibition increased the expansion of cell sheets three-fold (an effect maintained when Ca²⁺ was also elevated), implying better wound healing potential. We suggest that combining ROCK inhibition with elevation of Ca²⁺ could facilitate the fabrication of many types of cell graft.

Tissue Harvesting Site and Culture Medium Affect Attachment, Growth, and Phenotype of Ex Vivo Expanded Oral Mucosal Epithelial Cells

Transplantation of cultured oral mucosal epithelial cells (OMECs) is a promising treatment strategy for limbal stem cell deficiency. In order to improve the culture method, we investigated the effects of four culture media and tissue harvesting sites on explant attachment, growth, and phenotype of OMECs cultured from Sprague-Dawley rats. Neither choice of media or harvesting site impacted the ability of the explants to attach to the culture well. Dulbecco’s modified Eagle’s medium/Ham’s F12 (DMEM) and Roswell Park Memorial Institute 1640 medium (RPMI) supported the largest cellular outgrowth. Fold outgrowth was superior from LL explants compared to explants from the buccal mucosa (BM), HP, and transition zone of the lower lip (TZ) after six-day culture. Putative stem cell markers were detected in cultures grown in DMEM and RPMI. In DMEM, cells from TZ showed higher colony-forming efficiency than LL, BM, and HP. In contrast to RPMI, DMEM both expressed the putative stem cell marker Bmi-1 and yielded cell colonies. Our data suggest that OMECs from LL and TZ cultured in DMEM give rise to undifferentiated cells with high growth capacity, and hence are the most promising for treatment of limbal stem cell deficiency.

Successful Consecutive Expansion of Limbal Explants Using a Biosafe Culture Medium under Feeder Layer-Free Conditions

PURPOSE

Transplantation of in vitro cultured limbal epithelial stem cells (LESCs) is a treatment widely used for LESC deficiency. However, the number of limbal tissue donors is limited, and protocols for LESC cultivation often include compounds and/or feeder layers that can induce side effects and/or increase the cost of the culture procedure. We investigated the feasibility of obtaining more than one limbal primary culture (LPC) from the same biopsy using a culture medium in which several potentially harmful compounds were replaced at the same time by biosafe supplements, allowing the LESC cultivation without feeder layers.

MATERIALS AND METHODS

We established feeder layer-free LPCs with three culture media: (1) a modified supplemental hormonal epithelial medium, containing potential harmful components (cholera toxin, dimethylsulfoxide, and fetal bovine serum [FBS]), (2) IOBA-FBS, a medium with FBS but with no other harmful supplements, and (3) IOBA-HS, similar to IOBA-FBS but with human serum instead of FBS. Additionally, the same limbal explant was consecutively cultured with IOBA-HS producing three cultures. LPCs were characterized by real-time reverse transcription polymerase chain reaction and/or immunofluorescence.

RESULTS

LPCs cultured with the three media under feeder layer-free conditions showed cuboidal cells and no significant differences in the percentage of positive cells for limbal (ABCG2, p63, and K14) and corneal (K3, K12) proteins. Except for ABCG2, the relative mRNA expression of the LESC markers was significantly higher when IOBA-FBS or IOBA-HS was used. LPC1 showed characteristics similar to LPC0, while LPC2 cell morphology became elongated and the expression of some LESC markers was diminished.

CONCLUSION

IOBA-HS enables the culturing of up to two biosafe homologous LPCs from one limbal tissue under feeder layer-free conditions. The routine use of this culture medium could improve both the biosafety and the number of available LPCs for potential clinical transplantation, as well as decrease the expense of the culture procedure.

Oral and pharyngeal epithelial keratinocyte culture

Primary human oral epithelial cells are readily available and have been recently employed for tissue engineering. These cells are currently being widely utilized in multiple research efforts, ranging from the study of oral biology, mucosal immunity, and carcinogenesis to stem cell biology and tissue engineering. This chapter describes step-by-step protocols for the successful isolation and culture of human oral epithelial cells and fibroblasts, and techniques for their use in two-dimensional and three-dimensional culture systems. The described methods will enable to generate reconstituted tissues that resemble epithelial like structures in vitro, which can recapitulate some of the key features of the oral epithelium in vivo.

Effects of multiple agents on epithelial differentiation of rabbit adipose-derived stem cells in 3D culture

Mesenchymal stem cells have been given particular attention in tissue regeneration research due to their multipotency and proliferative activity. In this study, we investigated the possibility of epithelial differentiation of rabbit adipose-derived stem cells (rASCs) in an in vitro 3D culture system. The experimental procedure was performed with different contributing factors including all-trans retinoic acid (ATRA), epidermal growth factor (EGF), keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), and hydrocortisone in air-liquid interface culture, for modulating proliferation and providing a synergistic effect on epithelial differentiation of rASCs. After induction, immunofluorescence staining, western blot analysis, flow cytometry analysis, and quantitative real-time polymerase chain reaction assay have been performed to detect the expression of epithelial-specific markers and mesenchymal marker alpha-smooth muscle actin (α-SMA). The growth pattern and viability of cells were evaluated by transmission electron microscopy and Hoechst 33258 assay, respectively. After treated with optimized induction medium (including 2.5 μM ATRA, 20 ng/mL EGF, 10 ng/mL KGF, 10 ng/mL HGF, and 0.5 μg/mL hydrocortisone), rASCs were observed to display a stratified epithelial-like morphology, with the expression of cytokeratin 19 and cytokeratin 13 in 63.69%±2.63% and 22.17%±1.51%, respectively, and the relative expression level of cytokeratin 19 increased to 3.152 compared with 0.151 before induction. The expression of α-SMA decreased to 19.40%±1.45% after induction, but almost no expression of involucrin was detected. The results showed that the establishment of an epithelial-specific microenvironment may be a feasible way for epithelial differentiation of ASCs in vitro, and provided an alternative for research on epithelium regeneration.

Stem cell differentiation to epidermal lineages on electrospun nanofibrous substrates for skin tissue engineering

Bone marrow (BM) mesenchymal stem cells (MSC) capable of differentiating along the epidermal lineage on engineered nanofibrous scaffolds have great potential for bionanomaterial-cell transplantation therapy of skin wounds. MSC have been the focus of many tissue engineering studies, mainly because of their multipotential properties. We investigated the potential of human BM-derived MSC for epidermal cell differentiation in vitro on electrospun collagen/poly(l-lactic acid)-co-poly(3-caprolactone) (Coll/PLLCL) nanofibrous scaffolds. PLLCL and Coll/PLLCL nanofibrous scaffolds were fabricated by an electrospinning process and their chemical and mechanical characterization carried out by scanning electron microscopy (SEM), water contact angle determination, Fourier transform infrared spectroscopy, and tensile testing. The differentiation of MSC was carried out using epidermis inducing factors, including epidermal growth factor (EGF) and 1,25-dihydroxyvitamin D(3), in culture medium. The proliferation of MSC evaluated by cell proliferation assay showed that the number of cells grown on Coll/PLLCL nanofibrous scaffolds was significantly higher than those on PLLCL scaffolds. The SEM results showed that MSC differentiated on Coll/PLLCL nanofibrous scaffolds showed a round keratinocyte morphology and expressed keratin 10, filaggrin and partial involucrin protein by immunofluorescent microscopic studies. The interaction of MSC and nanofibers was studied and we concluded that the electrospun Coll/PLLCL nanofibers could mimic the native skin extracellular matrix environment and are promising substrates for advanced skin tissue engineering. Our studies on the differentiation of MSC along the epidermal lineage on nanofibrous scaffolds suggest their potential application in skin regeneration without regional differentiation.

Functional expression of the chemokine receptor XCR1 on oral epithelial cells

Chemokines are chemoattractant cytokines which act on specific receptors and play an important role in leukocyte migration as well as physiological and pathological processes. We investigated the role of the chemokine receptor XCR1 and its ligand lymphotactin (Lptn/XCL1) in the regulation of oral epithelial cell behaviour. In vitro XCR1 mRNA and cell surface protein expression was detected in normal oral keratinocytes and oral squamous cell carcinoma cell lines. Lymphotactin mediated intracellular activation of the ERK1/2 signalling pathway and stimulated migration, invasion, and proliferation of all cells through XCR1. Oral cancer cells showed a greater response to lymphotactin than normal keratinocytes and a direct relationship between receptor expression and migration, invasion, and proliferation was observed. Exposure of normal keratinocytes to lymphotactin resulted in increased adhesion to fibronectin but not collagen and stimulated MMP-2 and MMP-9 but not MMP-7 release, whereas exposure of cancer cells resulted in increased adhesion to both collagen and fibronectin and stimulated production of MMP-2, MMP-9, and MMP-7. We observed XCR1 but not lymphotactin to be expressed by epithelial cells in normal oral mucosa in vivo, whilst both were expressed and up-regulated in inflammatory oral disease and oral cancer including primary and metastatic disease. Lymphotactin mRNA and constitutive intracellular protein were detected in normal keratinocytes and oral cancer cell lines in vitro. These findings show that XCR1 and its ligand, lymphotactin, are expressed by oral epithelial cells and suggest that they play a role in regulating the behaviour of these cells.

Tissue engineering of composite grafts: Cocultivation of human oral keratinocytes and human osteoblast-like cells on laminin-coated polycarbonate membranes and equine collagen membranes under different culture conditions

In complex craniomaxillofacial defects, the simultaneous reconstruction of hard and soft tissue is often necessary. Until now, oral keratinocytes and osteoblast-like cells have not been cocultivated on the same carrier. For the first time, the cocultivation of human oral keratinocytes and human osteoblast-like cells has been investigated in this study. Different carriers (laminin-coated polycarbonate and equine collagen membranes) and various culture conditions were examined. Human oral keratinocytes and human osteoblast-like cells from five patients were isolated from tissue samples, seeded on the opposite sides of the carriers and cultivated for 1 and 2 weeks under static conditions in an incubator and in a perfusion chamber. Proliferation and morphology of the cells were analyzed by EZ4U-tests, light microscopy, and scanning electron microscopy. Cocultivation of both cell-types seeded on one carrier was possible. Quantitative and qualitative growth was significantly better on collagen membranes when compared with laminin-coated polycarbonate membranes independent of the culture conditions. Using perfusion culture in comparison to static culture, the increase of cell proliferation after 2 weeks of cultivation when compared with the proliferation after 1 week was significantly lower, independent of the carriers used. In conclusion, the contemporaneous cultivation of human oral keratinocytes and human osteoblast-like cells on the same carrier is possible, a prerequisite for planned in vivo studies. As carrier collagen is superior to laminin-coated polycarbonate membranes. Regarding the development over time, the increase of proliferation rate is lower in perfusion culture. Examinations of cellular differentiation over time under various culture conditions will be subject of further investigations.

Mucosal keratinocyte isolation: a short comparative study on thermolysin and dispase

New techniques for reconstructing large defects of the floor of the mouth include the use of cultured mucosal substitutes. The purpose of this study was to compare dispase and thermolysin for keratinocyte isolation. Keratinocyte yield per surface area of rabbit buccal mucosa was assessed by histology, cytokeratin 13 (CK13) staining, seeding efficiency analysis and cell diameter quantification. Surface areas of cultured mucosa were calculated. Histology showed that treatment by thermolysin resulted in incomplete separation of epidermis from dermis. Also, the absolute number of keratinocytes/cm(2) isolated mucosa, cell yield, cell size and seeding efficiencies was higher in the dispase group. A 3.45-fold larger graft could be reconstituted using dispase. The use of dispase, rather than thermolysin, to isolate cells from buccal mucosa is concluded to be favourable.

Towards optimization of an organotypic assay system that imitates human hair follicle-like epithelial-mesenchymal interactions

BACKGROUND

Human hair growth can currently be studied in vitro by the use of organ-cultured scalp hair follicles (HFs). However, simplified organotypic systems are needed for dissecting the underlying epithelial-mesenchymal interactions and as screening tools for candidate hair growth-modulatory agents.

OBJECTIVES

To optimize the design and culture conditions of previously published organotypic systems that imitate epithelial-mesenchymal interactions in the human HF as closely as possible.

MATERIALS AND METHODS

Continuous submerged organotypic 'sandwich' cultures were established. These consist of a pseudodermis (collagen I mixed with and contracted by human interfollicular dermal fibroblasts) on which one of two upper layers is placed: either a mixture of Matrigel basement membrane matrix (BD Biosciences, Bedford, MA, U.S.A.) and follicular dermal papilla fibroblasts (DPC), with outer root sheath keratinocytes (ORSK) layered on the top ('layered' system), or a mixture of Matrigel, DPC and ORSK ('mixed' system). Morphological and functional characteristics of these 'folliculoid sandwiches' were then assessed by routine histology, histomorphometry and immunohistochemistry.

RESULTS

In both 'layered' and 'mixed' systems, the ORSK formed spheroid epithelial cell aggregates, which retained their characteristic keratin expression pattern (i.e. cytokeratin 6). In the 'mixed' sandwich model the size of the epithelial cell aggregates was smaller, but the numbers of ORSK were significantly higher than in the 'layered' model at day 14 in the culture. ORSK proliferated better in the 'mixed' than in the 'layered' sandwich system, regardless of the calcium or serum content of the media, whereas apoptosis of ORSK was lowest in the 'mixed' system in serum-free, low calcium medium. The kinetics of proliferation and apoptosis of DPC, which retained their characteristic expression of versican, were similar in both systems. However, proliferation and apoptosis of DPC were higher in the presence of serum and/or under high calcium conditions.

CONCLUSIONS

Our results underscore the importance of structural design and medium composition for epithelial-mesenchymal interactions as they occur in the human HF. Specifically, we report a new organotypic submerged 'folliculoid sandwich' system with serum-free, low calcium medium and a mixture of interacting human DPC and ORSK, which offers several advantages over previously available assays. This system allows the standardized assessment of the effects of a test agent on the proliferation, apoptosis and key marker expression of human ORSK and DPC under substantially simplified in vitro conditions which approximate the in vivo situation.

Influence of donor age and culture conditions on tissue engineering of mucosa autografts

In oral surgery the transplantation of tissue engineered mucosa is used more frequently. The conventional single cell suspension culture method (SCSM) involves murine feeder cells and foetal calf serum. The explant technique (ET) has been used as alternative culture procedure. Aim was to study the efficacy of the ET and the SCSM without feeder cells to grow primary cultures and to test the effects of donor age, of extracellular matrix proteins (ECMP), and of autogenous serum on cell growth in explant cultures. These factors were assessed in cultures of 58 patients overall. In 48 cultures of 12 patients primary cell growth was compared between the ET and the SCSM. Eighteen of 24 cultures were established with the ET whereas only 3 of 24 were established with the SCSM. To test the influence of donor age on cell multiplication, the proliferation rate (DNA synthesis measured by bromodeoxyuridine uptake) and the overall growth (DNA content) was determined in cultures of five young and five old donors. In cultures from old donors (mean age 56 years) proliferation was lower but more sustained relative to the cultures from the young donors (mean age 25 years). In old donors overall in vitro cell growth was only 2/3 of that in young donors. In cultures of 20 donors the influence on cell adhesion and growth of the ECMP fibronectin and laminin was assessed by planimetry. While ECMP augmented explant adhesion, these substances did not enhance keratinocyte growth significantly. Comparing the influence of autogenous and foetal calf serum on cell growth no differences were observed in all cultures of the six donors. In conclusion, the ET without additional ECMP coating and with autogenous instead of foetal calf serum are now used to culture gingival keratinocytes for tissue engineering mucosa grafts. Consequently xenogenous components are avoided, being a considerable advantage.

Growth of normal oral keratinocytes and squamous cell carcinoma cells in a novel protein-free defined medium

A novel protein-free synthetic medium was developed for the culture of normal human oral keratinocytes. This medium, designated PFM-7, supports the serial cultivation of primary or secondary normal oral keratinocytes in protein-free, chemically defined conditions. Normal oral keratinocytes in PFM-7 exhibited nearly equal growth in mass culture without noticeable changes in morphology, response to added growth factors, or gene expression of growth factors and their receptors, compared to cells in Keratinocyte-SFM containing epidermal growth factor and bovine pituitary extract. Furthermore, PFM-7 supported the serial subcultivation of human squamous cell carcinoma cells and enabled both normal and malignant oral squamous cells derived from the same patient to grow under the same protein-free defined conditions. These results indicate that PFM-7 can be used for precise investigations of growth mechanisms, cell products, and gene expression associated with carcinogenesis of human epidermal cells.

Tissue engineering of skin

The skin plays a crucial role in protecting the integrity of the body's internal milieu. The loss of this largest organ is incompatible with sustained life. In reconstructive surgery or burn management, substitution of the skin is often necessary. In addition to traditional approaches such as split- or full-thickness skin grafts, tissue flaps and free-tissue transfers, skin bioengineering in vitro or in vivo has been developing over the past decades. It applies the principles and methods of both engineering and life sciences toward the development of substitutes to restore and maintain skin structure and function. Currently, these methods are valuable alternatives or complements to other techniques in reconstructive surgery. This review article deals with the evolution and current approaches to the development of in vitro and in vivo epidermis and dermis.