Construction and characterization of a tissue-engineered oral mucosa equivalent based on a chitosan-fish scale collagen composite

Tilapia fish waste: An asset for tissue engineering - A review

Fisheries and aquaculture output have exploded due to an alarming increase in consumption due to the global understanding of the nutritional advantages of fish. Inadvertently, the methods produce a massive amount of fish waste, posing a serious environmental threat. Recycling this waste has now become a major point of controversy that must be resolved. It is critical to emphasize the utility of discarded marine by-products for the creation of high-value commodities such as marine collagen (MC), which can be considered a sustainable solution. Because of its biocompatibility, biodegradability, safety, minimal immunogenicity, and low production costs, MC has various benefits over terrestrial collagen. Many academics have recently become interested in the use of MC as a scaffold. This review focuses on the intriguing contribution of MC in the production of MC-based scaffolds.

Recovery of Bioactive Compounds from Marine Organisms: Focus on the Future Perspectives for Pharmacological, Biomedical and Regenerative Medicine Applications of Marine Collagen

Marine environments cover more than 70% of the Earth's surface and are among the richest and most complex ecosystems. In terms of biodiversity, the ocean represents an important source, still not widely exploited, of bioactive products derived from species of bacteria, plants, and animals. However, global warming, in combination with multiple anthropogenic practices, represents a serious environmental problem that has led to an increase in gelatinous zooplankton, a phenomenon referred to as jellyfish bloom. In recent years, the idea of "sustainable development" has emerged as one of the essential elements of green-economy initiatives; therefore, the marine environment has been re-evaluated and considered an important biological resource. Several bioactive compounds of marine origin are being studied, and among these, marine collagen represents one of the most attractive bio-resources, given its use in various disciplines, such as clinical applications, cosmetics, the food sector, and many other industrial applications. This review aims to provide a current overview of marine collagen applications in the pharmacological and biomedical fields, regenerative medicine, and cell therapy.

Novel therapy using a fish scale collagen scaffold for rotator cuff healing in rat models

BACKGROUND

Large and massive rotator cuff tears are challenging for surgeons because of postoperative complications such as repaired site retears. Recently, collagen extracted from fish scales has gained more attention because fish byproducts are considered a safer collagen source than other animal-derived scaffolds. This study aimed to evaluate the biological efficacy of tilapia scale-derived collagen scaffolds for rotator cuff repair in rat models.

METHODS

The infraspinatus tendon was resected from the greater tuberosity of Sprague-Dawley rats. In the control group, the tendon edge was sutured directly to the humeral head. In the augmentation group, the repaired site was augmented with a tilapia scale-derived collagen scaffold. Histologic examinations were performed at 2 and 4 weeks postoperatively via safranin O and immunofluorescence staining (isolectin B4 and type II collagen) in the bone-tendon junction. For mechanical analysis, the ultimate failure load of the tendon-humeral head complex was evaluated at 6 weeks postoperatively.

RESULTS

During safranin O staining, the repaired enthesis demonstrated greater proteoglycan staining in the augmentation group than in the control group at 4 weeks postoperatively. Compared to controls, the augmentation group had significantly higher vascular staining with isolectin B4 at 2 and 4 weeks postoperatively, type II collagen expression at 4 weeks postoperatively, and ultimate failure load at 6 weeks postoperatively.

CONCLUSION

Augmentation therapy using tilapia scale-derived type I collagen scaffolds promoted angiogenesis and fibrocartilage regeneration at the enthesis and provided higher mechanical strength than controls.

Oral mucosa equivalents, prevascularization approaches, and potential applications

BACKGROUND

Oral mucosa equivalents (OMEs) have been used as in vitro models (eg, for studies of human oral mucosa biology and pathology, toxicological and pharmacological tests of oral care products), and clinically to treat oral defects. However, the human oral mucosa is a highly vascularized tissue and implantation of large OMEs can fail due to a lack of vascularization. To develop equivalents that better resemble the human oral mucosa and increase the success of implantation to repair large-sized defects, efforts have been made to prevascularize these constructs.

PURPOSE

The aim of this narrative review is to provide an overview of the human oral mucosa structure, common approaches for its reconstruction, and the development of OMEs, their prevascularization, and in vitro and clinical potential applications.

STUDY SELECTION

Articles on non-prevascularized and prevascularized OMEs were included, since the development and applications of non-prevascularized OMEs are a foundation for the design, fabrication, and optimization of prevascularized OMEs.

CONCLUSIONS

Several studies have reported the development and in vitro and clinical applications of OMEs and only a few were found on prevascularized OMEs using different approaches of fabrication and incorporation of endothelial cells, indicating a lack of standardized protocols to obtain these equivalents. However, these studies have shown the feasibility of prevascularizing OMEs and their implantation in animal models resulted in enhanced integration and healing. Vascularization in tissue equivalents is still a challenge, and optimization of cell culture conditions, biomaterials, and fabrication techniques along with clinical studies is required.

Full-Thickness Oral Mucoperiosteal Defects: Challenges and Opportunities

Regenerative engineering strategies for the oral mucoperiosteum, as may be needed following surgeries, such as cleft palate repair and tumor resection, are underdeveloped compared with those for maxillofacial bone. However, critical-size tissue defects left to heal by secondary intention can lead to complications, such as infection, fistula formation, scarring, and midface hypoplasia. This review describes current clinical practice for replacing mucoperiosteal tissue, including autografts and allografts. Potentially paradigm-shifting experimental regenerative engineering strategies for mucoperiosteal wound healing, such as hybrid grafts and engineered matrices, are also discussed. Throughout the review, the advantages and disadvantages of each replacement or regeneration strategy are outlined in the context of clinical outcomes, quality of life for the patient, availability of materials, and cost of care. Finally, future directions for research and development in the area of mucoperiosteum repair are proposed, with an emphasis on identifying globally available and affordable solutions for promoting mucoperiosteal regeneration. Impact statement Unassisted oral mucoperiosteal wound healing can lead to severe complications such as infection, fistulae, scarring, and developmental abnormalities. Thus, strategies for promoting wound healing must be considered when mucoperiosteal defects are incident to oral surgery, as in palatoplasty or tumor resection. Emerging mucoperiosteal tissue engineering strategies, described in this study, have the potential to overcome the limitations of current standard-of-care donor tissue grafts. For example, the use of engineered mucoperiosteal biomaterials could circumvent concerns about tissue availability and immunogenicity. Moreover, employment of tissue engineering strategies may improve the equity of oral wound care by increasing global affordability and accessibility of materials.

Mesenchymal stem cells: A comprehensive methods for odontoblastic induction

BACKGROUND

In the area of oral and maxillofacial surgery, regenerative endodontics aims to present alternative options to conventional treatment strategies. With continuous advances in regenerative medicine, the source of cells used for pulp tissue regeneration is not only limited to mesenchymal stem cells as the non-mesenchymal stem cells have shown capabilities too. In this review, we are systematically assessing the recent findings on odontoblastic differentiation induction with scaffold and non-scaffold approaches.

METHODS

A comprehensive search was conducted in Pubmed, and Scopus, and relevant studies published between 2015 and 2020 were selected following the PRISMA guideline. The main inclusion criteria were that articles must be revolving on method for osteoblast differentiation in vitro study. Therefore, in vivo and human or animal clinical studies were excluded. The search outcomes identified all articles containing the word "odontoblast", "differentiation", and "mesenchymal stem cell".

RESULTS

The literature search identified 99 related studies, but only 11 articles met the inclusion criteria. These include 5 odontoblastic differentiation induction with scaffold, 6 inductions without scaffolds. The data collected were characterised into two main categories: type of cells undergo odontoblastic differentiation, and odontoblastic differentiation techniques using scaffolds or non-scaffold.

CONCLUSION

Based on the data analysis, the scaffold-based odontoblastic induction method seems to be a better option compared to the non-scaffold method. In addition of that, the combination of growth factors in scaffold-based methods could possibly enhance the differentiation. Thus, further detailed studies are still required to understand the mechanism and the way to enhance odontoblastic differentiation.

Marine-Derived Collagen as Biomaterials for Human Health

Collagen is a kind of biocompatible protein material, which is widely used in medical tissue engineering, drug delivery, cosmetics, food and other fields. Because of its wide source, low extraction cost and good physical and chemical properties, it has attracted the attention of many researchers in recent years. However, the application of collagen derived from terrestrial organisms is limited due to the existence of diseases, religious beliefs and other problems. Therefore, exploring a wider range of sources of collagen has become one of the main topics for researchers. Marine-derived collagen (MDC) stands out because it comes from a variety of sources and avoids issues such as religion. On the one hand, this paper summarized the sources, extraction methods and characteristics of MDC, and on the other hand, it summarized the application of MDC in the above fields. And on the basis of the review, we found that MDC can not only be extracted from marine organisms, but also from the wastes of some marine organisms, such as fish scales. This makes further use of seafood resources and increases the application prospect of MDC.

Natural polymer-based hydrogels as prospective tissue equivalent materials for radiation therapy and dosimetry

Natural polymer-based hydrogels have been extensively employed in tissue engineering and biomedical applications, owing to their biodegradability and biocompatibility. In the present work, we have investigated the efficacy of hydrogels such as agarose, hyaluronan, gelatin, carrageenan, chitosan, sodium alginate and collagen as tissue equivalent materials with respect to photon and charged particle (electron, proton and alpha particle) interactions, for use in radiation therapy and dosimetry. Tissue equivalence has been investigated by computing photon mass energy absorption coefficient (μ_en/ρ), kinetic energy released per unit mass (KERMA), equivalent atomic number (Z_eq) and energy absorption build-up factors (EABF) relative to human tissues (soft tissue, cortical bone, skeletal muscle, breast tissue, lung tissue, adipose tissue, skin tissue, brain) in the energy range of 0.015-15 MeV. Ratio of effective atomic numbers (Z_eff) have been examined for tissue-equivalence in the energy range of 10 keV-1 GeV for charged particle interactions. Analysis using standard theoretical formulations revealed that all the selected natural polymers can serve as good tissue equivalent materials with respect to all human tissues except cortical bone. Notably, sodium alginate, collagen and hyaluronan are found to have radiation interaction characteristics close to that of human tissues. These results would be useful in deciding on the suitability of a natural polymer hydrogel as tissue substitute in the desired energy range.

Three Polymers from the Sea: Unique Structures, Directional Modifications, and Medical Applications

With the increase of wounds and body damage, the clinical demand for antibacterial, hemostatic, and repairable biomaterials is increasing. Various types of biomedical materials have become research hotspots. Of these, and among materials derived from marine organisms, the research and application of alginate, chitosan, and collagen are the most common. Chitosan is mainly used as a hemostatic material in clinical applications, but due to problems such as the poor mechanical strength of a single component, the general antibacterial ability, and fast degradation speed research into the extraction process and modification mainly focuses on the improvement of the above-mentioned ability. Similarly, the research and modification of sodium alginate, used as a material for hemostasis and the repair of wounds, is mainly focused on the improvement of cell adhesion, hydrophilicity, degradation speed, mechanical properties, etc.; therefore, there are fewer marine biological collagen products. The research mainly focuses on immunogenicity removal and mechanical performance improvement. This article summarizes the source, molecular structure, and characteristics of alginate, chitosan, and collagen from marine organisms; and introduces the biological safety, clinical efficacy, and mechanism of action of these materials, as well as their extraction processes and material properties. Their modification and other issues are also discussed, and their potential clinical applications are examined.

Marine Collagen as A Promising Biomaterial for Biomedical Applications

This review focuses on the expanding role of marine collagen (MC)-based scaffolds for biomedical applications. A scaffold-a three-dimensional (3D) structure fabricated from biomaterials-is a key supporting element for cell attachment, growth, and maintenance in 3D cell culture and tissue engineering. The mechanical and biological properties of the scaffolds influence cell morphology, behavior, and function. MC, collagen derived from marine organisms, offers advantages over mammalian collagen due to its biocompatibility, biodegradability, easy extractability, water solubility, safety, low immunogenicity, and low production costs. In recent years, the use of MC as an increasingly valuable scaffold biomaterial has drawn considerable attention from biomedical researchers. The characteristics, isolation, physical, and biochemical properties of MC are discussed as an understanding of MC in optimizing the subsequent modification and the chemistries behind important tissue engineering applications. The latest technologies behind scaffold processing are assessed and the biomedical applications of MC and MC-based scaffolds, including tissue engineering and regeneration, wound dressing, drug delivery, and therapeutic approach for diseases, especially those associated with metabolic disturbances such as obesity and diabetes, are discussed. Despite all the challenges, MC holds great promise as a biomaterial for developing medical products and therapeutics.

The effect of the carbodiimide cross-linker on the structural and biocompatibility properties of collagen-chondroitin sulfate electrospun mat

BACKGROUND

Collagen and chondroitin sulfate (CS) are an essential component of the natural extracellular matrix (ECM) of most tissues. They provide the mechanical stability to cone the compressive forces in ECM. In tissue engineering, electrospun nanofibrous scaffolds prepared by electrospinning technique have emerged as a suitable candidate to imitate natural ECM functions. Cross-linking with 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride/N-hydroxy succinimide can overcome the weak mechanical integrity of the engineered scaffolds in addition to the increased degradation stability under physiological conditions.

MATERIALS AND METHODS

This study has synthesized nanofibrous collagen-CS scaffolds by using the electrospinning method.

RESULTS

The results have shown that incorporation of CS in higher concentration, along with 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride/N-hydroxy succinimide, enhanced mechanical stability. Scaffolds showed more resistance to collagenase digestion. Fabricated scaffolds showed biocompatibility in corneal epithelial cell attachment.

CONCLUSION

These results demonstrate that cross-linked electrospun CO-CS mats exhibited a uniform nanofibrous and porous structure, especially for lower concentration of the cross-linker and may be utilized as an alternative effective substrate in tissue engineering.

Sustained curcumin release from PLGA microspheres improves bone formation under diabetic conditions by inhibiting the reactive oxygen species production

Background

Excessive reactive oxygen species production caused by type 2 diabetes conditions can disrupt normal bone metabolism and greatly impair bone regeneration.

Materials and methods

In the present study, curcumin (Cur)-loaded microspheres were incorporated into a fish collagen nano-hydroxyapatite scaffold to promote bone repair under diabetic conditions by inhibiting the reactive oxygen species production.

Results

The drug release kinetic study showed that the Cur release from the composite scaffolds lasted up to 30 days. The sustained curcumin release from the scaffold significantly inhibited the overproduction of reactive oxygen species in mesenchymal stem cells caused by diabetic serum. Moreover, the Cur-loaded scaffold also remarkedly alleviated the negative effects of diabetic serum on the proliferation, migration, and osteogenic differentiation of mesenchymal stem cells. When implanted into bone defects in type 2 diabetic rats, the Cur-loaded scaffold also showed a greater bone formation capability compared to the pure scaffold.

Conclusion

The results of this study suggested that the novel controlled Cur release system may provide a promising route to improve bone regeneration in type 2 diabetic patients.

Development of various composition multicomponent chitosan/fish collagen/glycerin 3D porous scaffolds: Effect on morphology, mechanical strength, biostability and cytocompatibility

The various composition multicomponent chitosan/fish collagen/glycerin 3D porous scaffolds were developed and investigated the effect of various composition chitosan/fish collagen/glycerin on scaffolds morphology, mechanical strength, biostability and cytocompatibility. The scaffolds were fabricated via freeze-drying technique. The effects of various compositions consisting in 3D scaffolds were investigated via FT-IR analysis, porosity, swelling and mechanical tests, and effect on the morphology of scaffolds investigated microscopically. The biostability and cytocompatibility tests were used to explore the ability of scaffolds to use for tissue engineering application. The average pore sizes of scaffolds were in range of 100.73±27.62-116.01±52.06, porosity 71.72±3.46-91.17±2.42%, tensile modulus in dry environment 1.47±0.08-0.17±0.03MPa, tensile modulus in wet environment 0.32±0.03-0.14±0.04MPa and biodegradation rate (at day 30) 60.38±0.70-83.48±0.28%. In vitro culture of human fibroblasts and keratinocytes showed that the various composition multicomponent 3D scaffolds were good cytocompatibility however, the scaffolds contained high amount of fish collagen excellently facilitated cell proliferation and adhesion. It was found that the high amount fish collagen and glycerin scaffolds have high porosity, enough mechanical strength and biostability, and excellent cytocompatibility.

Electrospun tilapia collagen nanofibers accelerating wound healing via inducing keratinocytes proliferation and differentiation

The development of biomaterials with the ability to induce skin wound healing is a great challenge in biomedicine. In this study, tilapia skin collagen sponge and electrospun nanofibers were developed for wound dressing. The collagen sponge was composed of at least two α-peptides. It did not change the number of spleen-derived lymphocytes in BALB/c mice, the ratio of CD4(+)/CD8(+) lymphocytes, and the level of IgG or IgM in Sprague-Dawley rats. The tensile strength and contact angle of collagen nanofibers were 6.72±0.44MPa and 26.71±4.88°, respectively. They also had good thermal stability and swelling property. Furthermore, the nanofibers could significantly promote the proliferation of human keratinocytes (HaCaTs) and stimulate epidermal differentiation through the up-regulated gene expression of involucrin, filaggrin, and type I transglutaminase in HaCaTs. The collagen nanofibers could also facilitate rat skin regeneration. In the present study, electrospun biomimetic tilapia skin collagen nanofibers were succesfully prepared, were proved to have good bioactivity and could accelerate rat wound healing rapidly and effectively. These biological effects might be attributed to the biomimic extracellular matrix structure and the multiple amino acids of the collagen nanofibers. Therefore, the cost-efficient tilapia collagen nanofibers could be used as novel wound dressing, meanwhile effectively avoiding the risk of transmitting animal disease in the future clinical apllication.

Construction and characterization of human oral mucosa equivalent using hyper-dry amniotic membrane as a matrix

BACKGROUND

Human amniotic membrane(HAM) as a graft material has been used in various fields. Hyper-dry amniotic membrane (HD-AM) is a novel dried amniotic membrane that is easy to handle and can be preserved at room temperature without time limitation. The purpose of this study was to investigate the useful properties of HD-AM in reconstruction of the oral mucosa.

METHODS

Human oral keratinocytes were isolated and seeded on HD-AM in serum-free culture system. Oral mucosa equivalent (OME) was developed and transplanted onto full-thickness wound on athymic mice. The wound healing was analyzed and the OME both before and after transplantation was analyzed with hematoxylin-eosin staining and immunohistochemical staining for Cytokines 10 (CK10), Cytokines 16 (CK16), and Ivolucrin (IVL).

RESULTS

Oral keratinocytes spread and proliferated well on HD-AM. Two weeks after air-lifting, OME had formed with good differentiation and morphology. We confirmed immunohistochemically that the expression of CK10 was positive in all suprabasal layers, as was CK16 in the upper layers, while IVL was present in all cell layers. Three weeks after transplantation to athymic mice, the newly generated tissue had survived well with the smallest contraction. The epithelial cells of newly generated tissue expressed CK10 throughout in all suprabasal layers, IVL was mainly in the granular layer, and CK16 positive cells were observed in all spinous layer and granular layer but were not expressed in the mouse skin, all of which were similar to native gingival mucosa.

CONCLUSIONS

The OME with HD-AM as a matrix revealed a good morphology and stable wound healing. This study demonstrates that HD-AM is a useful and feasible biomaterial for oral mucosa reconstruction.

Development of biomimetic tilapia collagen nanofibers for skin regeneration through inducing keratinocytes differentiation and collagen synthesis of dermal fibroblasts

In this study, tilapia skin collagen sponge and electrospun nanofibers were developed for wound dressing. The collagen sponge was composed of at least two α-peptides, and its denaturation temperature was 44.99 °C. It did not change the number of spleen-derived lymphocytes in BALB/c mice, the ratio of CD4+/CD8+ lymphocytes, and the level of IgG or IgM in Sprague-Dawley rat. The contact angle, tensile strength, and weight loss temperature of collagen nanofibers were 21.2°, 6.72±0.44 MPa, and 300 °C, respectively. The nanofibers could promote the viabilities of human keratinocytes (HaCaTs) and human dermal fibroblasts (HDFs), inducing epidermal differentiation through the gene expression of involucrin, filaggrin, and type I transglutaminase of HaCaTs, and they could also accelerate migration of HaCaTs with the expression of matrix metalloproteinase-9 and transforming growth factor-β1 (TGF-β1). Besides, the nanofibers could upregulate the protien level of Col-I in HDFs both via a direct effect and TGF-β1 secreted from HaCaTs, thus facilitating the formation of collagen fibers. Furthermore, the collagen nanofibers stimulated the skin regeneration rapidly and effectively in vivo. These biological effects could be explained as the contributions from the biomimic extracellular cell matrix structure, hydrophilicity, and the multiple amino acids of the collagen nanofibers.

Marine origin collagens and its potential applications

Collagens are the most abundant high molecular weight proteins in both invertebrate and vertebrate organisms, including mammals, and possess mainly a structural role, existing different types according with their specific organization in distinct tissues. From this, they have been elected as one of the key biological materials in tissue regeneration approaches. Also, industry is constantly searching for new natural sources of collagen and upgraded methodologies for their production. The most common sources are from bovine and porcine origin, but other ways are making their route, such as recombinant production, but also extraction from marine organisms like fish. Different organisms have been proposed and explored for collagen extraction, allowing the sustainable production of different types of collagens, with properties depending on the kind of organism (and their natural environment) and extraction methodology. Such variety of collagen properties has been further investigated in different ways to render a wide range of applications. The present review aims to shed some light on the contribution of marine collagens for the scientific and technological development of this sector, stressing the opportunities and challenges that they are and most probably will be facing to assume a role as an alternative source for industrial exploitation.

Sequential keratinocytic differentiation and maturation in a three-dimensional model of human artificial oral mucosa

BACKGROUND AND OBJECTIVE

Oral mucosa shortage may limit or condition some clinical approaches in maxillofacial, periodontal and implant treatment. The availability of a human oral mucosa model generated by tissue engineering could help clinicians to address the lack of oral mucosa. In this work, we carried out a sequential maturation and differentiation study of the epithelial cell layer of an artificial human oral mucosa substitute based on fibrin-agarose biomaterials with fibroblasts and keratinocytes.

MATERIAL AND METHODS

Histological, immunohistochemical and gene expression analyses were carried out in artificial human oral mucosa models developed and cultured for 1, 2 and 3 wk.

RESULTS

Artificial oral mucosa models showed expression of tight junction proteins and cytokeratins from the first week of in vitro development. Mature samples of 3 wk of development subjected to air-liquid conditions showed signs of epithelial differentiation and expressed specific RNAs and proteins corresponding to adherent and gap junctions and basement lamina. Moreover, these mature samples overexpressed some desmosomal and tight junction transcripts, with gap junction components being downregulated.

CONCLUSION

These results suggest that bioengineered human oral mucosa substitutes form a well-developed epithelial layer that was very similar to human native tissues. In consequence, the epithelial layer could be fully functional in these oral mucosa substitutes, thus implying that these tissues may have clinical usefulness.

Tissue engineering of oral mucosa: a shared concept with skin

Tissue-engineered oral mucosa, in the form of epithelial cell sheets or full-thickness oral mucosa equivalents, is a potential solution for many patients with congenital defects or with tissue loss due to diseases or tumor excision following a craniofacial cancer diagnosis. In the laboratory, it further serves as an in vitro model, alternative to in vivo testing of oral care products, and provides insight into the behavior of the oral mucosal cells in healthy and pathological tissues. This review covers the old and new generation scaffold types and materials used in oral mucosa engineering; discusses similarities and differences between oral mucosa and skin, the methods developed to reconstruct oral mucosal defects; and ends with future perspectives on oral mucosa engineering.

In vitro systems toxicology approach to investigate the effects of repeated cigarette smoke exposure on human buccal and gingival organotypic epithelial tissue cultures

Smoking has been associated with diseases of the lung, pulmonary airways and oral cavity. Cytologic, genomic and transcriptomic changes in oral mucosa correlate with oral pre-neoplasia, cancer and inflammation (e.g. periodontitis). Alteration of smoking-related gene expression changes in oral epithelial cells is similar to that in bronchial and nasal epithelial cells. Using a systems toxicology approach, we have previously assessed the impact of cigarette smoke (CS) seen as perturbations of biological processes in human nasal and bronchial organotypic epithelial culture models. Here, we report our further assessment using in vitro human oral organotypic epithelium models. We exposed the buccal and gingival organotypic epithelial tissue cultures to CS at the air-liquid interface. CS exposure was associated with increased secretion of inflammatory mediators, induction of cytochrome P450s activity and overall weak toxicity in both tissues. Using microarray technology, gene-set analysis and a novel computational modeling approach leveraging causal biological network models, we identified CS impact on xenobiotic metabolism-related pathways accompanied by a more subtle alteration in inflammatory processes. Gene-set analysis further indicated that the CS-induced pathways in the in vitro buccal tissue models resembled those in the in vivo buccal biopsies of smokers from a published dataset. These findings support the translatability of systems responses from in vitro to in vivo and demonstrate the applicability of oral organotypical tissue models for an impact assessment of CS on various tissues exposed during smoking, as well as for impact assessment of reduced-risk products.