In vitro reconstitution of skin: fibroblasts facilitate keratinocyte growth and differentiation on acellular reticular dermis

Development and Characterization of a Three-Dimensional Organotypic In Vitro Oral Cancer Model with Four Co-Cultured Cell Types, Including Patient-Derived Cancer-Associated Fibroblasts

Background/Objectives: Cancer organoids have emerged as a valuable tool of three-dimensional (3D) cell cultures to investigate tumor heterogeneity and predict tumor behavior and treatment response. We developed a 3D organotypic culture model of oral squamous cell carcinoma (OSCC) to recapitulate the tumor-stromal interface by co-culturing four cell types, including patient-derived cancer-associated fibroblasts (PD-CAFs). Methods: A stainless-steel ring was used twice to create the horizontal positioning of the cancer stroma (adjoining normal oral mucosa connective tissue) and the OSCC layer (surrounding normal oral mucosa epithelial layer). Combined with a structured bi-layered model of the epithelial component and the underlying stroma, this protocol enabled us to construct four distinct portions mimicking the oral cancer tissue arising in the oral mucosa. Results: In this model, α-smooth muscle actin-positive PD-CAFs were localized in close proximity to the OSCC layer, suggesting a crosstalk between them. Furthermore, a linear laminin-γ2 expression was lacking at the interface between the OSCC layer and the underlying stromal layer, indicating the loss of the basement membrane-like structure. Conclusions: Since the specific 3D architecture and polarity mimicking oral cancer in vivo provides a more accurate milieu of the tumor microenvironment (TME), it could be crucial in elucidating oral cancer TME.

Advances in tissue engineering and biofabrication for in vitro skin modeling

The global prevalence of skin disease and injury is continually increasing, yet conventional cell-based models used to study these conditions do not accurately reflect the complexity of human skin. The lack of inadequate in vitro modeling has resulted in reliance on animal-based models to test pharmaceuticals, biomedical devices, and industrial and environmental toxins to address clinical needs. These in vivo models are monetarily and morally expensive and are poor predictors of human tissue responses and clinical trial outcomes. The onset of three-dimensional (3D) culture techniques, such as cell-embedded and decellularized approaches, has offered accessible in vitro alternatives, using innovative scaffolds to improve cell-based models' structural and histological authenticity. However, these models lack adequate organizational control and complexity, resulting in variations between structures and the exclusion of physiologically relevant vascular and immunological features. Recently, biofabrication strategies, which combine biology, engineering, and manufacturing capabilities, have emerged as instrumental tools to recreate the heterogeneity of human skin precisely. Bioprinting uses computer-aided design (CAD) to yield robust and reproducible skin prototypes with unprecedented control over tissue design and assembly. As the interdisciplinary nature of biofabrication grows, we look to the promise of next-generation biofabrication technologies, such as organ-on-a-chip (OOAC) and 4D modeling, to simulate human tissue behaviors more reliably for research, pharmaceutical, and regenerative medicine purposes. This review aims to discuss the barriers to developing clinically relevant skin models, describe the evolution of skin-inspired in vitro structures, analyze the current approaches to biofabricating 3D human skin mimetics, and define the opportunities and challenges in biofabricating skin tissue for preclinical and clinical uses.

Patient-derived three-dimensional culture techniques model tumor heterogeneity in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) outcomes remain stagnant, in part due to a poor understanding of HNSCC biology. The importance of tumor heterogeneity as an independent predictor of outcomes and treatment failure in HNSCC has recently come to light. With this understanding, 3D culture systems, including patient derived organoids (PDO) and organotypic culture (OTC), that capture this heterogeneity may allow for modeling and manipulation of critical subpopulations, such as p-EMT, as well as interactions between cancer cells and immune and stromal cells in the microenvironment. Here, we review work that has been done using PDO and OTC models of HNSCC, which demonstrates that these 3D culture models capture in vivo tumor heterogeneity and can be used to model tumor biology and treatment response in a way that faithfully recapitulates in vivo characteristics. As such, in vitro 3D culture models represent an important bridge between 2D monolayer culture and in vivo models such as patient derived xenografts.

Novel application of autologous micrografts in a collagen-glycosaminoglycan scaffold for diabetic wound healing

BACKGROUND

Therapeutic strategies that successfully combine two techniques-autologous micrografting and biodegradable scaffolds-offer great potential for improved wound repair and decreased scarring. In this study we evaluate the efficacy of a novel modification of a collagen-glycosaminoglycan scaffold with autologous micrografts using a murine dorsal wound model.

METHODS

db/db mice underwent dorsal wound excision and were treated with a collagen-glycosaminoglycan scaffold (CGS), a modified collagen-glycosaminoglycan scaffold (CGS+MG) or simple occlusive dressing (Blank). The modified scaffold was created by harvesting full thickness micrografts and transplanting these into the collagen-glycosaminoglycan membrane. Parameters of wound healing, including cellular proliferation, collagen deposition, keratinocyte migration, and angiogenesis were assessed.

RESULTS

The group treated with the micrograft-modified scaffold healed at a faster rate, showed greater cellular proliferation, collagen deposition, and keratinocyte migration with higher density and greater maturity of microvessels. The grafts remained viable within the scaffold with no evidence of rejection. Keratinocytes were shown to migrate from the wound border and from the micrograft edges towards the center of the wound, while cellular proliferation was present both at the wound border and wound bed.

CONCLUSION

We report successful treatment of diabetic wounds with a novel collagen-glycosaminoglycan scaffold modified with full-thickness automicrografts. Differences in cellular migration and proliferation offer maiden evidence on the mechanisms of wound healing. Clinically, the successful scaffold engraftment, micrograft viability and improved wound healing offer promising results for the development of a new therapeutic modality for wound repair.

A novel skin brightening topical technology

Background

Effective skin lightening remains an unmet need in over‐the‐counter formulations.

Aims

This research examined a topical facial formulation containing hexylresorcinol, silymarin, 20% vitamin C, and 5% vitamin E in a proprietary anhydrous vehicle in skin explants for UVB photoprotective effects and clinical benefits.

Patients/Method

In vitro investigation examined 12 skin explants to assess the test product and vehicle. Six skin explants received 10 μL of the study product, and six skin explants received the 10 μL of the vehicle. After 96 hours, half the skin samples were exposed to 250 mJ/cm² of UVB radiation while the other half unexposed.

Clinically, 42 female subjects with normal or dry skin 35‐55 years with skin types I‐VI were enrolled possessing discoloration, uneven skin tone, and fine lines. The dermatologist investigator evaluated brightening, evenness, fine lines, wrinkles, and global appearance.

Results

Explants treated with the study product experienced no significant change in gene marker expression of pro‐collagen and pro‐inflammatory gene markers upon UVB exposure. In contrast, skin explants treated with the vehicle experienced significant decreases in pro‐collagen expression and significant increases in pro‐inflammatory gene marker expression. Clinically, the greatest improvement as compared to baseline was seen at week 12 (P < .001) with 45% improvement in brightening, 27% improvement in evenness, 25% improvement in lines, and 25% improvement in global facial appearance.

Conclusion

Hexylresorcinol, silymarin, 20% vitamin C, and 5% vitamin E in a proprietary anhydrous vehicle are effective in decreasing UVB‐induced photodamage in skin explants while clinically producing skin brightness improvement.

A new approach to the production of a biovital skin graft based on human acellular dermal matrix produced in-house, in vitro revitalized internally by human fibroblasts and keratinocytes on the surface

Patients with extensive and deep burns who do not have enough donor sites for autologous skin grafts require alternative treatment methods. Tissue engineering is a useful tool to solve this problem. The aim of this study was to find the optimal method for the production of a biovital skin substitute based on acellular dermal matrix (ADM) and in vitro cultured fibroblasts and keratinocytes. In this work, nine methods of ADM production were assessed. The proposed methods are based on the use of the following enzymes: Dispase II, collagenase I/ethylenediaminetetraacetic acid (EDTA), collagenase II/EDTA, and mechanical perforation using DermaRoller and mesh dermatome. The obtained ADMs were examined (both on the side of the basement membrane and on the "cut-off" side) by means of scanning electron microscopy, immunohistochemistry tests and strength tests. ADM was revitalized with human fibroblasts and keratinocytes. The ability of in-depth revitalization of cultured fibroblasts and their ability to secrete collagen IV was examined. The obtained results indicate that the optimal method of production of live skin substitutes is the colonization of autologous fibroblasts and keratinocytes on the scaffold obtained using two-step incubation method: Trypsin/EDTA and dispase II.

Skin wound repair: Results of a pre-clinical study to evaluate electropsun collagen-elastin-PCL scaffolds as dermal substitutes

The gold standard treatment for severe burn injuries is autologous skin grafting and the use of commercial dermal substitutes. However, resulting skin tissue following treatment usually displays abnormal morphology and functionality including scarring, skin contracture due to the poor elasticity and strength of existing dermal substitutes. In this study, we have developed a triple-polymer scaffold made of collagen-elastin-polycaprolactone (CEP) composite, aiming to enhance the mechanical properties of the scaffold while retaining its biological properties in promoting cell attachment, proliferation and tissue regeneration. The inclusion of elastin was revealed to decrease the stiffness of the scaffold, while also decreasing hysteresis and increasing elasticity. In mice, electrospun collagen-elastin-PCL scaffolds promoted keratinocyte and fibroblast proliferation, tissue integration and accelerated early-stage angiogenesis. Only a mild inflammatory response was observed in the first 2 weeks post-subcutaneous implantation. Our data indicates that the electrospun collagen-elastin-PCL scaffolds could potentially serve as a skin substitute to promote skin cell growth and tissue regeneration after severe burn injury.

Tissue/organ-derived bioink formulation for 3D bioprinting

Tissue/organ-derived bioink formulations open up new avenues in 3D bioprinting research with the potential to create functional tissue or organs. Printing of tissue construct largely depends on material properties, as it needs to be fabricated in an aqueous environment while encapsulating living cells. The decellularized extracellular matrix bioinks proved to be a potential option for functional tissue development in vivo and as an alternative to chemically cross-linked bioinks. However, certain limitations such as printability and limited mechanical strength need to be addressed for enhancing their widespread applications. By drawing knowledge from the existing literature, emphasis has been given in this review to the development of decellularized extracellular matrix bioinks and their applications in printing functional tissue constructs.

Decellularizing and Recellularizing Adult Mouse Kidneys

Decellularization is the process by which resident cells are lysed and cellular debris is removed from the tissue, leaving behind the extracellular matrix scaffold. The extracellular matrix scaffold can be used for three-dimensional culturing of cells. Here we describe methods of decellularizing whole and thick sections of mouse kidneys using a 0.1% sodium dodecyl sulfate (SDS) detergent solution and strategies to repopulate whole and thick sections of decellularized mouse kidneys with cells.

Correcting Nasojugal Groove with Autologous Cultured Fibroblast Injection: A Pilot Study

BACKGROUND

A new commercial drug that contains autologous cultured fibroblasts has been developed and approved by the United States Food and Drug Administration for improving the appearance of nasolabial folds. However, the treatment requires three sessions every 3-6 weeks. It is known that the skin overlying the nasojugal groove is thinner, and the wrinkle is generally shallower than nasolabial folds. Therefore, we hypothesized that the nasojugal groove could be improved by just one treatment session. Therefore, the purpose of this study was to evaluate the efficacy and safety of autologous cultured fibroblast injection to correct nasojugal grooves.

METHODS

Forty-six subjects with nasojugal grooves were enrolled in this study. They were injected with autologous cultured fibroblasts or placebo in one session. Blinded evaluators and subjects assessed the efficacy using a validated wrinkle assessment scale at 4, 12, and 24 weeks after the injection. Information of adverse events was collected at each visit.

RESULTS

Based on the evaluators' assessment at 24 weeks after the injection, 76% of subjects treated with autologous cultured fibroblasts showed improvement whereas 0% of subjects treated with placebo showed improvement (P < 0.0001). Based on self-assessment at 24 weeks after the injection, 72% of subjects treated with autologous cultured fibroblasts and 45% of subjects treated with placebo showed improvement (P = 0.0662). There were no serious adverse events related to autologous cultured fibroblast injection.

CONCLUSIONS

Autologous cultured fibroblast injection might be effective and safe to correct nasojugal grooves.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Scarring vs. functional healing: Matrix-based strategies to regulate tissue repair

All vertebrates possess mechanisms to restore damaged tissues with outcomes ranging from regeneration to scarring. Unfortunately, the mammalian response to tissue injury most often culminates in scar formation. Accounting for nearly 45% of deaths in the developed world, fibrosis is a process that stands diametrically opposed to functional tissue regeneration. Strategies to improve wound healing outcomes therefore require methods to limit fibrosis. Wound healing is guided by precise spatiotemporal deposition and remodelling of the extracellular matrix (ECM). The ECM, comprising the non-cellular component of tissues, is a signalling depot that is differentially regulated in scarring and regenerative healing. This Review focuses on the importance of the native matrix components during mammalian wound healing alongside a comparison to scar-free healing and then presents an overview of matrix-based strategies that attempt to exploit the role of the ECM to improve wound healing outcomes.

In vitro skin models to study epithelial regeneration from the hair follicle

The development of dermal equivalents (DEs) for the treatment of burns has contributed toward efficient wound closure. A collagen-glycosaminoglycan DE (C-GAG) grafted with hair follicles converted a full-thickness wound to partial-thickness resulting in complete wound closure and restored hair. In this study we compared the ability of both intact pilosebaceous units (PSU) or truncated hair follicles (THF) to regenerate a multilayered epidermis in vitro when implanted into de-epidermalized dermis (DED) or C-GAG with the epidermis generated in vivo using C-CAG. Keratinocytes explanted from the outer root sheath of PSU and THF in both DED and C-GAG but only formed a multilayered epidermis with PSU in DED. PSU were more effective at forming multilayered epidermis in DED than THF. Both DED and C-GAG skin expressed proliferation (PCNA), differentiation (K1, K10), hyperproliferation (K6, K16), basal (K14), putative stem cell (p63), extracellular matrix protein (Collagen IV), mesenchymal (vimentin) and adherens junction (β-catenin) markers. These data suggest DEs supported initial maintenance of the implanted hair follicles, in particular PSU, and provide an excellent model with which to investigate the regulation of hair follicle progenitor epithelial cells during epidermal regeneration. Although neither PSU nor THF formed multilayered epidermis in C-CAG in vitro, hair follicles implanted into engrafted C-GAG on a burns patient resulted in epithelial regeneration and expression of proliferation and differentiation markers in a similar manner to that seen in vitro. However, the failure of C-GAG to support epidermal regeneration in vitro suggests in vivo factors are essential for full epidermal regeneration using C-GAG.

Cutaneous Tissue Engineering and Lower Extremity Wounds (Part 1)

Tissue-engineered skin is a novel therapeutic with which difficult-to-heal lower extremity wounds may be treated. Such skins are products of cutaneous tissue engineering that provide an alternative for autologous or allogeneic tissue transplantation, thereby avoiding problems associated with donor site availability, the risk of infection, and scarring. Recently developed tissue-engineered skin equivalents have shown to be superior in certain ways to compression therapy for refractory venous ulcers and acute wounds. These biologic products behave similarly to autografts.

ECM and ECM-like materials - Biomaterials for applications in regenerative medicine and cancer therapy

Regenerative strategies such as stem cell-based therapies and tissue engineering applications are being developed with the aim to replace, remodel, regenerate or support damaged tissues and organs. In addition to careful cell type selection, the design of appropriate three-dimensional (3D) scaffolds is essential for the generation of bio-inspired replacement tissues. Such scaffolds are usually made of degradable or non-degradable biomaterials and can serve as cell or drug carriers. The development of more effective and efficient drug carrier systems is also highly relevant for novel cancer treatment strategies. In this review, we provide a summary of current approaches that employ ECM and ECM-like materials, or ECM-synthetic polymer hybrids, as biomaterials in the field of regenerative medicine. We further discuss the utilization of such materials for cell and drug delivery, and highlight strategies for their use as vehicles for cancer therapy.

Generation of Genetically Modified Organotypic Skin Cultures Using Devitalized Human Dermis

Organotypic cultures allow the reconstitution of a 3D environment critical for cell-cell contact and cell-matrix interactions which mimics the function and physiology of their in vivo tissue counterparts. This is exemplified by organotypic skin cultures which faithfully recapitulates the epidermal differentiation and stratification program. Primary human epidermal keratinocytes are genetically manipulable through retroviruses where genes can be easily overexpressed or knocked down. These genetically modified keratinocytes can then be used to regenerate human epidermis in organotypic skin cultures providing a powerful model to study genetic pathways impacting epidermal growth, differentiation, and disease progression. The protocols presented here describe methods to prepare devitalized human dermis as well as to genetically manipulate primary human keratinocytes in order to generate organotypic skin cultures. Regenerated human skin can be used in downstream applications such as gene expression profiling, immunostaining, and chromatin immunoprecipitations followed by high throughput sequencing. Thus, generation of these genetically modified organotypic skin cultures will allow the determination of genes that are critical for maintaining skin homeostasis.

A comparative analysis of advanced techniques for skin reconstruction with autologous keratinocyte culture in severely burned children: own experience

INTRODUCTION

The local treatment in burns larger than 50% of total body surface area is still the great challenge for surgeons.

AIM

This paper presents a review of different solutions for deep burn wound healing in children and the early outcomes of treatment with combined autologous cell culture technique.

MATERIAL AND METHODS

For this study, 20 children aged between 4 and 12 years with 55-65% of TBSA III grade burn injury were analyzed. A skin sample, 1 cm × 1 cm in size, for keratinocyte cultivation, was taken on the day of the burn. After necrotic tissue excision, the covering of the burned area with an isolated meshed skin graft was carried out between day 4 and 7. After 7 days of keratinocyte cultivation, the mentioned areas were covered with cells from the culture. We divided the burned regions, according to the way of wound closure, into 3 groups each consisting of 15 treated regions of the body. We used meshed split thickness skin grafts (SSG group), cultured autologous keratinocytes (CAC group), and both techniques applied in one stage (SSG + CAC group).

RESULTS

In the SSG group, the mean time for complete closure of wounds was 12.7 days. Wounds treated with CAC only needed a non-significantly longer time to heal - 14.2 days (p = 0.056) when compared to SSG. The shortest time to heal was observed in the group treated with SSG + CAC - 8.5 days, and it was significantly shorter when compared to the SSG and CAC groups (p < 0.001).

CONCLUSIONS

This study suggests that cultured keratinocytes obtained after short-time multiplication, combined with meshed autologous split thickness skin grafts, constitute the optimal wound closure in burned children.

Micropatterned dermal-epidermal regeneration matrices create functional niches that enhance epidermal morphogenesis

Although tissue engineered skin substitutes have demonstrated some clinical success for the treatment of chronic wounds such as diabetic and venous ulcers, persistent graft take and stability remain concerns. Current bilayered skin substitutes lack the characteristic microtopography of the dermal-epidermal junction that gives skin enhanced mechanical stability and creates cellular microniches that differentially promote keratinocyte function to form skin appendages and enhance wound healing. We developed a novel micropatterned dermal-epidermal regeneration matrix (μDERM) which incorporates this complex topography and substantially enhances epidermal morphology. Here, we describe the use of this three-dimensional (3-D) in vitro culture model to systematically evaluate different topographical geometries and to determine their relationship to keratinocyte function. We identified three distinct keratinocyte functional niches: the proliferative niche (narrow geometries), the basement membrane protein synthesis niche (wide geometries) and the putative keratinocyte stem cell niche (narrow geometries and corners). Specifically, epidermal thickness and keratinocyte proliferation is significantly (p<0.05) increased in 50 and 100 μm channels while laminin-332 deposition is significantly (p<0.05) increased in 400 μm channels compared to flat controls. Additionally, β1(bri)p63(+) keratinocytes, putative keratinocyte stem cells, preferentially cluster in channel geometries (similar to clustering observed in native skin) compared to a random distribution on flats. This study identifies specific target geometries to enhance skin regeneration and graft performance. Furthermore, these results suggest the importance of μDERM microtopography in designing the next generation of skin substitutes. Finally, we anticipate that 3-D organotypic cultures on μDERMS will provide a novel tissue engineered skin substitute for in vitro investigations of skin morphogenesis, wound healing and pathology.

An in vitro skin model to study the effect of mesenchymal stem cells in wound healing and epidermal regeneration

The development of new wound therapies, such as bioengineered skin equivalents, is an ongoing process. Multi-potent mesenchymal stem cells (MSCs) give rise to many tissue lineages and have been implicated in wound healing making them a potential candidate for cell-based bioengineered products for injured tissue. In this study, we investigated the mesenchymal/epithelial interactions of cultured MSCs in comparison to cultured fibroblasts on epidermal proliferation, differentiation, and extracellular matrix (ECM) protein expression using a de-epidermalized dermis (DED) skin model. We also studied whether MSCs can transdifferentiate to keratinocytes using the same model. Keratinocytes were cultured on unseeded DED or DED populated with fibroblasts or MSCs at an air-liquid interface to induce epidermal differentiation. Fibroblasts or MSCs were also seeded on the papillary surface of the DED alone or on the reticular surface. General histology and immunostaining was performed on the skin equivalents to examine the expression of pan keratin (K) (K1, K5, K6, and K18) and protein markers for epidermal differentiation (K10), hyperproliferation (K6), proliferation (PCNA), ECM component (collagen type IV), and mesenchymal marker (vimentin). Keratinocyte-fibroblast skin model and keratinocyte-MSC skin model both displayed an epidermal phenotype similar to epidermis in vivo. Positive expression of proliferation, differentiation and ECM protein markers was observed. MSCs failed to adopt an epithelial phenotype in the DED skin model. Our findings highlight the potential use of MSCs in bioengineered tissue for the treatment of wounds.

Asymmetric migration of human keratinocytes under mechanical stretch and cocultured fibroblasts in a wound repair model

Keratinocyte migration during re-epithelization is crucial in wound healing under biochemical and biomechanical microenvironment. However, little is known about the underlying mechanisms whereby mechanical tension and cocultured fibroblasts or keratinocytes modulate the migration of keratinocytes or fibroblasts. Here we applied a tensile device together with a modified transwell assay to determine the lateral and transmembrane migration dynamics of human HaCaT keratinocytes or HF fibroblasts. A novel pattern of asymmetric migration was observed for keratinocytes when they were cocultured with non-contact fibroblasts, i.e., the accumulative distance of HaCaT cells was significantly higher when moving away from HF cells or migrating from down to up cross the membrane than that when moving close to HF cells or when migrating from up to down, whereas HF migration was symmetric. This asymmetric migration was mainly regulated by EGF derived from fibroblasts, but not transforming growth factor α or β1 production. Mechanical stretch subjected to fibroblasts fostered keratinocyte asymmetric migration by increasing EGF secretion, while no role of mechanical stretch was found for EGF secretion by keratinocytes. These results provided a new insight into understanding the regulating mechanisms of two- or three-dimensional migration of keratinocytes or fibroblasts along or across dermis and epidermis under biomechanical microenvironment.

Plant-derived human collagen scaffolds for skin tissue engineering

Tissue engineering scaffolds are commonly formed using proteins extracted from animal tissues, such as bovine hide. Risks associated with the use of these materials include hypersensitivity and pathogenic contamination. Human-derived proteins lower the risk of hypersensitivity, but possess the risk of disease transmission. Methods engineering recombinant human proteins using plant material provide an alternate source of these materials without the risk of disease transmission or concerns regarding variability. To investigate the utility of plant-derived human collagen (PDHC) in the development of engineered skin (ES), PDHC and bovine hide collagen were formed into tissue engineering scaffolds using electrospinning or freeze-drying. Both raw materials were easily formed into two common scaffold types, electrospun nonwoven scaffolds and lyophilized sponges, with similar architectures. The processing time, however, was significantly lower with PDHC. PDHC scaffolds supported primary human cell attachment and proliferation at an equivalent or higher level than the bovine material. Interleukin-1 beta production was significantly lower when activated THP-1 macrophages where exposed to PDHC electrospun scaffolds compared to bovine collagen. Both materials promoted proper maturation and differentiation of ES. These data suggest that PDHC may provide a novel source of raw material for tissue engineering with low risk of allergic response or disease transmission.

Architectural characterization of organotypic cultures of H400 and primary rat keratinocytes

Organotypic epithelial structures can be cultured using primary or immortalized keratinocytes. However, there has been little detailed quantitative histological characterization of such cultures in comparison with normal mucosal architecture. The aim of this study is to identify morphological markers of tissue architecture that can be used to monitor tissue structure, maturation, and differentiation and to enable quantitative comparison of organotypic cultures (OCs) with normal oral mucosa. OCs of oral keratinocytes [immortalized H400 or primary rat keratinocytes (PRKs)] were generated using the three scaffolds of de-epidermalized dermis (DED), polyethylene terephthalate (PET), and collagen gels for up to 14 days. Cultures and normal epithelium were analyzed immunohistochemically and by using the semi-quantitative reverse transcriptase polymerase chain reaction (sq-RT-PCR) for E-cadherin, desmoglein-3, plakophilin, involucrin, cytokeratins-1, -5, -6, -10, -13, and Ki67. The epithelial thickness of OCs was measured in stained sections using image processing. Histological analysis revealed that air-liquid interface (ALI) cultures generated stratified organotypic epithelial structures by 14-days. The final thickness of these cultures as well as the degree of maturation/stratification (including stratum corneum formation) varied significantly depending on the scaffold used. For certain scaffolds, the immunohistochemical profiles obtained recapitulated those of normal oral epithelium indicating comparable in vitro differentiation and proliferation. In conclusion, quantitative microscopy approaches enabled unbiased architectural characterization of OCs. The scaffold materials used in the present study (DED, collagen type-I and PET) differentially influenced cell behavior in OCs of oral epithelia. H400 and PRK OCs on DED at the ALI demonstrated similar characteristics in terms of gene expression and protein distribution to the normal tissue architecture.

A multicenter, double-blind, placebo-controlled trial of autologous fibroblast therapy for the treatment of nasolabial fold wrinkles

BACKGROUND

Changes associated with aging are partly due to loss of collagen and elastin. Treatment with autologous fibroblasts grown in culture (azficel-T) can help correct the appearance of aging by replacing lost dermal constituents.

OBJECTIVE

To demonstrate the safety and effectiveness of autologous fibroblasts in the treatment of nasolabial fold (NLF) wrinkles.

METHODS AND MATERIALS

Adults with moderate to very severe NLF wrinkles were randomized to receive three treatments with autologous fibroblasts or placebo at 5-week intervals. Blinded evaluators and subjects assessed efficacy using a validated wrinkle assessment scale.

RESULTS

Three hundred seventy-two subjects were enrolled and underwent treatment. Seventy-eight percent of subjects treated with autologous fibroblast therapy and 48% of subjects treated with placebo achieved at least a 1-point improvement on the subject assessment at 6 months (p < 0.001), and 64% of subjects treated with autologous fibroblast therapy and 36% of those treated with placebo showed at least a 1-point improvement evaluator's assessment (p < 0.001). Adverse events were generally mild, and the treatment was well tolerated.

CONCLUSION

Autologous fibroblast therapy is safe and effective for the treatment of NLF wrinkles. The availability of autologous cell therapy marks the beginning of a new phase in aesthetic therapy.

Whole organ decellularization - a tool for bioscaffold fabrication and organ bioengineering

The use of synthetic and naturally-derived scaffolds for bioengineering of solid organs has been limited due to a lack of an integrated vascular network. Here, we describe fabrication of a bioscaffold system with intact vascular tree. Animal-donor organs and tissues, ranging in size up-to thirty centimeters, were perfused with decellularization solution to selectively remove the cellular component of the tissue and leave an intact extracellular matrix and vascular network. The vascular tree demonstrated sequential fluid flow through a central inlet vessel that branched into an extensive capillary bed and coalesced back into a single outlet vessel. In one example, the liver, we used central inlet vessels to perfuse human and animal liver cells through the bioscaffold to create a functional liver tissue construct in vitro. These results demonstrate a novel yet simple and scalable method to obtain whole organ vascularized bioscaffolds with potential for liver, kidney, pancreas, intestine and other organs' bioengineering. These bioscaffolds can further provide a tool to study cells in their natural three-dimensional environment, which is superior for drug discovery platform compared with cells cultured in two-dimensional petri dishes.

[Skin graft procedures in burn surgery]

Patients with extensive deep partial or full thickness burns require early excision of necrotic tissue, however, in many of these cases simultaneous autografting is not possible due to the general condition of the patient. In this instance temporary dressings like allogeneic or xenogeneic skin or foam dressings can be applied to minimize fluid and protein loss. In Europe glycerolized preserved allogeneic skin remains the treatment standard. Dermal replacements are considered to optimize the long-term outcome of split thickness skin grafting. Reduced contracture rates and increased pliability have been reported after additional dermal enhancement with either collagen-glycosaminoglycan matrix, acellular allogeneic dermis or collagen/elastin matrix. True regeneration of the dermis has not yet been observed. However, these materials are suitable for improvement of the wound bed and also the final result after split thickness skin transplantation.

Primary human dermal fibroblast interactions with open weave three-dimensional scaffolds prepared from synthetic human elastin

We present an elastic, fibrous human protein-based and cell-interactive dermal substitute scaffold based on synthetic human elastin. Recombinant human tropoelastin promoted primary human dermal fibroblast attachment, spreading and proliferation. Tropoelastin was cross-linked to form a synthetic elastin (SE) hydrogel matrix and electrospun into fibrous SE scaffolds. Fibroblasts attached to and proliferated across SE hydrogel scaffold surfaces for at least 14 days and deposited the extracellular matrix proteins fibronectin and collagen type I. To allow for the benefit of greater cell infiltration, SE was electrospun into open weave, fibrous scaffolds that closely mimic the fibrous nature of the skin dermis. 3D SE scaffolds were robust and consisted of flat, ribbon-like fibers with widths that are similar to native dermal elastic fibers. The scaffolds displayed elasticity close to that of natural elastin. 3D SE retained the ability to interact with primary human dermal fibroblasts, which consistently attached and proliferated to form monolayers spanning the entire scaffold surface. The open weave design, with larger spaces between individual fibers and greater fiber diameters beneficially allowed for substantial cell infiltration throughout the scaffolds.

Impact of microenvironment on the growth of primary human epidermal cells

Although the conditions for in vitro cultivation of adult stem cells and tissue are easily standardized, little is known about the optimal conditions for biointegration after transfer of the tissue graft, playing an important role in the treatment of defects especially soft-tissue skin injuries. To examine the influence of the microenvironment, we investigated the doubling time of primary epithelial cells in relation to the culture medium. Serum from patients of different age groups (n = 15, <20 years; n = 9, >20 years; and fetal calf serum) was pooled independently of age and added to culture medium of epithelial cells from a skin donor (10%). Number of cells was counted in vitro after 1 and 4 days of cultivation using a photometric extinction test. Results were plotted using quotient for calculating cell proliferation ([T4 -T1]:T1). Statistical significance was calculated by Wilcoxon test. Highest proliferation rate was achieved by cultivating the cells in the heterological serum admixture. Homologous serum admixtures in the cell cultures of <20 donators yielded a significantly higher proliferation rate than adult serum (P < 0.01). High regenerative capacity of skin in children has, thus far, mainly been attributed to the high plasticity of the cellular structures. Our study shows for the first time that the age-dependent regenerative capacity in vitro is also influenced by age-dependent humoral factors. In vivo cells from older patients may thus be transferred into an altogether suboptimal microenvironment. Responsible humoral factors should be more closely examined to optimize the clinical management of cellular transplants.

Cultured epithelial autografts in the treatment of facial skin defects: clinical outcome

PURPOSE

To report the treatment of facial skin defects by cultured epithelial autografts and its clinical outcome.

PATIENTS AND METHODS

Between 2002 and 2003, 18 patients with secondary facial skin defects (after tumor excision, trauma, or due to chronic wound healing dysfunction) were successfully treated with autologous cultivated keratinocytes. Overall, 12 patients were included in our study. At the time of this evaluation, the average time lapse after treatment with autologous cultivated keratinocytes was 13.1 months. From 9 of 12 patients a skin biopsy was taken, 12 of 12 patients were neurologically tested, and the results of 12 of 12 patients' esthetics were evaluated by photography and in written form with a standardized questionnaire.

RESULTS

Histologically, 9 of 12 patients showed a regular epithelial layer with evidence of basal cells of the basal membrane and conspicuously arranged connective tissue. The neurologic quality of the skin was discreetly reduced in 9 of 12 patients, but this was not experienced by the patient as a limitation. The wound closure was permanent in the case of all 12 patients. Scar tissue was found frequently, when the wound size was greater than 2.5 cm2. On the basis of the standardized questionnaire, 12 of 12 patients rated the degrees of their subjective satisfaction.

CONCLUSION

From the esthetic, histologic, and neurologic points of view, cultured epithelial autografts are an auspicious alternative to conventional grafting methods for facial skin replacement. Optimizing cell growth in vitro to decrease the cultivation period still remains an essential goal for the future to increase patient acceptance of the procedure as well.

Hyperbaric oxygen stimulates epidermal reconstruction in human skin equivalents

The crucial role of oxygen during the complex process of wound healing has been extensively described. In chronic or nonhealing wounds, much evidence has been reported indicating that a lack of oxygen is a major contributing factor. Although still controversial, the therapeutic application of hyperbaric oxygen (HBO) therapy can aid the healing of chronic wounds. However, how HBO affects reepithelization, involving processes such as keratinocyte proliferation and differentiation, remains unclear. We therefore used a three-dimensional human skin-equivalent (HSE) model to investigate the effects of daily 90-minute HBO treatments on the reconstruction of an epidermis. Epidermal markers of proliferation, differentiation, and basement membrane components associated with a developing epidermis, including p63, collagen type IV, and cytokeratins 6, 10, and 14, were evaluated. Morphometric analysis of hematoxylin and eosin-stained cross sections revealed that HBO treatments significantly accelerated cornification of the stratum corneum compared with controls. Protein expression as determined by immunohistochemical analysis confirmed the accelerated epidermal maturation. In addition, early keratinocyte migration was enhanced by HBO. Thus, HBO treatments stimulate epidermal reconstruction in an HSE. These results further support the importance of oxygen during the process of wound healing and the potential role of HBO therapy in cutaneous wound healing.

Tissue-engineered oral mucosa: a review of the scientific literature

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

Effect of In Vitro Gingival Fibroblast Seeding on the In Vivo Incorporation of Acellular Dermal Matrix Allografts in Dogs

BACKGROUND

Acellular dermal matrix allograft (ADMA) has been used in various periodontal procedures with successful results. Because ADMA has no blood vessels or cells, slower healing and incorporation are observed compared to a subepithelial connective tissue graft. Fibroblasts accelerate the healing process by regulation of matrix deposition and synthesis of a variety of growth factors. Thus, the objective of this study was to evaluate histologically if gingival fibroblasts affect healing and incorporation of ADMA in dogs when used as a subepithelial allograft.

METHODS

Gingival fibroblasts were established from explant culture from the connective tissue of keratinized gingiva collected from the maxilla of seven mongrel dogs. ADMA was seeded with gingival fibroblasts and transferred to dogs. Surgery was performed bilaterally, and the regions were divided into two groups: ADMA+F (ADMA containing fibroblasts) and ADMA (ADMA only). Biopsies were performed after 2, 4, and 8 weeks of healing.

RESULTS

The quantity of blood vessels was significantly higher in the ADMA+F group at 2 weeks of healing (Kruskal-Wallis; P <0.05). There was no statistical difference (P >0.05) in the number of cell layers, epithelial area, or inflammatory infiltrate between the two groups at any stage of healing.

CONCLUSION

The enhanced vascularization in vivo in early stages supports the important role of fibroblasts in improving graft performance and wound healing of cultured graft substitutes.

Vascularization and engraftment of a human skin substitute using circulating progenitor cell-derived endothelial cells

We seeded tissue engineered human skin substitutes with endothelial cells (EC) differentiated in vitro from progenitors from umbilical cord blood (CB-EC) or adult peripheral blood (AB-EC), comparing the results to previous work using cultured human umbilical vein EC (HUVEC) with or without Bcl-2 transduction. Vascularized skin substitutes were prepared by seeding Bcl-2-transduced or nontransduced HUVEC, CB-EC, or AB-EC on the deep surface of decellularized human dermis following keratinocyte coverage of the epidermal surface. These skin substitutes were transplanted onto C.B-17 SCID/beige mice receiving systemic rapamycin or vehicle control and were analyzed 21 d later. CB-EC and Bcl-2-HUVEC formed more human EC-lined vessels than AB-EC or control HUVEC; CB-EC, Bcl-2-HUVEC, and AB-EC but not control HUVEC promoted ingrowth of mouse EC-lined vessels. Bcl-2 transduction increased the number of human and mouse EC-lined vessels in grafts seeded with HUVEC but not with CB-EC or AB-EC. Both CB-EC and AB-EC-induced microvessels became invested by smooth muscle cell-specific alpha-actin-positive mural cells, indicative of maturation. Rapamycin inhibited ingrowth of mouse EC-lined vessels but did not inhibit formation of human EC-lined vessels. We conclude that EC differentiated from circulating progenitors can be utilized to vascularize human skin substitutes even in the setting of compromised host angiogenesis/vasculogenesis.

An In Vivo Mouse Model of Human Skin Substitute Containing Spontaneously Sorted Melanocytes Demonstrates Physiological Changes after UVB Irradiation

Human skin substitutes (HSS) have been developed for repairing burns and other acute or chronic wounds. But although the clinical utility of HSS is well known, scant attention has been paid to their cosmetic properties, especially with regard to color compatibility with the patient's complexion. In this study, we generated an HSS from mixed cell slurries containing keratinocytes and fibroblasts with and without melanocytes on the back of severe combined immunodeficient mice by means of a spontaneous cell-sorting technique. At 16 wk after grafting, Caucasian donor-derived HSS with melanocytes were macroscopically clearly darker than those without melanocytes, and a more darkly pigmented HSS was produced when cells from donors of African descent were seeded. Immunohistochemistry of c-kit, S-100, and HMB45, as well as Fontana-Masson staining and transmission electron microscopy (TEM) demonstrated that melanocytes spontaneously localized to the basal layer. Melanosome transfer to keratinocytes was correctly reorganized, and melanin was evenly dispersed in the basal and suprabasal layers. Colorimetric analysis showed a significantly lower L-value by day 14 following irradiation with 120 mJ per cm2 ultraviolet-B (UVB) (p<0.01), whereas epidermal thickness increased by 50% 1 d after exposure (p<0.01), indicating a normal physiological response to UVB irradiation. These findings suggest that HSS with spontaneously sorted melanocytes offer a means of treating both the structural and cosmetic aspects of skin conditions and trauma, such as pigmentary disorders and skin wounds, by allowing manipulation of the color and population of donor melanocytes.

Inosculation of tissue-engineered capillaries with the host's vasculature in a reconstructed skin transplanted on mice

The major limitation for the application of an autologous in vitro tissue-engineered reconstructed skin (RS) for the treatment of burnt patients is the delayed vascularization of its relatively thick dermal avascular component, which may lead to graft necrosis. We have developed a human endothelialized reconstructed skin (ERS), combining keratinocytes, fibroblasts and endothelial cells (EC) in a collagen sponge. This skin substitute then spontaneously forms a network of capillary-like structures (CLS) in vitro. After transplantation to nude mice, we demonstrated that CLS containing mouse blood were observed underneath the epidermis in the ERS in less than 4 days, a delay comparable to our human skin control. In comparison, a 14-day period was necessary to achieve a similar result with the non-endothelialized RS. Furthermore, no mouse blood vessels were ever observed close to the epidermis before 14 days in the ERS and the RS. We thus concluded that the early vascularization observed in the ERS was most probably the result of inosculation of the CLS network with the host's capillaries, rather than neovascularization, which is a slower process. These results open exciting possibilities for the clinical application of many other tissue-engineered organs requiring a rapid vascularization.

In vitro transfer of keratinocytes: Comparison of transfer from fibrin membrane and delivery by aerosol spray

There are a variety of approaches for the delivery of autologous keratinocytes to restore epithelial coverage of burns wounds that include utilizing cultured keratinocyte sheets, transfer of cultured keratinocytes using a membrane and more recently aerosol spraying of a keratinocyte suspension. The purpose of this study was to compare the effectiveness of direct aerosol delivery of a keratinocyte suspension with a fibrin transfer system to an in vitro wound model consisting of organotypical deepidermalized dermis (DED). A comparison was made between the number of keratinocytes delivered to DED with time, either by transfer from a fibrin membrane or using an aerosol. Additionally, the effect of application time of fibrin membranes to DED, on the number of keratinocytes delivered was investigated and compared with keratinocytes delivered by aerosol at the same time points. After 2 days culture little transfer of keratinocytes had occurred from the fibrin membrane to the DED, whereas 20% more cells were present on the DED than were initially delivered by aerosol spraying. After 7 days, aerosol-delivered cells were found to express cytokeratin K6, indicating a proliferative phenotype. The results from this study show that preconfluent keratinocytes can be delivered by aerosol, and thus may well find application clinically.