Intraoral grafting of an ex vivo produced oral mucosa equivalent: a preliminary report

Development and characterization of a canine oral mucosa equivalent in a serum-free environment

The objectives of this study were to develop a serum-free system for culturing canine oral keratinocytes, the construction and characterization of a canine ex vivo produced oral mucosa equivalent (EVPOME), and transduction green fluorescent protein (GFP) into keratinocytes as a post-grafting tracking marker. Dissociated canine buccal mucosa keratinocytes were cultured in a chemically defined serum-free medium, Epilife trade mark. First-passage keratinocytes were transfected with the GFP gene using a lentiviral vector, sorted by flow cytometer and seeded onto a dermal equivalent, AlloDerm(R) to form EVPOMEs. The EVPOME was characterized by histology and immunohistochemistry, for p63, Ki-67, and involucrin. Laser confocal microscopy was used to locate GFP-transfected keratinocytes within the EVPOME. Cultured canine oral keratinocytes grew rapidly over the first three passages and then the proliferative rate decreased. The canine EVPOME formed a well-stratified epithelial layer. The majority of p63 and Ki-67 immunopositive cells were located in the basal layer whereas cytoplasmic involucrin expression was seen in the suprabasal layers, similar to native canine buccal mucosa. Under laser confocal microscopy, significant green fluorescence was observed throughout the EVPOME. In conclusion, canine EVPOMEs were successfully fabricated in a defined serum-free system with similar characteristics to native buccal mucosa. GFP-transfected canine oral keratinocytes could be identified within the EVPOME.

Biological and biophysical principles in extracorporal bone tissue engineering. Part III

Over the last decade extracorporal bone tissue engineering has moved from laboratory to clinical application. The restoration of maxillofacial bones from cell harvesting through product manufacture and end-use has benefited from innovations in the fields of biomechanical engineering, product marketing and transplant research. Cell/scaffold bone substitutes face a variety of unique clinical challenges which must be addressed. This overview summarises the recent state of the art and future anticipations in the transplantation of extracorporally fabricated bone tissues.

[Autologous cultured skin substitutes]

Progress in cell culture and biomaterial technologies has resulted in commercially available autologous and allogeneic skin substitutes that are composed of keratinocytes and/or fibroblats, in part combined with allogeneic (fibrin) or xenogeneic (collagen, hyaluronan) matrix substances. So far, clinical testing of tissue-engineered products focused on chronic wounds (vascular leg ulcers, diabetic foot ulcers); another major indication, however, is large acute skin defects (burns). During the last decade, partly-controlled clinical trials have been performed with several cultured skin substitutes, studying primarily vascular leg ulcers; a few of these products have been approved for defined indications by the regulatory authorities of various countries. To fulfill regulatory requirements and be eligible for reimbursement, safety as well as cost-effectiveness have to be documented for these novel therapies in contrast to established methods for clearly defined clinical settings; this, in combination with restricted health care resources, is actually hampering the clinical breakthrough of tissue engineering in the treatment of skin wounds, despite undiminished research activities.

Ex vivo produced human conjunctiva and oral mucosa equivalents grown in a serum-free culture system

PURPOSE

We sought to develop full-thickness ex vivo produced human conjunctiva and oral mucosa equivalents using a serum-free culture system without a feeder layer and to compare conjunctiva and oral mucosa equivalents to assess their suitability as graft materials for eyelid reconstruction.

MATERIALS AND METHODS

Human conjunctival and oral mucosal keratinocytes were cultured, expanded, and seeded onto AlloDerm (LifeCell Corp, Branchburg, NJ), a cadaveric, acellular dermis, to produce ex vivo produced full-thickness mucosa equivalents. Histology of equivalents and their expression of immunoreactive Ki-67, a proliferation marker, and GLUT1, a membrane antigen seen in barrier tissues, were examined at 4, 11, and 18 days after seeding onto AlloDerm.

RESULTS

Progressive epithelial stratification was observed on day 4, 11, and 18 conjunctiva and oral mucosa equivalents. Ki-67 immunoreactivity progressively increased with cultured time in both types of equivalent, indicating the continued presence of actively proliferating cells. GLUT1 immunoreactivity, concentrated in the basal keratinocytes of stratified epithelia of both types of equivalents, mimicked native tissue and indicated a high glycolytic state of the basal cells.

CONCLUSIONS

Conjunctival and oral mucosal equivalents are similar to native tissue and demonstrate high proliferative and glycolytic states. Due to the similarity to conjunctiva, oral mucosal equivalents may be useful for eyelid reconstruction. Their advantages for surgical reconstruction include 1) ease of obtaining autogenous oral epithelium for expansion in vitro without the possibility of contaminating cellular- or serum-borne biologic agents, 2) growth of intact, confluent epithelia on rigid, transplantable human allogeneic dermis that may be surgically transplanted, and 3) reduced donor site morbidity and surgical time.

Development of a Tissue-Engineered Human Oral Mucosa: From the Bench to the Bed Side

The main objective of this publication is to make the reader aware of the complexity and steps that are necessary to make a Food and Drug Administration (FDA)-approved laboratory produced cell-based device, for use in clinical trials for reconstructive surgery. Most tissue-engineered cell-based devices are considered as 'human somatic cell therapy' and fall under the auspices of the Center of Biologic Evaluation and Research (CBER) and are considered a combination product by the FDA. We have illustrated the algorithm that is necessary to follow an Independent New Drug (IND) application by using our ex vivo produced oral mucosa equivalents (EVPOME), a tissue-engineered oral mucosa, as an example of a cell-based device that needs FDA approval prior to clinical application. By illustrating the experimental approach and presenting resulting data we attempt to explain each step that we address along the way.