Transcription and microRNA Profiling of Cultured Human Tympanic Membrane Epidermal Keratinocytes

State of the art regeneration of the tympanic membrane

PURPOSE OF REVIEW

One of the most common diseases of the tympanic membrane is a perforation, and tympanoplasty is one of the more common procedures in otolaryngology. Tympanic membrane regeneration and bioengineering aim to improve the success rate of the procedure, increase the availability of different scaffolds and provide innovative tools that will simplify the surgical technique and make it accessible for surgeons with varying expertise level. This review aims to raise awareness of current tissue engineering developments in tympanic membrane regeneration and how they may augment current clinical practices. We focus here on achievements in tympanic membrane cell cultures and on innovations in development of new scaffolds and growth factors that enhance regeneration of patient's native tympanic membranes.

RECENT FINDINGS

In recent years, great achievements were reached in the field of tympanic membrane regeneration in the three hallmarks of bioengineering: cells, scaffolds and bioactive molecules. New techniques for modeling normal tympanic membrane proliferation were developed, as well as for isolation and expansion of normal tympanic membrane keratinocytes from miniature samples of scarred tissue. Ongoing clinical trials aim to seal the perforation by applying different scaffolds infiltrated by growth factors on the tympanic membrane.

SUMMARY

Research efforts in tympanic membrane regeneration continue to seek the ideal single tissue-engineered substitute. Recent advances in tympanic membrane bioengineering include new types of scaffolds that may augment and provide a safe and effective alternative to the current gold-standard autograft. New bioactive molecules may simplify the surgical procedure and reduce surgical time by augmenting the native tympanic membrane regeneration. Several groups of bioengineering scientists and neurotologists are continuing to move forward and develop new strategies, seeking to create a fully functional tissue-engineered tympanic membrane.

The Feasibility to Isolate and Expand Tympanic Membrane Squamous Epithelium Stem Cells From Scarred Perforation Margins

HYPOTHESIS

The scarred rim of chronic tympanic membrane (TM) perforation contains keratinocytes with potential for regeneration while maintaining their morphological and genetic characteristics.

BACKGROUND

The squamous epithelium of the TM has a good regeneration capacity. Successful isolation and expansion of human TM keratinocytes (hTMKR) was reported from a full, en-bloc, healthy TM.

METHODS

Trimmed margins of the TM perforation (harvested during tympanoplasty) underwent enzymatic digestion (collagenase or trypsin) and were seeded either with serum-containing medium (SCM) or keratinocyte serum-free medium (KSFM) and progenitor cell growth medium (PR) (KSFM:PR, 1:1). Gene expression analysis by real-time qRT-PCR was used to compare between human TM cells derived from scarred perforation margins (hTMKR), normal human skin keratinocytes (NhSKR), and human fibroblasts.

RESULTS

Twelve patients were included in the study. In 9 of 12 cases (75%) single-cell isolation with fibroblastic or epithelial cell morphology (or both) was achieved. Cells seeded with KSFM:PR yielded epithelial morphology (hTMKR) while SCM culturing resulted in a fibroblastic morphology (hTMFib). Gene expression analysis revealed significant higher expression of VCAN (p = 0.002) and FOXC2 (p = 0.015) at the mRNA levels (normal hTMKR markers) in hTMKR compared to NhSKR. In addition, a comparison of gene expression between hTMKR and hTMFib revealed significantly higher levels of both VCAN (p = 0.045) and SLC6A14 (p = 0.036) among hTMKR.

CONCLUSION

For the first time, we developed a protocol to isolate hTMKR from scarred TM perforation margins. Furthermore, we succeeded in achieving tissue expansion that preserved the characteristic of healthy TM cells. This study bridges "regenerative medicine" approach with clinical and surgical objectives.