Repair of the tympanic membrane with urinary bladder matrix

Abstract

Objectives/hypothesis: To test urinary bladder matrix (UBM) as a potential treatment for tympanic membrane (TM) healing and regeneration.

Study design: This prospective pilot study was designed to provide both qualitative and semiquantitative assessment of temporal and spatial healing events in the chinchilla model of chronic TM perforations with and without UBM patching.

Methods: Bilateral myringotomies were performed and repeated as necessary to create subtotal perforations over an 8-week period. Myringoplasty was then performed, with left TMs serving as controls and right TMs receiving UBM patches. TMs were excised at 4 weeks, 8 weeks, and 12 weeks. Fixed tissue samples were characterized for gross morphology, then processed for microscopic evaluation.

Results: Chronic perforations were maintained with one or more repeated myringotomies. Although both control and patched TMs were thicker than native tissue, patched TMs were transparent and uniform in thickness without any inclusions. UBM patches were readily degraded and replaced by newly deposited and organized host tissue that recapitulated the native TM layers.

Conclusions: UBM scaffolds were an effective biological scaffold for TM closure and tissue remodeling, leading to thicker than normal anatomy but otherwise normal morphology. Future studies are required to determine functional and temporal outcomes as well as alternative patch orientations. The results show particular promise as a superior alternative means of reconstructing not only chronic TM perforations but also dimeric TMs associated with retraction pockets and atelectasis. Laryngoscope, 2009.

Fig. 1

(A) Number of TMs that required re-perforations, (B) the average time until each re-perforation, and (C) frequency for successive re-perforations for left and right TMs through the 8 week perforation period. As time progressed, the number of TMs requiring re-perforations decreased. Values represent means based on n = 11 for left and right TMs.

Fig. 2

(A) Average perforation size and (B) crust removal as an indicator of healing for left and right TMs through the 8 week perforation period. On average, perforations were maintained at a medium size despite indicators of healing. Perforations were scored based on their size: none = 0, small = 1 (less than 25%), medium = 2 (25% to 50%), and large = 3 (greater than 50%). Values represent means based on n = 11 for left and right TMs.

Fig. 3

Crust presence as an indicator of healing through the 12-week healing period for controls (left) and tympanic membranes (TMs) treated with urinary bladder matrix (UBM) patches (right). Crusts persisted on more of the right TMs after treatment with UBM patches with no perforations present. Values represent means based on n = 11 for left and right TMs.

Fig. 4

Examples of gross morphology of intact excised tympanic membranes (TMs) at 4 weeks, 8 weeks, and 12 weeks for controls (left) and TMs treated with urinary bladder matrix (UBM) patches (right). TMs treated with UBM patches appeared more uniform and transparent. TMs were visualized medially with a dissecting microscope. S = superior, I = inferior, P = posterior, and A = anterior regions of the TMs. Scale bar represents 5 mm, and dotted circles represent perforation areas without (left) and with (right) UBM patches.

Fig. 5

Representative histological sections (hematoxylin and eosin stained) of control (left) and tympanic membranes TMs treated with urinary bladder matrix (UBM) patches (right) at 4 weeks, 8 weeks, and 12 weeks. TMs treated with UBM patches exhibit larger but more uniform thicknesses across the tissue. Entire TM cross-sections were imaged with a dissecting microscope. M = mucosal side, E = squamous epithelial side, P = posterior region, and A = anterior region of the TMs. Scale bar represents 5 mm.

Fig. 6

Thickness of control tympanic membranes (TMs) (left) are less than TMs treated with urinary bladder matrix patches (right) at 4 weeks, 8 weeks, and 12 weeks. TM cross-sections were visualized with a 4× objective with light microscopy, and successive images were quantified based on thresholding the entire TM areas at a constant length (7.91 mm ± 0.41 mm) in successive images. Values were normalized to left and right native TMs of n = 2 and n = 3, respectively; for n = 2 and n = 3 left and right TMs at 4 weeks, respectively; for n = 4 for both left and right TMs at 8 weeks; and n = 2 for right TMs at 12 weeks (left TMs were not evaluated since all of them had perforations at 12 weeks).

Fig. 7

Representative histological sections stained with Masson’s trichrome of control tympanic membranes (TMs) (left) and TMs treated with urinary bladder matrix (UBM) patches (right) at 4 weeks, 8 weeks, and 12 weeks. TMs treated with UBM patches were thicker and exhibited more organized collagen and showed a layer of ciliated cells at 12 weeks (arrow). The epithelium of the control TMs at 12 weeks had grown around the edge of the perforation instead of closing. TMs were visualized with a 40× oil immersion objective with light microscopy. M = mucosal side, E = squamous epithelial side, P = posterior region, and A = anterior region of the TMs. Scale bar represents 40 μm. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Fig. 8

Control tympanic membranes (TMs) exhibited (A) small inclusions and (B) fibrous nodules (arrows) that were not evident in TMs treated with urinary bladder matrix patches. TMs were visualized with a 40× oil immersion objective with light microscopy. M = mucosal side, E = squamous epithelial side, P = posterior region, and A = anterior region of the TMs. Scale bar represents 40 μm. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]