Characterization of a decellularized rat larynx: comparison between microscopy techniques.

BACKGROUND: No effective method has yet been developed to efficiently reconstruct the larynx and restore its function. Decellularization has recently been tested for this purpose with very promising results. The goal of decellularization is to remove cells leaving an intact scaffold made of an extracellular matrix (ECM). Although the use of hematoxylin/eosin and Masson trichrome stains is widely accepted to highlight tissue structure, the methods based on evaluation of collagen and elastin are considered highly variable. The aim of this study was to develop a whole organ decellularization protocol and compare the qualitative and quantitative efficiency of some microscopy techniques for collagen and elastin detection in paraffin-embedded tissues. METHODS: H&E, Masson Trichrome and DAPI staining as well as DNA quantification were used to evaluate decellularization efficiency. Van Gieson stain, Picrosirius Red stain (PRS) and multiphoton laser scanning microscopy (MPM) were carried out for collagen detection and quantitative assessment. Polarized PRS was used to investigate collagen network, and Weigert stain and MPM were used to detect and estimate elastin content. RESULTS: The decellularization process removed the cellular components without affecting glycosaminoglycan, collagen and elastin content. Concerning collagen quantification, Van Gieson stain underestimated collagen content, while PRS, apparently less fading, did not reach reliable results when used as quantitative method. MPM effectively quantified collagen content. Collagen fibers were visualized much better under polarized light microscopy, allowing to underline that decellularization process affects the homogeneity of 3D collagen network. Concerning elastin detection, Weigert stain and MPM produced overlapping results. CONCLUSIONS: An efficient protocol to decellularize the whole larynx was developed, allowing the removal of cells without affecting ECM integrity. The results supported the use of non-polarized PRS to highlight collagen, even the thin fibers, second harmonic generation for major fibrillar collagens and polarized PRS for 3D collagen network. Concerning elastin, Weigert stain and MPM showed similar results, thus the use of MPM, rather than that of the Weigert stain, may be suitable to avoid the additional time and costs of a histological staining.

Oculo-auriculo-vertebral spectrum: going beyond the first and second pharyngeal arch involvement.

INTRODUCTION: Intracranial vascular, bone, and brain abnormalities might be observed in oculo-auriculo-vertebral spectrum (OAVS) patients even though these structures do not derive embryologically from the first and second pharyngeal arches. This neuroimaging study investigated their type, frequency and phenotype correlations among OAVS patients. METHODS: Thirty-five OAVS patients (mean-age 4.8 ± 6.0 years; age range 0.3-30, 14 females) underwent head CT (all patients) and brain MRI (32 patients); 19 patients had a more severe phenotype (Goldenhar syndrome). Internal carotid artery hypoplasia/agenesia and abnormal course, brain abnormalities, internal acoustic canal stenosis/aplasia, cochlear-vestibular malformations, facial nerve bony canal anomalies, and oval window atresia were recorded. RESULTS: Nine of 35 (26%) OAVS patients showed internal carotid artery anomalies; 18/32 (56%) had protean brain MRI abnormalities, ranging from tegmental cap anomaly to mild ventriculomegaly, which were associated with Goldenhar syndrome (p < 0.001) and concomitant cranial nerve abnormalities (p = 0.004); 11/35 (31%) disclosed cochlear-vestibular abnormalities including Michel deformity, common cavity, cochlear hypoplasia, and incomplete partition type-1 that were associated with Goldenhar syndrome (p = 0.01) and ipsilateral VIII cranial nerve abnormalities (p < 0.001); 16/35 (46%, 23 sides) presented facial nerve bony canal abnormalities that were associated with Goldenhar syndrome (p < 0.001) and ipsilateral VII cranial nerve (p < 0.001) and cochlear-vestibular (p < 0.001) abnormalities; and 23/31 (74%, 31 sides) showed oval window atresia, always with concomitant ossicular chain dysplasia. CONCLUSIONS: Intracranial vascular, bone, and brain abnormalities in OAVS patients are strikingly common and heterogeneous. As their detection might impact significantly on clinical and surgical management of affected patients, accurate neuroimaging investigations should be included in the diagnostic work-up of OAVS.