Different Patterns of Cartilage Mineralization Analyzed by Comparison of Human, Porcine, and Bovine Laryngeal Cartilages.

Laryngeal cartilages undergo a slow ossification process during aging, making them an excellent model for studying cartilage mineralization and ossification processes. Pig laryngeal cartilages are similar to their human counterparts in shape and size, also undergo mineralization, facilitating the study of cartilage mineralization. We investigated the processes of cartilage mineralization and ossification and compared these with the known processes in growth plates. Thyroid cartilages from glutaraldehyde-perfused male minipigs and from domestic pigs were used for X-ray, light microscopic, and transmission electron microscopic analyses. We applied different fixation and postfixation solutions to preserve cell shape, proteoglycans, and membranes. In contrast to the ossifying human thyroid cartilage, predominantly cartilage mineralization was observed in minipig and domestic pig thyroid cartilages. The same subset of chondrocytes responsible for growth plate mineralization is also present in thyroid cartilage mineralization. Besides mineralization mediated by matrix vesicles, a second pattern of cartilage mineralization was observed in thyroid cartilage only. Here, the formation and growth of crystals were closely related to collagen fibrils, which served as guide rails for the expansion of mineralization. It is hypothesized that the second pattern of cartilage mineralization may be similar to a maturation of mineralized cartilage after initial matrix vesicles-mediated cartilage mineralization.

Different expression of 25-kDa heat-shock protein (Hsp25) in Meckel's cartilage compared with other cartilages in the mouse.

The 25-kDa heat-shock protein (Hsp25) is expressed in the cartilage of the growth plate and suggested to function in chondrocyte differentiation and degeneration. Using immunohistochemistry, we examined the temporal and spatial occurrence of Hsp25 in Meckel's cartilage in embryonic mice mandibles, and in other types of cartilage in both embryonic and adult mice. In adults, Hsp25 immunoreactivity was detected in the hypertrophic chondrocytes located in growth plates of long bones and in non-osteogenic laryngeal and tracheal cartilages. No chondrocytes in the resting or proliferating phase exhibited Hsp25 immunoreactivity. In the embryonic mandibles, resting and proliferating chondrocytes in the anterior and intermediate portions of Meckel's cartilage showed Hsp25 immunoreactivity from the 12th day of gestation (E12) through E15, whereas those in the posterior portion showed little or no immunoreactivity. After E16, the overall Hsp25 immunoreactivity in Meckel's cartilage substantially reduced in intensity, and little or no immunoreactivity was detected in the hypertrophic chondrocytes located in the degenerating portions of Meckel's cartilage. The antisense oligonucleotide for Hsp25 mRNA applied to the culture media of the mandibular explants from E10 embryos caused significant inhibition of the development of the anterior and middle portions of Meckel's cartilage. These results suggested that Hsp25 is essential for the development of Meckel's cartilage and plays different roles in Meckel's cartilage from those in the permanent cartilages and the cartilages undergoing endochondral ossification.

Cartilage tissue engineering using thyroid chondrocytes on a type I collagen matrix.

OBJECTIVE/HYPOTHESIS: Reconstructive procedures of the head and neck often require materials that offer long-term structural support. A problem that many surgeons have encountered is identifying a material that offers this support without rejection of the implanted material This has led many surgeons to prefer autologous cartilage However, autologous cartilage is of limited supply. Cartilage tissue engineering has become a new modality that allows investigators to harvest a small piece of cartilage and extract its chondrocytes for expansion in culture. These chondrocytes are applied to a matrix that will act as a scaffold and allow for cartilage growth. Finding a compatible matrix seems to be the limiting step in the progress of this research. We describe a new approach of tissue creation using bovine collagen matrices as templates onto which cells are seeded. STUDY DESIGN: Laboratory research. METHODS: Chondrocytes obtained from thyroid cartilage of dogs were seeded onto bovine collagen type I matrices and grown in vitro. Chondrocyte seeded matrices were evaluated histologically. RESULTS: Thyroid chondrocytes expressed themselves phenotypically by producing type II collagen in the presence of this type I collagen matrix. CONCLUSIONS: This study offers the preliminary findings on an exciting new type of matrix worth exploring in the ability to successfully engineer cartilage.

Laryngeal histologic findings in infants with palatal defects with or without craniofacial malformations.

The objective of this study was to determine whether specimens from infants with palatal defects (PDs) with or without craniofacial malformations (CFMs) exhibit aberrant laryngeal histologic findings compared with specimens from normal infants. Ten laryngeal specimens from infants with PDs with or without CFMs were histologically compared with 7 laryngeal specimens defined as normal from the same collection. Both groups were similar in terms of demographics and airway manipulation. All infants were prelingual. Comparisons were made at 3 levels: supraglottic, glottic, and subglottic. Histologically, no significant differences in primary laryngeal structures were found between the PD with or without CFM group and the group defined as normal. Acquired and intubation-type injuries, such as inflammation, ulceration, capillary congestion, and scar tissue, were more prevalent and severe in the study group. The primary laryngeal histologic findings of specimens from individuals with PDs with or without CFMs do not differ substantially from those from normal individuals; however, individuals with PDs do appear to be somewhat more susceptible to intubation injury and other acquired laryngeal injury. Meticulous airway management is essential.

Tendinous insertions in the human thyroid cartilage plate: macroscopic and histologic studies.

The zones of tendinuous insertion and origin of the sternothyroid muscle, the thyrohyoid muscle, the inferior constrictor muscle of the pharynx and the external part of the cricothyroid muscle were studied in adult larynges by macroscopy and light microscopy. The sternothyroid muscle is inserted in the superior and inferior thyroid tubercula and also in a tendinous arch, which extends between the two tubercula. In contrast to the descriptions found in most textbooks, the sternothyroid muscle has no attachment to the oblique line. The thyrohyoid muscle and the thyropharyngeal part of the inferior constrictor muscle of the pharynx originate in ventral and dorsal symmetry at the oblique line. X-rays permit a measurement of their original angles, resulting in a mean value of 36 degrees. According to these measurements, and electromyographic findings by other authors, both muscles can be regarded as a bipennate muscle from a functional point of view. Histologic studies indicate that the oblique line's zone of origin structurally resembles an areal periosteal-diaphysary tendinous insertion. In the non-ossified thyroid cartilage, the insertions in the region of the thyroid tubercula are similar to chondral-apophysary insertions of tendons in the limb skeleton. After ossification of the thyroid cartilage, they show the shape of circumscribed periosteal-diaphysary insertions. Osteogenesis of the laryngeal skeleton therefore affects the structure of the thyroid tubercula's tendinous insertions. From a mechanical point of view, the insertions in the thyroid cartilage function as extension-checking mechanisms, and also serve to balance the different elastic modules of the tendinous tissue and the cartilaginous or bony tissue.(ABSTRACT TRUNCATED AT 250 WORDS)