A morphometric analysis of craniofacial growth and changes in spatial relations during secondary palatal development in human embryos and fetuses

Staged human embryos and fetuses in the Carnegie Embryological Collection were morphometrically analyzed to show craniofacial dimensions and changes in spatial relations, and to identify patterns that would reflect normal developmental events during palatal formation. Normal embryos aged 7–8 weeks postconception (Streeter-O'Rahilly stages 19–23) and fetuses aged 9–10 weeks postconception, in eight groups with mean crownrump (CR) lengths of 18–49 mm, were studied with cephalometric methods developed for histologic sections. In the 4-week period studied, facial dimensions increased predominantly in the sagittal plane with extensive changes in length (depth) and height, but limited changes in width. Growth of the mandible was more rapid than the nasomaxillary complex, and the length of Meckel's cartilage exceeded the length of the oronasal cavity at the time of horizontal movement of the shelves during stage 23. Simultaneously with shelf elevation, the upper craniofacial complex lifted, and the tongue and Meckel's cartilage extended forward beneath the primary palate. Analysis of spatial relations in the oronasal cavity showed that the palatomaxillary processes became separated from the tongue-mandibular complex as the head extended, and the tongue became positioned forward with growth of Meckel's cartilage. As the head position extended by 35°, the cranial base angulation was unchanged and the primary palate maintained a 90° position to the posterior cranial base. However, the sagittal position of the maxilla relative to the anterior cranial base increased by 20° between stages 19 and 23. In the late embryonic and early fetal periods, the mean cranial 128° and the mean maxillary position angulation of approximately 34° were similar to the angulations previously shown to be present later prenatally and postnatally. The results suggest that human patterns of cranial base angulation and maxillary position to the cranial base develop during the late embryonic period when the chondrocranium and Meckel's cartilage form the primary skeleton.     

Differential responses to parathyroid hormone‐related protein (PTHrP) deficiency in the various craniofacial cartilages

PTHrP null mutant mice exhibit skeletal abnormalities both in the craniofacial region and limbs. In the growth plate cartilage of the null mutant, a diminished number of proliferating chondrocytes and accelerated chondrocytic differentiation are observed. In order to examine the effect of PTHrP deficiency on the craniofacial morphology and highlight the differential feature of the composing cartilages, we examined the various cartilages in the craniofacial region of neonatal PTHrP deficient mice. The major part of the cartilaginous anterior cranial base appeared to be normal in the homozygous PTHrP deficient mice. However, acceleration of chondrocytic differentiation and endochondral bone formation was observed in the posterior part of the anterior cranial base and in the cranial base synchondroses. Ectopic bone formation was observed in the soft tissue‐running mid‐portion of the Meckel's cartilage, where the cartilage degenerates and converts to ligament in the course of normal development. The zonal structure of the mandibular condylar cartilage was scarcely affected, but the whole condyle was reduced in size. These results suggest the effect of PTHrP deficiency varies widely between the craniofacial cartilages, according to the differential features of each cartilage. Anat Rec 255:452–457, 1999. © 1999 Wiley‐Liss, Inc.     

Craniofacial structure in diastrophic dysplasia—a cephalometric study

Diastrophic dysplasia (DTD) is a well characterized, recessively inherited osteochondrodysplasia. Forty-eight patients with DTD were studied for craniofacial characteristics. Of these patients, 58% had cleft palate. A cephalometric analysis based on lateral cephalograms was performed. We observed a short anterior cranial base, vertical nasal bones, short and posteriorly positioned upper and lower jaws, increased anterior facial height, increase in the sagittal length of the body of the cervical vertebrae, and an abnormal dens of the second cervical vertebra. DTDST, in which mutations responsible for the disease occur, is a gene that codes for a sulphate transporter membrane protein. The craniofacial anomalies in DTD most likely result from deficient development and growth of cartilaginous structures and are probably due to defective sulfation of the proteoglycans of the cartilage. Am. J. Med. Genet. 72:266–274, 1997. © 1997 Wiley-Liss, Inc.     

Anatomical abnormalities in mandibulofacial dysostosis

A detailed dissection of the head and neck of a 7-month-old boy with mandibulofacial dysostosis is described and compared with other reported cases. A general growth retardation was found in the bones of the basicranium and calvaria as well as the face. The base of the skull was kyphotic, and the elements derived from the branchial arches articulated with the basicranium more anteriorly than usual. Certain middle ear structures were found to be extracranial. The facial muscles were generally normal except for the absence of elevators of the upper lip. The laryngeal cartilages were shortened anteroposteriorly, resulting in drastic reduction of the rima glottidis. The attachments of the masticatory muscles to the mandible suggested that the area of the temporomandibular joint had not completed normal differentiation, and that that part of the mandible which functioned as a condyle was actually an ossification around Meckel's cartilage. There was no infraorbital foramen, and the infraorbital neurovascular bundle was distributed instead to the palate. Clinical and functional correlations of the various defects are considered. Theories of pathogenesis are discussed on the basis of these findings. It is argued that these observations could be accounted for by an altered intercellular matrix with separate effects on skeletal growth and neural crest cell migration.     

Differential responses to parathyroid hormone-related protein (PTHrP) deficiency in the various craniofacial cartilages.

PTHrP null mutant mice exhibit skeletal abnormalities both in the craniofacial region and limbs. In the growth plate cartilage of the null mutant, a diminished number of proliferating chondrocytes and accelerated chondrocytic differentiation are observed. In order to examine the effect of PTHrP deficiency on the craniofacial morphology and highlight the differential feature of the composing cartilages, we examined the various cartilages in the craniofacial region of neonatal PTHrP deficient mice. The major part of the cartilaginous anterior cranial base appeared to be normal in the homozygous PTHrP deficient mice. However, acceleration of chondrocytic differentiation and endochondral bone formation was observed in the posterior part of the anterior cranial base and in the cranial base synchondroses. Ectopic bone formation was observed in the soft tissue-running mid-portion of the Meckel's cartilage, where the cartilage degenerates and converts to ligament in the course of normal development. The zonal structure of the mandibular condylar cartilage was scarcely affected, but the whole condyle was reduced in size. These results suggest the effect of PTHrP deficiency varies widely between the craniofacial cartilages, according to the differential features of each cartilage.     

Histological Development of the Fused Mandibular Symphysis in the Pig

The development of the mandibular symphysis in late fetal and postnatal pigs, Sus scrofa dom. (n = 17), was studied as a model for the early fusing symphysis of anthropoid primates, including humans. The suture-like ligaments occurring in species that retain a mobile symphysis are not present in the pig. Instead, cartilage is the predominant tissue in the mandibular symphysis prior to fusion. In late fetuses the rostrum of the fused Meckel's cartilages forms a minor posterior component of the symphysis whereas the major component is secondary cartilage, developing bilaterally and joined at the midline with mesenchyme. This remnant of Meckel's cartilage likely fuses with the flanking secondary cartilage. The overall composition of pig symphyseal histology in fetal and infant animals varies regionally and individually. Regions where the paired secondary cartilages abut in the midline resemble double growth plates. Chondrogenic growth in width of the symphysis is likely important in early stages, and central proliferation of mesenchyme is the probable source of new chondrocytes. Laterally, the chondrocytes hypertrophy near the bone fronts and are replaced by alveolar bone. Complete synostosis except for a small cartilage remnant had occurred in one 8-week-old postnatal specimen and all older specimens. Surprisingly, however, the initial phase of symphyseal fusion, observed in a 5-week-old postnatal specimen, involved intramembranous ossification of midline mesenchyme rather than endochondral ossification. Subsequently, fusion progresses rapidly at the anterior and labial aspects of the symphysis, leaving only a small postero-lingual cartilage pad that persists for at least several months. Anat Rec, 302:1372–1388, 2019. © 2018 Wiley Periodicals, Inc.     

Histochemical and Ultrastructural Study of Developing Gonial Bone With Reference to Initial Ossification of the Malleus and Reduction of Meckel's Cartilage in Mice

Development of mouse gonial bone and initial ossification process of malleus were investigated. Before the formation of the gonial bone, the osteogenic area expressing alkaline phosphatase and Runx2 mRNA was widely recognized inferior to Meckel's cartilage. The gonial bone was first formed within the perichondrium at E16.0 via intramembranous ossification, surrounded the lower part of Meckel's cartilage, and then continued to extend anteriorly and medially until postnatal day (P) 3.0. At P0, multinucleated chondroclasts started to resorb the mineralized cartilage matrix with ruffled borders at the initial ossification site of the malleus (most posterior part of Meckel's cartilage). Almost all CD31-positive capillaries did not run through the gonial bone but entered the cartilage through the site where the gonial bone was not attached, indicating the forms of the initial ossification site of the malleus are similar to those at the secondary ossification center rather than the primary ossification center in the long bone. Then, the reducing process of the posterior part of Meckel's cartilage with extending gonial bone was investigated. Numerous tartrate-resistant acid phosphatase-positive mononuclear cells invaded the reducing Meckel's cartilage, and the continuity between the malleus and Meckel's cartilage was completely lost by P3.5. Both the cartilage matrix and the perichondrium were degraded, and they seemed to be incorporated into the periosteum of the gonial bone. The tensor tympani and tensor veli palatini muscles were attached to the ligament extending from the gonial bone. These findings indicated that the gonial bone has multiple functions and plays important roles in cranial formation. Anat Rec, 302:1916–1933, 2019. © 2019 American Association for Anatomy     

Lack of association between avian cartilages of different embryological origins when maintained in vitro

The possibility that cartilages of differing embryological origins behave as separate types with respect to cell-to-cell associations was tested by placing the cut ends of transversely sectioned embryonic chick tibial cartilages (of mesodermal origin) in apposition to transversely sectioned Meckel's cartilages (a neural crest (ectodermal) cartilage) on the surface of a semi-solid organ culture medium and maintaining the combinations in vitro for five to ten days. Tibia-tibia and Meckel's cartilage-Meckel's cartilage (homotypic) combinations, which served as controls, became united by a common extracellular matrix and by the proliferation of chondroblasts. Analysis of combinations where one partner had been prelabelled with ³H-thymidine indicated that chondroblasts intermingled at the contact zone. In contrast, tibia-Meckel's cartilage (heterotypic) combinations became separated by a layer of fibrous tissue. The chondroblasts at the contact zone failed to intermingle. We conclude that avian embryonic chondrocytes are not all equivalent and that part of their non-equivalence could be related to their embryological origin either from the mesoderm or from the ectodermal neural crest.     

Stage-specific expression patterns of alkaline phosphatase during development of the first arch skeleton in inbred C57BL/6 mouse embryos

Timing and pattern of expression of alkaline phosphatase was examined during early differentiation of the 1st arch skeleton in inbred C57BL/6 mice. Embryos were recovered between 10 and 18 d of gestation and staged using a detailed staging table of craniofacial development prior to histochemical examination. Expression of alkaline phosphatase is initiated at stage 20.2 in the plasma membrane of mesenchymal cells in the distal region of the first arch. Expression is strongest in osteoid (unmineralised bone matrix) and presumptive periosteum at stage 21.32. Mineralisation begins at stage E23. Expression is present in the mineralised bone matrix. Secondary cartilages form in the condylar and angular processes by stage M24. The cartilaginous cells and surrounding cells in the processes are all alkaline phosphatase-positive and surrounded by the common periosteum, suggesting that progenitor cells of the processes, dentary ramus and secondary cartilages all originate from a common pool. Nonhypertrophied chondrocytes of Meckel's cartilage express alkaline phosphatase at stage M23. Expression in these chondrocytes is preceded by the expression in their adjacent perichondrium. This is true of chondrocytes in all other cranial cartilages examined. 3-D reconstruction of expression in Meckel's cartilage also revealed that the chondrocytes of Meckel's cartilage which express alkaline phosphatase and the matrix of which undergoes mineralisation are those surrounded by the alkaline phosphatase-positive dentary ramus. By stage 25, coincident with mineralisation in the distal section of Meckel's cartilage, most chondrocytes are strongly positive. The perichondria of malleus and incus cartilages express alkaline phosphatase at stage M24. Nonhypertrophied chondrocytes along these perichondria also express alkaline phosphatase. Superficial and deep cells in the dental laminae of incisor and 1st molar teeth become alkaline phosphatase-positive at the bud stage, stages 21.16 and 21.32, respectively. Dental papillae are negative until stage M24 when alkaline phosphatase expression begins in the dental papillae and follicles of the incisor teeth and the dental follicles of the 1st molar teeth. The dental papillae of the 1st molar teeth express alkaline phosphatase at stage 25. Expression in the dental papillae and follicles appears to coincide with cellular differentiation of follicle from papilla. The presumptive squamosal, ectotympanic and gonial membrane bones, lingual oral epithelial cells connected to the dental laminae of the incisor teeth, hair follicle papillae and sheath and surrounding dermis all express alkaline phosphatase in a stage-specific manner.     

Microanatomy of the Mandibular Symphysis in Lizards: Patterns in Fiber Orientation and Meckel's Cartilage and Their Significance in Cranial Evolution

Although the mandibular symphysis is a functionally and evolutionarily important feature of the vertebrate skull, little is known about the soft‐tissue morphology of the joint in squamate reptiles. Lizards evolved a diversity of skull shapes and feeding behaviors, thus it is expected that the morphology of the symphysis will correspond with functional patterns. Here, we present new histological data illustrating the morphology of the joint in a number of taxa including iguanians, geckos, scincomorphs, lacertoids, and anguimorphs. The symphyses of all taxa exhibit dorsal and ventral fibrous portions of the joints that possess an array of parallel and woven collagen fibers. The middle and ventral portions of the joints are complemented by contributions of Meckel's cartilage. Kinetic taxa have more loosely built symphyses with large domains of parallel‐oriented fibers whereas hard biting and akinetic taxa have symphyses primarily composed of dense, woven fibers. Whereas most taxa maintain unfused Meckel's cartilages, iguanians, and geckos independently evolved fused Meckel's cartilages; however, the joint's morphologies suggest different developmental mechanisms. Fused Meckel's cartilages may be associated with the apomorphic lingual behaviors exhibited by iguanians (tongue translation) and geckos (drinking). These morphological data shed new light on the functional, developmental, and evolutionary patterns displayed by the heads of lizards. Anat Rec 293:1350–1359, 2010. © 2010 Wiley‐Liss, Inc.     

Sonic hedgehog from pharyngeal arch 1 epithelium is necessary for early mandibular arch cell survival and later cartilage condensation differentiation

Background: Morphogenesis of vertebrate craniofacial skeletal elements is dependent on a key cell population, the cranial neural crest cells (NCC). Cranial NCC are formed dorsally in the cranial neural tube and migrate ventrally to form craniofacial skeletal elements as well as other tissues. Multiple extracellular signaling pathways regulate the migration, survival, proliferation, and differentiation of NCC. Results: In this study, we demonstrate that Shh expression in the oral ectoderm and pharyngeal endoderm is essential for mandibular development. We show that a loss of Shh in these domains results in increased mesenchymal cell death in pharyngeal arch 1 (PA1) after NCC migration. This increased cell death can be rescued in utero by pharmacological inhibition of p53. Furthermore, we show that epithelial SHH is necessary for the early differentiation of mandibular cartilage condensations and, therefore, the subsequent development of Meckel's cartilage, around which the dentary bone forms. Nonetheless, a rescue of the cell death phenotype does not rescue the defect in cartilage condensation formation. Conclusions: Our results show that SHH produced by the PA1 epithelium is necessary for the survival of post‐migratory NCC, and suggests a key role in the subsequent differentiation of chondrocytes to form Meckel's cartilage. Developmental Dynamics 244:564–576, 2015. © 2015 Wiley Periodicals, Inc.     

Cephalometric growth analyses of the human upper face region during the last two trimesters of gestation

This study was designed to demonstrate quantitative growth trends in the human upper face region before birth. Photographs of 68 sagittally sectioned fetal heads were measured using a series of linear and angular measurements for changing height, length and shape. Cross-sectional types of data were treated with a statistical model which tested for linearity of the data, correlation between growth changes and increasing fetal age, significance of the differences between rates of change in related upper face regions and the general significance of the trends shown in the study. Pooled data for the second and third trimesters suggested three distinct growth trends. Linear measurements of the cranial base, nasal area, and plate correlated significantly with increasing crown-rump length. Finally, a composite upper face profile for the sample suggested a relative migratio of the region downward and forward away from the anterior cranial base and the hypophyseal fossa. These three trends collectively demonstrated that the pattern of upper facial growth before birth involves progressive enlargement of a relatively static profile. It should be understood that this pattern is a group trend as shown by cross-sectional sampling of many individuals over a period of time with no individual being measured more than once. Conversely, variabilities in a specific individual's growth are most appropriately demonstrated by measuring that individual several times throughout some time span, i.e., by longitudinal sampling. Studies of the human fetus are restricted generally to the cross-sectional sampling technique. The close similarly of these prenatal trends with those reported for postnatal craniofacial growth suggests that certain patterns of facial growth in childhood can be seen as early as the beginning of the fetal period and emphasizes the continuum of human development.     

Matrix metallproteinases and TIMP-1 localization at sites of osteogenesis in the craniofacial region of the rabbit embryo

Background: The matrix metalloproteinases (MMPs) are a family of closely related enzymes, the principal members being the collagenases, gelatinases, and stromelysins. They are synthesized and secreted by connective tissue cells and are capable of degrading all the components of connective tissue matrices at physiological pH. Methods: Patterns of synthesis and distribution of MMPs and their inhibitor, tissue inhibitor of metalloproteinases-1 (TIMP-1), are documented in the craniofacial region at sites of bone formation during both intramembranous (e.g., calvaria, maxilla, and mandible) and endochondral ossification (e.g., cartilaginous cranial base and synchondroses) using indirect immunolocalization. Results: MMPs and TIMP-1 were detected both as bright intracellular accumulations, indicating active synthesis, and as diffuse matrix-bound extracellular deposits. Gelatinase-A had an extensive distribution in osteogenic tissues and was detected both in cells of the periosteum and spongiosum and as extracellular deposits in the osteoid layer of newly formed bone. In addition, gelatinase-AB synthesis was detected in osteoclasts. All regions of the early cartilaginous cranial base produced MMPs and TIMP-1 were also documented in early tooth germs and in Meckel's cartilage. Conclusions: These data document a prominent role for MMPs, and in particular gelatinase-A, in mediating matrix degradation during osteogenesis. Their detection in tooth germs and Meckel's cartilage further indicates a role for MMPs and TIMP-1 in matrix turnover during morphogenesis. © 1995 Wiley-Liss, Inc.     

Distribution of Matrix Proteins in Perichondrium and Periosteum During the Incorporation of Meckel's Cartilage into Ossifying Mandible in Midterm Human Fetuses: An Immunohistochemical Study

Immunohistochemical localization of versican and tenascin‐C were performed; the periosteum of ossifying mandible and the perichondrium of Meckel's cartilage, of vertebral cartilage, and of mandibular condylar cartilage were examined in midterm human fetuses. Versican immunoreactivity was restricted and evident only in perichondrium of Meckel's cartilage and vertebral cartilage; conversely, tenascin‐C immunoreactivity was only evident in periosteum. Therefore, versican and tenascin‐C can be used as molecular markers for human fetal perichondrium and fetal periosteum, respectively. Meckel's cartilage underwent endochondral ossification when it was incorporated into the ossifying mandible at the deciduous lateral incisor region. Versican immunoreactivity in the perichondrium gradually became weak toward the anterior primary bone marrow. Tenascin‐C immunoreactivity in the primary bone marrow was also weak, but tenascin‐C positive areas did not overlap with versican‐positive areas; therefore, degradation of the perichondrium probably progressed slowly. Meanwhile, versican‐positive perichondrium and tenascin‐C‐positive periosteum around the bone collar in vertebral cartilage were clearly discriminated. Therefore, the degradation of Meckel's cartilage perichondrium during endochondral ossification occurred at a different rate than did degradation of vertebral cartilage perichondrium. Additionally, the perichondrium of mandibular condylar cartilage showed tenascin‐C immunoreactivity, but not versican immunoreactivity. That perichondrium of mandibular condylar cartilage has immunoreactivity characteristic of other periosteum tissues may indicate that this cartilage is actually distinct from primary cartilage and representative of secondary cartilage. Anat Rec, 297:1208–1217, 2014. © 2014 Wiley Periodicals, Inc.     

Autophagy Prior to Chondrocyte Cell Death During the Degeneration of Meckel's Cartilage

The central portion of Meckel's cartilage degenerates almost immediately after birth. Whether autophagy is involved in this process remains unclear. Thus, to explore the role of autophagy during this process, we have detected the expression of autophagy and apoptosis‐related markers in embryonic mice. In E15, Beclin1 and LC3 expressions were weak and negative in Meckel's cartilage, respectively. In E16, chondrocytes of the central portion became hypertrophic. Moderate immunoreactivities of Beclin1 and LC3 were observed in prehypertrophic and hypertrophic chondrocytes of the central portion. In E17, the degradation occurred in the central portion and expanded anteriorly and posteriorly. Beclin1 expression was observed in Meckel's cartilage with an increase in the hypertrophic chondrocytes of the central portion. The expression of LC3 was detected specifically in terminally differentiated hypertrophic chondrocytes. The mRNA expressions of LC3 and Beclin1 from E15 to E17 significantly increased. This result is in accord with the histologic findings. Terminal deoxynucleotidyltransferase‐mediated dUTP‐biotin nick‐end labeling assay and Caspase 3 expression demonstrated that apoptosis was detected in the lateral part of terminal hypertrophic chondrocytes along the degeneration area of Meckel's cartilage. In addition, Bcl2 expression increased significantly from E15 to E17. These results indicate that autophagy is involved in hypertrophic chondrocytes during the degradation of Meckel's cartilage and occurs prior to chondrocyte cell death during this process. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

Comparison of amounts and properties of collagen and proteoglycans in condylar, costal and nasal cartilages

In this study we compared the compositions of extracellular matrices of condylar, costal and nasal cartilages to characterize differences in growth patterns in relation to matrix composition. Condylar, costal and nasal cartilages of 25- and 35-day-old rabbits were extracted and subjected to bio- and histochemical analysis to determine total amounts of collagen and amounts and aggregating properties of proteoglycans. We found that proteoglycan content and aggregate formation were greatest in nasal cartilage, and lower in costal and markedly lower in condylar cartilage. The amount of proteoglycans increased by varying amounts in all samples with age. Collagen content was highest in costal cartilage. In 25-day-old rabbits the quantity of collagen in condylar cartilage exceeded that in nasal cartilage. In 35-day-old rabbits the quantities were nearly the same. It is suggested that collagen does not only provide tensile strength, but counteracts forces responsible for interstitial growth such as osmotic pressure. Based on the results, it seems that the amount of proteoglycans is greater in cartilages, which have greater independent growth potential. Variations in increase in amount of proteoglycans with age could reflect differences in the timing of growth of such cartilages.     

Genetic disruption of CYP26B1 severely affects development of neural crest derived head structures,but does not compromise hindbrain patterning

Cyp26b1 encodes a cytochrome‐P450 enzyme that catabolizes retinoic acid (RA), a vitamin A derived signaling molecule. We have examined Cyp26b1^?/? mice and report that mutants exhibit numerous abnormalities in cranial neural crest cell derived tissues. At embryonic day (E) 18.5 Cyp26b1^?/? animals exhibit a truncated mandible, abnormal tooth buds, reduced ossification of calvaria, and are missing structures of the maxilla and nasal process. Some of these abnormalities may be due to defects in formation of Meckel's cartilage, which is truncated with an unfused distal region at E14.5 in mutant animals. Despite the severe malformations, we did not detect any abnormalities in rhombomere segmentation, or in patterning and migration of anterior hindbrain derived neural crest cells. Abnormal migration of neural crest cells toward the posterior branchial arches was observed, which may underlie defects in larynx and hyoid development. These data suggest different periods of sensitivity of anterior and posterior hindbrain neural crest derivatives to elevated levels of RA in the absence of CYP26B1. Developmental Dynamics 238:732–745, 2009. © 2009 Wiley‐Liss, Inc.     

Meckel's cartilage in the human embryo and fetus

This work studied the development of the ventral part of Meckel's cartilage in a series of human embryos (classified in stages) and fetuses. These stages appeared particularly important: stage 16, appearance of Meckel's cartilage; stage 20, beginning of membranous ossification of mandible; and stage 23, end of the embryonic period (8th week). The primitive bony nodule which develops from the embryonic mesenchyme appears as a double bony layer forming a groove containing the neurovascular bundle, into which the dental lamina is also invaginated. It was concluded that during the fetal period, the cartilage participates in the formation of the body of the mandible in an area close to the mental foramen via endochondral ossification. The cartilage disappears in parallel with the development of ossification by the sixth month. © 1994 Wiley-Liss, Inc.     

Aggregation of proteoglycans in cephalic, epiphyseal and articular cartilages in growing sheep

The purpose of this study was to determine whether there are age and site related differences in proteoglycan aggregation in craniofacial and epiphyseal cartilages from neonatal and two-month-old lambs. Proteoglycans were extracted using a dissociative extraction method, and aggregates and monomers separated with molecular sieving. Only a small proportion of the proteoglycans were isolated as aggregates in the articular and mandibular condylar cartilage of the neonatal animals, while in the nasal septal, epiphyseal and synchondrosal cartilages of the same animals the portion of proteoglycans isolated as aggregates, was 3 to 6 times as high. During the first 2 months of postnatal development the proportion of proteoglycans isolated as aggregates tripled in the articular and mandibular condylar cartilages, it decreased substantially in the anterior and posterior nasal septum, while it decreased slightly in the other cartilages. These observations indicate that there are age and site related differences in the extent of proteoglycans isolated as aggregates in cephalic, epiphyseal and articular cartilages.     

Clonal proliferation and cell density of chondrocytes isolated from human fetal epiphyseal, human adult articular and nasal septal cartilage. Influence of hormones and growth factors

The present study characterizes the cell density and cellular growth characteristics of functionally and morphogenetically different human cartilages. In fetal epiphyseal, in postnatal nasal septal and in articular cartilage the influence of aging on cell density and in vitro growth characteristics were investigated. Cell density was highest in fetal epiphyseal cartilage and lowest in articular cartilage. In vitro growth of isolated chondrocytes as measured by clonal growth in a semisolid assay was almost identically high in fetal epiphyseal and septal cartilage and significantly lower in articular cartilage. Cell density increased with age in the nasal septal cartilage whereas no age dependency was found in the other cartilages. The stimulatory effects of human biosynthetic insulin, human growth hormone and partially purified IGF I on clonal growth of chrondrocytes were assessed. Only IGF I stimulated clonal growth of chondrocytes and its stimulatory effect was significantly higher in postnatal than in fetal chondrocytes.