In vitro regulation of proliferation and differentiation within a postnatal growth plate of the cranial base by parathyroid hormone-related peptide (PTHrP).

Parathyroid hormone-related peptide (PTHrP) is known to be an important regulator of chondrocyte differentiation in embryonic growth plates, but little is known of its role in postnatal growth plates. The present study explores the role of PTHrP in regulating postnatal chondrocyte differentiation using a novel in vitro organ culture model based on the ethmoidal growth plate of the cranial base taken from the postnatal day 10 mouse. In vitro the ethmoidal growth plate continued to mineralize and the chondrocytes progressed to hypertrophy, as observed in vivo, but the proliferative zone was not maintained. Treatment with PTHrP inhibited mineralization and reduced alkaline phosphatase (ALP) activity in the hypertrophic zone in the ethmoidal growth plates grown ex vivo, and also increased the proliferation of non-hypertrophic chondrocytes. In addition, exogenous PTHrP reduced the expression of genes associated with terminal differentiation: type X collagen, Runx2, and ALP, as well as the PTH/PTHrP receptor (PPR). Activation of the protein kinase A pathway using 8-Br-cAMP mimicked some of these pro-proliferative/anti-differentiative effects of PTHrP. PTHrP and PPR were found to be expressed within the ethmoidal growth plate using semi-quantitative PCR, and in other cranial growth plates such as the spheno-occipital and pre-sphenoidal synchondroses. These results provide the first functional evidence that PTHrP regulates proliferation and differentiation within the postnatal, cranial growth plate. J. Cell. Physiol. 219: 688-697, 2009. (c) 2009 Wiley-Liss, Inc.

Craniofacial skeletal deviations following in utero exposure to the anticonvulsant phenytoin: monotherapy and polytherapy.

OBJECTIVE: To identify and quantify the craniofacial effects from prenatal exposure to phenytoin monotherapy and polytherapy using cephalometric, hand-wrist, and panoramic radiographs and to determine if such deviations persist with age. DESIGN: Craniofacial structures of 28 anticonvulsant-exposed individuals were evaluated using 20 landmarks in lateral cephalometric radiographs and 19 landmarks in frontal cephalometric radiographs. Skeletal maturity was assessed using hand-wrist radiographs. Dental maturity and the presence of dental anomalies were evaluated using panoramic radiographs. Eleven individuals were re-evaluated 7 years later, on average, to determine the persistence of any measured deviations. SETTING AND SAMPLE POPULATION: Department of Growth and Development, Harvard School of Dental Medicine and Massachusetts General Hospital. Patients were recruited from several sources. OUTCOME MEASURE: The evaluated dimensions included linear, angular, and proportional measures. RESULTS: The most common deviations were decreased height and length of the maxilla, decreased length of the posterior cranial base, length of the mandible, cranial width and level of the cribriform plate, and a decrease in the Wits Appraisal assessment. The deviations were more significant in the polytherapy-exposed individuals than in the monotherapyexposed individuals. These deviations, especially in the maxilla, persisted with age as revealed in a re-evaluation of 11 individuals. CONCLUSION: The craniofacial skeletal findings among individuals exposed in utero to phenytoin monotherapy or phenytoin polytherapy, when considered in aggregate, suggest a mild pattern of maxillary hypoplasia that becomes more pronounced with age.

Chloroform-induced olfactory mucosal degeneration and osseous ethmoid hyperplasia are not associated with olfactory deficits in Fischer 344 rats.

Adult female F-344 rats were trained (avoidance rate > 70%) over four days with a coupled tone- (n = 10 rats/dose) or 2 ppm acetaldehyde-cued (n = 6 rats/dose) foot shock paradigm. Rats were gavaged with chloroform dissolved in corn oil for 5 days/week for 3 week at 0 or 400 (tone-cued) or 0, 34, 100, or 400 (odor-cued) mg/kg body weight/day. Tone-cued response was reevaluated 6, 16, and 38 days after the first chloroform dose (day 1). Olfaction was assessed on days 6-7, 20-21, and 41-42 using 2 or 0.0002 ppm acetaldehyde. Nasal histopathology (n = 4-5 rats/dose) was assessed on days 6, 20, and 42. Significantly decreased body weights were observed following a single 100 or 400 mg/kg chloroform dose. Body weights in the 400 mg/kg/day chloroform group remained depressed for 17 days. Histopathology revealed degenerative changes in olfactory mucosa and underlying ethmoid turbinate bones that were essentially identical in nature and severity, including dose-response and progression, to those reported previously for chloroform gavage (Larson et al., Food Chem. Toxicol., 1995;33:443 456). At all dose level and sacrifice timepoints, however, regions of morphologically normal olfactory mucosa were present, especially in dorsal medial and ventral lateral regions of the nose. Neither odor- nor tone-cued avoidance behaviors were affected, indicating that even fairly severe and extensive chloroform-induced olfactory mucosal degeneration is not associated with a detectable olfactory deficit in rats.