Dual Sympathetic Input into Developing Salivary Glands.

Neuronal signaling is known to be required for salivary gland development, with parasympathetic nerves interacting with the surrounding tissues from early stages to maintain a progenitor cell population and control morphogenesis. In contrast, postganglionic sympathetic nerves arrive late in salivary gland development to perform a secretory function; however, no previous report has shown their role during development. Here, we show that a subset of neuronal cells within the parasympathetic submandibular ganglion (PSG) express the catecholaminergic marker tyrosine hydroxylase (TH) in developing murine and human submandibular glands. This sympathetic phenotype coincided with the expression of transcription factor Hand2 within the PSG from the bud stage (E12.5) of mouse embryonic salivary gland development. Hand2 was previously associated with the decision of neural crest cells to become sympathetic in other systems, suggesting a role in controlling neuronal fate in the salivary gland. The PSG therefore provides a population of TH-expressing neurons prior to the arrival of the postganglionic sympathetic axons from the superior cervical ganglion at E15.5. In culture, in the absence of nerves from the superior cervical ganglion, these PSG-derived TH neurons were clearly evident forming a network around the gland. Chemical ablation of dopamine receptors in explant culture with the neurotoxin 6-hydroxydopamine at early stages of gland development resulted in specific loss of the TH-positive neurons from the PSG, and subsequent branching was inhibited. Taken altogether, these results highlight for the first time the detailed developmental time course of TH-expressing neurons during murine salivary gland development and suggest a role for these neurons in branching morphogenesis.

Apoptosis in Early Salivary Gland Duct Morphogenesis and Lumen Formation.

Salivary glands are essential for the maintenance of oral health by providing lubrication and antimicrobial protection to the mucosal and tooth surfaces. Saliva is modified and delivered to the oral cavity by a complex multifunctional ductal system. During development, these ducts form as solid tubes, which undergo cavitation to create lumens. Apoptosis has been suggested to play a role in this cavitation process along with changes in cell polarity. Here, we show that apoptosis occurs from the very earliest stages of mouse salivary gland development, much earlier than previously reported. Apoptotic cells were observed in the center of the first epithelial stalk at early-stage embryonic day 12.5 (E12.5) according to both TUNEL staining and cleaved caspase 3 immunofluorescence. The presumptive lumen space was highlighted by the colocalization of a predictive lumen marker, cytokeratin 7. At E14.5, as lumens start to form throughout the glands, apoptotic expression decreased while cytokeratin 7 remained positive. In vitro inhibition of all caspases in E12.5 and E13.5 salivary glands resulted in wider ducts, as compared with the controls, and a defect in lumen formation. In contrast, no such defect in lumen formation was observed at E14.5. Our data indicate that apoptosis is involved during early stages of gland formation (E12.5 onward) and appears important for shaping the forming ducts.

Course of cystic fibrosis in 95 patients.

The course of 95 patients with cystic fibrosis is presented. Survivors have a mean follow-up period of over 14 years (minimum: 13 years). Of 45 patients diagnosed prior to extensive irreversible pulmonary involvement, only one has died and none is disabled. In contrast, of the other 50 patients diagnosed after substantial irreversible pulmonary disease was present, 26 have died. Mortality and morbidity has been greater in females. Possible factors contributing to the improving prognosis include early diagnosis, aggressive management with comprehensive care, easy access to specialized care, and improved antimicrobial therapy.

Course of cystic fibrosis in black patients.

Seventeen black patients showed typical sweat gland, gastrointestinal, and pulmonary manifestations of cystic fibrosis. There was an unusually high incidence of meconium ileus equivalent (35%). Three infant siblings of patients in this study had died of cystic fibrosis prior to referral of a family member to this center. One patient died at age four years after emotional problems interfered with the treatment program; status asthmaticus played a major role in his terminal respiratory failure. The remainder of the patients have had substantially less morbidity from pulmonary disease than a comparable, much larger group of white patients. Only one patient, age 28, who is married and employed full-time has severe pulmonary involvement as assessed by pulmonary function studies and chest roentgenogram. The 16 surviving patients have a mean age of 13 1/2 years after a mean follow-up period of 10 years. If black patients with cystic fibrosis survive infancy, they then, as a group, may have a relatively good prognosis.