elastin and Respiratory-Distress-Syndrome--Newborn

We have isolated mesenchymal stem cells (MSCs) from tracheal aspirates of premature infants with respiratory distress. We examined the capacity of MSCs to differentiate into myofibroblasts, cells that participate in lung development, injury, and repair. Gene expression was measured by array, qPCR, immunoblot, and immunocytochemistry. Unstimulated MSCs expressed mRNAs encoding contractile (e.g., ACTA2, TAGLN), extracellular matrix (COL1A1 and ELN), and actin-binding (DBN1, PXN) proteins, consistent with a myofibroblast phenotype, although there was little translation into immunoreactive protein. Incubation in serum-free medium increased contractile protein (ACTA2, MYH11) gene expression. MSC-conditioned medium showed substantial levels of TGF-beta1, and treatment of serum-deprived cells with a type I activin receptor-like kinase inhibitor, SB-431542, attenuated the expression of genes encoding contractile and extracellular matrix proteins. Treatment of MSCs with TGF-beta1 further induced the expression of mRNAs encoding contractile (ACTA2, MYH11, TAGLN, DES) and extracellular matrix proteins (FN1, ELN, COL1A1, COL1A2), and increased the protein expression of alpha-smooth muscle actin, myosin heavy chain, and SM22. In contrast, human bone marrow-derived MSCs failed to undergo TGF-beta1-induced myofibroblastic differentiation. Finally, primary cells from tracheal aspirates behaved in an identical manner as later passage cells. We conclude that human neonatal lung MSCs demonstrate an mRNA expression pattern characteristic of myofibroblast progenitor cells. Autocrine production of TGF-beta1 further drives myofibroblastic differentiation, suggesting that, in the absence of other signals, fibrosis represents the "default program" for neonatal lung MSC gene expression. These data are consistent with the notion that MSCs play a key role in neonatal lung injury and repair.

Topics: Actins; Cell Differentiation; Cells, Cultured; Collagen Type I; Collagen Type I, alpha 1 Chain; Elastin; Female; Gene Expression Profiling; Humans; Hydroxamic Acids; Infant, Newborn; Infant, Premature; Lung; Male; Mesenchymal Stem Cells; Microfilament Proteins; Muscle Proteins; Neuropeptides; Paxillin; Respiratory Distress Syndrome, Newborn; RNA, Messenger; Transforming Growth Factor beta1

During a series of studies investigating the maturational response to antenatal glucocorticoids, we observed that 70% of lambs delivered at 128 d gestation (term = 150 d), 24 h after a single injection of 0.5 mg/kg betamethasone or betamethasone + L-thyroxine (15 microgram/kg), developed pulmonary interstitial emphysema (PIE), compared with less than 5% of control animals or animals delivered 48 h or 7 d after hormone treatment. This study examined whether the lungs of animals that developed PIE were functionally or structurally different from those that did not. Lambs were mechanically ventilated for 40 min after cesarean section delivery. Hormone-treated animals with PIE were ventilated at similar peak inspiratory pressure (PIP) to control animals, whereas those without PIE were able to be ventilated at significantly lower PIP. Volume-dependent elastance (E2V), which provides an index of overdistension during mechanical ventilation, was lowest in PIE animals. Alveolar architecture was distorted in almost all ventilated animals, the most severe distortion occurring in PIE animals. There was no evidence of excessive alveolar wall thinning in PIE animals, although parenchymal collagen was 30% lower, and elastin 120% higher than in control animals. PIE was associated with structural differences, but not with overventilation.

Topics: Animals; Animals, Newborn; Betamethasone; Collagen; Elastin; Female; Gestational Age; Humans; Infant, Newborn; Lung; Pregnancy; Pulmonary Emphysema; Respiration, Artificial; Respiratory Distress Syndrome, Newborn; Sheep

The effect of exogenous surfactant treatment on lung and type II cell structure of ventilated lambs of 137-138 days gestational age was studied. Thirty-four lambs were delivered and randomized to control or 100 mg/kg of natural sheep surfactant treatment groups. Lungs from one group of lambs not treated with surfactant were fixed before ventilation, and the other animals were ventilated to maintain normal blood gas values for 3, 24, or 48 h. Morphometric assessment of the inflation-fixed lung parenchyma of ventilated lungs was compared with the architectural appearance of alveoli and alveolar ducts in the unventilated lungs. Mechanical ventilation resulted in distension of alveolar ducts accompanied by the shallowing and loss of well-defined alveoli and areas of atelectasis at 3 h. These abnormalities increased in severity after 24 and 48 h of ventilation. Surfactant treatment before ventilation significantly reduced the extent and degree of dilatation and concomitant atelectasis. The fraction of normal parenchyma was 38 +/- 7% in untreated lambs vs. 64 +/- 6% in treated lambs after 24 h of ventilation. After 48 h of ventilation, significant differences between control (39 +/- 6%) and surfactant-treated (55 +/- 6%) lambs were still evident. Alveolar type II cells contained approximately 15% lamellar bodies by volume. Neither surfactant treatment nor time of ventilation altered the volume density of lamellar bodies or other organelles, except for a decrease in glycogen from 8% in nonventilated lungs to 2.5% in lungs ventilated for 24 h. These findings indicate that a surfactant treatment at birth results in the maintenance of more normal parenchyma with less atelectasis during prolonged ventilation of the immature lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Animals, Newborn; Blood Gas Analysis; Collagen; Disease Models, Animal; Elastin; Humans; Infant, Newborn; Lung; Microscopy, Electron, Scanning; Pulmonary Alveoli; Pulmonary Atelectasis; Pulmonary Surfactants; Random Allocation; Respiration, Artificial; Respiratory Distress Syndrome, Newborn; Sheep

Topics: Adolescent; Adult; Age Factors; Alkalies; Amino Acids; Child; Child, Preschool; Elastin; Fetus; Gestational Age; Humans; Infant; Infant, Newborn; Lung; Respiratory Distress Syndrome, Newborn

Topics: alpha 1-Antitrypsin; Animals; Apgar Score; Disease Models, Animal; Elastin; Female; Fetal Hypoxia; Fetal Membranes, Premature Rupture; Gestational Age; Guinea Pigs; Haplorhini; Humans; Hyaline Membrane Disease; Infant, Newborn; Lung; Pregnancy; Pulmonary Surfactants; Respiratory Distress Syndrome, Newborn; Retrospective Studies; Sheep

Amino acid analysis of human fetal lung elastin was undertaken in 49 instances of live-born neonates, ranging from 380 g to full term, and in 3 abortuses of 12-14 wk gestation. The data suggest that formation of the cross-linking agents, desmosine and isodesmosine, occurs early, between 14 and 22 wk. The ratio of neutral to charged amino acids remains low until the 36th wk when it attains adult levels. The composition of elastin was independent of sex and duration of survival. In three neonatal pulmonary diseases (respiratory distress syndrome, atelectasis, and hemorrhage) ratios were significantly lower than those found in nondiseased lungs. This may be a reflection of immaturity or may be a predisposing factor in neonatal lung disease. The latter hypothesis is attractive and receives indirect support from the association of a more polar elastin with other diseases, including adult emphysema and atheromatous aortic change.Our finding of relatively high polarity in elastin from human fetal lung is consistent with previous observations in a variety of fetal organs of other species.

Topics: Age Factors; Amino Acids; Birth Weight; Chemical Phenomena; Chemistry; Elastin; Gestational Age; Hemorrhage; Humans; Infant, Newborn; Infant, Newborn, Diseases; Lung; Pulmonary Atelectasis; Respiratory Distress Syndrome, Newborn; Sex Factors