Jugoslov Med Biohem 2006; 25 (4): 403 DOI: 10.2298/JMB0604403P UC 577,1; 61 ISSN 0354-3447 Jugoslov Med Biohem 25: 403– 410, 2006 Nau~ni rad Scientific paper APPLICATION OF BIOMARKERS IN EVALUATION OF FETAL LUNG MATURITY Danica Popovi}1, Vojislav Miketi}2, Gorjana Matovi}1, Vuko Nikoli}1 1Centre for Clinical-Laboratory Diagnostics, Clinical Centre of Montenegro, Podgorica, Montenegro 2Clinic of Gynecology and Obstetrics, Clinical Centre of Montenegro, Podgorica, Montenegro Summary: In the process of maturation, alveolar epithelial cells produce surface-active material (surfac- tant) which consists mainly of phospholipids and, although to a significantly lesser degree, neutral lipids, pro- teins and carbohydrate. Pulmonary surfactant is synthesized in alveolar type-II granular pneumocytes and »packed« as lamellar bodies. Before delivery, the lamellar bodies diffuse through the bronchial tree into the amniotic fluid. Parameters which indicate the maturity of lungs, except the concentration of lamellar bodies, also are observed in the ratio against the quantity of surfactant with other components of the amniotic fluid (sphingomyelin and albumin). The study concerns the determination of the surfactant-to-albumin ratio and the lamellar body count in the amniotic fluid as predictors of fetal lung maturity. The research involved 90 preg- nant women with gestational age from 32 to 40 weeks. The samples of the amniotic fluid were obtained by amniocentesis and they were filtrated through special filters. The surfactant-to-albumin ratio was measured by the Fetal Lung Maturity II (FLM) test, on a TDX instrument (ABBOTT). The concentration of lamellar body count was measured on a hematology cell counter by the platelet channel, on the Cell Dyn 3700 instrument (ABBOTT). The average value of S/A ratio was 55.11 mg/g (min=6.96 mg/g, max=112.00 mg/g). The surfac- tant-to-albumin ratio of less than 39.00 mg/g predicts respiratory distress syndrome with the probability of 92%. The average value of LB was 69.4 × 109/L (min=4.2 × 109/L, max=199.0 × 109/L). Lamellar body concen- tration of 34.0 × 109/L or less predicts respiratory distress syndrome with the probability of 93%. The surfac- tant to albumin ratio increased with gestation (r=0.373, p<0.005), as did lamellar body concentration (r=0.934, p<0.001). The two tests correlated with each other, r=0.341, p<0.005. In 90 patients delivered with- in 72 hours the surfactant-to-albumin ratio and concentration of the lamellar body correctly predicted six cases of the respiratory distress syndrome. There was a high degree of positive correlation between gestational age and surfactant-to-albumin ratio, as to lamellar body concentration. Key words: fetal lung maturity, lamellar bodies, surfactant/albumin ratio, respiratory distress syndrome Introduction aimed at achieving the optimal conditions for the delivery. The research encompasses the attempt to In the process of fetal maturity, the lungs are the postpone the birth term, either by applying corticos- last vital organ that needs to develop in order to teroid therapy and improving the neonatal aeration enable life in the extrauterus environment. Because of technique, or by the surfactant treatment (1). During the importance of the lung function for survival, peri- early pregnancy there are none or just a few particle- natal research and care are directed to the examina- shaped materials in the amniotic fluid. In the 16th tion of its maturity. Unfortunately, until recently, lung week of gestation, the amniotic fluid is full of cells immaturity resulted in abrupt deaths of prematurely that fell off the amnion surface, from the skin or tra- born babies. Management in perinatology, contem- cheobronchial tree. They are very important in the porary maternal/fetal medicine and neonatology is antenatal diagnostics. In the process of maturation, the lungs start producing the detergent like material ’ surfactant that, forms a film on the alveolar surface. Address for correspondence: The most common complication, that the preterm Danica Popovi} Centre for Clinical-Laboratory Diagnostics newborn infant faces is the respiratory distress syn- Clinical Centre of Montenegro drome (RDS), or the hyaline membrane disease. Ljubljanska bb, 81 000 Podgorica, Montenegro Tel.: +381 81 245-422 Under normal conditions, the sufficient concen- e-mail: [email protected] tration of the pulmonary surfactant reduces the sur- 404 Popovi} et al: Application of biomarkers in evaluation of fetal lung maturity face tension in the alveoli so that, at the end of the emerging of phosphatidylglycerol (5, 6). The substi- expirium, the walls of the alveoli do not collapse or fix. tution of phosphatidylinositol with phosphatidylglyc- When there is not enough surfactant, the alveoli col- erol is probably an outcome of the reduced concen- lapse, and each breath should have the higher nega- tration of free inositol in circulation in the lung tissue tive tension in order to make the alveoli open. during the later gestation (7). Phosphatidylglycerol Depending on the level of difficulty, it may happen constitutes 11% of the surface active molecules. that the premature baby cannot open the alveoli There is an opinion that claims that the premature again, or can do, it but becomes exhausted trying to infants whose surfactant lacks phosphatidylglycerol breathe. In that case, it is necessary to provide addi- have a bigger percentage of RDS, but some research- tional oxygen and mechanical ventilation in order to es proved that PG is not necessary for the functioning keep regular oxygenation (2). of the surfactant, i.e. absence of PG will not cause RDS (7, 8). Pulmonary surfactant consists of phospholipids and protein with the surface active properties, and it The presence of the specific surfactant proteins covers the alveolar surface and terminal airways. was noted for the first time in 1973. Recently, 4 speci- Alveolar surface, consists of the alveolar wall, the film fic surfactant proteins were described, and their func- that covers the wall, and the alveolar pores at the tion was explained as well. In line with the nomencla- contact surface, in contact with the air. The alveolar ture introduced by Possmayer in 1988, proteins called wall is made up of a one-layer epithelium which con- SP-A, SP-B, SP-C, and SP-D are hydrosoluble, while tains the pores, called the Kohn’s pores. Regarding SP-B and SP-C are small hydrophobe proteins that the epithelial cells, 85% belongs to type-I cells, while come out from the precursor of the bigger proteins. the rest of 15% are type-II cells (pneumocytes) with Proteins in the composition of the surfactant have cytoplasmic granular bodies (lamellar bodies) and many functions. SP-A and SP-B are essential for form- microvilli on the surface. Type-II cells produce and ing the tubular myelin and grouping of lamellar bodies, store the pulmonary surfactant and react as a pre- which is important for the preserving and secretion of cursor of cells type-I which also have a phagocyte surfactant. SP-A is a metabolic regulator which con- activity. The liquid phase of the limiting lining is called trols the secretion and the repeated input of other sur- hypophase, and its surface is the surface film or air- factant components using the specific membrane liquid interface. The molecular surfactants are con- receptors on the type-II cells, and it represents a non- centrated on the air-liquid contiguous surface with immune protein of the ultimate defense. SP-D has only the polar side turned to the liquid phase and the non- been isolated a short time ago and has many structu- polar side turned to the air phase. These molecules ral and functional similarities with SP-A, but the precise reduce the surface tension on the air-liquid contigu- role of SP-D is still to be identified. SP-D does not asso- ous surface, and that provides the stability of the alve- ciate with surfactant lipids or participate in surfactant oli at the end of the expirium, preventing their col- function. Surfactants from which the SP-D is removed lapse. Other functions of the surfactant are: preven- retain the features of the surface active molecules, but tion of edema by the effect of the transepithelial fluid it is still assumed that SP-D has the role of the ultimate activation and the bacteria phagocytosis stimulation defense protein (9). SP-B grows along with the pro- with the help of the macrophage, which gives the sur- gression of the gestational age, and it is localized in res- factant an important role in the ultimate line of the piratory epithelial cells only in the distal lung. This pro- tein is the extreme simulator of the lipid surfactant lungs’ defense. adsorption and formation of the surface film (10). The The surfactant contains 70’80% of phospho- lack of SP-B in premature infants manifests in the lipids, about 10% of proteins, about 10% of neutral strong form of RDS that is not likely to be cured with lipids (especially cholesterol) and about 5 % of carbo- the surfactant treatment. About 30% of newborn hydrates. 80% of phospholipids make the phos- infants who die of unexplained acute RDS lack the SP- phatidylcholine. About 50% of phosphatidylcholine is -B protein. The lack of SP-B in humans and mice is saturated, and saturation on both C-atoms is carried related to the lack of lamellar bodies in type-II cells, as out by the palmitic acid (3, 4). Most of the other phos- well as to the lack of the conversion of proSP-C into SP- phatidilholin has unsaturated fatty acids on the sec- C. That is the reason why these newborn infants do not ond C-atom. The saturated phosphatidylcholine is have SP-B or active SP-C.