Surfactant Protein D Levels in Umbilical Cord Blood and Capillary Blood of Premature Infants. The Influence of Perinatal Factors

Abstract

Surfactant protein D (SP-D) is a collectin that plays an important role in the innate immune system and takes part in the surfactant homeostasis by regulating the surfactant pool size. The aims of this study were to investigate the values of SP-D in umbilical cord blood and capillary blood of premature infants and to relate the levels to perinatal conditions. A total of 254 premature infants were enrolled in the present study. Umbilical cord blood was drawn at the time of birth and capillary blood at regular intervals throughout the admission. The concentration of SP-D in umbilical cord blood and capillary blood was measured using ELISA technique. The median concentration of SP-D in umbilical cord blood was twice as high as in mature infants, 769 ng/mL (range 140 -2,551), with lowest values in infants with intrauterine growth retardation (IUGR) and rupture of membranes (ROM). The median concentration of SP-D in capillary blood day 1 was 1,466 ng/mL (range 410 -5,051 ng/mL), with lowest values in infants born with ROM and delivered vaginally. High SP-D levels in umbilical cord blood and capillary blood on day 1 were found to be more likely in infants in need for respiratory support or surfactant treatment and susceptibility to infections. We conclude that SP-D concentrations in umbilical cord blood and capillary blood in premature infants are twice as high as in mature infants and depend on several perinatal conditions. High SP-D levels in umbilical cord blood and capillary blood on day 1 were found to be related to increased risk of RDS and infections. R espiratory distress syndrome (RDS) is a main contributor to increased mortality and morbidity among premature infants. RDS is caused by lack of pulmonary surfactant leading to atelectasis and ventilation-perfusion mismatch of the lungs (1). Biochemically, pulmonary surfactant is a mixture of phospholipids and associated proteins which are synthesized, stored, secreted and recycled by type II cells in the airways (2). This mixture forms a monolayer at the air-liquid interface which lowers the surface tension, stabilizes alveoli and terminal airways at low lung volume and prevents alveolar collapse at the end of the expiration. Treatment with synthetic or naturally developed surfactant has been associated with a decline in the mortality of RDS among premature infants (3,4).Four specific surfactant proteins have been identified, called surfactant protein (SP) A-D. SP-B and SP-C have been characterized as hydrophobic polypeptides that enhance the adsorption of lipid to the surface of the alveoli (5), while SP-A and SP-D are hydrophilic and participate in the innate host defense immune system. SP-D binds to macrophages and neutrophils and promotes phagocytosis and killing of bacteria, fungi, and viruses (6). Polymorphism in the amino acid residue 11 of the SPD gene has been found to increase severity of respiratory syncytial virus infection and susceptibility to tuberculosis (7,8).SP-A and SP-B are instrumental in surfactant storage in lamellar bodies and i...

The Effect of Intrauterine Growth Restriction on Circulating Surfactant Protein D Concentrations in the Perinatal Period

“…In accordance with others, 19 our data suggest a postnatal increase in circulating SP-D concentrations, probably due to the physiological reabsorption of lung liquid across the pulmonary epithelium to the circulation during initiation of breathing. 43 Furthermore, we found higher neonatal SP-D concentrations compared with maternal ones.…”

“…38 Furthermore, experimental and clinical data suggest increased SP-D expression after glucocorticoid treatment both in vivo and in cultured tissue. 39 However, a previous study 19 including premature IUGR infants demonstrated lower umbilical cord blood SP-D concentrations. The authors speculated that the decreased production of total lung fluid (due to diminished amount of substrates) 7 may account for this result.…”

“…The authors speculated that the decreased production of total lung fluid (due to diminished amount of substrates) 7 may account for this result. 19 Amniotic fluid SP-D levels have been reported to increase with progressing gestational age. 40 Thus, amniotic fluid levels of SP-D have been suggested as a marker of lung maturation.…”

“…15 Additionally, several studies suggest that elevated serum SP-D reflects reduced lung function, worsening health status and other poor outcomes in patients with lung disease. [19][20][21][22] Thus, serum SP-D has been proposed as a promising reliable biomarker for tracking disease progression and predicting clinical outcomes in respiratory distress syndrome of the newborn and in adult chronic obstructive pulmonary disease. [19][20][21][22] However, the physiological profile and regulatory mechanisms of circulating SP-D in the perinatal period of human fullterm IUGR pregnancies have not been, up to the present, investigated.…”

Physiological concentration of calcium inhibits elastase-induced cleavage of a functional recombinant fragment of surfactant protein D

“…Numerous studies use ELISA technique as a means of quantifying SP-D (Postle et al, 1999;Hull et al, 1997;Dahl et al, 2006;Hohwy et al, 2006;Ooi et al, 2007). In this study Western blots on samples of cleaved rfhSP-D reveal that the antibody used (raised against the CRD and thus recognising both NhSP-D and rfhSP-D) recognises cleavage products of rfhSP-D from all 4 enzymes (Fig.…”