Human amniotic membrane as newly identified source of amniotic fluid pulmonary surfactant

Abstract

Pulmonary surfactant (PS) reduces surface tension at the air-liquid interface in the alveolar epithelium of the lung, which is required for breathing and for the pulmonary maturity of the developing foetus. However, the origin of PS had never been thoroughly investigated, although it was assumed to be secreted from the foetal developing lung. Human amniotic membrane (hAM), particularly its epithelial cell layer, composes the amniotic sac enclosing the amniotic fluid. In this study, we therefore aimed to investigate a potential contribution of the cellular components of the hAM to pulmonary surfactant found in amniotic fluid. We identified that cells within the native membrane contain lamellar bodies and express all four surfactant proteins as well as ABCA3. Lipidomic profiling by nanoESI – MS/MS revealed the presence of the essential lipid species as found in PS. Also, the biophysical activity of conditioned cell culture supernatant obtained from hAM was tested with captive bubble surfactometry. hAM supernatant showed the ability to reduce surface tension, similar to human PS obtained from bronchoalveolar lavage. This means that hAM produces the essential PS-associated components and can therefore contribute as second potential source of PS in amniotic fluid aside from the foetal lung.

Sub-Regional Differences of the Human Amniotic Membrane and Their Potential Impact on Tissue Regeneration Application

“…In addition, the histocompatibility antigen class I-G (HLA-G) a protein, which induces apoptosis of CD8b T cells and fosters T helper cell type (Th)2 response, showed higher mRNA expression in reflected amnion than in placental amnion ( Han et al, 2008 ). In line with this, analysis of conditioned medium from reflected hAM explants showed a trend toward higher concentrations of the immune-modulatory surfactant protein D ( Lemke et al, 2017 ). However, the immune-modulatory surfactant protein A was predominantly found in the placental amnion tissue ( Lee et al, 2010a ).…”

“…In hAMSCs both regions were negative for OCT-4. However, there was a trend toward higher SSEA-4 expression in placental hAMSCs ( Lemke et al, 2017 ). The reason for the contradictory data could result from differences in preparation, isolation and cultivation methods, and density of the cells.…”

“…In isolated hAECs, contradictory data exist regarding the expression of OCT-4. One group found the placental hAECs to have a tendency toward higher OCT-4 expression compared to reflected hAECs ( Lemke et al, 2017 ), while another group found no differences between reflected, placental, and umbilical hAECs for OCT-4, SOX-2, and NANOG expression ( García-López et al, 2019 ). Although different cellular sub-populations were detected within one region by means of immunostaining (only in the nucleus/only in the cytoplasm/in both compartments), there were no differences in these sub-populations between the regions ( García-López et al, 2019 ).…”

Lung Surfactant Accelerates Skin Wound Healing: A Translational Study with a Randomized Clinical Phase I Study

“…In support of this finding, human amniotic membranes release pulmonary surfactant into the amniotic fluid 33 . Accordingly, the use of amniotic membranes has attracted increasing attention to stimulate skin wound healing and enhanced regeneration has been reported of chronic, non-healing 43 or burn wounds 44,45 with reduced post-burn scarring 46 .…”

“…phospholipids and the hydrophobic surfactant proteins SP-B and SP-C which ease the absorption and spreading of the surfactant film, phosphatidylglycerol (PG) 29,30 , DPPC 18 , SP-B 31 and SP-C 32 have anti-inflammatory and antibacterial 15 properties 8,14 . Interestingly, surfactant proteins are also secreted by amniotic 33 , skin 34 and mucosal cells 35 . In scarless fetal wound healing, high amounts of SP-C were found in contrast to almost undectable amounts in adult keratinocytes and fibroblasts.…”