Defining a New Standard: Human Platelet Lysate Supports Proliferation and Differentiation of Primary Respiratory Epithelial Cells

Air-liquid interface (ALI) cultures consisting of well-differentiated primary respiratory epithelial cells (PRECs) provide a versatile in vitro model for pharmacological studies and to investigate host-pathogen interactions. Proliferation and differentiation of PRECs require complex media containing several growth factors, hormones, and nutrients. Usually, some of these essential components are provided by the addition of fetal calf serum (FCS). However, several disadvantages of FCS and, most importantly, ethical concerns regarding the method of serum collection have encouraged researchers to find alternatives. Human platelet lysate (hPL) has emerged as a promising alternative to FCS for supporting cell expansion in vitro. In the present study, we investigated the effects of different concentrations of hPL on the proliferation of porcine PRECs and their subsequent differentiation under ALI conditions. Cell morphology was assessed by phase-contrast microscopy, while cell proliferation was evaluated using the ClickTech EdU Cell Proliferation Kit and visualization of proliferating cells by fluorescence microscopy. Differentiation under ALI conditions was monitored by immunofluorescence staining of ciliated cells and the establishment of an intact epithelial barrier was confirmed by measuring transepithelial electrical resistance (TEER). We found that 5% hPL supported efficient cell growth and the subsequent formation of a functional, well-differentiated airway epithelium comparable to or even better than 10% FCS. Thus, hPL offers a reproducible, ethically sound, and scalable alternative to FCS for complex cell culture models in respiratory research, drug development, and host-pathogen interaction studies. LO_SCPLOWAYC_SCPLOW SO_SCPLOWUMMARYC_SCPLOWRespiratory epithelial cells from the lungs of slaughtered animals, such as pigs, can be used for cell culture models to study respiratory diseases and drug development. Air-liquid interface (ALI) cultures closely mimic the natural environment of the airways by exposing the cells to air, making them a valuable alternative to animal experiments. To grow and mature properly, these cells require nutrients and growth factors that are commonly supplied by serum from unborn calves (FCS). However, for ethical and scientific reasons, the use of FCS should be avoided. Therefore, we evaluated whether human platelet lysate (hPL) derived from expired blood donations could replace FCS in ALI cultures. We found that adding 5% hPL to the medium supported efficient cell growth and the development of a well-differentiated airway epithelium. This approach enables the use of an improved and ethically superior model of the (porcine) respiratory tract in accordance with the 3Rs principle.