Cellular reporter systems for high-throughput screening of interactions between bioactive matrices and human mesenchymal stromal cells.

Mesenchymal stromal cells (MSC) and factors secreted by them are essential components of the hematopoietic stem cell (HSC) niche within the bone marrow microenvironment. It has been shown that the extracellular matrix (ECM) can influence HSC-supportive potential of MSC and is a prerequisite for the proper signaling of morphogens. Therefore, we aimed at the identification of ECM components and candidate morphogens capable of enhancing the expression of HSC-supportive proteins in human MSC, namely, angiopoietin-1 (Ang-1) and stromal cell-derived factor 1 (SDF-1). For this purpose, highly sensitive secreted dual reporter constructs for Ang-1 and SDF-1 were established. These newly designed dual reporter systems enable continuous monitoring of the Ang-1 and SDF-1 promoter activity in an immortalized human MSC line cultured on ECM/morphogen microarrays. Reporter arrays showed that Ang-1 and SDF-1 expression can be induced by different ECM/morphogen combinations. In addition, continuous monitoring of promoter activity allows delineating time-dependent effects of the ECM and morphogens. Thus, we identified that collagen I and vitronectin in combination with Wnt3a favored SDF-1 expression over time, while only transiently inducing the expression of Ang-1. Taken together, the newly developed reporter systems allow for the monitoring of Ang-1 and SDF-1 promoter activity induced by morphogens and the ECM in a combinatorial and high-throughput manner. This technology might therefore be helpful to optimize culture conditions, which favor the activity of MSC as feeder cells for various types of stem and progenitor cells.