Gene-Chip Analysis of Cord Blood Derived CD34+ Cells Expanded on Bioartificial Materials.

Expansion of hematopoietic stem cells from neonatal cord blood is an important issue for clinical uses since the number of CD34+ cells in individual cord blood samples is limited and often not sufficient for a successful engraftment in adult individuals. In vivo, hematopoietic stem cells reside in the bone marrow in close vicinity to stromal cells and extracellular matrix molecules. We have established a culture system for the ex vivo expansion of CD34+ cord blood cells utilizing fibrillar collagen 1 as a bioartificial matrix to enable cellular adhesion during cell culture. CD34+ hematopoietic stem cells were isolated via immunomagnetic separation from umbilical cord blood after informed consent and cultivated in presence of recombinant cytokines and reconstituted collagen 1 fibrils as matrix. After seven days of cultivation, expansion of cells, expression of surface molecules cells and expansion of colony forming units were assessed. Additionally gene expression profiling was performed with Affymetrix HG U133A chips interrogating 22,253 probe sets. As control, CD34+ cells were expanded in liquid culture without fibrillar collagen.

The overall expansion of CD34+ cells was 4.2 fold + 1.7 compared to 11.1 fold + 2.9 for the control sample. The number of colony forming units (CFU) was increased in the collagen 1 containing samples was elevated (65.1 + 10.3 compared to 26.1 + 7.6 in the control). Gene expression analysis with chip technology showed up regulation of several cytokines (e.g. interleukin 8, interleukin 1a) and also of transcription factors with antiproliferative features like BTG2. The chip data have been verified with quantitative PCR using the Taqman technology.

Our data support the idea that direct contact of CD34+ cells with fibrillar collagen 1 results in a delay in cell cycle progression which prevents a subsequent differentiation into more committed progenitors. Therefore fibrillar collagen 1 may serve as supportive matrix for the ex vivo expansion of cord blood derived CD34+ cells.