Whole blood for DNA extraction and serum samples for growth factor measurements were stored at -80°C within the MedUni Vienna Biobank facility. Post-storage isolation of DNA was done on a Corbett X-tractor Gene CAS 1820 semi-automated nucleic acid extraction system (Qiagen, Hilden, Germany) using a Macherey Nagel Nucleospin 96 blood kit (Macherey Nagel, Dueren, Germany). Quantification of genomic DNA by Warburg-Christian method (260/280 nm) on a Nanodrop spectrophotometer (PEQLAB Biotechnologie GmbH, Erlangen, Germany) revealed an average nucleic acid concentration of 25 ng/µL. ApoE genotyping of 1:10 (v/v in Buffer BE, Macherey Nagel) diluted aliquots was performed on a ABI TaqMan® 7900HT Real Time(RT)-PCR thermocycler (Applied Biosystems, Rotkreuz, Switzerland). For this, pre-designed TaqMan SNP-Genotyping assays to distinguish the ApoE ε4 allele from ε2 and ε3 at amino acid position 112 (ApoE rs429358, Assay ID C_3084793_20, Applied Biosystems) and the ApoE ε2 allele from ε3 and ε4 at amino acid position 158 (rs7412, Assay ID C_904973_10, Applied Biosystems) were purchased. RT-PCR was accomplished in a total reaction volume of 5µL using TaqMan® Genotyping Master Mix (Applied Biosystems) in a 384-well format according to the standard protocol supplied by the manufacturer. Thermal conditions: enzyme activation for 10 minutes at 95°C, followed by 45 cycles of alternating denaturation (15 seconds, 95°C) and primer annealing/elongation (1 minute, 60°C). Allelic discrimination was achieved using SDS 2.3 software (Applied Biosystems).