Among other aspects the present invention relates to cell culture conditions for producing high molecular weight vWF in particular highly multimericWF with a high specific activity and ADAMTS 13 with a high specific activity. The cell culture conditions of the present invention can include for example a cell culture medium with an increased copper concentration and/or cell culture supernatant with a low ammonium (NH4+) concentration. The present invention also provides methods for cultivating cells in the cell culture conditions to express high molecular weight vWF and rA13 having high specific activities.
