## 2 Materials and Methods
### Flow Cytometry Analysis of Surface Antigens  
To verify that cells used for differentiation express typical MSC surface marker flow cytometry was performed for a representative donor after the first passage of cells to examine the expression of characteristic clusters of differentiation (CD). The four clusters tested for were CD44, CD73, CD90, and CD105. The co-expression of all four surface antigens is viewed as highly characteristic but not specific for MSCs [15]. Therefore, the co-expression of these four surface antigens is defined as a minimal criterion for declaring cells as MSC-like cells, as stated by the ISCT [15].  
We examined the expression of the respective surface antigens for one donor to show that the isolated subpopulations of cells express MSC-like surface antigens. All five donors were anonymized before a single representative donor was chosen by blind drawing. Cells were washed in phosphate buffered saline (PBS), centrifuged, and resuspended in standard cell culture medium. Afterwards, the cells were counted using the Neubauer counting chamber and split into two 2.5 mL reaction tubes (Greiner Bio-One GmbH), with each tube containing at least 5 \(\times\) 10\({}^{5}\) cells per tissue sample. In the next step, 100 \(\upmu\)L of an antibody-PBS mixture containing a PBS/1% FBS pre-mix, CD73 PerCP-eFluor71 antibody (catalogue no. 46-0739-41), CD44 eFluor 450 antibody (catalogue no. 48-0441-80), CD105 APC antibody (catalogue no. 17-1057-41), and CD90 FITC antibody (catalogue no. 11-0909-41) (all Thermo Fisher Scientific GmbH, Dreieich, Germany, used at the concentration recommended by the manufacturer) were added to one of the two tissue samples for flow cytometry. A total of 100 \(\upmu\)L of a PBS/1% FBS pre-mix, lacking the antibodies, was used for negative controls. Once assembled, all samples were vortexed and stored in complete darkness, at 4 \({}^{\circ}\)C, for 30 min. Afterwards, all samples were washed in PBS/1% FBS pre-mix, centrifuged, resuspended in 2% paraformaldehyde in PBS, and, once again, stored in darkness at 4 \({}^{\circ}\)C. After 15 min, the cells were washed in PBS, centrifuged, resuspended in PBS/1% FBS pre-mix, and vortexed to create an even suspension and transferred to 12 \(\times\) 75 mm round bottom tubes. For compensation, single antibody stainings were performed on compensation beads (catalogue no. 552843), according to the manufacturer's protocol. Prepared samples were measured with an BD LSR II X flow cytometer, equipped with 405, 488, and 633 nm lasers (BD biosciences, Franklin Lakes, NJ, USA). Voltage settings were FSC = 368 and SSC = 242 V and fluorescence detection settings were FITC = 308, PerCP-eFluor 710 = 390, APC = 412, and eFluor 450 = 198 V, based on unstained controls. Results were analysed using the FlowJo 10.5.3 software (FlowJo LLC, Ashland, OR, USA). Compensation was calculated based on single stained compensation beads, and the applied settings are reported in Supplementary Table S1. Cells of interest were separated from cell debris, using forward scatter (FSC) and side scatter (SSC) signals, and the cell doublets were subsequently excluded. Afterwards, the percentage of cells staining positive for individual fluorescence dyes was determined where gates were set, using the respective unstained control as reference.