## Materials and Methods  
### Preparation of Porous Si-Ca-P Monophasic Ceramic (SCP-c)  
SCP-c powder was synthetized in our laboratory, according to a previously described processing method [3]. For specific information related to its mechanical behavior and physicochemical characterization, please consult the following publications [15; 16]. The ceramic was synthetized from commercial-grade calcium hydrogen phosphate anhydrous (CaHPO4; Panreac S.L.U., Barcelona, Spain), calcium carbonate (CaCO3 > 99.0 wt %; Fluka-Sigma Aldrich Quimica SL, Madrid, Spain) with an average particle size of 13.8 \(\upmu\)m, and silicon oxide (SiO2 > 99.7 wt %; Strom Chemicals UK Ltd., Cambridge, UK) with an average particle size <50 \(\upmu\)m. We can briefly describe the process of obtaining the porous Si-Ca-P material as a solid state reaction from the above-mentioned stoichiometric products that were homogenized, milled and isostatically preset, followed by a thermal treatment at 1300 \({}^{\circ}\)C/3 h and annealing at 1200 \({}^{\circ}\)C/24 h.  
For the present investigation, SCP-c was cut in disc shapes of 7 mm in diameter and 3 mm in length, and gas-plasma was used for sterilization (Sterrad-1005 TM, ASP, Irvine, CA, USA). Immediately before its use, each disk was placed in a well of a 24-well plate containing fetal bovine serum (FBS) (Sigma, St. Louis, MO, USA) and incubated at 37 \({}^{\circ}\)C for 1 h in a cell culture incubator to favour cell adhesion to the surface of the material. After that, disks were dried under dry heat at the same temperature.  
Isolation, Characterization and Primary Culture of Adult Human Bone Marrow-Derived Mesenchymal Stem Cells (ahMSCs)  
_ah_MSCs were isolated as previously described [17] and characterized following the criteria of International Society of Cell Therapy (ISCT) [18] (data not shown).  
After cell expansion, _ah_MSCs of passage 3 (P3) were prepared for use in all subsequent experiments. For examination of attachment and proliferation assays, cells were seeded onto the top of disc-shaped SCP-c at a density of 5 \(\times\) 10\({}^{3}\) cells-cm\({}^{-2}\) in a 48-well plate and cultured with growth medium (GM) which consists of Dulbecco's Minimal Essential Medium (DMEM) (Sigma-Aldrich, St. Louis, MO, USA) supplemented with 10% (\(v/v\)) FBS and routine antibiotics (penicillin/ streptomycin). To conduct osteogenic differentiation studies, three SCP-c scaffolds were placed in transwell inserts in 6-well plates (Sigma-Aldrich, Corning, NY, USA) and _ah_MSCs were seeded on the bottom of the wells at a density of 5 \(\times\) 10\({}^{3}\) cells cm\({}^{-2}\) and cultured with GM. Cells seeded onto tissue culture-treated polystyrene (TCPS) culture plate (Sigma-Aldrich, Corning, NY, USA) served as a positive control.  
Plates were incubated at 37 \({}^{\circ}\)C in a humidified atmosphere consisting of 95% air and 7.5% CO\({}_{2}\). Some of the _ah_MSCs cell cultures were also induced to osteogenic differentiation replacing the GM by osteogenic differentiation medium (OM) from the 21 st day, which consisted of the GM supplemented with l-ascorbic acid-2-phosphate (0.2 mM; Sigma-Aldrich, St Louis, MO, USA), dexamethasone (10 nM; Sigma-Aldrich, Corning, NY, USA), and \(\beta\)-glycerolphosphate (10 nM; Merck, Darmstadt, Germany).