Giemsa dye

The cells (10⁴) were seeded onto 10 cm Petri dishes and incubated for 14 days. Afterward, they were fixed with 70% ethanol and stained with Giemsa dye (PanEco, Russia). The Total Lab ver. 2.0 software, Colony Counter module (Nonlinear Dynamics, Newcastle upon Tyne, UK), was used to determine the number of colonies and their sizes.

The following substances and reagents were used in the experiments without additional purification: 300 Bloom gelatin of Type A derived from porcine skin collagen, urea (ultra-pure grade), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide) (EDC), and ammonium chloride—all from Sigma-Aldrich Inc. (St. Louis, MO, USA); a 40% aqueous solution of glyoxal (GXL) and a 96% aqueous solution (v/v) of ethanol—both from Reakhim (Moscow, Russian Federation). Dulbecco’s modified Eagle’s medium (Nutrient Mixture F-12 (DMEM/F12), alanyl–glutamine and Giemsa dye were purchased from PanEco (Moscow, Russian Federation). Fetal bovine serum (FBS), antibiotic/antimycotic, and HEPES were purchased from Gibco Inc. (Billings, MT, USA). Basic fibroblast growth factor (bFGF) was purchased from Peprotech (Cranbury, NJ, USA). A Human Albumin ELISA Kit, Picogreen QuantiT™, Live/Dead^® Cell Viability/Cytotoxicity Kit and PrestoBlue™ Cell Viability Reagent were purchased from Invitrogen Corp. (Carlsbad, CA, USA). DNeasy Blood & Tissue Kit was obtained from QIAGEN (Hilden, Germany). A neodymium-containing contrasting solution for scanning electron microscopy (SEM) was obtained from Glaucon LLC (Moscow, Russian Federation). All aqueous solutions were prepared using deionized water of Milli-Q quality generated with a Simplicity Water Purification System (Millipore, Molsheim, France).