• Bone mesenchymal stem cells (BMSCs) are an attractive source of cells with potential applications in ocular regenerative medicine. However, the low differentiation efficiency in the traditional two-dimensional (2-D) culture system limits their application for clinical therapy. The authors describe a simple and innovative 3-D culture environment and assess the potential for BMSCs to differentiate into a variety of cell types in the 3-D system.

    They isolated and cultured BMSCs of rhesus monkeys using a density gradient centrifugation and adherence screening method. Cells at passage three were cultured by hanging drop and formed spheres. After three days, the spheres were collected and plated onto culture plates and maintained in a floating state by a rotary method for 10 days.

    Under appropriate induction conditions, the sphere cells were induced into adipocytes, osteoblasts, epithelial progenitors and neuronal cells. Differentiated cells were identified by histochemical staining, immunofluorescence and reverse transcription-polymerase chain reaction.

    As the neuronal cells were derived from neuronal spheres, the authors speculate that the 3-D spheroid culture might resemble the natural growth niche of developing neuronal cells in the body, enhancing cell–cell and cell–paracrine factor interaction. The sphere-derived cells are more likely to differentiate towards the neuronal lineage compared with the monolayer cells. It is worth noting that the differentiation cells expressed only weak GFAP (glial cell marker), which is different with typical neuronal differentiation of BMSCs.

    They conclude that this culture method in vitro may provide a useful way to gain insight into the mechanisms of differentiation of BMSCs, particularly the switching from one cell lineage into another. Moreover, it has potential applications for regenerative medicine for the treatment of ocular surface and ocular neurodegenerative diseases, such as glaucoma or senile macular degeneration.