Dental Pulp Stem Cells for Retinal Nerve Regeneration

Objectives: In this study we investigated the therapeutic paracrine effects of human dental pulp stem cells (DPSC) in comparison with human bone marrow-derived mesenchymal stem cells (BMSC) and adipose-derived stem cells (ADSC) on the neuroprotection and axogenic regeneration of primary adult retinal ganglion cells (RGC) in an in vitro rat RGC injury model.
Methods: The number of surviving RGC and the length/number of RGC neurites were quantified using βIII-tubulin immunocytochemical staining following co-culture of axotomised rat RGC with human DPSC, BMSC or ADSC in a “transwell” system. Specific Fc-receptor inhibitors were used to assess the role of various neurotrophic growth factors (NTFs). Conditioned medium from cultured DPSC/BMSC/ADSC was assayed for the secreted NTFs using specific ELISAs. A PCR array was used to determine the expression of a range of NTF and NTF receptor (NTFR) genes in the DPSC, BMSC and ADSC.
Results: DPSC promoted neuroprotection (i.e. increased survival) of the injured RGC and the regeneration of their neurites to a significantly greater extent than achieved by BMSC or ADSC. This therapeutic effect was neutralized by specific Fc-NTF receptor inhibitors to NGF, BDNF, NT-3, VEGF, GDNF and PDGF. DPSC secreted higher levels of specific NTFs including NGF, BDNF and VEGF compared with BMSC/ADSC. Stem cell-derived NGF appeared predominantly responsible for the induced neuritogenesis whereas PDGF was exclusively neuroprotective. PCR array analysis identified the neuropeptide VGF as a novel DPSC-derived factor demonstrating significant neuroprotective properties in the RGC co-culture system.
Conclusions: Human DPSC promoted significant NTF-mediated RGC survival and neurite outgrowth and may be considered as an advantageous paracrine-mediated stem cell therapy for retinal neuroprotection and nerve repair.