Differentiation of Mesenchymal Stem Cells into Retinal Progenitor Cells

Characterization of Progenitor Retinal Cells It is in this context that rigorous identification and characterization of progenitor retinal cells acquires an urgent need. The authors performed several immunodetections: Pax6, TUBB3, bestrophin 2, glial fibrillary acidic protein, RPE65, OPN1 SW, neu66 and rhodopsin. Of this panel, the authors do not show the immunostaining performance of Pax6, RPE65, neu66 or rhodopsin. Nor was any molecular characterization performed, or phagocytic activity analysis by fluorescent latex bead uptake, or calcium imaging as described in several reports dealing with progenitor retinal cell biology [6, 7] . The described immunophenotype alone seems insufficient to define a cell lineage in this context. As an example, bestrophin 2 has also been described in colonic goblet cells [8] . There are also several rather intriguing errors in the list of bibliographic references. In the introduction, reference 1, a widely quoted paper, does not correspond to the one first listed by the authors, namely Jeganathan VS, Palanisamy M: Treatment viability of stem cells in ophthalmology [Curr Opin Ophthalmol 2010; 21: 213–217]. We assume that the correct and absent paper is most probably Baker PS, Brown GC: Stem-cell therapy in retinal disease [Curr Opin Ophthalmol 2009; 20: 175–181], a reference not alluded to at any point in the paper. The authors refer to a previous paper published by their group in reference No. 5, but again, No. 5 in the list submitted is a publication from a different group. The reference they would seem to be quoting is the one listed as 6. This mistake occurs twice. Reference 10, mentioned together with others in the results section, does not refer to retinal precursor cells as quoted in the text. The authors quote from reference No. 15 as follows: ‘... According to Moalem et al., this differentiation induction has been attributed to the specific protective action of the tissue-specific autoimmune cells ...’. This is not a finding supported by the paper of Moalem et al. [9] , which in fact refers to protection given to axons by T cells through a proposed induction of a resting state, in a crush injury model of the optic nerve. The word ‘differentiation’ is not even mentioned in their paper. To sum up, the findings of Moviglia et al. [1] fall short of providing evidence for their conclusions, for the following reasons: MSCs were not characterized as suggested by the International Society Consensus; the revolutionary mechanism proposed by the authors to induce transdifferentiation is widely unknown in peerreviewed published material and their final product, progenitor retinal cells, have not been characterized fully. Nor does the confusing maze generated by referencing published material contribute to clarify these issues. In addition, the final sentence of this contribution is of concern. The authors state that ‘... these promising results have prompted us Dear Editor, We read the paper by Moviglia et al. [1] entitled ‘In vitro differentiation of adult adipose mesenchymal stem cells into retinal progenitor cells’, published in Opthalmic Research, with great interest. Issues that in our opinion require attention from the authors are listed below.