October 2016
Volume 57, Issue 13
Open Access
Letters to the Editor  |   October 2016
Author Response: Possibility of Cytoplasmic Transportation Between Donor–Host Cell Following Photoreceptor Transplantation
Author Affiliations & Notes
  • Tiago Santos-Ferreira
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
  • Manuela Völkner
    German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany;
  • Oliver Borsch
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
  • Jochen Haas
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
  • Peter Cimalla
    Technische Universität Dresden, Faculty of Medicine Carl Gustav Carus, Department of Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden, Germany;
  • Praveen Vasudevan
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
  • Peter Carmeliet
    University of Leuven, Vesalius Research Center, Department of Oncology, Leuven, Belgium;
  • Denis Corbeil
    Technische Universität Dresden, Biotechnology Center, Dresden, Germany; and the
  • Stylianos Michalakis
    Center for Integrated Protein Science Munich CiPSM, Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
  • Edmund Koch
    Technische Universität Dresden, Faculty of Medicine Carl Gustav Carus, Department of Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden, Germany;
  • Mike O Karl
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
    German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany;
  • Marius Ader
    Technische Universität Dresden, CRTD–Center for Regenerative Therapies Dresden, Dresden, Germany;
Investigative Ophthalmology & Visual Science October 2016, Vol.57, 5336-5337. doi:10.1167/iovs.16-20687
  • Views
  • PDF
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Tiago Santos-Ferreira, Manuela Völkner, Oliver Borsch, Jochen Haas, Peter Cimalla, Praveen Vasudevan, Peter Carmeliet, Denis Corbeil, Stylianos Michalakis, Edmund Koch, Mike O Karl, Marius Ader; Author Response: Possibility of Cytoplasmic Transportation Between Donor–Host Cell Following Photoreceptor Transplantation. Invest. Ophthalmol. Vis. Sci. 2016;57(13):5336-5337. doi: 10.1167/iovs.16-20687.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
We thank Liang and colleagues1 for their interest and thoughtful analysis of our recent article describing the integration of stem cell–derived photoreceptor transplants into mouse models of cone–rod dystrophy.2 The authors raise a crucial issue in the field of photoreceptor transplantation: Do donor photoreceptors following transplantation into the subretinal space structurally integrate into the host tissue, fuse with the endogenous cells (cell–cell fusion), or do the latter cells take up cytoplasmic biomaterials from donor cells? 
We have already considered these potential pitfalls, and a series of experiments has been conducted to clarify this concern.3 These include (1) single-cell analysis following transplantation of enhanced green fluorescent protein (eGFP)–labeled donor photoreceptors into Discosoma sp. red fluorescent protein (DsRed)–labeled hosts by imaging flow cytometry; (2) Cre/lox technology in which photoreceptors isolated from a conditional mouse reporter line containing a loxP-flanked stop cassette upstream of the tdTomato reporter gene were transplanted into photoreceptor-specific Cre-recombinase–expressing hosts; and (3) independent labeling of cytoplasm (using transgenic mice expressing eGFP under a neural retina zipper [Nrl] promoter) and nucleus (either by 5-ethynyl-2′-deoxyuridine [EdU] or Y-chromosome staining) of male donor cells following transplantation into female wild-type hosts. Collectively, our new data demonstrate that cytoplasmic content is transferred from donor to host photoreceptors without translocation of the nucleus. Thus, the majority of potentially newly integrated photoreceptors with fluorescently stained cytoplasm in the outer nuclear layer represent host photoreceptors rather than donor photoreceptors, thus contradicting the common view that transplanted photoreceptors structurally integrate into the retinal tissue. The mechanism by which donor and host photoreceptors exchange cytoplasmic biomaterials is currently unknown and does not represent “classical” fusion events that lead to the formation of binucleated heterokaryons, as previously described, for example, following transplantation of bone marrow–derived donor cells.4 Instead and excitingly, the observed cell material transfer might involve tunneling nanotubes and/or extracellular membrane vesicles such as exosomes. However, all new experiments mentioned above have been performed using primary donor photoreceptors isolated from, and transplanted into, wild-type mice. It remains to be clarified whether pluripotent stem cell–derived donor photoreceptors and host photoreceptors in disease models show a similar propensity for intercellular material transfer. 
In view from a different angle, the intercellular interaction observed between donor and host photoreceptors might represent an unexpected mechanism for the treatment of blinding diseases that need to be further explored. Given the improvements in visual performance following transplantation of rod5,6 or cone-like photoreceptors,7 transplanted cells might be useful vectors, and hence therapeutic biological tools, for supporting and repairing affected photoreceptors without substituting them. Another potential approach to regenerate murine photoreceptors, the reprogramming of Müller cells by spontaneous cell fusion with transplanted hematopoietic stem and progenitor cells was recently reported.8 
Altogether, our recent observations further support our strategy that for the development of a photoreceptor replacement therapy, the selection of appropriate animal models is of utmost importance. Severely degenerated models with significant loss of cone and rod photoreceptors, like the Cpfl1/rho−/− double transgenic mouse line described in our study,2 might represent benchmark models for photoreceptor replacement approaches, as they recapitulate the potential disease stage of patients most likely recruited for initial clinical trials and do not show the described transfer of cytoplasmic materials.2,9,10 
Again, we thank the authors for their critical analysis and suggestions as we believe that such debates are essential in this growing field for paving the way to successful clinical translation of cell-based therapies to treat retinal degeneration. 
References
Liang C, Zhang JJ, Chen D. Possibility of cytoplasmic transportation between donor–host cell following photoreceptor transplantation. Invest Ophthalmol Vis Sci. 2016; 57: 5335.
Santos-Ferreira T, Völkner M, Borsch O, et al. Stem cell-derived photoreceptor transplants differentially integrate into mouse models of cone-rod dystrophy. Invest Ophthalmol Vis Sci. 2016; 57: 3509–3520.
Santos-Ferreira T, Llonch S, Borsch O, Postel K, Haas J, Ader M. Retinal transplantation of photoreceptors results in donor-host cytoplasmic exchange. Nat Commun. 2016; 7: 13028.
Alvarez-Dolado M, Pardal R, Garcia-Verdugo JM, et al. Fusion of bone-marrow-derived cells with Purkinje neurons cardiomyocytes and hepatocytes. Nature. 2003; 425: 968–973.
Pearson RA, Barber AC, Rizzi M, et al. Restoration of vision after transplantation of photoreceptors. Nature. 2012; 485: 99–103.
Barber AC, Hippert C, Duran Y, et al. Repair of the degenerate retina by photoreceptor transplantation. Proc Natl Acad Sci U S A. 2013; 110: 354–359.
Santos-Ferreira T, Postel K, Stutzki H, Kurth T, Zeck G, Ader M. Daylight vision repair by cell transplantation. Stem Cells. 2014; 33: 79–90.
Sanges D, Simonte G, Di Vicino U, et al. Reprogramming Müller glia via in vivo cell fusion regenerates murine photoreceptors. J Clin Invest. 2016; 126: 3104–3116.
Eberle D, Kurth T, Santos-Ferreira T, Wilson J, Corbeil D, Ader M. Outer segment formation of transplanted photoreceptor precursor cells. PLoS One. 2012; 7: e46305.
Singh MS, Charbel Issa P, Butler R, et al. Reversal of end-stage retinal degeneration and restoration of visual function by photoreceptor transplantation. Proc Natl Acad Sci U S A. 2013; 110: 1101–1106.
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×