Laser injury promotes migration and integration of retinal progenitor cells into host retina.
OBJECTIVE
The migration and integration of grafted cells into diseased host tissue remains a critical challenge, particularly in the field of retinal progenitor cell (RPC) transplantation. It seems that natural physical barriers at the outer retina can impede the migration of grafted RPCs into the host retina. The purpose of this study was to investigate the integration and differentiation of murine RPCs transplanted into the subretinal space of mice with laser-induced damage to the outer retina.


METHODS
RPCs were harvested from the neural retinas of postnatal day 1 enhanced green fluorescent protein (GFP) mice. Retinal photocoagulation was performed using a diode laser. Two microl containing approximately 6x10(5) expanded RPCs in suspension were injected into the subretinal space of the recipient animals following laser treatment. Cell morphometry was performed to assess the integration of donor cells. Immunohistochemistry and western blot were performed on recipient retinas.


RESULTS
Three weeks after transplantation, 1,158+/-320 cells per eye had migrated into the recipient outer nuclear layer (ONL). Most of these cells resided in the ONL around the retinal laser lesion. A subpopulation of these cells developed morphological features reminiscent of mature photoreceptors, expressed photoreceptor specific proteins including synaptic protein, and appeared to form synaptic connections with bipolar neurons. Retinal photocoagulation resulted in a significantly increased expression of matrix metalloproteinase-2 (MMP-2), MMP-9, and cluster differentiation 44 (CD44s), and a decreased expression of neurocan.


CONCLUSIONS
Transplanted RPCs migrate and integrate into the laser-injured ONL where they differentiate into photoreceptors with morphological features reminiscent of mature photoreceptors, express synaptic protein, and appear to form synaptic connections with retinal bipolar neurons. Following retinal photocoagulation, the enhanced level of integration of grafted RPCs is partially associated with increased expression of MMP-2 and, to a lesser extent, MMP-9, together with decreased levels of inhibitory molecules.
Jiang
Caihui
C
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
Klassen
Henry
H
Zhang
Xinmei
X
Young
Michael
M
D000818:Animals; D002454:Cell Differentiation; D002465:Cell Movement; D002478:Cells, Cultured; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D018960:Hyaluronan Receptors / Q000378:metabolism; D007834:Lasers; D008028:Light Coagulation; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism; D058580:Neurocan; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology; D011509:Proteoglycans / Q000378:metabolism; D011832:Radiation Injuries / Q000601:surgery*; D012160:Retina / Q000166:cytology / Q000293:injuries* / Q000601:surgery; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D005456:Fluorescent Dyes; D018960:Hyaluronan Receptors; C507576:Ncan protein, mouse; D009419:Nerve Tissue Proteins; D058580:Neurocan; D011509:Proteoglycans; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9