ObjectiveTo observe the effect of lysophosphatidylcholine acyltransferase-1 (LPCAT1) deficiency on the structure and electrophysiology of the murine retina. MethodsRd11 mice (Lpcat1 homozygous mutant, n=60) and wild-type C57BL/6J mice (n=60) were used in this study. Immunohistochemistry was performed to determine the expression of LPCAT1 in the mouse retina. Retinas of rd11 mice and age-matched control mice at postnatal 3, 6, 9-day and 2, 4, 6, 8-week were paraffin embedded,sectioned and hematoxylin eosin stained, and full-field electroretinograms (F-ERG) were also recorded at these time points. Statistics were based on independent samples t-test. ResultsLPCAT1 was absent in rd11 mice retina. In wild-type C57BL/6J mice retina, LPCAT1 was expressed most strongly in the inner segment of photoreceptor cells, weak in the ganglion cell layer. Rd11 mouse exhibited retinal degeneration and eventual photoreceptor cell loss. Retinas of rd11 mice showed nearly half of the photoreceptor cells missing around postnatal week 4,and by 6-week after birth only two layers of nuclei remained. At postnatal week 8,nearly all photoreceptor cells were lost. Dark-adapted F-ERG showed reduced rod-driven response at 2 and 4 weeks of age, which was flattened by 6 and 8 weeks of age. By 2 weeks of age, no significant difference was found in b-wave amplitude between rd11 eyes [(72.8±15.6) μV] and C57BL/6J eyes [(105.2±21.1) μV] (t=-2.760, P=0.025). Compared with age-matched control mice [(231.8±32.0)μV], rod response of rd11 mice [(20.6±6.4) μV] decreased obviously at postnatal week 4 (t=-14.471, P=0.000). Cone response was nearly normal at 2 and 4 weeks of age but substantially reduced at 6 weeks of age, which was flattened by 8 weeks of age. At 2 and 4 weeks after birth, no significant difference was found in b-wave amplitude between rd11 eyes [(46.8±7.2), (78.0±8.2) μV] and C57BL/6J eyes [(42.8±6.4), (91.4±9.4) μV] (t=0.930, -2.401; P=0.379, 0.043). Compared with age-matched control mice [(116.2±12.9) μV], cone response of rd11 mice [(17.2±2.0) μV] decreased obviously at postnatal week 6 (t=-17.008, P=0.000). ConclusionThe layers of photoreceptor cells nuclei in rd11 mice decreases with age, and its F-ERG reflection is unusual.
Stargardt disease (STGD) is an inherited disorder of retinal pigment epithelium. Three genes have been found to be implicated in STGD including Abca4 (adenosine triphosphate-binding cassette, sub-family A, member 4), Elovl4 (elongation of very long chain fatty acids protein 4) and Prom1 (prominin-1). Target genes can be delivered to the retina by various methods such as lentivirus (LV) vectors, adeno-associated virus (AAV) vectors and non-viral nano-particles. The Abca4-/-, Elovl4-/- and Prom1-/- mice model are used to study the pathogenesis mechanism and treatment of STGD. Retinal function improved significantly upon gene therapy in these models. Based on these works using animal model, phase Ⅰ/Ⅱa clinical trial of Abca4-associated STGD gene therapy are underway. AsaLV vector, equine infectious anemia virus (EIAV) is used to carry the Abca4 gene. These studies will evaluate three dose levels of the EIAV vector for safety, tolerability and biological activity. Moreover, some preclinical attempts to deliver Abca4 via AAV have been made usingamodified AAV vectors because of the large size of the ABCA4 cDNA. The good responses in animal models render STGDavery attractive object for human gene therapy after the successful of the phase Ⅰ/Ⅱ clinical trials of Leber′s congenital amaurosis.