Retinal degeneration processes and transplantation of retinal pigment epithelial cells: past, present and future trends

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part II: Cell and Tissue Engineering Therapies

Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 y.o. people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting on intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, different treatment options have to be considered. Cell therapy is a very promising alternative to drug-based approaches for AMD treatment. Cells delivered to the affected tissue as a suspension have shown poor retention and low survival rate. A solution to these inconveniences has been the encapsulation of these cells on biomaterials, which contrive to their protection, gives them support, and favor their retention of the desired area. We offer a two-papers critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In this second part we review the preclinical and clinical cell-replacement approaches aiming at the development of efficient AMD-therapies, the employed cell types, as well as the cell-encapsulation and cell-implant systems. We discuss their advantages and disadvantages and how they could improve the survival and integration of the implanted cells.

Astragaloside IV protects retinal pigment epithelial cells from apoptosis by upregulating miR‑128 expression in diabetic rats

The present study aimed to investigate the protective effects exerted by astragaloside‑IV (AIV) on retinal pigment epithelial (RPE) cells of rats with diabetes mellitus (DM), and to explore the underlying molecular mechanisms. For this purpose, a rat model of DM was established by injecting rats with an intraperitoneal injection of streptozotocin. AIV was then intragastrically administered. An electroretinogram (ERG) was used to assess retinopathy and TUNEL staining was used to detect the level of apoptosis of RPE cells. Western blot analysis was used to determine protein expression in RPE cells in vitro and in vivo. AIV was found to be able to significantly increase body weight and decrease blood glucose levels in rats with DM in a dose‑dependent manner. Compared with the rats with DM, the rat rod cell response a wave, b wave, maximum response b wave, photopic (photo)‑ERG b wave and oscillatory potential (OP) p4 wave latency significantly decreased and the amplitude of OP Os1 wave increased significantly in the rats with DM treated with AIV for 11 weeks. In addition, AIV significantly decreased the apoptotic levels of RPE cells from rats with DM and significantly decreased the protein expression levels of Bax/Bcl‑2, Fas/FasL, active caspase‑3, active caspase‑8, active caspase‑9, homeobox B3 (HOXB3), p‑phosphoinositide 3‑kinase (PI3K)/PI3K, p‑AKT/AKT and p‑p70S6K1/p70S6K1, whereas it significantly increased miR‑128 expression in the RPE cells from rats with DM. In vitro, AIV significantly inhibited the high glucose (HG)‑induced apoptosis of RPE cells by increasing miR‑128 expression and Bcl‑2 and FasL protein expression in vivo. On the whole, the findings of the present study demonstrate that AIV treatment protects RPE cells of diabetic rats from apoptosis, and that these effects may be associated with the upregulation of miR‑128 expression.

Epidermal growth factor: the driving force in initiation of RPE cell proliferation

BACKGROUND

To analyze whether epidermal growth factor (EGF) exerts regulatory effects on proliferation and differentiation in ARPE19 cells after different incubation periods (24 vs. 48 h) for obtaining ideal conditions for feasible rejuvenation and autologous transplantation of retinal pigment epithelial cells (RPE cells).

METHODS

To evaluate gene expression patterns of RPE-specific differentiation and proliferation markers as well as transcriptional and translational changes of beta-catenin (ß-catenin)-signaling markers by fluorescence activated cell sorting (FACS) and reverse transcription - polymerase chain reaction (RT-PCR) after 24 h of EGF treatment.

RESULTS

After 24 h of EGF treatment, a significant decrease of retinal pigment epithelium-specific protein 65 (RPE 65), cellular retinaldehyde-binding protein (CRALBP) and cytokeratin 18 in ARPE-19 cells was scaled. In addition, an increase of cyclin D1 expression and a significant decrease of glycogen synthase kinase-3beta (GSK-3ß) and beta-catenin (ß-catenin) were equally observed after 24 and 48 h of EGF treatment. Cell-cycle studies revealed an increase of ARPE cells in S-G2/M phase after 24 h of EGF treatment.

CONCLUSIONS

Our data demonstrate the induction of proliferation and upregulation of the ß-catenin signaling pathway by EGF even after 24 h of incubation. As ideal cell culture conditions are essential for maintaining RPE-specific phenotypes, short incubation times enhance RPE cell quality for feasible rejuvenation and subsequent autologous transplantation of RPE cells.