Diabetic retinopathy (DR) is a common, potentially devastating microvascular complication of diabetes. It is a leading cause of acquired blindness among working-age people. Current therapeutic options, such as laser photocoagulation, corticosteroids, anti-vascular endothelial growth factor agents and vitrectomy, are limited by their considerable side effects. Therefore, developing novel, mechanism-based therapeutic strategies is highly desirable for clinical management of DR. Adult bone marrow derived mesenchymal stem cells (BM-derived MSCs) offer the potential to open a new frontier in medicine.
This work performed to evaluate the possible therapeutic effect of BMMSCs and their exosomes in the treatment of diabetic retinopathy.
*Ten young male albino rats were used to isolate the BMMSCs and their exosomes.
*Sixty-four adult male albino rats were randomly divided into six groups :
Group I (control group; n=24): Twenty-four rats were divided equally into three subgroups; Ia, Ib and Ic.
Group II (affected group; n=8): Each rat was received a single intraperitoneal injection of STZ (60 mg/kg body weight), freshly dissolved in 0.2 mL of citrate buffer (0.1 mol/L, pH 4.5). A week later, rats were fasted, and blood glucose levels were determined; the rats with blood glucose levels higher than 250 mg/dL were considered diabetic.
Group III (DR + stem cell; n=8): Rats were treated as group II, then eight weeks after induction of diabetes, rats were injected intravitreally with a single dose of BMMSCs.
Summary & conclusion
050
Group IV (DR+ exosomes; n=8): Rats were treated as group II, then eight weeks after induction of diabetes, rats were injected intravitreally with single dose of PKH26 labelled MSC-Exosomes.
Group V (DR +stem cell + exosomes; n=8): Rats were treated as group II, then eight weeks after induction of diabetes rats were injected with BMMSCs and PKH26 labelled MSC-Exosomes together intravitreally in the same doses as group III and IV.
Group VI (recovery group; n=8): Rats were treated as group II and left for 12 weeks without treatment.
Rats of groups II were sacrificed 8 weeks after induction of diabetes. Rats of other groups (III, IV, V, VI) were sacrificed 12 weeks after induction of diabetes. Retinal samples were taken and processed for:
I-Histological studies:
Paraffin sections of 5-7 μm thickness, mounted on glass slides for:
a- Hematoxylin and Eosin stain to examine the histological changes in the different groups.
a- Periodic Acid Schiff (PAS) reaction for demonstration of glycogen deposition in retina.
II-Immunohistochemical staining:
a- Immunohistochemical staining for VEGF.
b- Immunohistochemical staining for vimentin.
c- Mesenchymal stem cells by detection of CD105 marker.
III-Transmission electron microscopic examination.
Summary & conclusion
051
The study revealed the following results:
Affected group showed apparent reduced retinal thickness, ganglion cells were disorganized, disturbed and widely separated. cytoplasmic vacuolation of the outer and inner nuclear cells and retinal pigment epithelium, pyknosis of most retinal cells with noticeable neovascularization. Immunohistochemical examination revealed marked PAS staining, significant VEGF and vimentin immunoreactivity. Electron microscopic examination confirmed the results.
Stem cell treated group showed little improvement in diabetic retinopathy induced by STZ (less vacuolations, pyknosis, neovascularization, wide separation of some cells and significant decrease (P˂0.05) in PAS staining and VEGF and vimentin immunoreactivity compared with group II.
Exosomes treated group showed slightly disorganized retinal cells with cytoplasmic vacuolations, apparently normal mitochondria with different sizes and shapes, with significant decrease (P˂0.05) in PAS staining and VEGF and vimentin immunoreactivity compared with group II.
Stem cells and exosomes group showed nearly normally arranged retinal layers and the same ultrastructure of retina. There was a significant decrease (P˂0.05) in PAS staining and also significant decrease in VEGF and vimentin immunoreactivity compared with group II.
Recovery group: There was no improvement in samples taken after 12 weeks of STZ injection. |
