S1PR1 and diabetes mellitus: Densitometric analysis of the bands demonstrated a significant increase in PLA1A (p = 0.042; Mann–Whitney test), AGK (p < 0.001; Mann–Whitney test), S1PR1 (p < 0.001; Mann–Whitney test), and SPL (p = 0.032; Mann–Whitney test) expressions in vitreous fluid samples from PDR patients compared to control patients without diabetes (Figure 3).