Use of Raman spectroscopy to identify active spermatogenesis and Sertoli-cell-only tubules in mice

Microdissection testicular sperm extraction (micro-TESE) has become the first line therapy to harvest spermatozoa for men with nonobstructive azoospermia. However, the pitfall is that the selection of seminiferous tubules depends on subjective assessment of the colour and size of tubules, which cannot guarantee successful retrieval of spermatozoa. The aim of this study was to determine whether Raman spectroscopy (RS) could distinguish tubules with spermatogenesis from Sertoli-cell-only (SCO) tubules, and potentially serve as a useful tool to improve sperm retrieval rates. Fourteen male adult mice were divided into two groups: SCO group received a single intraperitoneal injection of busulfan (40 mg per kg body weight), and the control group received a placebo dose of 0.9% saline solution. Mice were sacrificed after 4 weeks, and the testicular tissue was assessed by RS and then confirmed with histopathology. The results indicated that tubules with spermatogenesis had intensified Raman peaks at 748, 1124, 1309, 1446 and 1658 cm^-1 compared to SCO tubules, except a decreased peak at 1582 cm^-1 . RS was able to distinguish the two groups with a sensitivity of 91.2% and specificity of 82.9%. In conclusion, RS may serve as a useful diagnostic tool prior to sperm retrieval.