Evaluation of the efficacy of creatine chemical exchange saturation transfer imaging in assessing testicular maturity

PURPOSE: Microscopic testicular sperm extraction is the most effective treatment for NOA, but the sperm retrieval rate is low and depends on testicular maturity. However, there are limited useful tests to assess testicular maturity. Chemical exchange saturation transfer (CEST) imaging is a new magnetic resonance imaging (MRI) technique that can image the distribution of trace substances in vivo. We focused on the potential role of creatine (Cr) in testes and hypothesized that Cr‐CEST could indicate intratesticular spermatogenesis. METHODS: We performed Cr‐CEST by using 7T MRI on wild‐type C57B6/J mice and several types of male infertility models such as Sertoli‐cell only (SCO) (Kit(w)/Kit(wv)), maturation arrest (MA) (Zfp541 knockout mouse and Kctd19 knockout mouse), and teratozoospermia (Tbc1d21 knockout mouse). After performing Cr‐CEST, histological analysis was performed. RESULTS: The SCO and MA models showed decreased CEST signal intensity (p < 0.05), while no reduction was observed in the teratozoospermia model (p = 1.0). CEST signal intensity increased as the spermatogenesis stage progressed from the SCO model to the MA and teratozoospermia models. Furthermore, CEST signal intensity was reduced in 4‐week‐old wild‐type mice with immature testes (p < 0.05). CONCLUSIONS: This study suggests that Cr‐CEST evaluates intratesticular spermatogenesis noninvasively and provides a new therapeutic strategy for treating male infertility.