Generation of humanized LDHC knock-in mice as a tool to assess human LDHC-targeting contraceptive drugs

Background: Lactate dehydrogenase C (LDHC) is specifically expressed in male germ cells and plays critical roles in glycolysis. Glycolysis is required to supply energy for sperm motility. Previous studies showed that Ldhc knock-out mice exhibit impaired sperm motility.

Objectives: We established human LDHC knock-in (hLDHC KI) mice and examined whether hLDHC KI mice can be used to assess LDHC-targeting drugs.

Material and methods: HLDHC was knocked-in to the mouse Ldhc (mLdhc) allele using the CRISPR/Cas9 system. Mating tests, sperm motility examinations with a computer-assisted sperm analysis (CASA) system, and in vitro fertilization (IVF) were performed. Furthermore, the effect of an LDH inhibitor was analyzed with CASA and IVF.

Results: HLDHC was detected at the protein level in hLDHC KI spermatozoa. hLDHC KI mice exhibited comparable sperm motility and male fertility to wild-type (WT) mice. When we performed IVF using the LDH inhibitor more specific to hLDHC than mLDHC, fertilization rates were reduced in hLDHC KI mice but not in WT mice.

Discussion and conclusion: Our results reveal that hLDHC can rescue the absence of mLDHC. Differences in the effect of the LDH inhibitor between WT and hLDHC KI mice indicate that hLDHC KI mice can be a good model to assess hLDHC inhibitors for preclinical contraceptive studies.