Background: LPAR5 is one of receptors for LPA (hemolytic phosphatidic acid) involved in regulating different pathological conditions, including pain, itching, brain inflammation and cancer. In microglia, LPAR5 signaling increased proinflammatory factors such as TNFα, IL-1β, IL-6, CXCL10, CCL5, CXCL12, nitric oxide (NO) and reactive oxygen species (ROS), then caused cerebral inflammation. LPAR5 is high-expressed in the dorsal root ganglion and function in modulating pain signal. LPA can induce neuropathic pain via LPAR1 or LPAR5 and upregulates neuropathic pain markers. In tumor cells, LPAR5 plays cancer-promoting and cancer-suppressing functions. LPAR5 is highly expressed in cancer-related macrophages and is positively correlated with its phagocytosis and antigen presentation. 

Application: The humanized mice can be used for the efficacy or safety evaluation of related drugs in tumor, cerebral inflammation and analgesic, et al. 

Model validation: Mouse Lpar5 mRNA was only detectable in wild-type C57BL/6 mice. Human LPAR5 mRNA was exclusively detectable in dorsal root ganglion of homozygous B-hLPAR5 mice. LPAR5 protein was not detectable in spleen, lung, stomach and colon. LPAR5 protein was detectable in brain and dorsal root ganglion in both wild-type C57BL/6 mice and homozygous B-hLPAR5 mice, as the LPAR5 antibody was cross-reactive between human and mouse.

Western blot analysis of LPAR5 protein expression in homozygous B-hLPAR5 mice by WB. Various tissues were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hLPAR5 mice (H/H), and then analyzed by western blot with anti-LPAR5 antibody (Aviva Systems, ARP65254_P050). 40 μg total proteins were loaded for western blotting analysis. GAPDH were detected as internal control. LPAR5 was not detectable in spleen, lung, stomach and colon. LPAR5 was detectable in brain and dorsal root ganglion in both wild-type C57BL/6 mice and homozygous B-hLPAR5 mice, as the LPAR5 antibody was cross-reactive between human and mouse. DRG: dorsal root ganglion. M: marker.

Strain specific analysis of LPAR5 mRNA expression in wild-type C57BL/6 mice and B-hLPAR5 mice by RT-PCR. DRG RNA were isolated from wild-type C57BL/6 mice (+/+) and homozygous B-hLPAR5 mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human LPAR5 primers. Mouse Lpar5 mRNA was only detectable in wild-type mice Human LPAR5 mRNA was exclusively detectable in homozygous B-hLPAR5 mice but not in wild-type mice. DRG: dorsal root ganglion.