Bone loss in MPTP mouse model of Parkinson's disease is triggered by decreased osteoblastogenesis and increased osteoclastogenesis.

Bone loss is a non-motor symptom of Parkinson's disease (PD). It is unclear whether a patient’s
immobility or the endocrine changes in the body causes bone deterioration. To address this issue,
we used an animal model of the disease where Swiss albino mice were injected with 1-methyl-4-
phenyl-1,2,3,6-tetrahydropyridine (MPTP) on day 1 and were left untreated for eight weeks.
Behavioral phenotypes of PD, and striatal acetylcholinesterase and dopamine levels were
measured. Cortical and trabecular bones were assessed by μ-CT and histology. Gene expression
studies were done through quantitative real-time PCR. Effect of MPP+ and MPTP-treated mice
serum on MC3T3E-1, SH-SY5Y, and primary osteoclast cells were also studied. Our results
demonstrated that MPTP treatment leads to PD like symptoms. It shows a loss of trabecular bone
mass and quality by decreasing osteoblast and increased osteoclast number and activity. This
effect was accompanied by reduced osteogenic and elevated osteoclastogenic genes expression.
While MPP+ had a cytotoxic effect on dopaminergic neurons, it did not affect bone cells.
However, ex-vivo treatment of the serum from MPTP treated mice decreased osteoblastogenesis
and increased osteoclastogenesis in cell culture. In conclusion, our study suggests that MPTP
induced parkinsonian features in mice leads to trabecular bone loss by decreased bone formation
and increased bone resorption due to changes in the serum circulating factors. This study
characterizes the microarchitectural and cellular changes in the skeleton of a mouse model of PD
that can be further utilized to investigate therapeutic avenues to treat bone loss in PD patients.