Divergent Requirements for Glutathione Biosynthesis During Osteoclast Differentiation In Vitro and In Vivo

Glutathione (GSH) is the most abundant antioxidant in the cell, and it is responsible for neutralizing reactive oxygen species (ROS). ROS can promote osteoclast differentiation and stimulate bone resorption and are some of the primary drivers of bone loss with aging and loss of sex steroids. Despite this, the role of GSH biosynthesis during osteoclastogenesis remains controversial. Here, we show that the requirements for GSH biosynthesis during osteoclastogenesis in vitro and in vivo are unique. Using a metabolomics approach, we discovered that both oxidative stress and GSH biosynthesis increase during osteoclastogenesis. Inhibiting GSH biosynthesis in vitro via the pharmacological or genetic inhibition of glutamate cysteine ligase (GCLC) prevented osteoclast differentiation. Conversely, the genetic ablation of GCLC in myeloid cells using LysMCre resulted in a decrease in bone mass in both male and female mice. The decreased bone mass of the LysMCre;Gclc mice was attributed to increased osteoclast numbers and elevated bone resorption. Collectively, our data provide strong genetic evidence that GSH biosynthesis is essential for the regulation of osteoclast differentiation and bone resorption in mice. Moreover, these findings highlight the necessity of complementing in vitro studies with in vivo genetic studies.