In a recent study “Friction-Induced Mitochondrial Dysregulation Contributes to Joint Deterioration in Prg4 Knockout Mice” in the International Journal of Molecular Sciences lead by graduate student Kimberly Waller, they studied mice with the gene for lubricin (PRG4) knocked out and found upregulation of the caspase cascade in their cartilage. Injecting lubricin into the joints of these mice prevented this inflammatory and pro-apoptotic response and reduced friction in the joint.