Determining the role of a novel human OA-associated SIRT5 allele in osteoarthritis development

The National Institute of Arthritis and Musculoskeletal and Skin Diseases awarded Ohio University $665,615 on August 15, 2026, under the Arthritis, Musculoskeletal and Skin Diseases Research program (CFDA 93.846) to investigate the role of a novel SIRT5 allele in osteoarthritis development.

The research examines how altered SIRT5 activity in chondrocytes disrupts cellular metabolism and joint inflammation to increase osteoarthritis susceptibility. The recipient will conduct studies on a rare coding mutation in SIRT5 (F101L substitution) identified in a family with early-onset osteoarthritis, using genome-edited mice carrying the human SIRT5 mutation to understand how decreased SIRT5 activity alters synovial joint homeostasis and promotes disease development. The work builds on prior findings demonstrating that SIRT5-dependent lysine demalonylation maintains chondrocyte metabolic balance and that SIRT5 expression declines with aging in both mice and humans.

Performance takes place in Ohio. The period of performance extends through June 30, 2031. This is a Project Grant, a form of assistance funding supporting discrete research projects under NIAMS' mandate to support research into the causes, treatment, and prevention of arthritis and musculoskeletal diseases.

Abstract

Osteoarthritis (OA) is a debilitating disease characterized by loss of joint space, degeneration of cartilage at articular surfaces, and remodeling of bone and other joint tissues. Although IT is the major cause of disability in the aged population, not a single disease modifying drug is available. The functions and identities of the biological processes that pose vulnerabilities to OA and need to be targeted therapeutically are not known. We propose that altered sirtuin 5 (SIRT5) activity in chondrocytes disrupts cellular metabolism and inflammation of the joint to confer heightened susceptibility to OA. Our recently published work has demonstrated SIRT5-dependent lysine demalonylation (MAK) plays a pivotal role in maintaining chondrocyte metabolic balance. We showed that SIRT5 expression in cartilage declines during aging in both mice and human and this decrease leads to a higher level of MAK and dysregulated chondrocyte cellular metabolism. Both SIRT5 systemic and cartilage specific knockout mice have early onset OA and develop more severe OA pathology compared with WT when challenged with a high-FAT-diet. We have identified a rare coding mutation in SIRT5 that dominantly segregates in a family with OA. The mutation results in substitution of an evolutionally invariant phenylalanine to leucine (F101L) in the catalytic domain. Our preliminary data indicate that SIRT5F101L is hypomorphic. Overexpression of the F101L mutant in primary chondrocytes results in higher MAK level and decreased expression of cartilage ECM genes and upregulation of inflammatory genes. We used precise genome editing to introduce the human SIRT5 mutation (F101L) into C57BL/6J mice. While our data indicates that SIRT5 is important for chondrocyte homeostasis, we do not understand how decreased SIRT5 activity alters synovial joint homeostasis to promote OA development. The SIRT5F101L mice harboring the hypomorphic human mutation provides US with a unique opportunity to determine how reduced SIRT5 activity alters chondrocyte metabolism and joint inflammation in vivo. The overall objective of this project is to determine mechanistically how the SIRT5F101L mutant alters chondrocyte metabolism and joint inflammation and test if the SIRT5F101L mutant allele is sufficient to alter susceptibility to injury- obesity-, or aging- induced OA in mice. Our central hypothesis is that the SIRT5F101L mutant mice will have metabolic dysfunction and increased inflammation in chondrocytes that will render them more susceptible to OA. We will test this hypothesis via two aims. In aim 1 we use a genetically modified mouse that harbors the human F101L mutation to test if SIRT5F101L alters the response to joint injury or aging and a high-FAT diet induced obesity. In aim 2 we use primary chondrocytes isolated from WT and SIRT5F101L mice to quantify changes in mitochondrial metabolism and anaerobic glycolysis and investigate the molecular targets of SIRT5. We will also investigate the joint pathologies of double mutant mouse lines (SIRT5F101L:RIPK2104ASP, increased pathway activity or SIRT5F101L:RIPK2-/-, reduced pathway activity) to explore the genetic interaction between SIRT5 and RIPK2.