Early removal of the infrapatellar fat pad beneficially alters the pathogenesis of moderate stage idiopathic knee osteoarthritis in the Dunkin Hartley guinea pig

Abstract

Background: The infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain unknown. To determine the influence of this depot on joint health, this study determined the progression of osteoarthritis (OA) following excision of the IFP in a rodent model of naturally-occurring disease. Methods: Male Dunkin-Hartley guinea pigs (n=10) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Treadmill-based gait analysis was performed prior to IFP removal and monthly thereafter. Animals were harvested at 7 months of age. Both knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC). Results: Fibrous connective tissue (FCT) developed in place of the native fat pad. Gait demonstrated no significant differences between IFP removal and contralateral limbs. MicroCT OA scores were improved in knees with the FCT. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and inflammatory mediators in FCTs compared to IFPs. This was corroborated via IHC for select inflammatory mediators. Discussion/Conclusion: Formation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. A decrease in inflammatory mediators at transcript and protein levels may be associated with these improvements. The IFP may therefore play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits.

The Corpus Adiposum Infrapatellare (Hoffa’s Fat Pad)—The Role of the Infrapatellar Fat Pad in Osteoarthritis Pathogenesis

“…A meta-analysis from Great Britain showed that 23.1% of IFPs were resected, 62.4% were partially resected and 9.8% were preserved with no difference in postoperative patient satisfaction between these groups [2]. In accordance with this low rate of IFP-preserving surgical procedures, one recent experimental animal study demonstrated that preservation of IFP may have a negative impact on the development of OA [66]. After removal of the IFP in the rodent model of guinea pigs, fibrous connective tissue developed at the site of the previously resected IFP after a couple of months.…”

“…After removal of the IFP in the rodent model of guinea pigs, fibrous connective tissue developed at the site of the previously resected IFP after a couple of months. Comparing IFP-resected and IFP-preserved knees in those rodents, reduced OA-associated damage to subchondral bone and articular cartilage was observed in IFP-resected knees [66]. However, the definite consequences of IFP resection or preservation during TKA are controversially discussed and not fully understood.…”