The infrapatellar fat pad is affected by injury induced inflammation in the rabbit knee: use of dexamethasone to mitigate damage.

Abstract

OBJECTIVE AND DESIGN:

The health of the infrapatellar fat pad (IFP) has been linked to pain, joint inflammation, and the onset of post-traumatic osteoarthritis. Thus, early inflammation effects on the IFP could have long term sequelae on joint integrity. This study was designed to characterize the natural history of the IFP in a model of surgically induced knee injury and inflammation, and to test the efficacy of one intra-articular (IA) administration of dexamethasone (DEX) immediately following surgery.

METHODS:

An IA bone drill hole injury to the rabbit knee was conducted and immediately treated with DEX (n = 12). Early and late post-surgical time-points were investigated (48 h and 9 weeks) and the outcome measures were analysis of IFP histology, mRNA levels for relevant molecules, and protein levels for a subset of cytokines. Data were analyzed against a surgical control (injury without treatment; n = 12), a surgical sham (capsular incision only; n = 12), and normal control (n = 6).

TREATMENT:

Single IA injection of DEX (0.5 mg/kg), administered at the completion of surgery.

RESULTS:

IFPs from injured joints exhibited significantly increased cellularity and early fibrosis at 48 h post surgery. While the histological inflammation from a capsular incision alone resolved, knee injured animals progressed to a significantly more fibrotic IFP by 9 weeks. DEX significantly lowered histological scores at 48 h, but not at the 9 weeks. DEX did not influence mRNA levels for IL-1β, 6, and 8, however, protein analysis indicated that IL-8 levels were lower in DEX treated joints. DEX resulted in significantly elevated expression of mRNA for MCP-1, leptin, and VEGF.

CONCLUSION:

One IA administration of a glucocorticoid appears to mitigate the initial inflammation within the joint, but is not sufficient to protect the joint to 9 weeks post-surgery.

• Authors: Bryan J Heard, Nathan M Solbak, May Chung, Yamini Achari, Nigel G Shrive, Cyril B Frank, David A Hart
• Journal: Inflammation research : official journal of the European Histamine Research Society ... [et al.] (Inflamm Res) Vol. 65 Issue 6 Pg. 459-70 (Jun 2016) ISSN: 1420-908X [Electronic] Switzerland
• PMID: 26898767 (Publication Type: Journal Article)

Chemical References

• Anti-Inflammatory Agents
• Cytokines
• Leptin
• RNA, Messenger
• Vascular Endothelial Growth Factor A
• Dexamethasone

Topics

• Adipose Tissue (drug effects, pathology)
• Animals
• Anti-Inflammatory Agents (pharmacology, therapeutic use)
• Cytokines (genetics, metabolism)
• Dexamethasone (pharmacology, therapeutic use)
• Female
• Fibrosis
• Injections, Intra-Articular
• Knee Injuries (complications, drug therapy, pathology)
• Knee Joint (drug effects, pathology)
• Leptin (genetics)
• RNA, Messenger (metabolism)
• Rabbits
• Vascular Endothelial Growth Factor A (genetics)