Effects of supplemental intra-articular lubricin and hyaluronic acid on the progression of posttraumatic arthritis in the anterior cruciate ligament-deficient rat knee

Abstract

Background: Lubricin and hyaluronic acid lubricate articular cartilage and prevent wear. Because lubricin loss occurs after anterior cruciate ligament injury, intra-articular lubricin injections may reduce cartilage damage in the anterior cruciate ligament-deficient knee.

Purpose: This study was conducted to determine if lubricin and/or hyaluronic acid supplementation will reduce cartilage damage in the anterior cruciate ligament-deficient knee.

Study design: Controlled laboratory study.

Methods: Thirty-six male rats, 3 months old, underwent unilateral anterior cruciate ligament transection. They were randomized to 4 treatments: (1) saline (phosphate-buffered saline [PBS]), (2) hyaluronic acid (HA), (3) purified human lubricin (LUB), and (4) LUB and HA (LUB+HA). Intra-articular injections were given twice weekly for 4 weeks starting 1 week after surgery. Knees were harvested 1 week after the final injection. Radiographs of each limb and synovial fluid lavages were obtained at harvest. Histologic analysis was performed to assess cartilage damage using safranin O/fast green staining. Radiographs were scored for the severity of joint degeneration using the modified Kellgren-Lawrence scale. Synovial fluid levels of sulfated glycosaminoglycan, collagen II breakdown, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and lubricin were measured using enzyme-linked immunosorbent assay (ELISA).

Results: Treatment with LUB or LUB+HA significantly decreased radiographic and histologic scores of cartilage damage (P = .039 and P = .015, respectively) when compared with the PBS and HA conditions. There was no evidence of an effect of HA nor was the LUB effect HA-dependent, suggesting that the addition of HA did not further reduce damage. The synovial fluid of knees treated with LUB had significantly more lubricin in the synovial fluid at euthanasia, although there were no differences in the other cartilage metabolism biomarkers.

Conclusion: Supplemental intra-articular LUB reduced cartilage damage in the anterior cruciate ligament-transected rat knee 6 weeks after injury, while treatment with HA did not.

Clinical relevance: Although longer term studies are needed, intra-articular supplementation (tribosupplementation) with lubricin after anterior cruciate ligament injury may protect the articular cartilage in the anterior cruciate ligament-injured knee.

Figure 1

Mean OARSI scores for the PBS, HA, LUB, and LUB+HA treatment groups. The LUB and LUB+HA were significantly less than those of the PBS and HA groups (p<0.05). The error bars represent ± 1 standard deviation.

Figure 2

Images taken of the samples with the median OARSI score for each treatment group: A) PBS, B) HA, C) LUB, and D) LUB+HA. Note the loss of superficial zone cells (S), proteoglycan (P) and increased surface fibrillation (F) in the PBS- and HA-treated sections.

Figure 3

Mean modified Kellgren-Lawrence scores for the PBS, HA, LUB, and LUB+HA treatment groups. The LUB and LUB+HA were significantly greater than those of the PBS and HA groups (p<0.05). The error bars represent ± 1 standard deviation.

Figure 4

Lateral images taken of the right (R, treated) and contralateral control left knees (L, ACL intact) with the median modified Kellgren_Lawrence (KL) score for each treatment group: A) PBS, B) HA, C) LUB, and D) LUB+HA. In the PBS- and HA-treated groups, patellar spurring (P) and contour irregularity (C) are prominent.

Figure 5

Mean lubricin concentrations in the synovial fluid lavages at the time of joint harvest as a function of treatment group. The concentration was adjusted by comparing the urea concentration in serum and synovial fluid to obtain the dilution factors. The error bars represent ± 1 standard deviation.