A Drug Eluting Scaffold for the Treatment of Arthrofibrosis

Abstract

Introduction: The inflammatory cascade and production of prostaglandins may play a role in the pathogenesis of arthrofibrosis, a debilitating condition after joint replacement and other orthopedic procedures. Cyclooxygenase 2 (COX-2) inhibitors may mitigate the inflammatory response and formation of arthrofibrosis, but oral delivery is associated with risk of systemic side effects in many patients. The nonsteroidal anti-inflammatory drug, celecoxib, may have therapeutic benefits for arthrofibrosis, but current methods for its local delivery (e.g., biologically derived microspheres) are not translatable to immediate clinical use. Therefore, we investigated the use of a drug scaffold for sustainable intra-articular delivery of therapeutic doses of celecoxib.

Materials and methods: Celecoxib was eluted from clinically approved biodegradable collagen membranes over 7 days as measured by UV spectroscopy and high-performance liquid chromatography/mass spectroscopy. Eluted concentrations of celecoxib were examined for toxicity (live/dead staining) and profibrotic gene expression (real-time-quantitative polymerase chain reaction) in rabbit knee capsular fibroblasts in vitro.

Results: Sustained concentrations of celecoxib eluted from the membrane over 7 days from both a wet and dry scaffold, with a burst release (30-45%) of celecoxib in the first 2 h. Rabbit cells treated with eluted concentrations experienced a toxic response to the burst release doses, and inhibitory effects on profibrotic genes were seen in response to the sustained doses eluted from the scaffold.

Conclusions: This study characterized the novel use of collagen scaffolds for intra-articular drug delivery to treat arthrofibrosis. Scaffolds exhibit celecoxib release through an initial burst release followed by sustained release of antifibrotic doses over 7 days. Thus, collagen scaffolds are promising for clinician-directed treatment of arthrofibrosis.

Keywords: arthrofibrosis; collagen; joint replacement.

FIG. 1.

Elution study design and loaded scaffold. (A) Two protocols (wet and dry) were used to study the elution of celecoxib from the scaffold. These designs are nearly identical, with the dry protocol requiring 24 h for the loaded membrane to dry before beginning the elution study. (B, C) The physical differences between the wet and dry protocols immediately before beginning the elution study display a more translucent and pliable wet scaffold.

FIG. 2.

SEM images of scaffold. (A–C) High-resolution images of the scaffold before loading celecoxib reveal the topography of the scaffold's surface. (D–F) SEM images of the scaffold after loading with celecoxib show the swelling of the collagen sheets (D) and a flattening of the textured surface (D–F). SEM, scanning electron microscopy.

FIG. 3.

Celecoxib elution from scaffold. (A–C) The elution profile for the wet scaffold between 0–8 h (A), 0–24 h (B), and 0–7 days (C) shows a large burst release within the first 2 h (∼43%) with ∼63% of total drug eluted by 7 days. (D–F) The dry scaffold allows for a lower burst release at 2 h (∼35%) and a higher total drug released at 7 days (∼90%).

FIG. 4.

Toxicity of eluted doses of celecoxib on rPOG cells. (A) Live/dead staining shows rPOG cells decreasing in density beginning at 100 μM, with nearly complete cell death at 200 μM. (B) rPOG cells saw a 50% reduction in live cells at 83 μM of celecoxib. (C, D) Toxic concentrations of rPOG (red dotted line) plotted against eluted concentrations of celecoxib from the scaffold reveal an initial cytotoxic burst release from wet and dry scaffolds (C), with every subsequent time point for the dry scaffold eluting subtoxic doses of drug (D). rPOG, rabbit primary outgrowth cells.

FIG. 5.

rPOG cellular response to eluted doses of celecoxib. (A) RNA was extracted at days 0, 3, and 7 of rPOG cells treated with low (5 μM) and moderate (30 μM) doses of celecoxib. (B) Decreased expression of profibrotic markers was observed at 7 days among rPOG cells treated with moderate doses of celecoxib (30 μM).

APPENDIX FIG. A1.

A plot of standard concentrations of celecoxib was used to measure the elution of celecoxib from dry and wet scaffolds. Absorbance at 252 nm was used as this has been previously reported in the literature as the UV absorbance of the celecoxib molecule.^A1

APPENDIX FIG. A2.

A repeated elution study of the wet scaffold using mass spectroscopy (MS) was used to confirm the data observed previously with UV-spectroscopy. This revealed a similar elution pattern observed in previous experiments, although with higher variability. This variability is believed to be a result of the ultrahigh resolution of MS, with certain reads potentially picking up non-representatively high/low doses of eluate.