R. Porter (Little Rock, US)
University of Arkansas for Medical Sciences Center for Musculoskeletal DiseasePresenter Of 1 Presentation
12.1.3 - A Chondrogenesis Reporter Rat for Evaluating Strategies to Stimulate Cartilage Repair
Abstract
Purpose
To support the preclinical development of novel treatments for cartilage injury, we generated a transgenic rat strain that can noninvasively report chondrogenesis for correlation with endpoint measures of tissue repair.
Methods and Materials
All animal studies were pre-approved by the local institutional ethics committee. A transgene was constructed in which the dual expression of bioluminescent (firefly luciferase) and fluorescent (mCherry) reporters is controlled by regulatory sequences from rat Col2a1. A transgenic line was established on a Lewis background and characterized by serial bioluminescence imaging and ex vivo measurement of reporter levels. The sensitivity and specificity of the strain were assessed using an osteochondral defect model in 6 month old or 2 year old rats. To stimulate healing, some defects were treated with rat bone marrow stromal cell aggregates.
Results
Bioluminescence imaging of the strain revealed substantive signal from cartilaginous regions, including the appendicular synovial joints, spine, sternum, nose, and pinnae. Bioluminescent radiance declined with postnatal development yet remained detectable in aged animals. Explant imaging, immunohistochemistry, and gene expression confirmed that both firefly luciferase and mCherry expression were localized to cartilage. Implantation of wild type bone marrow stromal cells into osteochondral defects made in young adult reporter rats led to a temporal elevation of intra-articular reporter activity concurrent with cartilaginous tissue repair (Figure 1). For aged rats, higher variability in bioluminescence signal was associated with generally poor repair of the cartilage phase with some restoration of the osseous phase. While mCherry-positive cells were detected in aged repair tissue, senescence associated β-galactosidase and p16INK4A immunostaining indicated the presence of abundant senescent cells (Figure 2). Ongoing studies are determining the influence of senolytic drug delivery on reporter activity and cartilage formation.
Conclusion
The reporter strain can serve as an initial preclinical model for testing strategies to stimulate chondrogenesis within articular cartilage defects.
Moderator Of 1 Session
- Participants will be provided novel insights into the processes of morphogenetic development involved in cartilage signaling and homeostasis and of the levels of regulation of tissue inflammation and immunity, including at the epigenetic level.