Comparative effects of bone morphogenetic proteins and Sox9 overexpression on matrix accumulation by bovine anulus fibrosus cells - Implications for anular repair

Study Design. An in vitro biologic study comparing the effects of a series of bone morphogenetic proteins (BMPs) and Sox9 on the extracellular matrix accumulation by bovine anulus fibrosus (AF) cells. Objective. To compare the effects of adenoviral-mediated overexpression of various BMPs and Sox9 on extracellular matrix accumulation by AF cells in vitro. Summary of Background Data. Repair of the disrupted AF, which is perceived to be a potential therapy to diminish nucleus pulposus (NP) herniation, may also offer a treatment strategy for severe symptomatic degenerative disc disease. To date, no systematic comparison of a large group of growth factors in the AF has been published. In this study, we compared the effects of the adenoviralmediated overexpression of 12 BMPs and Sox9 on extracellular matrix production by AF cells. Methods. Adult monolayer-cultured bovine AF cells were transduced with adenoviral vectors containing human BMP and green fluorescence protein (GFP) genes (AdBMPs), or Sox9 and GFP genes (AdSox9), or GFP gene alone (AdGFP, as negative control). Proteoglycan and collagen accumulation, and cell proliferation were measured for each of the treatment groups 6 days after viral transduction. Results. AF cells transduced with BMP-2, -3, -5, -7, -8, -12, -13, -14, and -15, and Sox9 accumulated significantly more collagen than AF cells transduced with AdGFP ( control). AF cells transduced with AdBMP-2, -4, -7, -10, -12, and -13, and AdSox9 accumulated significantly more proteoglycans than AF cells transduced with AdGFP. Conclusion. We have demonstrated the relative effectiveness of 12 different BMPs and Sox9 on the stimulation of proteoglycan and/or collagen accumulation by AF cells. This study is the first to compare the relative effectiveness of various BMPs and Sox9 on extracellular matrix accumulation by AF. This information should prove useful to those seeking to develop a strategy for repair of the AF in humans.