Department of Orthopaedic Surgery, University of California San Francisco, USA.
Department of Preventative and Restorative Dental Sciences, University of California San Francisco, USA; Department of Epidemiology and Biostatistics, University of California San Francisco, USA.
Osteoarthritis Cartilage. 2019 Jun;27(6):956-964. doi: 10.1016/j.joca.2019.01.013. Epub 2019 Feb 2.
Intradiscal biologic therapy is a promising strategy for managing intervertebral disc degeneration. However, these therapies require a rich nutrient supply, which may be limited by the transport properties of the cartilage endplate (CEP). This study investigated how fluctuations in CEP transport properties impact nutrient diffusion and disc cell survival and function.
Human CEP tissues harvested from six fresh cadaveric lumbar spines (38-66 years old) were placed at the open sides of diffusion chambers. Bovine nucleus pulposus (NP) cells cultured inside the chambers were nourished exclusively by nutrients diffusing through the CEP tissues. After 72 h in culture, depth-dependent NP cell viability and gene expression were measured, and related to CEP transport properties and biochemical composition determined using fluorescence recovery after photobleaching and Fourier transform infrared (FTIR) spectroscopy.
Solute diffusivity varied nearly 4-fold amongst the CEPs studied, and chambers with the least permeable CEPs appeared to have lower aggrecan, collagen-2, and matrix metalloproteinase-2 gene expression, as well as a significantly shorter viable distance from the CEP/nutrient interface. Increasing chamber cell density shortened the viable distance; however, this effect was lost for low-diffusivity CEPs, which suggests that these CEPs may not provide enough nutrient diffusion to satisfy cell demands. Solute diffusivity in the CEP was associated with biochemical composition: low-diffusivity CEPs had greater amounts of collagen and aggrecan, more mineral, and lower cross-link maturity.
CEP transport properties dramatically affect NP cell survival/function. Degeneration-related CEP matrix changes could hinder the success of biologic therapies that require increased nutrient supply.
椎间盘内生物治疗是治疗椎间盘退变的一种很有前途的策略。然而，这些治疗方法需要丰富的营养供应，而这可能受到软骨终板（CEP）转运特性的限制。本研究探讨了 CEP 转运特性的波动如何影响营养物质的扩散以及椎间盘细胞的存活和功能。
从六个新鲜的尸体腰椎（38-66 岁）中采集人 CEP 组织，将其放置在扩散室的开口侧。在室腔内培养的牛椎间盘核（NP）细胞仅由通过 CEP 组织扩散的营养物质滋养。培养 72 小时后，测量 NP 细胞的存活深度和基因表达，并与使用荧光恢复后光漂白和傅里叶变换红外（FTIR）光谱法确定的 CEP 转运特性和生化组成相关联。
在所研究的 CEP 中，溶质扩散系数变化近 4 倍，渗透性最低的 CEP 似乎具有较低的聚集蛋白聚糖、胶原-2 和基质金属蛋白酶-2 基因表达，以及从 CEP/营养界面的存活距离明显缩短。增加室腔细胞密度会缩短存活距离；然而，对于低扩散性 CEP，这种效应消失了，这表明这些 CEP 可能无法提供足够的营养扩散来满足细胞的需求。CEP 中的溶质扩散系数与生化组成有关：低扩散性 CEP 具有更多的胶原和聚集蛋白聚糖、更多的矿物质和更低的交联成熟度。
CEP 转运特性对 NP 细胞的存活/功能有很大影响。与退变相关的 CEP 基质变化可能会阻碍需要增加营养供应的生物治疗的成功。
