Experimental Study on Nicotine-Nicotine acts directly on growth plate chondrocytes to delay enchondral ossification through the alpha7 homopentameric neuronal nicotinic acetylcholine receptor-

我们研究了尼古丁对人生长板软骨细胞的影响，生长板软骨细胞是软骨骨化的主要成分。这些软骨细胞是从额外的人类手指中提取的。人和小鼠生长板软骨细胞都表达α7烟碱型乙酰胆碱受体(NAChR)，它构成了功能性的同戊受体。尼古丁以浓度依赖的方式抑制悬浮培养的人生长板软骨细胞的基质合成和肥大分化。α7 nAChR的特异性拮抗剂甲基琥珀酸乌头碱(MLA)在体外可逆转尼古丁对人生长板软骨细胞基质合成和功能性钙内流的抑制作用。在体内，母体尼古丁暴露导致α7nAChR+/+胎儿骨骼生长延迟，但在α7nAChR-/-胎儿中没有，这意味着尼古丁对骨骼生长迟缓是通过胎儿α7nAChR特异性地介导的。这些结果表明，吸烟产生的尼古丁直接作用于生长板软骨细胞，减少基质合成，抑制肥大分化，从而通过α7nAChR延迟软骨骨化，导致骨骼生长延迟，骨折修复延迟或骨不连。

We investigated the effect of nicotine on human growth plate chondrocytes, a major component of enchondral ossification. The chondrocytes were derived from extra human fingers. Both human and murine growth plate chondrocytes expressed alpha7 nicotinic acetylcholine receptor(nAChR), which constitutes functional homopentameric receptors. Nicotine inhibited matrix synthesis and hypertrophic differentiation in human growth plate chondrocytes in suspension culture in a concentration-dependent manner. Methyllycaconitine(MLA), a specific antagonist of alpha7 nAChR, reversed the inhibition of matrix synthesis and functional calcium influx by nicotine in human growth plate chondrocytes in vitro. In vivo, maternal nicotine exposure resulted in delayed skeletal growth of alpha7 nAChR+/+fetuses but not in alpha7 nAChR-/-fetuses, implying that skeletal growth retardation by nicotine is specifically mediated via fetal alpha7 nAChR. These results suggest that nicotine, from cigarette smoking, acts directly on growth plate chondrocytes to decrease matrix synthesis, suppress hypertrophic differentiation, and consequently to delay enchondral ossification via alpha7 nAChR, leading to delayed skeletal growth and delayed fracture repair or non-union.