Heersche J N, Reimers S M, Wrana J L, Waye M M, Gupta A K
MRC Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, ON, Canada.
Proc Finn Dent Soc. 1992;88 Suppl 1:173-82.
We investigated whether the expressed phenotype of osteoblasts and odontoblasts is changing with increasing maturity of the cells. Thus we determined, using in situ hybridization techniques, whether the expression of mRNA's for osteocalcin and the alpha 1 type 1 collagen chain was different in newly developed and more mature cuboidal osteoblasts of the primary and secondary spongiosa of radii of 8 day old rats, in mature cuboidal and older flat osteoblasts in the metatarsals of pig embryos, and in apical and coronal odontoblasts of the developing unerupted molars of pig embryos. The results indicate that newly differentiated osteoblasts in the primary spongiosa of the 8 day rat radius contained approximately the same amount of type 1 collagen message as more mature osteoblasts in the secondary spongiosa. Osteocalcin mRNA, on the other hand, was undetectable in the newly differentiated osteoblasts but clearly detectable in the mature osteoblasts of the secondary spongiosa. When we compared expression of osteocalcin and collagen type 1 mRNA in mature cuboidal and older flat osteoblasts, we found that the amount of osteocalcin mRNA relative to collagen type 1 mRNA was higher in flat osteoblasts than in cuboidal osteoblasts. In odontoblasts, however, the steady state level of collagen type 1 mRNA was higher in the older coronal odontoblasts, and the level of osteocalcin message lower, when compared to the younger apical odontoblasts. The results indicate that relative levels of osteocalcin and collagen mRNA in osteoblasts and odontoblasts vary depending on the stage in their secretory lifetime. This heterogeneity of the osteoblast and odontoblast population suggests that the composition of the matrix produced by these cells also differs.
我们研究了成骨细胞和成牙本质细胞的表达表型是否会随着细胞成熟度的增加而发生变化。因此，我们使用原位杂交技术确定，在8日龄大鼠桡骨初级和次级海绵骨中，新发育的和更成熟的立方形成骨细胞中骨钙素和α1Ⅰ型胶原链的mRNA表达是否不同；在猪胚胎跖骨中成熟的立方形和成牙本质细胞与更成熟的扁平成骨细胞中是否不同；以及在猪胚胎未萌出的发育磨牙的根尖和冠部成牙本质细胞中是否不同。结果表明，8日龄大鼠桡骨初级海绵骨中新分化的成骨细胞所含的Ⅰ型胶原信息与次级海绵骨中更成熟的成骨细胞大致相同。另一方面，新分化的成骨细胞中未检测到骨钙素mRNA，但在次级海绵骨的成熟成骨细胞中可清楚检测到。当我们比较成熟立方形和成牙本质细胞与更成熟的扁平成骨细胞中骨钙素和Ⅰ型胶原mRNA的表达时，我们发现扁平成骨细胞中相对于Ⅰ型胶原mRNA的骨钙素mRNA量高于立方形成骨细胞。然而，在成牙本质细胞中，与较年轻的根尖成牙本质细胞相比，较成熟的冠部成牙本质细胞中Ⅰ型胶原mRNA的稳态水平更高，而骨钙素信息水平更低。结果表明，成骨细胞和成牙本质细胞中骨钙素和胶原mRNA的相对水平因它们分泌寿命的阶段而异。成骨细胞和成牙本质细胞群体的这种异质性表明，这些细胞产生的基质组成也不同。
