Di Nino Dana L, Crochiere Marsha L, Linsenmayer Thomas F
Department of Anatomy and Cellular Biology, Tufts University Medical School, Boston, Massachusetts 02111, USA.
Dev Dyn. 2002 Nov;225(3):250-9. doi: 10.1002/dvdy.10160.
We previously observed that the perichondrium (PC) and the periosteum (PO) negatively regulate endochondral cartilage growth through secreted factors. Conditioned medium from cultures of PC and PO cells when mixed (PC/PO-conditioned medium) and tested on organ cultures of embryonic chicken tibiotarsi from which the PC and PO have been removed (PC/PO-free cultures) effect negative regulation of growth. Of potential importance, this regulation compensates precisely for removal of the PC and PO, thus mimicking the regulation effected by these tissues in vivo. We have now examined whether two known negative regulators of cartilage growth (retinoic acid [RA] and transforming growth factor-beta1 [TGF-beta1]) act in a manner consistent with this PC/PO-mediated regulation. The results suggest that RA and TGF-beta1, per se, are not the regulators in the PC/PO-conditioned medium. Instead, they show that these two factors each act in regulating cartilage growth through an additional, previously undescribed, negative regulatory mechanism(s) involving the perichondrium. When cultures of perichondrial cells (but not periosteal cells) are treated with either agent, they secrete secondary regulatory factors into their conditioned medium, the action of which is to effect precise negative regulation of cartilage growth when tested on the PC/PO-free organ cultures. This negative regulation through the perichondrium is the only activity detected with TGF-beta1. Whereas, RA shows additional regulation on the cartilage itself. However, this regulation by RA is not "precise" in that it produces abnormally shortened cartilages. Overall, the precise regulation of cartilage growth effected by the action of the perichondrial-derived factor(s) elicited from the perichondrial cells by treatment with either RA or TGF-beta1, when combined with our previous results showing similar--yet clearly different--"precise" regulation by the PC/PO-conditioned medium suggests the existence of multiple mechanisms involving the perichondrium, possibly interrelated or redundant, to ensure the proper growth of endochondral skeletal elements.
我们之前观察到，软骨膜（PC）和骨膜（PO）通过分泌因子对软骨内软骨生长起负调节作用。将PC和PO细胞培养的条件培养基混合（PC/PO条件培养基），并在去除了PC和PO的胚胎鸡胫跗骨器官培养物（无PC/PO培养物）上进行测试，结果显示对生长有负调节作用。具有潜在重要性的是，这种调节精确地补偿了PC和PO的去除，从而模拟了这些组织在体内的调节作用。我们现在研究了两种已知的软骨生长负调节因子（视黄酸[RA]和转化生长因子-β1[TGF-β1]）的作用方式是否与这种PC/PO介导的调节一致。结果表明，RA和TGF-β1本身并不是PC/PO条件培养基中的调节因子。相反，研究表明这两种因子各自通过一种额外的、以前未描述的涉及软骨膜的负调节机制来调节软骨生长。当用这两种试剂中的任何一种处理软骨膜细胞（而非骨膜细胞）培养物时，它们会向其条件培养基中分泌二级调节因子，在无PC/PO器官培养物上进行测试时，这些因子的作用是对软骨生长进行精确的负调节。通过软骨膜的这种负调节是TGF-β1检测到的唯一活性。而RA对软骨本身还有额外的调节作用。然而，RA的这种调节并不“精确”，因为它会使软骨异常缩短。总体而言，用RA或TGF-β1处理从软骨膜细胞中引发的软骨膜衍生因子的作用对软骨生长进行的精确调节，再结合我们之前的结果，即PC/PO条件培养基显示出类似但明显不同的“精确”调节，这表明存在多种涉及软骨膜的机制，这些机制可能相互关联或冗余，以确保软骨内骨骼元件的正常生长。
