Lim M, Elfman F, Dohrman A, Cunha G, Basbaum C
Department of Anatomy, University of California, San Francisco 94143, USA.
Dev Biol. 1995 Oct;171(2):521-30. doi: 10.1006/dbio.1995.1301.
Submucosal glands secrete most of the mucus that lubricates the tracheal surface and protects it from irritants and infection. These glands develop postnatally in the rat, permitting convenient study of the mechanisms controlling this process. One such mechanism involves degradation of the supportive connective tissue matrix at the front of the growing glands. We recently showed that tracheal gland cell invasion of collagen gels in vitro is dependent on secretion of a 72-kDa type IV collagenase. In the present study, we show that the activity of this enzyme (also referred to as matrix metalloproteinase-2 or gelatinase A) is elevated at the time of gland development in vivo. That this increase is at least partly mediated at the level of steady-state mRNA was indicated by semiquantitative PCR analysis of gland-enriched, microdissected tissue samples. Immunohistochemistry revealed that the enzyme was present at the interface between the glands and extracellular matrix. In situ hybridization revealed that the cognate mRNA was present in epithelial cells of glands undergoing morphogenesis (particularly Postnatal Day 7) but not in those of adult glands or the surface epithelium. At all ages, stromal cells below the surface epithelium were labeled; labeling intensity was highest at the time and location of gland morphogenesis. These findings suggest that the 72-kDa type IV collagenase is developmentally regulated in gland and stromal cells at the level of steady-state mRNA and plays a role in the degradation of extracellular matrix during tracheobronchial gland morphogenesis.
黏膜下腺分泌大部分黏液，这些黏液润滑气管表面并保护其免受刺激物和感染。这些腺体在大鼠出生后发育，便于研究控制这一过程的机制。其中一种机制涉及在生长中的腺体前端支持性结缔组织基质的降解。我们最近发现，气管腺细胞在体外对胶原凝胶的侵袭依赖于一种72 kDa的IV型胶原酶的分泌。在本研究中，我们表明，这种酶（也称为基质金属蛋白酶-2或明胶酶A）的活性在体内腺体发育时升高。对富含腺体的显微切割组织样本进行的半定量PCR分析表明，这种增加至少部分是在稳态mRNA水平介导的。免疫组织化学显示，该酶存在于腺体与细胞外基质的界面处。原位杂交显示，同源mRNA存在于正在进行形态发生的腺体的上皮细胞中（特别是出生后第7天），但不存在于成年腺体或表面上皮的上皮细胞中。在所有年龄段，表面上皮下方的基质细胞都被标记；标记强度在腺体形态发生的时间和位置最高。这些发现表明，72 kDa的IV型胶原酶在腺体和基质细胞中在稳态mRNA水平上受到发育调控，并在气管支气管腺体形态发生过程中参与细胞外基质的降解。
