Accelerated apoptosis in the Timp-3–deficient mammary gland
Jimmie E. Fata, … , Roger A. Moorehead, Rama Khokha
Jimmie E. Fata, … , Roger A. Moorehead, Rama Khokha
Published September 15, 2001
Citation Information: J Clin Invest. 2001;108(6):831-841. https://doi.org/10.1172/JCI13171.
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Article

Accelerated apoptosis in the Timp-3–deficient mammary gland

Abstract

The proapoptotic proteinase inhibitor TIMP-3 is the only molecule of this family thought to influence cell death. We examined epithelial apoptosis in TIMP-3–deficient mice during mammary gland involution. Lactation was not affected by the absence of TIMP-3, but glandular function, as measured by gland-to-body weight ratio and production of β-casein, was suppressed earlier during post-lactational involution than in controls. Histological examination revealed accelerated lumen collapse, alveolar-epithelial loss, and adipose reconstitution in Timp-3–/– females. Epithelial apoptosis peaked on the first day of involution in Timp-3–null glands but at day 3 in wild-type littermates. Unscheduled activation of gelatinase-A was evident by zymography and correlated with earlier fragmentation of fibronectin in Timp-3–/– mammary. To obtain independent evidence of the proapoptotic effects of TIMP-3 deficiency, we introduced recombinant TIMP-3–releasing pellets into regressing Timp-3–/– mammary tissue and showed that this treatment rescued lumen collapse and epithelial apoptosis. Ex vivo, involuting Timp-3–/– mammary tissue demonstrated accelerated epithelial apoptosis that could be reduced by metalloproteinase inhibition. The physiological relevance of TIMP-3 became apparent as Timp-3–/– dams failed to reestablish lactation after brief cessation of suckling. Thus, TIMP-3 is a critical epithelial survival factor during mammary gland involution.

Authors

Jimmie E. Fata, Kevin J. Leco, Evelyn B. Voura, Hoi-Ying E. Yu, Paul Waterhouse, Gillian Murphy, Roger A. Moorehead, Rama Khokha

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Figure 3

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(a and b) Hoescht stain revealed numerous apoptotic bodies (yellow arrow...
(a and b) Hoescht stain revealed numerous apoptotic bodies (yellow arrow) within lumens of Timp-3–null mammary glands at 1di, compared with markedly less in wild-type lumens at 1di. (c and d) Many apoptotic bodies were evident at 3di within still-existing lumens of wild-type tissue. In contrast, at 3di, few lumens existed in Timp-3–deficient tissue, and apoptotic cells were less abundant. (e) Quantification of apoptosis in involuting mammary glands from both genotypes revealed clear differences in the rate of cell death. The amount of apoptosis in wild-type tissue during mammary gland involution peaked at 3di. In contrast, apoptosis peaked at 1di in Timp-3–null mammary gland, with successive decreases thereafter. Significant differences in the amount of apoptosis between involuting wild-type and Timp-3–deficient mammary glands were found at 1di and 3di. *P < 0.05. The total amount of apoptosis from 10L to 7di did not significantly differ between wild-type and Timp-3–deficient mammary glands. Images and quantifications are derived from the area immediately distal to the lymph node. Scale bar in a–d, 50 μm.