Parathyroid hormone/parathyroid hormone‐related peptide modulates growth of avian sternal cartilage via chondrocytic proliferation

Abstract

Parathyroid hormone (PTH; 10 À7 to 10 À15 M) decreased terminal chondrogenesis in the avian sterna. During the first half of an 8-day culture, 100 nM PTH (1-34) significantly increased sternal length and downregulated the deposition of type X collagen and its mRNA expression. However, it remains unclear how PTH increased cartilaginous growth. In this study, we examined growth by both cell proliferation and analysis of cyclin d1 and collagen mRNA. Types II, IX, and X collagens and cyclin d1 mRNA were quantified through real-time RT-PCR, while Ki-67 was used as an immunohistochemical proliferation marker. Extracellular matrix content was measured through mRNA quantification of types II, IX, and X collagen and observing deposition of the same collagens. PTH significantly increased the proliferation marker Ki-67 in the sternal cephalic region. There was less type II and X collagen in PTHtreated sterna with concomitant decreases in mRNA production, suggesting that proliferation was the major contributor to cartilage growth in the presence of PTH/PTH-related peptide receptor activation. In conclusion, these experiments demonstrated that PTH increased cartilage growth by upregulating cell proliferation or other extracellular matrix components. Anat Rec, 290:155-167, 2007Rec, 290:155-167, . 2007 Wiley-Liss, Inc.

In vitro regulation of proliferation and differentiation within a postnatal growth plate of the cranial base by parathyroid hormone‐related peptide (PTHrP)

“…Proliferation of chondrocytes in this location in vivo disappeared between days 10 and 17, and was absent in control explants, but present in explants cultured in PTHrP for 7 days. Similarly, increased cell division was observed in chick embryonic sterna and postnatal growth plate chondrocytes when exposed to PTH or PTHrP (Farquharson et al, 2001;Harrington et al, 2007), and mouse embryonic metatarsi (Guo et al, 2002).…”

PTH Stimulated Growth and Decreased Col‐X Deposition are Phosphotidylinositol‐3,4,5 Triphosphate Kinase and Mitogen Activating Protein Kinase Dependent in Avian Sterna

“…The chick sternum tissue is easy to handle, measure, and provides enough material for biochemical, morphological, and molecular biological analysis. This tissue has the added advantage that each sternum has multiple chondrocyte developmental stages (Hirsch and Svoboda, 1998;Harrington, et al, 2007).…”

“…Sterna processed for Col-II, -IX, and -X immunohistochemistry were cut into three pieces, two lateral plates and keel (Harrington et al, 2007). The spine and lateral plates were removed longitudinally along the medial keel, maintaining cephalic-caudal and medial-lateral orientations.…”

“…The sterna were incubated for 1.5-3 hr in 0.1% testicular hyaluronidase (280 U/mg; Sigma), and washed in phosphate buffered saline (PBS). Tissues were fixed and prepared as previously described (Hirsh et al, 1997;Harrington et al, 2004Harrington et al, , 2007. Monoclonal antibodies specific for Col-II, IX, or X [1:200; Developmental Studies Hybridoma Bank, Iowa City, IA; (Schmid and Linsenmayer, 1985)] were used.…”

Immunolocalization of PTHrP in the parotid glands of three rodents species: Clethrionomys glareoulus, Microtus arvalis and white Swiss mice.

“…Later studies have shown that PTHrP is produced not only in neoplastic tissues but also by many healthy human and animal tissues: thyroid gland, parathyroid gland, pituitary gland, salivary gland, urinary bladder, kidney, mammary gland, testis, epididymis, cartilage, osteoblasts, vascular smooth muscle cells [2,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. PTHrP is a very conservative peptide.…”