5, when lymphatic competence and commitment CHIR99021 GSK-3 are first detected and at EDs 10.5 and 11.5, when LEC progenitors bud off from the cardinal vein [8,11]. The finding that at EDs 9.5 and 10.5, RAR-�� was also expressed by some cells in clusters near cardinal veins raises the possibility that surrounding cells might contribute, by indirect effects, to the induction of lymphatic competence by RA. However, our observation that incubation of human umbilical vein endothelial cells with RA increased LYVE-1 mRNA expression by >2-fold (p = 0.042; online suppl. fig. S2A) and also increased LYVE-1 protein levels (online suppl. fig. S2B, C), suggests that the effects of RA are directly mediated by endothelial cells.

To investigate whether RA also promotes lymphatic competence and commitment in viv
Calcitonin, discovered more than 40 years ago [1, 2], exerts potent anti-resorptive effects on bone that are mediated by direct binding of calcitonin to its receptor on osteoclasts [3�C6]. Calcitonin is a small, 32-amino-acid peptide hormone produced by parafollicular cells (C cells) in the thyroid gland [7] and secreted in response to excess calcium in serum [8]. Various exogenous sources of calcitonin exist, of which salmon is among the most potent [7]. Calcitonin is approved for the treatment of osteoporosis and other diseases involving accelerated bone turnover [9�C11]. Calcitonin administration has been limited to either the subcutaneous or intranasal route [9]. Major obstacles to oral delivery of proteins include the high acid content of the digestive tract and the extensive array of proteases present there.

As a result, degradation of most peptides occurs before absorption into the bloodstream. Another barrier to uptake of many macromolecules is poor absorption through biological membranes [12, 13]. An optimal formulation of a medicinal peptide would facilitate transport through the acidic compartment as well as influx across the intestinal membrane. Attempts have been made to formulate calcitonin for oral administration [12�C23]. 8-(N-2-hydroxy-5-chloro-benzoyl)-amino-caprylic acid (5-CNAC), a molecule based on the Eligen technology, has proven useful preclinically and clinically in combination with calcitonin to facilitate calcitonin absorption from the intestinal lumen into the bloodstream [9, 10, 24].

Eligen technology employs low-molecular-weight compounds (termed drug delivery agents or carriers) that interact weakly and noncovalently with proteins, increasing their lipophilicity and, consequently, their ability to cross the gastrointestinal epithelium [25]. The carrier 5-CNAC makes drug available systemically by means of transcellular absorption, a common drug absorption pathway, without Drug_discovery compromising the integrity of the intestinal epithelium [26�C28].