Cellular phenotypes and spatio‐temporal patterns of lymphatic vessel development in embryonic mouse hearts

Abstract

Di‐stereoblock polylactides (di‐sb‐PLA: PLLA‐b‐PDLA) having high molecular weight (Mn > 100 kDa) were successfully synthesized by two‐step ring‐opening polymerization (ROP) of L‐ and D‐lactides using tin(2‐ethylhexanoate) as a catalyst. By optimizing the polymerization conditions, the block sequences were well regulated at non‐equivalent feed ratios of PLLA and PDLA. This synthetic method consisted of three stages: (1) polymerization of either L‐ or D‐lactide to obtain a PLLA or PDLA prepolymer with a molecular weight less than 50 kDa, (2) purification of the obtained prepolymer to remove residual lactide, and (3) polymerization of the enantiomeric lactide in the presence of the purified prepolymer. Their 13C and 31P NMR spectra of the resultant di‐sb‐PLAs strongly supported their di‐stereo block structure. These di‐sb‐PLAs, having weight‐average molecular weights higher than 150 kDa, were fabricated into polymer films by solution casting and showed exclusive stereocomplexation. The thermomechanical analysis of the films revealed that their heat deformation temperature was limited probably because of their low crystallinity owing to the non‐equivalent PLLA/PDLA ratio. The blend systems of the di‐sb‐PLAs having complementary stereo‐sequences (the one with a long PLLA block and the other with long PDLA block) were also prepared and characterized to enhance the sc crystallinity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 794–801, 2010

Epicardium is required for cardiac seeding by yolk sac macrophages, precursors of resident macrophages of the adult heart

“…One well established marker for cells of the monocyte/macrophage lineage is CD68 (Micklem et al, 1989). LYVE1 has also been reported to mark blood lineages including macrophages (Flaht et al, 2012), in addition to marking developing cardiac lymphatics (Flaht-Zabost et al, 2014). At E14.5, CD68 + and LYVE1 + cells were concentrated either within or adjacent to the epicardium, the epithelial layer that covers the surface of the heart (Fig.…”

Comparative and Developmental Anatomy of Cardiac Lymphatics

“…Nowadays, modern techniques allow lymphatic endothelial cells (LEC) with specific markers to be easily demonstrated in various species on histological, confocal microscope sections and by the use of the “whole mount” immunohistochemical method [22–25]. For detection of LEC it is recommended to demonstrate at least two markers simultaneously, such as Lyve-1 and Prox-1.…”

“…As development of lymphatics commonly followed blood vessel formation in the body of the embryo, the same sequence was observed in developing organs, such as the heart; that is, the lymphatics occurred later than blood vessels. The species studied were rats, mice, and birds such as quail and chicken [22–25]. …”

“…This may indicate that cardiac lymphatics may derive from the earliest cardiac veins. On the other hand, Prox-1 + /Lyve-1 − strands of cells, clusters, and finally tubules were found to invade the great arteries from the mediastinum of mouse fetuses at 12-13 dpc (Figure 2) and Prox-1 + /QH1 + strands of cells of quail fetuses at HH 26–36 stages, respectively [24, 25]. Contrary to what has been described in quail hearts the Prox-1-positive cells spread simultaneously on the arterial pole and on the atrial surface (the ventral and the dorsal aspect) of the developing mouse heart.…”

“…Contrary to what has been described in quail hearts the Prox-1-positive cells spread simultaneously on the arterial pole and on the atrial surface (the ventral and the dorsal aspect) of the developing mouse heart. These cells formed clusters and strands and subsequently, that is, at later stages of development, tubules/vessels that were CD31 and Lyve-1-positive (Figure 3) [25]. The mouse cardiac lymphangiogenesis proceeded on both surfaces of the heart: dorsal and ventral towards the apex in later stages of development.…”