{'fraction_non_alphanumeric': 0.022920759659463, 'fraction_numerical': 0.010478061558611657, 'mean_word_length': 6.1069767441860465, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Non‐lumenal lymphatic/blood endothelial cell connections exist at the capillary level in unstimulated adult rat mesenteric microvascular networks

Recent observations from our laboratory suggest that lymphatic and blood endothelial cells physically interact at the capillary level in adult microvascular networks. The objective of this study was to 1) examine the endothelial cell structure and phenotypes at lymphatic/blood vessel connections and 2) to determine whether physical connections provide sites of fluid conductance. Mesenteric tissues were harvested from adult male Wistar rats (350 25 g) and labeled for PECAM and LYVE‐1, Prox‐1, or Podoplanin. Direct lymphatic/blood endothelial cell connections were supported by continuous PECAM junctional labeling in < 1 µm optical sections using confocal microscopy. While PECAM labeling identified both lymphatic and blood capillaries at locations of direct lymphatic/blood endothelial cell connections, LYVE‐1, Prox1, and Podoplanin expression did not extend along the blood capillary segments. PECAM positive lymphatic sprouts, structurally similar to blood capillary sprouts, also lacked observable lymphatic marker labeling. At 21/21 sites of connections, BSI‐lectin labeling via intra‐mesenteric artery injection did not identify the lymphatic vessel. These observations suggest that non‐lumenal lymphatic/blood endothelial cell connections exist in unstimulated adult microvascular networks and highlight the potential for lymphatic/blood endothelial cell plasticity.