Lymphatic vessels in human adipose tissue

Abstract

Despite being considered present in most vascularised tissues, lymphatic vessels have not been properly shown in human adipose tissue (AT). Our goal in this study is to investigate an unanswered question in AT biology, regarding lymphatic network presence in tissue parenchyma. Using human subcutaneous (S-) and visceral (V-) AT samples with whole mount staining for lymphatic specific markers and three-dimensional imaging, we showed lymphatic capillaries and larger lymphatic vessels in the human VAT. Conversely, in the human SAT, microcirculatory lymphatic vascular structures were rarely detected and no initial lymphatics were found.

More fat, less migration: breast density as a predictor of sentinel lymph node non-visualization in breast cancer

“…The rarity of lymphatic capillaries within human subcutaneous adipose tissue, as recently reported by Redonda et al [ 6 , 7 ], supports our finding that breast density plays an important role in the success of the lymphoscintigraphy protocol.…”

Characterizing Lymphangiogenesis and Concurrent Inflammation in Adipose Tissue in Response to VEGF-D

“…Obesity presents a chronic, inflammatory remodeling process in adipose tissue. Inflammation-associated lymphangiogenesis is often necessary to ameliorate inflammation, but despite increased expression of VEGF-C and VEGF-D reported in obesity, lymphatic vessels remain sparse in adipose tissue and those present demonstrate reduced function (Arngrim et al, 2013; Redondo et al, 2020). In this study we demonstrate that locally increasing VEGF-D levels specifically in the adipose tissue of Adipo-VD mice augmented lymphatic vessel structure formation in subcutaneous adipose depots.…”

“…Characterization of lymphatics in healing mouse hearts identified two separate mechanisms or subpopulations of cells, sprouting lymphangiogenesis and isolated LECs, contributing toward expanding lymphatics; the cell source of the new LECs was unclear (Gancz et al, 2019). Recently, an imaging study identified LYVE1+ cells from both endothelial and hematopoietic lineage within human adipose tissue (Redondo et al, 2020). This study reinforced that hematopoietic LYVE1+CD45+ cells associate with adipose lymphatics, but they do not form their structure.…”

“…The lymphangiogenic proteins vascular endothelial growth factor C (VEGF-C) and -D (VEGF-D), ligands for VEGFR-3, are elevated in adipose tissue during obesity (Karaman et al, 2015;Chakraborty et al, 2019). In humans, lymphatic density varies greatly from adipose depot to depot, but local lymphatic vessel function may still impact local adipose health (Redondo et al, 2020;Varaliova et al, 2020). In mice, lymphatics are absent in brown adipose tissue, rare in gonadal white adipose tissue, and sparse in subcutaneous adipose depots.…”

Homeostatic maintenance of the lymphatic vasculature

“…PD-L1 high LECs are protected from IFN-γinduced apoptosis, which is promoted by T cells that are recruited to the LN during resolution of the immune response [104]. VEGF-D-induced expansion of lymphatic vasculature in the adipose tissue, that under homeostasis has relatively few lymphatic vessels [109], is also reversible [110]. By contrast, mycoplasma-induced airway inflammation promotes lymphatic vessel hyperplasia that is sustained after inflammation resolution [111].…”