6.3.1 Liver Sinusoidal Endothelial Cells (LSECs)
LSECs are a highly specialized type of endothelial cells that constitute the barrier
between the blood and hepatocytes in liver sinusoids. They possess small pores—
fenestrations that determine the healthy phenotype of LSECs. Fenestrations with the
diameter ca. 150 nm enable the molecules’ trafficking between the blood and
hepatocytes across sinusoids [146, 147]. However, among other LSECs’ specific
features, the fenestrations are lost within 2–3 days after introducing cells into a
culture [148]. Therefore, it is necessary to take this fact into account while planning
the research involving LSECs. However, their isolation protocol has been well
established over past decades; it involves a few steps such as perfusion of the
selected organ, digestion of the connective tissue, purification of cell suspension,
and separation of chosen cells’ fractions [149].
The isolation of liver cells followed by Raman spectroscopy measurements
based on above-mentioned protocol was previously reported for hepatocytes [150],
hepatic stellate cells [151], and LSECs [152]. Morphologically, LSECs display a
typical fenestrated shape and have a size around 30 µm and round-shaped nucleus
(size around 6 µm) which seems to be densely packed in contrast to a very thin
cytoplasm. With use of Raman spectroscopy, LSECs can be characterized by relatively intense DNA/RNA signals at 787 and 1585 cm
−1 (Fig. 6.7) arising from the
nucleus. Raman spectroscopic studies reveal also the ability of these cells to form
LDs. Moreover, detailed analysis of LDs shows their chemical composition
heterogeneity; they can be composed mainly of triacylglyceroles of saturated or
monounsaturated fatty acids. LDs assigned as saturated are characterized by the
Raman profile of saturated fatty acids with specific marker bands at 1064, 1130,
1305, 1444, and 2880 cm
−1 , and on the other hand, bands at 1267, 1657, and
3015 cm
−1 are characteristic for unsaturated lipids [90]. The comparison of Raman
spectra obtained from isolated LSECs and a cultured cell line (TSECs—Transfected
Sinusoidal Endothelial Cells [153]) reveals some differences. The characteristic,
strong nuclear DNA signals are no longer so intense as in primary LSECs, and the
cytoplasm seems to be much more thicker as the Raman spectrum is more pronounced for TSECs. On the other hand, both cell types possess lipid droplets that
also, in some cases, are heterogenic in composition as it is observed for isolated
LSECs.
6.3.2 Cardiac Microvascular Endothelial Cells (CMECs)
The heart consists of different cell types including endothelial cells, cardiomyocytes, and fibroblasts. The cross—talk between them has the greatest impact on
maintaining the cardiac homeostasis and autoregulation. The cell–cell communication is realized with numerous cardioactive factors secreted in both directions:
from microvascular endothelial cells to cardiomyocytes and vice versa [154, 155].
180
K. Czamara et al.
LSECs are a highly specialized type of endothelial cells that constitute the barrier
between the blood and hepatocytes in liver sinusoids. They possess small pores—
fenestrations that determine the healthy phenotype of LSECs. Fenestrations with the
diameter ca. 150 nm enable the molecules’ trafficking between the blood and
hepatocytes across sinusoids [146, 147]. However, among other LSECs’ specific
features, the fenestrations are lost within 2–3 days after introducing cells into a
culture [148]. Therefore, it is necessary to take this fact into account while planning
the research involving LSECs. However, their isolation protocol has been well
established over past decades; it involves a few steps such as perfusion of the
selected organ, digestion of the connective tissue, purification of cell suspension,
and separation of chosen cells’ fractions [149].
The isolation of liver cells followed by Raman spectroscopy measurements
based on above-mentioned protocol was previously reported for hepatocytes [150],
hepatic stellate cells [151], and LSECs [152]. Morphologically, LSECs display a
typical fenestrated shape and have a size around 30 µm and round-shaped nucleus
(size around 6 µm) which seems to be densely packed in contrast to a very thin
cytoplasm. With use of Raman spectroscopy, LSECs can be characterized by relatively intense DNA/RNA signals at 787 and 1585 cm
−1 (Fig. 6.7) arising from the
nucleus. Raman spectroscopic studies reveal also the ability of these cells to form
LDs. Moreover, detailed analysis of LDs shows their chemical composition
heterogeneity; they can be composed mainly of triacylglyceroles of saturated or
monounsaturated fatty acids. LDs assigned as saturated are characterized by the
Raman profile of saturated fatty acids with specific marker bands at 1064, 1130,
1305, 1444, and 2880 cm
−1 , and on the other hand, bands at 1267, 1657, and
3015 cm
−1 are characteristic for unsaturated lipids [90]. The comparison of Raman
spectra obtained from isolated LSECs and a cultured cell line (TSECs—Transfected
Sinusoidal Endothelial Cells [153]) reveals some differences. The characteristic,
strong nuclear DNA signals are no longer so intense as in primary LSECs, and the
cytoplasm seems to be much more thicker as the Raman spectrum is more pronounced for TSECs. On the other hand, both cell types possess lipid droplets that
also, in some cases, are heterogenic in composition as it is observed for isolated
LSECs.
6.3.2 Cardiac Microvascular Endothelial Cells (CMECs)
The heart consists of different cell types including endothelial cells, cardiomyocytes, and fibroblasts. The cross—talk between them has the greatest impact on
maintaining the cardiac homeostasis and autoregulation. The cell–cell communication is realized with numerous cardioactive factors secreted in both directions:
from microvascular endothelial cells to cardiomyocytes and vice versa [154, 155].
180
K. Czamara et al.