Tissue distribution of the laminin beta1 and beta2 chain during embryonic and fetal human development

Abstract

Laminins are the major glycoproteins present in all basement membranes. Previously, we showed that perlecan is present during human development. Although an overview of mRNA-expression of the laminin beta1 and beta2 chains in various developing fetal organs is already available, a systematic localization of the laminin beta1 and beta2 chains on the protein level during embryonic and fetal human development is missing. Therefore, we studied the immunohistochemical expression and tissue distribution of the laminin beta1 and beta2 chains in various developing embryonic and fetal human organs between gestational weeks 8 and 12. The laminin beta1 chain was ubiquitously expressed in the basement membrane zones of the brain, ganglia, blood vessels, liver, kidney, skin, pancreas, intestine, heart and skeletal system. Furthermore, the laminin beta2 chain was present in the basement membrane zones of the brain, ganglia, skin, heart and skeletal system. The findings of this study support and expand upon the theory that these two laminin chains are important during human development.

Fig. 1

Localization of the laminin β1 chain during gw 8 and 9 in human embryogenesis. a Immunostaining for laminin β1 chain in BMZs of neuroectoderm (open arrows) and capillaries (arrowheads). Loose mesenchyme cells (LM) and neuronal cells (N) showed no staining for the laminin β1 chain. b BMZs (arrows) and mesenchymal cells (M) of the choroid plexus exhibited staining for the laminin β1 chain. c Localization of the laminin β1 chain in BMZs of a sinusoid (S) of developing liver (arrows). Hepatocytes (asterisk) were negative for the laminin β1 staining at gw 8. d Immunostaining for laminin β1 chain in the endoneurium of spinal ganglia (arrows). e The laminin β1 chain in the ECM of cardiomyocytes (arrowheads) and in BMZs of pericardium. f Detection of the laminin β1 chain in Bowman’s capsule (arrows) and in glomerular basement membranes (arrowheads) of the developing kidney. Mesenchymal cells (M) showed no staining for the laminin β1 chain. Bars 15 μm in a, b, c, d, e, and f

Fig. 2

Localization of the laminin β2 chain during gw 8 and 9 in human embryogenesis. a BMZs of neuroectoderm (arrows) were positive for immunostaining of the laminin β2 chain, whereas neuroectodermal cells (N) showed no staining. b BMZs (arrows) of the choroid plexus exhibited staining for the laminin β2 chain, whereas mesenchymal cells (M) showed only weak staining. c Localization of the laminin β2 chain in the BMZ of a capillary of neuronal tissue (arrows). d Immunostaining for the laminin β2 chain in the endoneurium of spinal ganglia (arrows). e The laminin β2 chain in the ECM of cardiomyocytes (arrowheads) and in BMZs of peri- and endocardium (open arrows). f The interterritorial matrix (arrowheads) of chondrocytes showed positive staining for the laminin β2 chain, whereas the proliferating chondrocytes themselves (arrows) exhibited no staining. Skeletal muscle cells (asterisk) were negative for the laminin β2 chain. Bars 15 μm in a, b, c, d, e, and f

Fig. 3

Localization of the laminin β1 chain in various organs during human embryogenesis. a At gw 10, hepatocytes of developing liver revealed distinct staining for the laminin β1 chain (arrowheads). b The laminin β1 chain was detected in mesenchymal cells (M, arrows) of the intestine at gw 12. c Positive staining for the laminin β1 chain was seen in BMZs of skeletal muscle cells (open arrows) and in BMZs of capillaries (arrows) at gw 12. d Staining for the laminin β1 chain in the pericellular and interterritorial matrix (arrowheads) of rib cartilage anlagen at gw 12. Chondrocytes (arrows) revealed no specific staining for the laminin β1 chain. e At gw 8, BMZs of glands of the developing pancreas exhibited positive staining for the laminin β1 chain (arrows). The pancreatic gland itself (asterisk), and mesenchymal cells (M), were negative for the laminin β1 chain. f Detection of the laminin β1 chain in the lens capsule of the eye (arrows) and BMZs of capillaries (arrowheads). g BMZs of transversal sections of skeletal muscle cells showed positive staining for the laminin β1 chain (open arrows). Bars 15 μm in a, b, d, e, and g; 60 μm in c and f