Pigmented spleens in C57BL mice

Abstract

Approximately 15% of our highly inbred C57BL/6 mice show a spleen with a pigmented cranial part. Microscopically, abundant aggregates of pigment granules are observed primarily scattered between cells of the red pulp. They give a positive reaction with Perls' Prussian blue and stain heavily with silver-methenamine. Most of the granules are stored in macrophages. In some cases a number of granules are surrounded by a membrane. This abnormality may be designated haemosiderosis. In the present study we demonstrate that it is not related to the consumption of iron within the range normally found in laboratory animal diets. This suggests a genetic origin, although confirmation would require further research. If so, comparison with human idiopathic haemochromatosis is tempting. However, contrary to the human condition, organs other than the spleen are not affected, with exception of the liver. This organ contains minor deposits of pigment granules. Nor do affected animals appear to show any ill effects. Nevertheless, it seems worthwhile to investigate whether this phenomenon in C57BL mice could serve as a model for the human disease provided that a practical criterium becomes available for detection in the intact animal.

Lack of hepcidin gene expression and severe tissue iron overload in upstream stimulatory factor 2 ( USF2 ) knockout mice

“…We found this accumulation to fluctuate greatly between mice, suggesting that it may depend on the 129͞Sv ϫ C57BL͞6 hybrid strain background of each animal. This natural iron storage has been previously reported in C57BL͞6 mice and was described to occur mainly in splenic macrophages (16,17). Surprisingly, in spleen of Usf2 Ϫ/Ϫ mice, iron levels remained very low (Fig.…”

Synthesis and in Vivo Evaluation of [123I]Melanin-Targeted Agents

“…For all new radiotracers tested, radioactive signal was observed in the eyes, which supported the specific uptake in melanin-rich tissues; however, the study was conducted in C57BL/6J mice that have high melanin pigmentation in the eyes , (as well as skin, hair, and spleen). − Because of the large differences between murine and human ocular geometry as well as uveal melanin content, radioactivity uptake in the eyes may not be an issue for clinical transfer . Additionally, the first in human study of a similar benzamide-type radiotracer developed by our research group ([ 18 F]­MEL050) , indicated that the radiotracer is safe with suitable biodistribution for PET imaging…”

Extradermal melanin transfer? Lack of macroscopic spleen melanization in old C57BL/6 mice with de-synchronized hair cycle.

“…Some authors question the actual nature of the splenic pigment. Hemosiderosis (Veninga et al, 1989) is a less probable reason of splenic pigmentation (Weissman, 1967;Sundberg, 1991;Van der Heijden et al, 1995). There is also controversy be-Lack of spleen melanosis in old C57BL/6 mice tween melanin and lipofuscin -pigments of different characters and origin (Kent, 1976;Double et al, 2008).…”

“…The occurence of splenic melanosis varies between particular reports (10-21%, Weissman, 1967;8-34%, Crichton et al, 1978;15%, Veninga et al, 1989;23%, van der Heijden et al, 1995;14-80%, Plonka et al, 2005b) but rarely exceeds 30% (34% for female C57BL/6J and 31% for female C57BL/IOScSn, Crichton et al, 1978; 50-80% for female C57BL/6 in late catagen/early telogen, Plonka et al, 2005b). As the reason of this pigmentatory effect some authors suggested haemosiderins (Veninga et al, 1989) or lipofuscin (Crichton et al, 1978), but most of them, starting with Weissman (1967) and followed by Sundberg (1991), van der Heijden et al (1995, and recently by us (Plonka et al, 2005b), insist that melanin is the pigment responsible for the phenomenon.…”

“…The phenomenon of splenic melanosis in young C57BL/6 animals has been known for over 40 years (Weissman, 1967), but its biochemical, physiological and genetic basis remains poorly understood. The black pigment was found mainly in the extracellular space of the red pulp or in macrophages (Veninga et al, 1989), in the dorso-cranial part (anterior pole) (Van der Heijden et al, 1995) or the posterolateral aspects of the spleen (Weissman, 1967). Some authors identify the melanin-bearing splenic cells as "melanophores" (Van der Heijden et al, 1995) akin to melanocytes.…”