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Spleen pigmentation in young C57BL mice is caused by accumulation of melanin
A van der Heijden1, J E van Dijk, A G Lemmens
1Department of Laboratory Animal Science, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Abstract:
It has been previously reported that in 2 C57BL mouse sublines a dark pigmentation of the cranial part of the spleen occurs in up to 30% of the animals within the populations. It was not clear whether this discoloration is caused by melanosis, lipofuscinosis or haemosiderosis. With the use of light and electron microscopy of stained spleen sections, we identified the pigment in 14 out of 60 C57BL mice aged 8-10 wks. In the mice with pigmented spleens there was accumulation of melanin, predominantly in melanophores. Literature data indicate that apart from melanin, lipofuscin and haemosiderin can be observed in splenic macrophages provided that the mice are older than those studied by us. We conclude that melanin is the principal pigment causing spleen discoloration in young C57BL mice. Splenic melanosis displays inter-individual variation, but its relevance from a pathophysiological point of view remains obscure.
Insights
Dark spleen pigmentation in young C57BL mice is caused by melanin accumulation. This splenic melanosis occurs in some mice, but its pathological significance is currently unknown.
Area of Science:
- Veterinary Pathology
- Mouse Models in Research
- Histology
Background:
- C57BL mice sublines can exhibit cranial spleen pigmentation.
- The cause of this splenic discoloration (melanosis, lipofuscinosis, or haemosiderosis) was previously unclear.
Purpose of the Study:
- To identify the pigment responsible for spleen discoloration in young C57BL mice.
- To investigate the cellular origin of the pigment.
Main Methods:
- Light and electron microscopy were used on stained spleen sections.
- Histological examination of spleens from 60 C57BL mice (aged 8-10 weeks).
Main Results:
- Pigment identified in 14 out of 60 mice.
- The pigment was identified as melanin, primarily accumulated in melanophores.
- Melanin is the principal pigment in young mice; other pigments like lipofuscin and haemosiderin are found in older mice.
Conclusions:
- Melanin is the primary pigment causing spleen discoloration in young C57BL mice.
- Splenic melanosis shows inter-individual variation.
- The pathophysiological relevance of splenic melanosis in these mice remains undetermined.