Development and histology of mouse penile spines

Penile spines are keratinized dermal structures that are present in many mammals including rodents, carnivores, and primates. These occur in most primate species, including the chimpanzee, but have been lost during human evolution. Across mammals, there is substantial diversity in the form and size of penile spines making it difficult to determine their functional significance. In mice and chimpanzees, penile spines form simple curved spikes covering a dermal papilla. Preliminary evidence indicates that penile spines contain neurologic structures related to sensing mechanical vibration. Meissner’s corpuscles are a type of nerve ending found in sensory skin and are mechanoreceptors responsible for detection of low vibration or light touch sensations. However, systematic study of the innervation of penile spines or the presence of Meissner’s corpuscles has not been conducted. The purpose of this study is to investigate the development of penile spines in mice ranging from 2 days to 1 year of age. By utilizing hematoxylin and eosin staining, neutral red staining, periodic acid-Schiff staining and immunohistochemistry, we investigate the formation of penile spines and their potential association with Meissner’s corpuscles. Histological analysis reveals that cellular structures in the dermal papilla match the Meissner’s corpuscle. IHC for S100 identified neural structures in the mouse penis that appear to correspond with some spines. These results can elucidate the function of these penile spines and suggest that they may serve a sensory function.