Abstract
Hot spring or hot spa bathing (Onsen) is a traditional therapy for the treatment of certain ailments. There is a common belief that hot spring bathing has therapeutic effects for wound healing, yet the underlying molecular mechanisms remain unclear. To examine this hypothesis, we investigated the effects of Nagano hot spring water (rich in carbonate ion, 42°C) on the healing process of the skin using a nude rat skin wound model. We found that hot spring bathing led to an enhanced healing speed compared to both the unbathed and hot-water (42°C) control groups. Histologically, the hot spring water group showed increased vessel density and reduced inflammatory cells in the granulation tissue of the wound area. Real-time RT-PCR analysis along with zymography revealed that the wound area of the hot spring water group exhibited a higher expression of matrix metalloproteinases-2 and -9 compared to the two other control groups. Furthermore, we found that the enhanced wound healing process induced by the carbonate ion-enriched hot spring water was mediated by thermal insulation and moisture maintenance. Our results provide the evidence that carbonate ion-enriched hot spring water is beneficial for the treatment of skin wounds.
Highlights
Balneotherapy, a water immersion therapeutic method for treatment of many types of diseases, is a traditional therapy practiced by many countries around the world[1,2,3]
The wound area was smaller in the hot spring water group than the other two groups after four weeks, and statistical significance was attained at six weeks
To explore the possible molecular mechanisms responsible for the enhanced wound healing induced by the hot spring water, we investigated the expression of matrix metalloproteinase (MMP)-2 and MMP-9 mRNA, two important regulators in maintaining the extracellular matrix, angiogenesis, and tissue repair
Summary
Balneotherapy, a water immersion therapeutic method for treatment of many types of diseases, is a traditional therapy practiced by many countries around the world[1,2,3]. In Japan, hot springs are popular in almost all regions of the country, due to the high density of active volcanoes[4]. There has been a long history of Japanese people bathing in hot springs for both sanitation and enjoyment. There have been many reports that have shown that hot spring water may have some therapeutic effects for the treatment of various diseases, such as cardiovascular disease[5,6,7,8], atopic dermatitis[9,10], ankylosing spondylitis[11], asthma[12], inflammatory arthritis[13], rheumatic disease[14], and rhinosinusitis[15]. In Japan’s Warring States Period (1493–1590), hot spas were used for treating wounded
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