| Summary: | 碩士 === 國立陽明大學 === 生物藥學研究所 === 91 === Abstract
Dioscorea spp., a Dioscoreaceae herbal medicine, has been widely used
as a remedy for anti-aging and health promotion. Recent researches indicated
that the cell number and plasticity of stem cells had great contribution for aging
and age-related disease. In addition, raised morbidity and mortality resulted
from infection in the elderly is related with immunosenescence. Therefore, the
present research tried to explore whether Dioscorea spp. adiminstration could
serve as a immunomodulator and have on effect cell regeneration in order to
find out the most important bioactivity of Dioscorea spp.
In the aspect of immunomodulation, we examined whether
polysaccharide isolated from Dioscorea spp. tubers could enhance protective
immunity induced by oral Pneumovax ® 23 vaccine. We tried different
adiminstration ways to examine whether Dioscorea polysaccharide could
promote systemic and mucosal immunity, which induced Pneumovax ® 23
vaccine — specific serum IgG and mucosal IgA antibody response respectively.
We have found that mice were vaccinated by gastric intubation with
Pneumovax ® 23 vaccine and supplied with Dioscorea polysaccharides shortly
in daily drink could enhance specific antibody response.
Stem cells have long been regarded as undifferentiated cell capable of
proliferation, self-renewal, production of a large number of differentiated
progeny, and regeneration of tissue. Recent reports showing that stem cell fate
specification can be controlled by their enviroment. Stem cells also exist in the
adult tissues, including, brain, liver, bone marrow and other tissues. Adult stem
cells hold great promise for regenerative medicine, tissue repair. This researchtried to examine whether methanol extract of tubers from Dioscorea spp. could
enhance stem cells or progenitor cells proliferation, differentiation and
regeneration of tissue. We found that, methanol extract of Dioscorea could
enhance neuronal progenitor proliferation and differentiation in vitro. This
bioactivity may be beneficial to neurogenesis or neuroregeneration.
Bone is remodeled continuously during adulthood through the resorption
of senescent bone by osteoclasts and the subsequent formation of new bone
by osteoblasts. We proved that methanol extract of Dioscorea stimulated
proliferation of osteoprogenitor cells and promoted alkaline phosphatase
activity, which is a bone formation biological marker of osteoblast. Also, we
developed an ovariectomized (OVX) in vivo model to demonstrate the action of
methanol extract of Dioscorea in postmenopausal estrogen deficient
osteoporosis. Then, The related genes for bone formation and bone resorption
were analyed by RT-PCR and histomorphometry. The oral dose of 40
mg/kg/day methanol extracts of Dioscorea could enhance bone formation in
ovariectomized mice.
Recent papers reported that advanced glycation end - products (AGE) in
the body were particularly related with age, diabetes and its complications
such as nephropathy, nephropathy or vascular disease. We developed an
animal model to demonstrate the action of methanol extrate isolated from
Dioscorea in AGE- induced diabetic complications. The strategy was to
promote degration and clearance of advanced glycation end - products. Our
results showed that methanol extract of Dioscorea could decrease serum level
of advanced glycation end - products and prevent kidney and liver from
pathological changes.
In this study, we demonstrated that Dioscorea polysaccharides did haveimmunomodulatory effects in both systemic and mucosal immunity induced by
Pneumovax® 23 vaccine vaccination. Besides, the methanol extrate of
Dioscorea not only enhanced bone formation in ovariectomized mice but also
stimulated the proliferation and differentiation of progenitor cell in brain and
bone marrow. It could also decrease AGE-induced diabetic complications. Our
studies suggested that anti-ageing effects of methanol extrate isolated from
Dioscorea may mediate by regulating the growth and differentiation of stem
cells.
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