Bone Marrow Stem Cells

The vast majority of bone mass is achieved in the human adult by the age of 18, with a small amount accumulated up to the age of 30. In a healthy adult, bone remodeling is a balance between bone resorption, via osteoclasts, and bone formation, by osteoblasts. Changes in levels of endogenous hormone and mechanical load, due to age-related changes in physical activity, determine the extent of bone remodeling.

The prospect of bone repair and prevention Reduced activity of osteoblasts observed with aging is due in part to estrogen and progesterone deficiency. Loss of bone mass, also attributed to reduced activity of osteoblasts, is responsible for enhanced risk or fractures and reduced bone fracture repair. Of those over the age of 70, only 31 to 36% are predicted to have normal bone mass. Many people in the aging population are affected by hip fractures: up to 20% of hip fracture patients die within the first year, and only 30% ever regain prefracture function (Akesson et al., 2003). A major consequence of the aging population is the inability to replace or repair aging tissue. The bone marrow contains stem cells that are progenitors for osteoblasts, capable of forming bone cartilage and other connective tissue. Osteoprogenitor cells may provide a potential therapy for bone repair, reconstructing bone tissue in the area of injury.

Mending broken or damaged bones through bone grafts is a common practice performed by doctors in the United States every year. Although not all patients are eligible for this commercial process, including aged patients whose quality and quantity of bone are not sufficient, there is hope for these patients. Bone engineering has made great strides in developing therapies that colonize damaged areas and form new bone. A group in China has recently shown that engraftment of bone marrow stem cells was capable of repairing segmental bone defects in sheep metatarsus (Li et al., 2005). Bone marrow stem cells were enriched over a Percoll density gradient and implanted with porous-TCP in a sheep metatarsus defect. Compared to controls, the stem cell implants healed the bone defect more efficiently and quicker. The use of a biological scaffold, a hydrogel, in concert with bone marrow stem cell cultures also provided new bone formation when transplanted into a region of bone defect (Srouji et al., 2004). A three-dimensional hydrogel scaffold that contained an osteogenic subpopulation of bone marrow stem cells was transplanted into rat tibia and examined six weeks postimplantation. Due to the decrease in skeletal bone formation and rate of fracture repair seen with aging, the fact that the scaffold and stem cells induced bone repair is promising as a potential therapy. If bone tissue could be engineered to interchange senescent or apoptosing cells with a fresh supply from stem cells, the effects of aging on bone could be mitigated.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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