Any embryonic cell at the stage of 2 or 4 cells is capable in itself to reform an embryo: it is a totipotent cell. But then, this ability disappears.

Stem cells collected at a later stage (morula or blastula) may, in turn, differentiate into any cell in any organ: they are pluripotent. These are the so-called embryonic stem cells.

Adult cells (found in some organs), are, multipotent because they can not differentiate in some cell types. Both embryonic and adult cells represent a great hope for organ repair, but the techniques of differentiation are still poorly understood.

Both systems have potential advantages and distinct shortcomings - for example, the tumorigenic potential of embryonic stem cells, or the difficulty to obtain stem cells in adult organs and their culture in vitro.

Furthermore, the use of differentiated cells obtained from a supernumerary embryo (i.e., an embryo developed during in vitro fertilization in the context of medically assisted procreation) would raise the same risk of rejection as in the conventional transplants.

Therapeutic cloning, in which a cell nucleus (or DNA) of the patient himself would be used to establish the source of embryonic stem cells, would circumvent this problem. It is though banned currently in many countries for ethical reasons.

Barack Obama promised to lift restrictions imposed by the Bush administration to research on embryonic cells. A first step has been done. Two days after his inauguration as President of the United States, the American Drug Agency, the FDA approves the first clinical trial in the world, of therapy derived from embryonic stem cells.

When you are diagnosed with osteoporosis or at high risk, your doctor will prescribe medication for treatment or prevention. Are you getting the right medication for you?

Factors you will want to consider are:

1. Your doctor’s advice
2. Side effects
3. Does the drug have a good success record?
4. How you prefer taking medication (pills, liquid, injections, or spray etc.)
5. Cost
6. How the drug works for you.

To help you with this process, the pros and cons of well-known osteoporosis medications are summarized below:

Teriparatide (Forteo)

Pros: activates bone- building cells, increases bone density, and reduces spinal fractures for patients with severe osteoporosis

Cons: requires a daily injection into the leg or stomach; more expensive than other options; may cause dizziness, nausea and leg cramps; cannot be taken for more than 18 to 24 months

Ralozifene (Evista)

Pros: for postmenopausal women not taking hormone therapy; decreases rate of bone loss; prevents spinal fractures; provides benefits of estrogen without other estrogen effects; may reduce breast cancer risk

Cons: may increase hot flashes and increase risk of blood clots

Bisphosphonates (Fosamax, Bonival, Actonel, Reclast)

Pros: these drugs slow bone breakdown and prevent spinal fractures; are prescribed to men and women for prevention and treatment; tablets or injections are available; variety of dosing schedules (e.g. daily, weekly, monthly). Reclast? is an exception in that it is only available to postmenopausal women as a yearly injection. Fosamax? and Actonel? have been effective in preventing hip fractures as well as spinal fractures.

Cons: Common side effects are nausea, stomach pain, and loose bowel movements. With Fosamax? and Actonel? there is a low risk of ulcers in the esophagus and a rare risk of jaw breakdown after dental work.

Calcitonin (Fortical, Miacalcin)

Pros: slows bone breakdown; prevents spinal fractures; helps control pain; available to men and women with osteoporosis; choice of synthetic or natural hormone

Cons: taken as an injection or nasal spray; studies show that it may not be as effective as some drugs in increasing bone density; side effects can include nasal dryness and swelling.

Hormone Therapy (HT)

Pros: for postmenopausal women; used for prevention and treatment; also relieves symptoms of menopause; increases bone density and prevents spine fractures

Cons: long-term use can increase risk of breast cancer, heart disease, and stroke; alternatives are explored before this option is chosen for osteoporosis; other side effects include depression, headaches, breast tenderness, and weight gain.

Careful Medication Choice is an Important Part of Osteoporosis Management

Your choice of medication is a personal decision in consultation with your doctor. Medication is an important part of osteoporosis management. There are four other very important ways to manage osteoporosis, which work with medication to strengthen bones and prevent fractures. They are:

• Regular exercise
• Balanced diet with calcium and vitamin D supplements
• Avoiding or reducing smoking, caffeine and alcohol
• Taking steps to prevent falls and fractures

Stem cells are the holy grail of modern biology. These root cells can, with proper stimulation, be used to produce virtually any type of cell in the body. Until now, the best source of stem cells has been human embryos. These have typically been obtained from fertility clinics. Considerable research is also underway to clone stem cells derived from non-embryonic tissue. The possibility of deriving stem cells from nonviable, asexually produced blastocysts might solve, at least for some, the ethical debate currently raging on the direction of therapeutic stem cell research. The other problem with present human ES cell technology is the critical problem of histocompatibility as the cells obtained from embryos derived during in vitro fertilization procedures, or from foetal sources, are essentially cells from another individual (allogeneic). This means that they, or any cells made from them, would be at risk of being rejected if transplanted into a human being. To solve this problem, the biotechnology industry is trying to manufacture embryonic cells identical to a human adult, this is to say, autologous embryonic cells. To do this one of the following methods will eventually certainly have to be employed and recent research shows that parthenogenesis might not only be pssible but less ethically controversial.

(1) Somatic Cell Nuclear Transfer: In this technique, commonly known as “Human Therapeutic Cloning” a patient’s body cell is combined with an egg cell that has its DNA removed. As a result the body cell’s DNA is reprogrammed back to an embryonic state, and totipotent stem cells are produced identical to the patient.

(2) Ooplasmic Transfer: In the reverse of nuclear transfer, ooplasmic transfer involves the removal of the cytoplasm of an oocyte and transferring it into the body cell of a patient thereby transforming the patient’s cell into a primitive stem cell.

(3) Parthenogenesis: In this technique a woman’s oocyte is directly activated without the removal of its DNA to begin development on its own, forming a preimplantation embryo from which totipotent stem cells are isolated.

Tell us more about the technique of parthenogenesis, which appears to both reduce transplantation problems and possibly be less controversial:

Parthenogenesis is derived from the Greek words for ‘virgin birth’. In modern biology, it refers to a form of reproduction in which an ovum develops into a new individual without having been fertilised. In many social insects, such as the honeybee and the ant, the unfertilised eggs give rise to the male drones and the fertilized eggs to the female workers and queens. Charles Bonnet discovered the phenomenon of parthenogenesis in the 18th century. In 1900, biologists were able to encourage artificial parthenogenesis in some species. Jacques Loeb reported in that year that he was able to induce unfertilised frog eggs to grow by scratching them with a needle. Since that time various chemical and mechanical means have been used to produce artificial parthenogenesis in numerous animals including rabbits. However, in most cases the resulting developments abnormal. In 1936, Gregory Pincus induced parthenogenesis in mammalian (rabbit) eggs by temperature change and chemical agents. No successful experiments with human parthenogenesis have been reported. The phenomenon is rarer among plants (where it is called parthenocarpy) than among animals. Unusual patterns of heredity can occur in parthenogenesis organisms and offspring produced by some types are identical in all inherited respects to the mother. While the ancient Greeks may have been mystified by many elements of molecular biology, they would have easily been able to grasp parthenogenesis, a concept rooted in their oldest myths. Athena, daughter of Zeus, was among the most important of the Greek deities. The Parthenon is the name of the temple of Athena on the Acropolis. She was the patron goddess of Athens, and was associated with everything from warfare and urban development to fertility and weaving. The birth of Athena was most unusual. Those classical scholars amongst you will probably recall that Zeus swallowed his first wife Thetis when she became pregnant, because he feared that she would bear him a son would steal his throne. After a few months he developed a severe headache and he went to his fellow god Hephaestus who history declares was good enough to split his head open with an axe. It is documented that Athena then emerged fully-grown and wearing a suit of armour, from the head of Zeus.

Would parthenogenesis really be ethically acceptable?

The parthenogenetic creation of primate embryos with subsequent production of stem cells suggests a new, perhaps somewhat less ethically controversial direction in research aimed at treating human diseases with stem cell-derived therapies. There is no doubt that the Catholic Church would denounce it on the basis of two couples not being involved in the creation of the initial embryo but they would have certain difficulties explaining when exactly a life force actually entered the cell to make it a potential human being. This would become more difficult if human parthenogenesis was found to occur by some simple method such as heating or electrifying the cell, which is one of the reasons that I maintain that life is a continium. Anyway, it is now known that a team of scientists from Mayo Clinic, Sloan Kettering Cancer Centre and Wake Forest University working with a Massachusetts biotechnology company recently managed to create primate embryos parthenogenetically. The research involved stimulating a monkey egg to grow without any help from sperm. The researchers used chemicals to signal the eggs not to eject half of their chromosomes (as they would do in sexual reproduction) and command the eggs to start dividing. In this case the resulting mass of 100 or so cells, known as the blastocyst, cannot become a viable organism when produced with the new technique. Four of 28 parthogenetic eggs developed into blastocysts. The researchers were able to derive a single stem cell line from one of the blastocysts.

Moreover, they were able to tease stem cells derived from the asexually derived embryos to produce numerous types of cells including brain, heart and smooth muscle cells. A particularly promising development was the report that the researchers were also able to produce midbrain dopamine neurons, with the hope is that some day such cells could replace dysfunctional cells in the brains of patients with central nervous disorders such as Parkinson’s disease and Huntington’s disease. This study suggests an alternative to human therapeutic cloning as differentiated cell types derived in vitro by parthenogenesis eliminate the requirement to produce or disaggregate a normal, competent embryo and may circumvent the ethical concerns voiced by some, positively impacting the debate in stem cell research,” the researchers noted in Science.

How long will it be before human parthenogenesis is achieved?

Researchers from the same biotech company that supported the current research, Advanced Cell Technologies, created considerable controversy in November of last year when they announced they had cloned human embryos. The embryos had not grown beyond six cells and had not produced stem cells. While the race is on to create parthenogenetic human embryos, considerable doubts remain regarding the safety and efficacy of this approach. Researchers believe that the male DNA that mixes with the females DNA in the egg probably has an important role to play in gene activation in at least some kinds of stem cells. For example, studies in mice produced parthenogenetically suggest that those stem cells differentiate more readily into neurons than into other cell types such a muscle. The hypothesis that such cells would indeed be immune-privileged also remains unproven.