This is class 107's biology blog. Please refrain from using inappropriate terms. Instead, use proper ENGLISH.

Tuesday, January 26, 2010

Eyes Without a Face: Stem Cell Research

1. Case Study: Students to read an article ‘Eyes without a Face – Stem cell research and corneal implants’, and prepare a group consultation (5-6 students per group) involving discussion of the following topics and the possible conclusion to the case:

a. Stem cell function: differentiate adult and embryonic

b. Corneal-limbus stem cells — their function and use in transplants

c. Amniotic membrane use in cornea transplantation

d. Cornea transplant success and failure

e. Concerns with stem cell use in cornea transplants

2. Students will conduct online research to find out the possible outcome of the case study. Groups are to post their findings and conclusion in the Health Science blog & each student is to reflect the learning point from the other group.

9 comments:

  1. a. The difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.
    adapted from: http://stemcells.nih.gov/info/basics/basics5.asp

    b. Corneal limbal stem cell transplantation surgically replaces critical stem cells at the limbus (the area where the conjunctiva meets the cornea). Host stem cells normally reside in this area. Transplantation is done when the host stem cells have been damaged such that it is unable to recover.
    Conditions such as severe chemical burns, Stevens-Johnson syndrome, and severe contact lens overwear may cause persistent nonhealing corneal epithelial injury. These defects are a result from failure of corneal epithelial stem cells to produce sufficient epithelial cells to repopulate the cornea. If untreated, persistent nonhealing corneal epithelial defects are vulnerable to infection, which can lead to scarring, perforation, or both. Under these circumstances, a corneal transplant, which replaces only the central cornea and not the limbus, is insufficient; stem cells are needed to produce new cells that repopulate the cornea, restoring the regenerative capacity of the ocular surface.
    Corneal limbal stem cells can be transplanted from the patient's healthy eye or from a cadaveric donor eye. The patient's damaged corneal epithelial stem cells are removed by a partial-thickness dissection of the limbus (ie, all the epithelium and the superficial stroma of the limbus). Donor limbal tissue, which is prepared by a similar dissection, is sutured into the prepared bed.

    c. One major difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.
    adapted from: http://stemcells.nih.gov/info/basics/basics5.asp

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  2. Cornea transplant has 90% in the first year and 62% after 10 years.

    The cornea is the outermost surface of the eye and is subject to trauma, injury, and every day wear and tear. The stem cells of the cornea are located at the limbus . The purpose of corneal stem cells is to maintain a healthy eye surface and replace cells that are lost and blinked away. Limbus stem cells can be transplanted for severe eye injuries. During this procedure, some stem cells are taken from the healthy eye, or a donor's eye, and then transplanted to the affected eye.  

    Amniotic membrane is used to treat patients with persistent corneal defects not amenable to other medical treatment as an alternative to tarsorraphy and conjunctival flap.

    Stem cells are used to replenish dying cells and regenerate damaged tissues.

    Concerns with stem cell use are blood loss,infection,heals slowly,failure and high cost.

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  3. d. The risk of graft failure is highest in the first year after transplant, and drops to a low but steady rate over longer time periods. For the first six months after receiving a transplant, the major risk is ocular surface disease, such as infection or ulcer.
    Risk:
    long term
    -patients might reject their graft. Fortunately, medications are available to treat either ocular surface disease or rejection. Patients should receive frequent follow-up, and they need to come in immediately for a checkup if they notice any problems developing with their graft.
    -another major cause of graft failure is endothelial cell failure. The endothelial cells line the inner surface of the cornea and continuously pump fluid to keep the cornea clear. There are a finite number of these cells and they do not get replaced. If the endothelial cells become diseased or damaged or if there are too few of the cells to keep up with the job, the cornea becomes cloudy. Our analysis identified several risk factors for endothelial failure, including small graft size, as well as pre-existing conditions such as diabetes.
    Glaucoma increased the risk of all three major types of graft failure, including endothelial failure, rejection, and ocular surface disease. Glaucoma is a leading cause of blindness in the United States. Glaucoma affects nearly 1 out of 20 Americans and it targets any age group, even newborns. Scientific literature had previously recognized that elevated intraocular eye pressures associated with glaucoma could cause endothelial cell damage. However, it was surprising to find that glaucoma also increased the risk of rejection and ocular surface disease. This is likely due to the preservatives in the glaucoma eye drops. This finding is important because it may help doctors to more effectively manage their glaucoma patients and the glaucoma medications they prescribe.
    source: http://www.cornea.org/study_database.html

    e. Used to treat patients with persistent corneal defects not amenable to other medical treatments and as an alternative to tarsorraphy and conjunctival flap.
    Effective in promoting re-epithelialization of cornea and conjunctiva
    May also prevent fibrosis during ocular surface construction and recurrence of symblepharon after lysis procedure.

    from: http://dro.hs.columbia.edu/amt.htm
    By: Michelle Loh, Emily Wu, Goh Ching Fan, Dionne Choo and Wong Jing Yi.

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  4. This comment has been removed by the author.

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  5. I think the transplant will be successful as long as she receives frequent follow-up, and they need to come in immediately for a checkup if they notice any problems developing with their graft.

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  6. A) Stem cell function: differentiate adult and embryonic.
    Answer:
    Adult stem cell:
    The term adult stem cell refers to any cell which is found in a developed organism that has two properties: the ability to divide and create another cell like itself and also divide and create a cell more differentiated than itself. Adult stem cell treatments have been successfully used for many years to treat leukemia and related bone/blood cancers through bone marrow transplants.[24] Adult stem cells are also used in veterinary medicine to treat tendon and ligament injuries in horses.
    Embryonic Cell:
    It takes approximately four to five days old in humans and consisting of 50–150 cells. They can develop into each of the more than 200 cell types of the adult body when given sufficient and necessary stimulation for a specific cell type. They do not contribute to the extra-embryonic membranes or the placenta.

    B) Corneal-limbus stem cells — their function and use in transplants.
    Answer:
    The cornea is used together with the lens, it refracts light, accounting for approximately two-thirds of the eye's total optical power. It is used to cure blindness and vision impairment. The cornea has the remarkable property that it does not contain any blood vessels, making it relatively easy to transplant.

    C) Amniotic membrane use in cornea transplantation.
    Answer:
    Amniotic membrane transplantation is a safe procedure for pterygium removal. Amniotic membrane transplantation offers practical alternative to conjunctival auto graft transplantation for extensive pterygium removal. Amniotic membrane transplantation are tissues that is acquired from the innermost layer of the human placenta and is used to replace and heal damaged mucosal surfaces including successful reconstruction of the ocular surface.

    D) Cornea transplant success and failure.
    There is a 40% chance of failure. Complications that can occur include infection, glaucoma, retinal detachment, cataract formation, and rejection. Graft Rejection occurs mostly in 5% to 30% of all the patients. The symptoms of rejection include persistent discomfort, sensitivity to light, redness, or a change in vision. If the rejection is too serious, the surgery will have to be repeated. Successful operations will lead to restored vision after the the eye has healed fully. Some patients take a year to heal fully. Patients with keratoconus, corneal scars, early bullous keratopathy, or corneal stromal dystrophies have the highest rate of transplant success. The highest chance of success now is 60%.

    E) Concerns with stem cell use in cornea transplants.
    Answer:
    Disease transmission through contamination with bacteria, viruses or other infections agents.It use used commercially available fribin tissue.

    Conclusion: Yes it will work. The chances of success is more than the failure.

    Tam Wai Hang, Sean Phua ,Wen Yue, Elgin Patt,Zheng En,

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  7. Group members: Jing Jie, Marcus, Wei Hong, Zong Wei, Shawn

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  8. a. Stem cells are used to replenish dying cells and regenerate damaged tissues.d. Cornea transplant has 90% in the first year and 62% after 10 years.

    b. The cornea is the outermost surface of the eye and is subject to trauma, injury, and every day wear and tear. The stem cells of the cornea are located at the limbus . The purpose of corneal stem cells is to maintain a healthy eye surface and replace cells that are lost and blinked away. Limbus stem cells can be transplanted for severe eye injuries. During this procedure, some stem cells are taken from the healthy eye, or a donor's eye, and then transplanted to the affected eye.

    c. Amniotic membrane is used to treat patients with persistent corneal defects not amenable to other medical treatment as an alternative to tarsorraphy and conjunctival flap.

    d. Cornea transplant has 90% in the first year and 62% after 10 years.a. Stem cells are used to replenish dying cells and regenerate damaged tissues.

    e. Concerns with stem cell use are blood loss,infection,heals slowly,failure and high cost.

    Done by : Neo Wei Hong, Chua Zong Wei, Lim Jing Jie, Shawn Lim, Marcus Au

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  9. A.One major difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent*. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.Embryonic stem cells can be grown relatively easily in culture. Adult stem cells are rare in mature tissues, so isolating these cells from an adult tissue is challenging, and methods to expand their numbers in cell culture have not yet been worked out. This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.
    *Pluripotent-Capable of giving rise to several cell types.

    Source:http://stemcells.nih.gov/info/basics/basics5.asp

    B.by harvesting a small bit of limbal tissue from a patient's good eye, growing it in the laboratory and transplanting it back into the patient's eye. This procedure, direct limbal stem cell transplant, was performed on a patient for the first time in April 2001. Till date over 250 patients have been treated at LVPEI with this technique, with almost 70% success. Thirty patients also underwent corneal transplantation with good visual recovery in 80% cases.
    Limbal stem cell culturing is useful for patients needing large amounts of stem cell replacement, where too many cells taken from the donor eye may cause a deficiency there. In autograft the patient's own tissue is used (after culturing) to treat the diseased eye.

    http://patientcare.lvpei.org/eye-hospital/clinical-services/stem-cell.html

    C. Amniotic membrane surrounds an embryo. Its function is to protect the embryo during the development. By injecting them into the eye, which is stem cell therapy, the body would not reject them easily. The stem cells can heal scar-like tissues back to normal.

    http://www.sciencedaily.com/releases/2009/04/090409103350.htm

    http://en.wikipedia.org/wiki/Amnion

    D. Stem cell corneal research complications
    Complications include all of the following:
    Graft rejection
    Infection (intraocular and corneal)
    Wound leak
    Glaucoma
    Graft failure
    High refractive error (especially astigmatism, myopia, or both)
    Recurrence of disease (with herpes simplex or hereditary corneal stromal dystrophy).

    http://www.merck.com/mmpe/sec09/ch102/ch102m.html

    E. The cells could replicate uncontrollably or not properly differentiate which could cause cancer.

    source:http://www.cordbloodbankupdates.com/what-are-some-concerns-with-stem-cell-use-in-cornea-transplants/

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