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12/14/09
Dupont Essay Rough Draft- you need a title
Imagine a life of almost total blindness.-I do not like this opening sentence. It is
too vague for me. This is the struggle many face every day because of failed attempts to
treat disorders damaging the eye surface such as ocular burns.-I feel like you are going
to list a couple of diseases, but you only state one. In the past, such disorders-plural,
right, you need to list more, like alkali burns-what is this? which damage corneal cellsgeneral reader will now know what these are, were a problem for surgeons and patients
and posed a challenge to treat completely because scarring and epithelial defects often
remained after treatment.-break this sentence up. Poor flow. The most common form of
treatment was a complete corneal transplant, you need to describe what the cornea is
way before this. One, remember the reader. Two, general to specific. You cant discuss
the specifics of corneal transplants without discussing the cornea first. replacing the
transparent layer in the front of the eye with healthy corneal tissue from a donor.punctuation goes after the citation only (Tsai et al., 2000). You need transitions. You are
going to bash the technique. The reader should be aware of this. Unfortunately, Corneal
transplants have a rejection rate of up to 30 percent, require a long recovery time and
fail to improve vision or alleviate symptoms 66% of the time (Pfister, 1994;Burman &
Sangwan, 2008). You need to transition. Go through this manuscript and place the
appropriate transitions between sentences. It is not clear where you are going when you
start with ocular. Ocular surface scarring and the formation of vessels and capillaries as
well as other epithelial defects can persist following a transplant. The integrity of the
corneal epithelium is supported by limbal cells-this sentence came out of left field.
Transition., a type of stem cell. According to Dua & Azuara-Blanco (2000), stem cells are
essential for cell regeneration and repair and help maintain homeostasis.-you don’t
need “according to” to just say what stem cells are. You need to tell a story. Set up the
stem cells as the solution. You discuss the disease, then the current treatment, the
negatives of that treatment and then the savior, stem cells. For example: Due to these
side effects, one hope for the future may be the use of limbal stem cells to… This lets
the reader know where you are going. Guide them. The cells can produce more stem
cells and can differentiate and become different, specialized cells.-Need a more clear
explanation of stem cells. These properties give them unique opportunities with regards
to ocular surface reconstruction because they can differentiate and become corneal
cells, replacing the damaged ones and restoring vision.-You don’t need such complexity.
Stem cell are cells that can become any other type of cell including corneal cells.
Therefore, they can be used to replace the damaged ones. See how simple it can be.
Simplify. Pelligrini, an ocular surgeon, first used limbal stem cells in sheet form to treat
patients with corneal damage in 1997 (Sullivan & Clynes, 2007). Transition? You are
jumping. Limbal stem cell transplants have yielded promising results and are now used
to treat ocular surface disorders by the medical community. I am stopping here. You
need to work on the order and the transitions as well as simplification of the story. Do
this for the entire manuscript. 6.5/10
Limbal stem cells reside in a supportive environment called the stem cell niche.
Research by Charukamnoetkanok (2006) supports that the stem cell niche, named the
Palisades of Vogt, protects limbal cells and helps maintain their amazing properties.
Their ability to differentiate into different celll types gives them the property to replace
whatever cell type needs them the most. (Li et al. 2007). Limbal cells can differentiate
into different cell types more rapidly than corneal epithelial cells can, making them
more effective in corneal transplants (Pfister, 1994). The corneal epithelium requires
constant renewal, the source of this renewal comes from the limbus. Since many ocular
disorders damage the epithelial surface of the cornea, a limbal transplant will replace
damaged cells by differentiating into corneal cells after the transplant and thus
improving visual acuity.
Scientists have begun exploring the potential of limbal stem cells in corneal
surface reconstruction. Use of autograft, the transplantation of tissue from one part of
the body to another; and allograft, the transplantation of tissue from one person to
another, transplantations of limbal stem cells as an alternative to corneal transplants is
increasing across the world. Autograft transplantations are used in patients with
unilateral ocular damage, damage in only one eye. Limbal cells are taken from the
healthy opposite eye and transplanted into the damaged eye. Limbal stem cells can be
expanded on an amniotic membrane and then transplanted but that isn’t always
required. Amniotic membrane use to expand limbal stem cells in combination with this
procedure allows for more rapid re-epitheliazation and may help prevent infection
(Meller et al., 2002). Allograft transplantations are used in patients with bilateral ocular
damage, damage in both eyes. Limbal cells are taken from relatives and transplanted
into both eyes. Even though tissue is matched and living donors are preferred,
immunosuppressants are still required following the surgery. Both allograft and
autograft surgeries have improved the corneal surface more than standard corneal
transplants (Ozdemir et al., 2004).
Research has shown that autograft transplants yield better outcomes than
allograft transplants. In an experiement by Ozdemir et al. (2004), limbal allograft
transplant patients had a follow up period that was 4 months longer than the autograft
patients and only 11% of transplants resulted in functional vision whereas with limbal
autografts it was 80%. The authors also explained how it is more difficult to reduce
formation of capillaries with allograft transplants. Cappilary and vessel formation
regressed in all patients with autograft transplants but only in 4/9 patients who
underwent allograft transplantations. The authors believe the failure of many allograft
transplantations is due to the advanced stage of ocular surface destruction that the
patients in the allograft group of the experiment had. Many people do not have a choice
between autograft and allograft surgery. Autograft surgery is only available to those
with unilateral ocular surface disorder since the limbal cells must be derived from the
healthy contralateral eye. Allograft surgeries are probably less effective because the
limbal cells are derived from another person. The authors speculate that perhaps the
role of allograft transplantations, instead of to completely treat, should be to stabilize
the ocular surface for future surgeries.
There have been significant advancements made towards better understanding
corneal surface disorders. This has led to the introduction of many new and effective
types of surgery being made available across the globe. Promising research and studies
have shown limbal allograft and limbal autograft surgeries to be some of the most
efficient types to treat ocular surface disorders. So far, limbal stem cells have restored
vision to many blinded by ocular surface disorders and given them the opportunity to
live a better life. The worker in a factory that received an alkali burn, the child from a
third world nation with vitamin A deficiency, and the beach lover that didn’t wear
sunglasses and damaged the corneal surface of her eye all faced a bleak future before
the introduction of limbal stem cell transplantations. By continuing to explore the vast
potential of these limbal stem cells, further uses and applications can be discovered. The
full potential of limbal stem cells and their astonishing healing properties has yet to be
unearthed.
References
Burman, S., & Sangwan, V. (2008). Cultivated Limbal Stem Cell Transplantation for
Ocular Surface Reconstruction. Clinical Ophthalmology, 2(3), 489-502.
Charukamnoetkanok, P. (2006). Corneal Stem Cells: Bridging the Knowledge Gap.
Seminars in Ophthalmology, 21, 1-7.
Dua, H.S., & Azura-Blanco, A. (2000). Limbal Stem Cells of the Corneal Epithelium.
Survey of Opthalmology, 44, 415-425.
Meller, D., Pires, R.T.F., & Tseng, S.C.G. (2002). Ex Vivo Preservation and Expansion of
Human Limbal Epithelial Stem Cells on Amniotic Membrane Cultures. Br J
Ophthalmol, 86, 463-471.
O’ Sullivan, F., & Clynes, M. (2007). Limbal Stem Cells, a Review of their Identification
and Culture for Clinical Use. Cytotechnology, 53(1-3), 101-106.
Ozdemir, O., Tekeli, O., Ornek, K., Arslanpence, A., & Yalcindag, N.F. (2004). Limbal
Autograft and Allograft Transplantations in Patients with Corneal Burns. Eye, 18,
241-248.
Pfister, R.R., (1994). Corneal Stem Cell Disease: Concepts, Categorization, and
Treatment by Auto-and Homotransplantation of Limbal Stem Cells. The Contact
Lens Association of Opthalmologists, 20, 64-72
Tsai, J., Li, L.,& Chen, J. (2000). Reconstruction of Damaged Corneas by
Transplantation of Autologous Limbal Epithelial Cells. The New England Journal
of Medicine, 343, 86-93.
Li,W., Hayashida, Y., Chen, Y., Tseng S. (2007). Niche regulation of corneal epithelial
stem cells at the limbus. Cell Research, 17, 26-36.
The number below will change with each revision. These numbers are simply indicative
of the amount of improvement required at this point. When you receive a 9 or greater,
the review is ready. DrT
6/10