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Limbal Stem Cell Deficiency & its management
1. LIMBAL STEM CELL
DEFICIENCY & ITS
MANAGEMENT
Dr. Karan Bhatia
DOMS, DNB
Department of Cornea & Refractive Surgery
M. M. Joshi Eye Institute, Hubli, Karnataka
2. Introduction – Concept of stem cell
Specialized
Undifferentiated
Self-renewing
Capable of indefinite proliferation
Responsible for cellular
replacement & regeneration
3. Limbal stem cells
• Present in the Palisades ofVogt in the Limbus
• CHARACTERISTICS:
1.Poorly differentiated cells
2.Primitive cytoplasm
3.Long cell cycle duration
• FUNCTIONS:
1.Maintain normal corneal epithelium
2.Barrier – Prevent conjunctivalization of cornea
4. Tseng, S. C. G. and Sun,T.T. (2000) In: Corneal Surgery:Theory,Technique, andTissue. (F. S. Brightbill, ed.), Mosby-Year Book, Inc., St. Louis, Missouri, pp. 12.
SC (Parent)
SC
(Daughter
)
SC
SC SC TAC
PMC
TDC
SC – Stem Cell
TAC –Transiently Amplifying Cells
PMC – Post-mitotic Cells
TDC –Terminally Differentiating
Cells
Result of this migration & differentiation Corneal epithelium renewed every 7–10 days
5. THOFT’s XYZ Hypothesis
• X vector – combination of proliferation
& centripetal migration of basal
epithelial cells
• Y vector – As basal epithelial cells
divide they give rise to suprabasal cells
that form stratified layers of cornea
• Z vector – shedding of squamous
epithelial cells from surface of cornea
into tear film
Corneal epithelial maintenance
X + Y = Z
i.e. if corneal epithelium is to be maintained,
cell loss must be balanced by cell replacement
6. Limbal stem cell deficiency - Definition
Clinical entity
where
source for newly generated corneal epithelial cells damaged
causing severe derangement of ocular surface
7. Classification (based on extent of
deficiency)
Partial/Focal Total
• Partial/focal loss of stem cell
function
• Rest of limbus – normal
• Total loss of limbal stem cells
• No Normal area
Examples
• Multiple surgeries at limbus
• Cryotherapy
• Pterygium
• Less severe thermal/chemical burns
Examples
• Severe chemical/thermal burns
• Steven Johnson Syndrome
• Advanced Cicatrical Pemphigoid
• Contact lens wear
8. Limbal Stem cell – dysfunction versus
destruction
LSC DYSFUNCTION LSC DESTRUCTION
• Usually, primary or hereditary
• Can be part of ocular/systemic anomalies
• Due to abnormal microenvironment of
limbal tissues stem cells never achieve
normal function
• Bilateral
• Less severe
• Acquired loss of functioning of stem cells
• Associated with severe ocular surface
damage
• Unilateral
Examples
• Aniridia
• Keratitis associated with multiple endocrine
deficiencies
Examples
• Chemical/thermal burns
• SJS, ocular pemphigoid
• Multiple surgeries, cryotherapy to limbus
• Contact lens wear
11. Jain R, Sureka S, DasAV, Basu S, SangwanVS. Cell BasedTherapy for Ocular Surface Reconstruction. DOSTimes. 2013; 19(4);17-28
Fibrovascular pannus
Persistent Epithelial
Defects
Loss of limbal
palisades ofVogt
Scarring
Extensive
symblepharon
Destruction of BM
Corneal Melting
Lid Anomalies
12. Diagnosis
History & Clinical signs
Impression Cytology
• Can detect presence of goblet cells on cornea
• Can be used to perform immunohistochemistry of for
different markers
• Corneal epithelium specific K3/K12
• Conjunctiva K-19
Histopathology of pannus
Flurophotometry
15. Surgery steps
• Release symblepharon
• Insert speculum
• Conjunctival peritomy (4-5 mm from limbus)
• Remove conjunctival pannus
• Haemostasis (cautery/adrenaline)
16. Conjunctival limbal autograft (CLAU)
1st described by Kenyon andTseng in
1989
Indication Unilateral partial/total
LSCD chemical injury, multiple
surgeries or contact lens use
17. • 2 strips of limbal conjunctival grafts 6-7 limbal arc
lengths removed
• Lenticule 1 mm clear cornea + 1 mm limbus + 3
mm bulbar conjunctiva = 5 mm
• Lenticules sutured with 10-
0 nylon & 8-0 vicry sutures
AMT patch can be used to cover lesion site
Recommendation (to prevent donor site LSCD) –
<6 clock hours
Partial thickness limbal graft (40-60µ)
18. Conjunctival limbal allograft
• Indication – Bilateral LSCD, Unilateral LSCD (one eyed)
• Donor – Living related person/ HLA matched cadaver
Living related allograft Cadaver allograft
Chance of LSCD Yes No
360˚ coverage Not possible with one
donor
Possible
Simultaneous PK tissue Not available Available
Chance of rejection Less More
Viability of stem cells More Doubtful
19. Excision same as autograft
Donor Lenticules
Suturing of 4
lenticules from 2
donors inTotal LSCD
20. Keratolimbal allograft (KLAL)
• Indication – Partial/Total Bilateral LSCD
Unilateral LSCD (one eyed)
• Donor – Cadaveric tissue within 72 hours of death (50 years)
Conjunctival limbal gaft Keratolimbal allograft
Chances of LSCD in donor More Less
Suturing Easy, less mismatch Difficult, more mismatch
Simultaneous PK tissue Not available Available
Chances of rejection More Less
Viability of stem cells More Doubtful
21. • Corneo-scleral Rim
• Excised with 7.5 trephine
• Excess peripheral rim excised (leaving 1 mm
sclera peripheral to limbus
• Posterior 1/2 to 2/3 of ring removed (lamellar
dissection)
• Ring shaped limbal tissue sutured to recipient
limbal area
• + Penetrating/Lamellar Keratoplasty
22. Cultured LSC transplantation
• Principle – Harvesting a small
population of limbal epithelium which
presumably contains LSC
cultivating these cells under
controlled laboratory conditions
• Donor – Autograft/ Allograft
• Indications -
Autograft Allograft
U/L LSCD
B/L Partial LSCD
B/LTotal LSCD
U/LTotal LSCD (one eyed)
• Amniotic membrane with cultured
stem cells is transferred sutured with
limbus by 10-0 Nylon & conjunctiva with
8-0 vicryl
• BCL put
• Simultaneous PK/DALK can be done
Ocular surface epithelia covering the cornea, limbus, and conjunctiva. The conjunctival epithelium differs from the limbal corneal epithelium in that it has mucin-expressing goblet cells. Some of the limbal basal epithelial cells are considered to be stem cells (SCs) for the corneal epithelium. By means of centripetal movement (open arrow), SCs generate corneal transient amplifying cells (TACs) located in the corneal epithelial basal layer. Both SCs and TACs are regarded as progenitor cells in the proliferative compartment, and they give rise to postmitotic cells of the suprabasal layers, as well as terminally differentiated cells of the super fi cial layers. The latter two cell types belong to the differentiative compartment. Suprabasal cell movement at the limbus creates a barrier to separate the conjunctival epithelium from the corneal epithelium (solid arrow).
1.
Any surgical treatment in an inflamed eye NOT give desired results
Active inflammation detrimental to transplanted stem cells. Inflammation causes greater Stem cell damage than primary injury itself
Supportive therapy to prevent further complications
AMT application in acute stage of insult serves as a biological bandage
Prabasawat et al reported that AMT within 5 days of grade II-III chemical burns resulted in faster epithelial healing as well as decreased corneal haze and LSCD.
A newer approach involves the implantation of ProKera—an FDA-approved class II medical device consisting of a sheet of cryopreserved amniotic membrane clipped into a dual symblepharon ring system — during the acute stage of chemical injury or SJS. It allows for an early intervention, at bedside, promoting the beneficial effect of reduction of inflammation and early healing of epithelial defect of the corneaand conjunctiva.
Conservative Mx- lubricants, anti-inflammatory agents, BCL
Gas permeable Scleral CL fluid interphase appears to aid re-epithelialization through oxygenation, moisture & protection.
Definitive treatment of Partial LSCD – surgical
SSCE – removal of conjunctival epithelium that is covering a sector of cornea and limbus or adjacent bulbar conjunctiva, so that corneal epithelial cells may regrow over denuded surface.