Re-epithelialization

Prophylactic acyclovir, valacyclovir or famvir is given to patients with a history of recurrent herpes simplex, starting a day before the procedure and continuing for 10 days until full re-epithelialization is achieved. 

Useful with shallow boxcar and rolling scars. CO2 and/or Er YAG lasers are utilized for this technique. After the treatment, silicone sheeting, gauze and tube netting are placed over the treated area and maintained for 24 h (the silicone sheeting remains for another 48 h). The patient is instructed to soak the treated area every 2-4 h with cold water for 20 min and then apply an occlusive ointment. Re-epithelialization is completed in 10 days. A new treatment can be performed after 6-8 weeks. 

Gentian violet solution is used to delineate the areas to be treated. Refrigerant topical anesthesia is used to freeze the skin prior to the procedure. Holding the skin taut, the dermabrader treats one anatomic unit at a time. Post-operatively, patients may have an open or closed dressing system, use antiviral agents, antibacterials and corticosteroids. The re-epithelialization is complete in 5-7 days and residual erythema is common for up to 4 weeks. 

The model concerning wound healing occurs in two phases (1) pro-inflammatory responses (Glaser and Kiecolt-Glaser 2005 Moore 1999 Tidball 2005 Whelan et al. 2005) which are needed to ensure adequate clearance of pathogen at the site of tissue injury, as well as, (2) re-epithelialization and neovascularization events (Frantz et al. 2005 Moore 1999 Naldini and Carraro 2005 Olah and Caldwell 2003 Whelan et al. 2005) to ensure proper wound closure. It is important to note that the resolution of pathogen clearance is essential in order for the wound closure processes to take place (Robson 1997). 

Upon resolntion of the pathogen, the second phase of wonnd healing occurs where re-epithelialization and neovascularization are essential for wound closure. Formation of new blood vessels (angiogenesis) (Barcelos et al. 2005 Roy et al. 2008), fibrin matrices (Midwood et al. 2006), and collagen deposits (Seppinen et al. 2008) are all events that promote the wound closure process. 

Normal skin appears to be devoid of PDGF receptors. Animal studies illustrate that rapid expression of both a and P receptor subunits is induced upon generation of an experimental wound (e.g. a surgical incision). Receptor expression is again switched off following re-epithelialization and complete healing of the wound. 

If there are no signs of improvement after 7 days, or if complete re-epithelialization has not occurred after 14 days, consider other forms of therapy. Avoid continuous administration for periods exceeding 21 days because of potential ocular toxicity. 

In severe ocular bums with complete loss of the limbal vascularization, other than the predictable impossibility of secondary re-epithelialization, there is an immediate risk of necrosis for the anterior segment. In order to restore the limbal circulation and to block the evolution towards a necrosis or an aseptic ulceration, a Tenon s plastics may be realized. It consists in the making of a Tenon s advancement flap located at the level of the limbus [4-8]. The intervention must be realized as soon as the necrotic tissues have been removed. The dissection starts in the equatorial region and continues at the back of the conjunctival sacs. The flaps must be 1-2 mm thick. Their elastic consistency helps their advancement. The flap is sutured to the... 

Forman DM, Pancholi S, Jarvis-Evans J et al. (1996) A simple organ culture model for assessing the effects of growth factors on corneal re-epithelialization. Exp Eye Res 62 555-564... 

Irrigate eyes with tepid water until pH returns to neutral and remains so for 30 min after irrigation is discontinued (Brodovsky et al, 2000). Time until decontamination after ocular exposure is important since phosgene oxime is absorbed within seconds. Corneal ulcers should be treated with atropine ophthahnics to prevent synechiae formation and other ophthahnics to aid in re-epithelialization (Brodovsky et al, 2000 Grant and Schuman, 1993). 

Two-thirds of patients treated with cyclophosphamide orally for 4 months plus intravenous 5-fluorouracil and methotrexate for breast cancer developed Barrett s epithelium (16), perhaps as a result of esophagitis, rather than through mucosal re-epithelialization by undifferentiated stem cells (17). 

Solutions made up in the clinic should be considered unstable and, although some may retain potency for relatively long periods, as a rule should not be stored for more than 3-4 days. Concentrated antibiotic preparations are likely to retard comeal re-epithelialization and their use should be curtailed once the infection is under control. Commercial strength ophthalmic drops can then be introduced. In general, the frequency of topical antibiotic administration should be reduced once the infection is under control, based upon the clinical appearance of the comeal lesion. 

Re-epithelialization of comeal defects appears to depend in part upon the interaction of MMPs with matrix adhesion proteins on the exposed stromal surface to form the scaffolding for migrating basal epithelial cells (Fini et al 1996). Relative overexpression of MMPs may be a significant factor in refractory or indolent ulceration and in chronic superficial erosion in the horse. 

Heparin (1000 lU/ml) has been used to promote re-epithelialization in chronic refractory ulceration in the horse. Its mode of action is unknown but it may have an indirect antiproteinase activity by impeding the extravasation of leukocytes into the tear film. 

All topical anaesthetic agents delay comeal re-epithelialization and mask the presence of a fornix-based foreign body or ectopic cilia. They should not be used in the routine management of ocular pain. 

After a peel, the skin needs to heal as quickly as possible in order to maintain homeostasis of the whole organism. Tretinoin accelerates re-epithelialization if used before the peeling. For this it must be used at a dose of 0.05%-0.1%, sometimes to the point of irritative dermatitis. Ideally, the treatment should start 3-4 weeks before a TCA-SAS peel. It is accepted scientifically that the preventive application of tretinoin promotes post-peel healing of the skin. In contrast, applying tretinoin during the post-peel period appears to slow down skin regeneration. Not all peels require this help with re-epitheliazation. 

The process of wound healing after thermal injury (e.g. from laser treatment) involves re-epithelialization that starts within the first few hours after injury and continues throughout the different proliferative phases of skin repair. Viable keratinocytes (Figure 3.2) that are at the edge of the wound and have not suffered lethal or sublethal heat shock... 

TCA-SAS should be preceded by several weeks of skin preparation to even out and reduce the thickness of the stratum corneum, reduce melanocyte activity and enhance re-epithelialization. ETCA, on the other hand, is applied on unprepared skin, as the acid and the post-peel cream penetrate evenly the risk of pigmentary changes (basic protocol) is extremely low and re-epithelialization takes place without prestimulation. 

Trichloroacetic acid (TCA) in a simple aqueous solution (TCA-SAS) is the peel most widely used to partially or completely remove the papillary dermis. Strict pre-peel preparation is required to even out penetration, reduce melanocyte activity and accelerate post-peel re-epithelial-ization. The main purpose of post-peel care is to coimter complications (see Chapter 14). 

Unideep was designed to make pre-peel preparation as easy as possible, at the same time as maintaining rapid re-epithelialization and limiting the risks of post-peel complications. Unideep is a by-product of Easy TCA (ETCA) technology and is a medium-depth peel that reaches the papillary dermis. 

After re-epithelialization, dermal collagen is regenerated over a 2- to 3-month period. 

Open healing is slower than when the re-epithelializing wound is covered. This does not matter for intraepidermal peels, as the dermis is still covered by several layers of living and protective keratinocytes. On the other hand, when it comes to medium or deep peels, this is of major importance. Peels have an advantage over laser or mechanical abrasive treatments in that they leave a layer of skin in place. This layer of skin is of course dead, but it offers pro-... 

Post-peel hydration is also important. The skin should not be allowed to dry out while it is re-epithelializing after a medium or superficial peel it needs to be hydrated. Proper hydration prevents pruritus and delayed healing. Hydration after a deep peel is essential after the first week. 

Premature re-peeling should be avoided a re-peel should not be done if re-epithelialization is not complete. 

Applying topical tretinoin (aU-frans-retinoic acid) before a peel can often reduce the incidence of miHa. However, the undesirable effects of retinoic acid in combination with a deep or medium peel must be taken into account. Retinoic acid increases the depth of penetration of caustic agents, could increase the risk of hyperpigmentation and, if it is applied too soon after a medium or deep peel, slows down the rate of re-epithelialization. 

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