- Email: [email protected]
RDEB: regeneration is not enough
Journal of Plastic, Reconstructive & Aesthetic Surgery (2008) 61, 1421e1422
EDITORIAL
RDEB: regeneration is not enough Recessive Dystrophic Epidermolysis Bullosa (RDEB) is an inherited blistering skin disease characterized at molecular level by mutations of the COL7A1 gene which encodes for type VII collagen. Type VII collagen is an integral part of the dermo-epidermal junction that has been well characterized by Burgeson and Christiano.1 The clinical severity of the condition will depend on the mutation present and Dong and Murrel have reported more than 320 pathogenic mutations2 and Woodley et al have characterized the molecular mechanisms underlying the mutations.3 The spectrum of disease is very wide ranging from minor dystrophy in the nails to the more severe forms where there is a significant fragility of the skin with recurrent wounds, infection, scarring, deformity, failure to thrive and premature death from squamous cell carcinoma.4 Although there are many supportive managements to ameliorate the effects of the disease, there is currently no treatment for the underlying cause; defective and deficient type VII collagen. The main treatment strategies have focused on the replacement of the abnormal collagen VII using genetic, cell or protein based approaches. Mavilio et al have used genetically modified epidermal stem cells to treat junctional epidermolysis bullosa.5 A tissue engineered construct comprising a fibroblast-populated collagen gel on which a stratified keratinized layer of epidermal cells has been grown has been reported to accelerate and maintain the healing of wounds in RDEB. The allogeneic cells are derived from cultures of neonatal foreskin and are of reduced immunogenicity due to their serial passaging in culture.6 Cell based strategies have focused primarily on dermal fibroblasts. This has been based on gene-transfection studies using skin grafts to nude mice which revealed the gene transferred fibroblasts supplied higher amounts of collagen VII to the newly formed DEJ than gene-transferred keratinocytes.7 This was a very important observation as previously it had been thought that in vivo most type VII collagen comes from the keratinocytes. As Chen and Woodley discuss in the commentary to Goto et al’s paper, the fibroblast is a much easier cell to work with than the keratinocyte and is much less susceptible to growth arrest and differentiation. Indeed as fibroblasts can be passaged 20e30 times in vitro a single, genetically modified
fibroblast can be expanded to greater than 1020 cells.8 A recent clinical study looking a intradermal injections of allogenic fibroblasts in six patients with RDEB indicated a positive response. This response was better in the least severe clinical forms and appeared to be related to a stimulation of autologous collagen VII production.9,10 The roles of the keratinocyte and fibroblast in the formation of the DEJ have been investigated in an in vitro model of the fibroblast populated collagen lattices onto which keratinocytes are seeded. The model is allowed to developed at the air liquid interface to allow keratinocyte stratification.11 Animal models for RDEB have been problematic as knock out mice with absent Collagen VII cannot survive. Targeted inactivation has been attempted but it is the hypomorphic mouse model which holds the greatest promise for long term in vivo recovery experiments.12e14 The hypomorphic mouse model has been developed by Professor Leena Bruckner-Tuderman’s group in the Department of Dermatology at the University of Freiburg. This is the transgenic EB mouse model Col7a1flNeo/flNeo. This is an immunocompetent animal model for dystrophic EB (DEB). These mice express collagen VII at about 10% of normal levels and their phenotype closely resembled characteristics of severe human DEB, including mucocutaneous blistering, nail dystrophy, and mitten deformities of the extremities. The advantages of this model is that the pathology is caused by a reduced level of normal collagen VII, but not by interference of mutated molecules which would generate a variety of abnormal structures leading to high mortality rate at birth. The Col7a1flNeo/flNeomice survive to adulthood; it makes this model ideally suited for evaluation of novel therapeutic strategies. The severe forms of RDEB are devastating in their impact on the lives of the patient and extremely challenging to manage. A recent experience with a patient referred with a circumferential forearm SCC (Figure 1) underlined this challenge in terms of anaesthesia, patient handling as well as reconstructive strategies. The use of Integra, and mixed autogenic mesh graft and allogenic keratinocyte spray (Figure 2) has achieved an effective cover but for how long (Figure 3)? Earlier this year I discussed the new logo of BAPRAS e the salamander and described it as an inspired choice for
1748-6815/$ - see front matter ª 2008 Published by Elsevier Ltd on behalf of British Association of Plastic, Reconstructive and Aesthetic Surgeons. doi:10.1016/j.bjps.2008.10.008
1422
Editorial reconstructive surgeons.15 Briefly e the salamander is of the order Urodele e the only adult vertebrates capable of regeneration. Regeneration is the goal of all Plastic Surgeons. Or is it? My patient with severe RDEB does not want simple regeneration. He has a genetic abnormality and imperfectly provides collagen VII to the dermoepidermal junction. He does not want more of the same he wants some thing more than regeneration. He wants, needs, regeneration plus a new gene. There is no doubt that this is going to happen, not tomorrow but some time in the future. And looking at that future it is evident that there will be an ever increasing interaction between surgeons and scientists. A partnership that needs planning, preparation and support as we train surgeons for the future.
References Figure 1
Figure 2
Removing the SCC.
Second stage Integra with allogenic cell spray.
Figure 3
Fully healed.
1. Burgeson RE, Christiano AM. The dermal-epidermal junction. Curr Opin Cell Biol 1997;9:651e658. 2. Dang N, Murrell DF. Mutation analysis and characterization of COL7A1 mutations in dystrophic epidermolysis bullosa. Exp Dermatol 2008;17:553e568. 3. Woodley DT, Hou Y, Martin S, et al. Characterization of molecular mechanisms underlying mutations in dystrophic epidermolysis bullosa using site-directed mutagenesis. J Biol Chem 2008;283:17838e17845. 4. Mallipeddi R. Epidermolysis bullosa and cancer. Clin Exp Dermatol 2002;27:616e623. 5. Mavilio F, Pellegrini G, Ferrari S, et al. Correction of junctional epidermolysis bullosa by transplantation of genetically modified epidermal stem cells. Nat Med 2006;12:1397e1402. 6. Falabella AF, Valencia IC, Eaglstein WH, et al. Tissue-engineered skin (Apligraf) in the healing of patients with epidermolysis bullosa wounds. Arch Dermatol 2000;136:1225e1230. 7. Goto M, Sawamura D, Ito K, et al. Fibroblasts show more potential as target cells than keratinocytes in COL7A1 gene therapy of dystrophic epidermolysis bullosa. J Invest Dermatol 2006;126:766e772. 8. Chen M, Woodley DT. Fibroblasts as target cells for DEB gene therapy. J Invest Dermatol 2006;126:708e710. 9. Wong T, Gammon L, Liu L, et al. Potential of fibroblast cell therapy for recessive dystrophic epidermolysis bullosa. J Invest Dermatol 2008;128:2179e2189. 10. Uitto J. Epidermolysis bullosa: prospects for cell-based therapies. J Invest Dermatol 2008;128:2140e2142. 11. Marionnet C, Pierrard C, Vioux-Chagnoleau C, et al. Interactions between fibroblasts and keratinocytes in morphogenesis of dermal epidermal junction in a model of reconstructed skin. J Invest Dermatol 2006;126:971e979. 12. Jiang QJ, Uitto J. Animal models of epidermolysis bullosa e targets for gene therapy. J Invest Dermatol 2005;124:xiexiii. 13. Heinonen S, Mannikko M, Klement JF, et al. Targeted inactivation of the type VII collagen gene (Col7a1) in mice results in severe blistering phenotype: a model for recessive dystrophic epidermolysis bullosa. J Cell Sci 1999;112:3641e3648. 14. Fritsch A, Loeckermann S, Kern JS, et al. A hypomorphic mouse model of dystrophic epidermolysis bullosa reveals mechanisms of disease and response to fibroblast therapy. J Clin Invest 2008;118:1669e1679. 15. Burd A. Salamanders, lizards and ubiquitous stem cells. J Plast Reconstr Aesthet Surg 2008;61:121e123.
Andrew Burd, Editor, JPRAS, Hong Kong E-mail address: [email protected]
EDITORIAL
RDEB: regeneration is not enough Recessive Dystrophic Epidermolysis Bullosa (RDEB) is an inherited blistering skin disease characterized at molecular level by mutations of the COL7A1 gene which encodes for type VII collagen. Type VII collagen is an integral part of the dermo-epidermal junction that has been well characterized by Burgeson and Christiano.1 The clinical severity of the condition will depend on the mutation present and Dong and Murrel have reported more than 320 pathogenic mutations2 and Woodley et al have characterized the molecular mechanisms underlying the mutations.3 The spectrum of disease is very wide ranging from minor dystrophy in the nails to the more severe forms where there is a significant fragility of the skin with recurrent wounds, infection, scarring, deformity, failure to thrive and premature death from squamous cell carcinoma.4 Although there are many supportive managements to ameliorate the effects of the disease, there is currently no treatment for the underlying cause; defective and deficient type VII collagen. The main treatment strategies have focused on the replacement of the abnormal collagen VII using genetic, cell or protein based approaches. Mavilio et al have used genetically modified epidermal stem cells to treat junctional epidermolysis bullosa.5 A tissue engineered construct comprising a fibroblast-populated collagen gel on which a stratified keratinized layer of epidermal cells has been grown has been reported to accelerate and maintain the healing of wounds in RDEB. The allogeneic cells are derived from cultures of neonatal foreskin and are of reduced immunogenicity due to their serial passaging in culture.6 Cell based strategies have focused primarily on dermal fibroblasts. This has been based on gene-transfection studies using skin grafts to nude mice which revealed the gene transferred fibroblasts supplied higher amounts of collagen VII to the newly formed DEJ than gene-transferred keratinocytes.7 This was a very important observation as previously it had been thought that in vivo most type VII collagen comes from the keratinocytes. As Chen and Woodley discuss in the commentary to Goto et al’s paper, the fibroblast is a much easier cell to work with than the keratinocyte and is much less susceptible to growth arrest and differentiation. Indeed as fibroblasts can be passaged 20e30 times in vitro a single, genetically modified
fibroblast can be expanded to greater than 1020 cells.8 A recent clinical study looking a intradermal injections of allogenic fibroblasts in six patients with RDEB indicated a positive response. This response was better in the least severe clinical forms and appeared to be related to a stimulation of autologous collagen VII production.9,10 The roles of the keratinocyte and fibroblast in the formation of the DEJ have been investigated in an in vitro model of the fibroblast populated collagen lattices onto which keratinocytes are seeded. The model is allowed to developed at the air liquid interface to allow keratinocyte stratification.11 Animal models for RDEB have been problematic as knock out mice with absent Collagen VII cannot survive. Targeted inactivation has been attempted but it is the hypomorphic mouse model which holds the greatest promise for long term in vivo recovery experiments.12e14 The hypomorphic mouse model has been developed by Professor Leena Bruckner-Tuderman’s group in the Department of Dermatology at the University of Freiburg. This is the transgenic EB mouse model Col7a1flNeo/flNeo. This is an immunocompetent animal model for dystrophic EB (DEB). These mice express collagen VII at about 10% of normal levels and their phenotype closely resembled characteristics of severe human DEB, including mucocutaneous blistering, nail dystrophy, and mitten deformities of the extremities. The advantages of this model is that the pathology is caused by a reduced level of normal collagen VII, but not by interference of mutated molecules which would generate a variety of abnormal structures leading to high mortality rate at birth. The Col7a1flNeo/flNeomice survive to adulthood; it makes this model ideally suited for evaluation of novel therapeutic strategies. The severe forms of RDEB are devastating in their impact on the lives of the patient and extremely challenging to manage. A recent experience with a patient referred with a circumferential forearm SCC (Figure 1) underlined this challenge in terms of anaesthesia, patient handling as well as reconstructive strategies. The use of Integra, and mixed autogenic mesh graft and allogenic keratinocyte spray (Figure 2) has achieved an effective cover but for how long (Figure 3)? Earlier this year I discussed the new logo of BAPRAS e the salamander and described it as an inspired choice for
1748-6815/$ - see front matter ª 2008 Published by Elsevier Ltd on behalf of British Association of Plastic, Reconstructive and Aesthetic Surgeons. doi:10.1016/j.bjps.2008.10.008
1422
Editorial reconstructive surgeons.15 Briefly e the salamander is of the order Urodele e the only adult vertebrates capable of regeneration. Regeneration is the goal of all Plastic Surgeons. Or is it? My patient with severe RDEB does not want simple regeneration. He has a genetic abnormality and imperfectly provides collagen VII to the dermoepidermal junction. He does not want more of the same he wants some thing more than regeneration. He wants, needs, regeneration plus a new gene. There is no doubt that this is going to happen, not tomorrow but some time in the future. And looking at that future it is evident that there will be an ever increasing interaction between surgeons and scientists. A partnership that needs planning, preparation and support as we train surgeons for the future.
References Figure 1
Figure 2
Removing the SCC.
Second stage Integra with allogenic cell spray.
Figure 3
Fully healed.
1. Burgeson RE, Christiano AM. The dermal-epidermal junction. Curr Opin Cell Biol 1997;9:651e658. 2. Dang N, Murrell DF. Mutation analysis and characterization of COL7A1 mutations in dystrophic epidermolysis bullosa. Exp Dermatol 2008;17:553e568. 3. Woodley DT, Hou Y, Martin S, et al. Characterization of molecular mechanisms underlying mutations in dystrophic epidermolysis bullosa using site-directed mutagenesis. J Biol Chem 2008;283:17838e17845. 4. Mallipeddi R. Epidermolysis bullosa and cancer. Clin Exp Dermatol 2002;27:616e623. 5. Mavilio F, Pellegrini G, Ferrari S, et al. Correction of junctional epidermolysis bullosa by transplantation of genetically modified epidermal stem cells. Nat Med 2006;12:1397e1402. 6. Falabella AF, Valencia IC, Eaglstein WH, et al. Tissue-engineered skin (Apligraf) in the healing of patients with epidermolysis bullosa wounds. Arch Dermatol 2000;136:1225e1230. 7. Goto M, Sawamura D, Ito K, et al. Fibroblasts show more potential as target cells than keratinocytes in COL7A1 gene therapy of dystrophic epidermolysis bullosa. J Invest Dermatol 2006;126:766e772. 8. Chen M, Woodley DT. Fibroblasts as target cells for DEB gene therapy. J Invest Dermatol 2006;126:708e710. 9. Wong T, Gammon L, Liu L, et al. Potential of fibroblast cell therapy for recessive dystrophic epidermolysis bullosa. J Invest Dermatol 2008;128:2179e2189. 10. Uitto J. Epidermolysis bullosa: prospects for cell-based therapies. J Invest Dermatol 2008;128:2140e2142. 11. Marionnet C, Pierrard C, Vioux-Chagnoleau C, et al. Interactions between fibroblasts and keratinocytes in morphogenesis of dermal epidermal junction in a model of reconstructed skin. J Invest Dermatol 2006;126:971e979. 12. Jiang QJ, Uitto J. Animal models of epidermolysis bullosa e targets for gene therapy. J Invest Dermatol 2005;124:xiexiii. 13. Heinonen S, Mannikko M, Klement JF, et al. Targeted inactivation of the type VII collagen gene (Col7a1) in mice results in severe blistering phenotype: a model for recessive dystrophic epidermolysis bullosa. J Cell Sci 1999;112:3641e3648. 14. Fritsch A, Loeckermann S, Kern JS, et al. A hypomorphic mouse model of dystrophic epidermolysis bullosa reveals mechanisms of disease and response to fibroblast therapy. J Clin Invest 2008;118:1669e1679. 15. Burd A. Salamanders, lizards and ubiquitous stem cells. J Plast Reconstr Aesthet Surg 2008;61:121e123.
Andrew Burd, Editor, JPRAS, Hong Kong E-mail address: [email protected]