The human body consists of a number of very complex, highly specialised organs which perform a variety of functions that are essential to life and health. One of the main functions of the skin, the largest of the human organs, is to maintain the integrity of the body. It does this by acting as a physical barrier, preventing micro-organisms and other potentially harmful substances from entering the body. When the integrity of the skin is damaged through injury, a self-protective mechanism is triggered and the reparative wound healing process begins. Under normal circumstances the wound healing process culminates in the skin recuperating its normal characteristics and functions at the site of the injury, with only a small visible mark being left behind. However, in some cases the wound healing process may become altered leading to the production of abnormal scars, such as keloids. Keloid scars are formed from scar tissue at the site of an injury, as a result of excessive tissue repair that extends beyond the boundaries of the original wound. These scars are characterised by excess collagen deposition produced during the wound healing process. It is estimated that as many as 20% of the black and Hispanic population are affected by keloid scarring. In addition to the aesthetic aspect, keloid scars can also be painful, itchy and prone to become infected. Keloid scar formation can be triggered by skin injuries caused by, for example, acne, wounds, shaving, burns, and surgical incisions. The mechanism by which keloid scars form is currently not well understood and consequently no effective treatments exist to date.This thesis describes an investigation into the mechanical properties of single keloid and normal skin fibroblast cells for the purpose of establishing if there is a quantitative difference between the two types of cells. This information will be of benefit to researchers looking for a better understanding of the keloid formation mechanism and for those seeking improved treatments. An atomic force microscope (AFM) was employed to indent single Keloid and normal skin fibroblast cells taken from five patients. Values for the apparent Young's modulus of the cells were then calculated by fitting the experimental data using Hertz's model. Apparent Young's modulus values were then compared. The findings of the analysis indicate that statistically, there is a significant difference in the Young's modulus values of normal and keloid cells, with keloid cells exhibiting substantially greater stiffness than normal skin fibroblast cells. To enable the keloid and normal skin fibroblast cells to be studied in as close to their natural, physiological environment as is possible the AFM experiments described in this thesis were undertaken in a phosphate buffered saline (PBS) solution. In such cases the use of a fluid medium presents additional complexities, not least of which is the introduction of a hydrodynamic drag force due to viscous friction of the cantilever with the liquid which can affect the experimental data obtained and consequently any material properties calculated as a result of using these data. In order to investigate the effect of dragging force on the experimental data obtained from the AFM a novel integrated finite element based model was developed. The model, described in this thesis, provides quantification of the drag force in AFM measurements of soft specimens in fluids, consequently enabling more accurate interpretation of the data obtained from AFM experimentation. The model is validated using extensive data obtained from AFM experimentation undertaken in a number of fluids of different viscosities, at a variety of tip velocities and platform-tip separations and by comparison with an existing analytical model. The novel model is shown to accurately account for drag forces in AFM in fluid media without the need for extrapolation of experimental data and can be employed over the range of tip geometries and velocities typically utilised in AFM experimentation.The work described in this thesis demonstrates that the AFM is a valuable tool that can be used to successfully investigate the mechanical properties of biological samples in fluids. It was shown that increased accuracy in the interpretation of data obtained from AFM experimentation can be obtained by taking into account the hydrodynamic drag force due to viscous friction of the cantilever with the liquid. The investigation into the mechanical behaviour of keloid cells described in this thesis significantly adds to the yet small body of research undertaken on keloid cells to date. The findings of the investigation will provide valuable information that will be of benefit in the future to researchers looking to develop effective treatments for the prevention, reduction or removal of keloid scars.

Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast activity results in abnormal collagen deposition. Scientific literature related to the morphological features of keloids especially at an ultrastructural level is outdated. Therefore the aim of this study was to reassess present knowledge of the ultrastructural features of keloids and possibly through this process identify new cellular therapeutic targets. The research was conducted on normal (control) and keloid human skin samples collected from consenting patients undergoing keloid removal and skin transplantation surgeries at the Steve Biko Academic Hospital. The tissue structure of normal/control skin and keloids as well as mast cell and collagen distribution were evaluated using histological techniques. Transmission electron microscopy techniques were undertaken in order to investigate morphological and ultrastructural features of cells of the epidermis and dermis. A further detailed analysis of the ultrastructure of keloid fibroblasts and mast cells was undertaken. The findings of this study have lead to a new hypothesis related to keloid formation. Increased fibroblast activity, intracellular collagen production and fibroblast and mast cell interactions were seen in keloid tissue. Changes in the morphology of keratinocytes and melanocytes were observed, where the cytoplasmic processes of both cells were shorter and cells were packed closer together in keloids. Keloid tissue appeared to be in a hyperproliferative state similar to that of the granulation phase of wound healing. Increased amounts of collagen were found in the extracellular matrix (ECM) of keloid tissue. This is the first study in which the abnormal accumulation of insoluble collagen fibrils was observed in the cytoplasm. Degranulation of mast cells had occurred and these cells were found in close association with fibroblasts. In some instances phagocytosis of collagen by mast cells was also observed. These observations have led to the hypothesis that transforming growth factor β (TGF-β) derived from mast cells, inhibits keratinocyte proliferation and stimulates increased collagen production through increased expression of lysyl oxidase (LOX) by fibroblasts. Intracellular insoluble collagen formation then occurs due to the rapid, intracellular removal of the C terminal pro-peptide sequence by C-proteinase which initiates the cascade of insoluble collagen fibre formation within the fibroblast. Normally this process occurs only within the ECM in response to the increasing mass of collagen and in an attempt to establish normal tissue homeostasis the mast cells engulf the bundles of collagen fibres. Increased stress on the epidermal layer causes increased keratinocyte proliferation, which results in further growth factor mediated replication of fibroblasts. This creates an endless cycle of collagen synthesis, mast cell degranulation and mast cell mediated collagen phagocytosis, physical stress on the epidermal layer and subsequent growth factor release and fibroblast activation, collagen synthesis and subsequent crowding of keratinocytes and melanocytes. In conclusion, this study identified keloid formation as a defect of procollagen synthesis and processing. Phagocytosis of collagen by mast cells indicates that accumulation of these cells may be a secondary effect to excessive collagen synthesis. In addition, the release of interleukins, mediators and growth factors may further stimulate collagen fibril formation with the imbalance toward increased synthesis. This study also identified and confirmed the findings of other studies that procollagen C-proteinase is an important therapeutic target. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Anatomy / MSc / Unrestricted

No description available.

Au-Yeung, Ching. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 108-126). / Abstracts in English and Chinese. / ABSTRACT --- p.II / DEDICATION --- p.IV / ACKNOWLEDGMENTS --- p.IV / Chapter 1 --- INTRODUCTION TO KELOID SCARRING - THE PATHOGENESIS AND TREATMENT --- p.3 / Chapter 1.1 --- The Pathogenesis of Keloid Scarring --- p.3 / Chapter 1.2 --- The Impact of Keloid Scarring --- p.6 / Chapter 1.3 --- The Treatment of Keloid Scarring --- p.7 / Chapter 1.4 --- Summary --- p.12 / Chapter 1.5 --- Aim of the study --- p.14 / Chapter 2 --- APOPTOSIS AND KELOID PATHOLOGY --- p.15 / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Material and methods --- p.25 / Chapter 2.3 --- Results --- p.34 / Chapter 2.4 --- Discussions --- p.41 / Chapter 2.5 --- Summary --- p.64 / Chapter 2.6 --- Conclusions --- p.66 / Chapter 2.7 --- Further research plans --- p.67 / Chapter 3 --- LASER INTERACTION IN KELOID SCARRING --- p.68 / Chapter 3.1 --- Introduction --- p.68 / Chapter 3.2 --- Material and method --- p.86 / Chapter 3.3 --- Results --- p.89 / Chapter 3.4 --- Discussions --- p.94 / Chapter 3.5 --- Summary and conclusion --- p.102 / Chapter 3.6 --- Further research plans --- p.105 / Chapter 4 --- CONCLUSIONS --- p.106 / REFERENCES --- p.108

Keloids are a fibroproliferative disorder of unknown etiology developing in the skin after injury or spontaneously. The aim of this thesis is to gain deeper insight into the role of TGF-β and its signaling pathway proteins, SMADs, in the pathogenesis of keloids and describe the gene expression profile in different keloid sites in the search for potential target genes for future treatment. Further aim is to develop an instrument to describe the quality of life of patients with keloids. We find cultured keloid fibroblasts to express an increased level of TGF-β1 mRNA and a decreased level of TGF-β3 mRNA compared to control skin. Keloid derived fibroblasts exhibit significantly decreased mRNA levels of TGF-β receptor type II (TβRII) and the ratio of TβRI/TβRII mRNA expression is increased. This suggests that a certain expression pattern of TGF-β subtypes and receptors may be important in keloid pathogenesis. Analysis of keloid derived fibroblasts reveal decreased SMAD3 mRNA expression and decreased ratio of SMAD2/SMAD3 mRNA implicating a disturbed SMAD signaling. Keloid fibroblasts up-regulate SMAD4 protein after stimulation with TGF-β1 and display diminished levels of the inhibitory proteins SMAD6 and 7. This may contribute to unlimited and deregulated TGF-β signaling leading to increased extracellular matrix production (ECM). The gene expression pattern is described in fibroblasts from different keloid sites using microarrays covering the whole human genome. This study reveals 105 regulated genes (79 genes are up- and 26 down-regulated) resulting in a unique gene expression profile in different sites of keloids, where progression or regression of the keloid process took place. In cells from the central part of keloids with clinical signs of regression, an up-regulation of apoptosis inducing genes as ADAM12 and ECM degrading genes as MMP19 is found. These genes may contribute to regression of keloids and might be possible future target genes for treatment. Overexpression of apoptosis inhibitors as AVEN and down-regulation of angiogenesis inhibiting genes as PTX3 found at the active margin of keloids may be responsible for the invasive character of the keloid margin. We develop a disease specific questionnaire to measure the quality of life of patients with keloids. We find two scales, psychological and physical impairment, describing the dimensions of quality of life in patients with scars. These two scales are independent of each other and show a high test-retest reliability. Single items which clinically characterize the disease show correlations to these scales. The results of this study demonstrate for the first time a severe impairment of quality of life of patients suffering from keloids and hypertrophic scars. In conclusion the described alteration in TGF-β expression and its receptors, the disrupted SMAD signaling pathway and the unique gene expression patterns in different keloid sites provide new knowledge on ECM formation and degradation in keloids. Regulatory genes in ECM homeostasis may be future target genes for keloid prevention, regression and treatment. The disease specific quality of life instrument of patients with keloids and scars is a useful tool to estimate success in future therapeutic efforts over time.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2008. / Härtill 4 uppsatser.

Keloid disease (KD) is a cutaneous fibroproliferative tumour characterised by heterogeneity, locally aggressive invasion and therapeutic resistance. Clinical, histological and molecular differences between the keloid scar centre and margin as well as recent evidence of the importance of epithelial-mesenchymal interactions (EMI) in KD pathobiology contribute to the complexity and diversity of KD, which coupled with the lack of a validated animal model have hindered research and effective management. Despite significant progress in the field of KD research, reliance on conventional monolayer cell culture and whole tissue analysis methods have failed to fully reflect the natural architecture, pathology and complexity of KD in vivo. In order to address these challenges, a site-specific in situ approach was therefore employed here for the first time in KD research. The first aim of this work was to compare the value of this contemporary approach with traditional methods of tissue dissection. The second aim was to compare the genomic expression between well-defined, distinct keloid sites and normal skin (NS). The third aim was to develop and explore hypotheses arising from this site-specific gene expression profiling approach, so as to enhance understanding of KD pathobiology as a basis for improved diagnostic and therapeutic strategies in future KD management. The fourth aim was to probe these hypotheses with relevant functional in vitro studies. The current site-specific in situ approach was achieved through a combination of laser capture microdissection and whole genome microarray, allowing separation of epidermis from dermis for keloid centre, margin and extralesional sites compared with NS. This in situ approach yielded selective, accurate and sensitive data, exposing genes that were overlooked with alternative methods of dissection. Identification of significant upregulation of the aldo-keto reductase enzyme AKR1B10 in all three sites of the keloid epidermis (KE) in situ, implicated dysregulation of the retinoic acid (RA) pathway in KD pathogenesis. This hypothesis was supported by showing that induced AKR1B10 overexpression in NS keratinocytes reproduced the keloid RA pathway expression pattern. Moreover, co-transfection with a luciferase reporter plasmid revealed reduced RA response element activity. Paracrine signals released by AKR1B10-overexpressing keratinocytes into conditioned medium resulted in TGFβ1 and collagen upregulation in keloid fibroblasts, suggesting the disturbed RA metabolism exerts a pro-fibrotic effect through pathological EMI, thus further supporting the hypothesis of RA deficiency in KE. Gene expression profiling further revealed an upregulation of NRG1 and ErbB2 in keloid margin dermis. Exogenous NRG1 led to enhanced keloid fibroblast migration with increased Src and PTK2 expression, which were attenuated with ErbB2 siRNA studies. Together with the observed failure to recover this expression with NRG1 treatment, suggested the novel KD pathobiology hypothesis that NRG1/ErbB2/Src/PTK2 signaling plays a role in migration at the keloid margin. In addition to these hypotheses, LCM methodology with comprehensive analysis of the data permitted the development of additional novel working hypotheses that will inform future KD research, including inflammatory gene dysregulation and cancer-like stem cells that may contribute to the therapeutic resistance characteristic of KD.

Orientador: Konradin Metze / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T20:44:11Z (GMT). No. of bitstreams: 1 Ferro_DanielaPeixoto_D.pdf: 2964245 bytes, checksum: 202d309cf65f632d47c7811d4958535d (MD5) Previous issue date: 2015 / Resumo: A aplicação integrada de técnicas modernas, como a Geração do Segundo Harmônico (SHG) e os tempos de vida da fluorescência (FLIM), com análise de imagens matemáticas nos permitem visualizar detalhes não vistos por microscopia de luz convencional. O objetivo deste estudo foi investigar se isto também pode ser aplicado para a investigação de tecido cicatricial. Foram estudados 28 casos de preparações histológicas de rotina, de quelóides, cicatrizes hipertróficas e normais. A Fluorescência de dois fótons e SHG foram obtidas por um microscópio multifóton (LSM 780 NLO-Zeiss), em objetiva de 40X e excitados por um laser Mai Tai de Ti: Safira (comprimento de onda de 940 nm). Foram adquiridas imagens em 3D e foram criadas imagens justapostas a fim de comparar diferentes cicatrizes ou várias regiões no interior da mesma cicatriz com análise de imagens informatizadas. Variáveis de Textura derivadas a partir da matriz de coocorrência das imagens de fluorescência mostraram diferenças significativas entre as cicatrizes normais, cicatrizes hipertróficas e quelóides. Para a análise do FLIM, foi utilizado um sistema composto por um microscópio confocal (LSM780-NLO- Zeiss), com objetiva de 40x e um sistema FLIM acoplado. As amostras foram excitadas por um laser de diodo a 405nm. Estudamos secções não coradas de 32 casos processados rotineiramente de tecido cicatricial incluídos em parafina. As áreas das regiões centrais e periféricas foram selecionadas aleatoriamente e comparadas. Os tempos de vida de fluorescência das hemácias serviram como padrão interno. Os tempos de vida do colágeno em áreas centrais em todos os tipos de cicatrizes foram significativamente mais longo do que em áreas periféricas. Houve correlação positiva entre os tempos de vida de fluorescência das hemácias e as fibras de colágeno entre os casos. Em resumo, o SHG e a técnica Flim revelam em cicatrizes rotineiramente processadas, características morfológicas dos tecidos, que não podem ser detectadas por microscopia de luz convencional / Abstract: The integrated application of modern techniques such as Second Harmonic Generation (SHG) and fluorescence lifetime imaging (FLIM) with mathematical image analysis enable us to visualize details not seen by conventional light microscopy. The aim of this study was to investigate whether this could also be true for the investigation of scar tissue. 28 routine histological preparations of keloids, hypertrophic and normal scars were studied. Two-photon fluorescence and SHG was obtained by a multiphoton microscope (LSM 780 NLO-Zeiss (at 40X objective magnification) and a Mai Tai Ti: Sapphire laser with excitation at 940 nm wavelength. 3D reconstructed patchwork images were created in order to compare different scars or various regions inside the same scar with computerized image analysis. Texture variables derived from the co- occurrence matrix of the fluorescence images showed significant differences between normal scars, hypertrophic scars and keloids. For FLIM analysis we used a system composed of a confocal microscope Zeiss LSM780 Upright-NLO with the 40x objective and a FLIM detection system. The samples were excited by a laser diode at 405nm. We studied unstained sections of 32 routinely processed and paraffin-embedded cases of scar tissue. Randomly selected areas of the central and peripheral regions were compared. The fluorescence lifetimes of red blood cells served as internal standard. Lifetimes of collagen in central areas of all scar types were significantly longer than in the periphery. There was a significant positive correlation between the fluorescence lifetimes of red blood cells and collagen fibers among the cases. In summary, SHG and FLIM techniques reveal in routinely processed scar tissue morphological characteristics, which cannot be detected by conventional light microscopy / Doutorado / Biologia Estrutural, Celular, Molecular e do Desenvolvimento / Doutora em Fisiopatologia Médica

Orientador: Marco Antonio Rodrigues Fernandes / Resumo: Um queloide é uma cicatriz elevada, de contornos irregulares, que se estende além das bordas de uma excisão cirúrgica ou trauma de pele por uma formação excessiva de colágeno na derme durante o processo de reparação do tecido conjuntivo. A formação de queloides pode surgir através de falhas nas sequencias regulatórias, nos fatores de crescimento e nas interações queratinócito-fibroblastos, evoluindo com retardo na senescência e apoptose. Terapias adjuvantes à cirurgia de queloides são necessárias em função do alto índice de recidiva. A radioterapia percutânea pós operatória evidencia bons resultados já que os queloides recentes são ricos em fibroblastos, altamente sensíveis à radiação. Neste trabalho foi realizada uma meta-análise, baseada em estudos publicados em artigos científicos, visando verificar os resultados da realização de radioterapia em pacientes portadores de queloides, que foram submetidos à cirurgia para retirada da lesão com subsequente irradiação do leito cicatricial. Os artigos científicos analisados apontaram 1310 pacientes submetidos à radioterapia em cicatrizes queloidianas, em regiões anatômicas diversas, dos quais, o índice de recidiva médio foi de 16,73%. Os estudos concluem que a aplicação da radioterapia após cirurgia de queloide contribui para minimizar os índices de recorrência da lesão, quando comparada com apenas a cirurgia isolada. / Abstract: A keloid is a high scar, irregularly shaped that extends beyond the borders of a surgical excision or skin trauma by excessive formation of collagen in the dermis during the repair process of connective tissue. Keloid formation may arise through regulatory sequence failures, growth factors, and keratinocyte-fibroblast interactions, evolving with delayed senescence and apoptosis. Adjuvant therapies for keloid surgery are necessary because of the high relapse rate. Postoperative percutaneous radiotherapy shows good results since recent keloids are rich in fibroblasts, highly sensitive to radiation. In this work, a meta-analysis was performed, based on studies published in scientific articles, aiming to verify the results of radiotherapy in patients with keloids who submitted surgery to remove the lesion with subsequent cicatricial bed irradiation. The scientific articles analyzed showed 1310 patients submitted to radiotherapy in keloid scars, in different anatomical regions, of which, the average recurrence rate was 16.73%. The studies conclude that the application of radiotherapy after keloid surgery contributes to minimize lesion recurrence rates, when compared with only isolated surgery. / Mestre

O quelóide é um tumor fibroso benigno que ocorre durante a cicatrização da pele em indivíduos geneticamente predispostos. A cicatrização é um processo biológico complexo e depende da interação de diferentes estruturas teciduais e de um grande número de tipos celulares residentes e infiltrativos, que produzem citocinas. A interleucina 8 (IL-8), citocina pró-inflamatória, é super-expressa pelos fibroblastos durante o desenvolvimento do tecido de granulação, acelerando o processo de cicatrização. Como o quelóide resulta de uma reparação tecidual anormal após lesão da pele, o presente estudo teve por objetivo determinar a expressão dos receptores da IL-8, CXCR1 e CXCR2, e a capacidade proliferativa, pelo ciclo celular, dos fibroblastos queloideanos cultivados e extraídos ex vivo, por citometria de fluxo. Fibroblastos de cicatriz queloideana e de pele normal foram obtidos de 21 pacientes da raça negra, com idade variando entre 10 e 40 anos, de lesões com até 2 anos de evolução. Em nosso estudo constatamos expressão reduzida dos receptores para a IL-8, CXCR1(35,7%±11,2) e CXCR2 (27,8%±11,3), em fibroblastos de cicatriz queloideana cultivados, comparando com a pele normal (44,1±16,2 e 46,3±27,1 respectivamente). Entretanto, essa diferença só foi significante para o receptor CXCR2. A baixa expressão desses receptores poderia ser decorrente da atividade de metaloproteinases, que regulam a expressão de proteínas da superfície celular, através de clivagem enzimática, ou a capacidade reduzida de internalização e a reciclagem de receptores, mantida por filamentos de actina do citoesqueleto, que nos fibroblastos do quelóide estão diminuídos. Em relação ao ciclo celular de fibroblastos cultivados do quelóide e da pele normal, verificamos diferenças não significantes da capacidade de replicação (fase S do ciclo celular) e de apoptose. No quelóide observamos significante aumento de células na fase G2/M, indicando aumento da velocidade de divisão celular. Para confirmar esses achados estudamos o ciclo celular de fibroblastos extraídos ex vivo, da porção periférica e central do quelóide e da pele normal. Os fibroblastos da porção periférica apresentaram porcentagem significantemente maior de células com capacidade replicativa, fase S do ciclo (22,9% ± 11,6), em relação à porção central (4,7% ± 2,9) e à pele normal (6,8% ± 4,9), e maior velocidade de divisão celular, fase G2/M (18,6 ± 12,0), em relação à porção central (35,6 ± 7,0) e pele normal (32,3 ± 6,9). Verificamos que a porção central apresentou maior porcentagem de células em apoptose (7,0% ± 2,1), comparado à porção periférica (4,9% ± 1,9) e pele normal (2,0% ± 0,86). Esses dados indicam que as células da porção periférica do quelóide parecem ser responsáveis pela elevada taxa de proliferação, justificando o crescimento expansivo a partir das margens da cicatriz queloideana, com desenvolvimento de lesão semelhante a tumor, bem como a porção central ser responsável pela fibrose, contendo células quiescentes e apoptóticas. Esses resultados sugerem modulação diferencial das reações celulares através das vias de sinalização para proliferação ou morte celular programada. Neste sentido, a baixa expressão dos receptores da IL-8, CXCR1 e principalmente de CXCR2, nos fibroblastos do quelóide sugere capacidade reduzida da IL-8 em promover cicatrização acelerada. A baixa atividade da IL-8 sobre os fibroblastos queloideanos estaria promovendo desregulação da resposta inflamatória e com isso atraindo novas células inflamatórias para o local e produzindo sinais alterados, como grande produção da citocina TGFβ. Essa desregulação do processo de cicatrização, com alteração de citocinas e da matriz extracelular, poderia ser responsável pelas duas populações de fibroblastos, uma proliferativa na periferia e outra quiescente e apoptótica na porção central. Finalizando, podemos concluir que nossos resultados correspondem às alterações histológicas e clínicas do quelóide que se expande nos limites da lesão. / A keloid is a benign fibrous tumor that occurs during wound healing in genetically predisposed individuals. Healing is a complex biological process and depends on the interaction of different tissue structures and a great number of resident and infiltrative cell types. The interleukin-8 (IL-8), a proinflammatory chemokine, showed higher expression in fibroblasts during the development of the granulation tissue, promoting more rapid tissue maturation. Since keloids result from abnormal wound healing, the objective of the present study was to determine the expression of CXCR1 and CXCR2, IL-8 receptors, and the proliferation capacity, throughout the cell cycle, of the keloid fibroblasts extracted ex vivo and those submitted to in vitro cultivation. Normal skin and keloid scar fibroblasts were obtained from 21 African-Brazilian patients, aged from 10 to 40 years, whose lesions had evolved for no longer than 2 years. Expression of receptors and the cell cycle was assessed by flow cytometry. We showed lower expression of the CXCR1 (35,7% ± 11,2) and CXCR2 (27,8%±11,3) in keloid fibroblasts, when compared with normal skin (44,1 ± 16,2 e 46,3 ± 27,1 respectively), but the difference was not significant for the CXCR1 receptor. This lower expression of IL-8 receptors in keloid fibroblasts could be due to the action of metalloproteinases, which regulate the surface protein enzymatically, or fibroblastic cytoskeleton conditions, which influence receptor internalization and recycling. The distribution assessment of cell cycle phases of fibroblasts cultivated from keloid scars and normal skin did not show significant difference in replication capacity and apoptosis. The keloid fibroblasts presented a significantly higher proportion of cells in the G2/M phase, suggesting higher rate of cell division. To confirm these results we studied the cell cycle of fibroblasts extracted ex vivo, now separated by central and peripheral portions of keloid and normal skin. The peripheral fibroblasts showed significant high cell proportions in phase S (22,9% ± 11,6), compared with the central portion (4,7% ± 2,9) and normal skin (6,8% ± 4,9), and higher cells in division phase G2/M (18,6% ± 12,0), compared with the central portion (35,6% ± 7,0) and normal skin (32,3% ± 6,9). The central portion showed higher proportion of apoptosis (7,0% ± 2,1), compared with the peripheral portion (4,9% ± 1,9) and normal skin (2,0% ± 0,86). These results suggest that the keloid peripheral cells could be responsible for the proliferation rate, justifying the expansive keloid growth at the borders of the keloid scar, in a similar fashion to tumor development and the central portion being responsible for fibrosis, with quiescent and apoptotic cells. These results suggest a differentiated modulation of cell reactions by signal pathways for programmed cellular proliferation or death. In this sense, the low expression of the IL-8 receptors CXCR1 and CXCR2 in keloid fibroblasts suggests a diminished capacity of IL-8 to promote accelerated healing. This low expression of IL-8 receptors in keloid fibroblasts could promote the dysregulation of the inflammatory response and thus attract more inflammatory cells to the site, producing different signals, such as a high production of the TGFβ cytokine. This dysregulation of the healing process, with changed cytokine and extracellular matrix expression, could be responsible for two different cell populations of fibroblasts, one proliferation at the periphery and the other fibrotic at the center of the lesion, with apoptotic and quiescent cells. Finally, we conclude that our results correspond to the histological and clinical changes of keloids that grow beyond the wound boundaries.