Keloids result from an exaggerated response to wound healing of the skin. They grow beyond the original boundaries of the injury to the skin, causing cosmetic deformities, and there is no known treatment that consistently prevents their occurrence or recurrence. The existence of families in which multiple members are affected with keloids over several generations and that certain ethnic groups are more likely to develop keloids than others imply that certain genes may predispose people to keloid formation. Surprisingly, little is known about the genetic factors contributing to keloids in individuals of African or Hispanic ancestry, which are the two ethnic groups most likely to develop keloids. There is also little known about the differences between the normal skin of those who keloid and the normal skin of those that do not.
The research aims of this application will test the hypothesis that specific genetic variations confer susceptibility to keloid formation in those individuals at greatest risk: subjects of African and Hispanic ancestry. They will also test the hypothesis that there exist uncharacterized genes and gene isoforms, in keloids as well as in the normal skin of individuals that keloid that are critical to keloid pathogenesis. A keloid registry has been established to better characterize subjects and families of African and Hispanic descent with keloids. The registry has 117 families and 136 unrelated individuals with sporadic keloids to date and enrollment is ongoing. As part of enrollment a medical history, dermatologic evaluation and venipuncture are performed. Plasma and serum are aliquoted and genomic DNA is extracted and stored. In participants with a family history of keloids, the other family members (both affected and unaffected individuals) are invited to participate.
Specific Aim 1 is to Identify Susceptibility Loci in Families with Keloids. Linkage analysis will be performed on all of the members of a family with familial keloids. The location of disease-causing loci within each family will be found by identifying the genetic markers that are co-inherited with the keloid phenotype. A logarithm of the odds (LOD) score will be calculated based upon the genetic markers co-segregating with the keloid phenotype within the family. A LOD score of three or more will be used to determine if a region is linked with the keloid phenotype. Candidate genes within these identified loci will be examined to identify variants that co-segregate with keloid formation.
Specific Aim 2 is to Identify Genetic Variations Associated with Keloids. All exons in the genome (i.e. the exome) will be sequenced using high-throughput sequencing in selected members of families with keloids. Rare sequence variations identified in the affected family members will be further examined to identify variants that co-segregate with keloid formation. These candidate genes will be sequenced in other families that have a history of keloid formation as well as in unrelated individuals with sporadic keloids.
Specific Aim 3 is t determine the differences in gene expression between keloid skin and normal skin.
This aim i s two-fold in nature. Sub-Aim 3.1 is to determine the differences in gene expression between keloidal fibroblasts and normal fibroblasts, while Sub-Aim 3.2 is to determine the differences in gene expression between normal fibroblasts from keloid-prone individuals and normal fibroblasts from those that do not keloid. Primary fibroblasts will be isolated from keloid tissue obtained from surgical treatments. Primary fibroblasts from perilesional normal tissue from the same individual will also be obtained. Control primary fibroblasts will be obtained from age, sex and race-matched control individuals with no personal or family history of keloids. In both sub-aims, whole transcriptome sequencing will be performed on RNA from the primary fibroblasts and differences in gene expression between the different cells will be assessed. Findings will be confirmed with Northern blot analysis and/or real-time PCR.
These research aims will serve as the platform for my career development plan and will be coupled with training aims which include: 1) biostatistical analysis and methodology; 2) the analysis of high content/high complexity data sets; and 3) research management and manuscript/grant writing skills. These training aims will be achieved via didactic courses, experiential learning, and mentored studies. Together, the research and training aims of the K23 proposal will provide the training, experience, and preliminary data for future R01 grant applications. This career development plan will prepare me to become a successful independent investigator and attain my long-term career goal of becoming a national leader in keloids and genetics.
To gain insight into why keloids form in some individuals but not in others, a registry of patients and families with keloids has been established. Studies using families and tissue samples will be performed to find genes and genetic variations that contribute to keloid formation. The proposed studies hold the promise of finding new targets for the prevention and treatment of keloids.
|Stewart, Jacob; Glass 2nd, Donald A (2018) Plasma Angiotensin-converting Enzyme Levels in Patients With Keloids and/or Hypertension. Wounds 30:E71-E72|
|Rutherford, Audrey; Glass 2nd, Donald A (2017) A case-control study analyzing the association of keloids with hypertension and obesity. Int J Dermatol 56:e187-e189|
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