Bio

Professional Education


  • Doctor, University College Dublin (2009)

Stanford Advisors


Publications

Journal Articles


  • Scarless wound healing: chasing the holy grail. Plastic and reconstructive surgery Walmsley, G. G., Maan, Z. N., Wong, V. W., Duscher, D., Hu, M. S., Zielins, E. R., Wearda, T., Muhonen, E., McArdle, A., Tevlin, R., Atashroo, D. A., Senarath-Yapa, K., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2015; 135 (3): 907-917

    Abstract

    Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

    View details for DOI 10.1097/PRS.0000000000000972

    View details for PubMedID 25719706

  • The role and regulation of osteoclasts in normal bone homeostasis and in response to injury. Plastic and reconstructive surgery McArdle, A., Marecic, O., Tevlin, R., Walmsley, G. G., Chan, C. K., Longaker, M. T., Wan, D. C. 2015; 135 (3): 808-816

    Abstract

    Bone is a dynamic tissue, with a range of diverse functions, including locomotion, protection of internal organs, and hematopoiesis. Optimum treatment of fractures and/or bone defects requires knowledge of the complex cellular interactions involved with bone healing and remodeling. Emerging data have underscored the importance of osteoclasts in this process, playing a key role both in normal bone turnover and in facilitating bone regeneration. In this review, the authors discuss the basic principles of osteoclast biology, including its cellular origins, its function, and key regulatory mechanisms, in addition to conditions that arise when osteoclast function is altered.

    View details for DOI 10.1097/PRS.0000000000000963

    View details for PubMedID 25719699

  • Identification and specification of the mouse skeletal stem cell. Cell Chan, C. K., Seo, E. Y., Chen, J. Y., Lo, D., McArdle, A., Sinha, R., Tevlin, R., Seita, J., Vincent-Tompkins, J., Wearda, T., Lu, W., Senarath-Yapa, K., Chung, M. T., Marecic, O., Tran, M., Yan, K. S., Upton, R., Walmsley, G. G., Lee, A. S., Sahoo, D., Kuo, C. J., Weissman, I. L., Longaker, M. T. 2015; 160 (1-2): 285-298

    Abstract

    How are skeletal tissues derived from skeletal stem cells? Here, we map bone, cartilage, and stromal development from a population of highly pure, postnatal skeletal stem cells (mouse skeletal stem cells, mSSCs) to their downstream progenitors of bone, cartilage, and stromal tissue. We then investigated the transcriptome of the stem/progenitor cells for unique gene-expression patterns that would indicate potential regulators of mSSC lineage commitment. We demonstrate that mSSC niche factors can be potent inducers of osteogenesis, and several specific combinations of recombinant mSSC niche factors can activate mSSC genetic programs in situ, even in nonskeletal tissues, resulting in de novo formation of cartilage or bone and bone marrow stroma. Inducing mSSC formation with soluble factors and subsequently regulating the mSSC niche to specify its differentiation toward bone, cartilage, or stromal cells could represent a paradigm shift in the therapeutic regeneration of skeletal tissues.

    View details for DOI 10.1016/j.cell.2014.12.002

    View details for PubMedID 25594184

  • Impact of surgical innovation on tissue repair in the surgical patient. British journal of surgery Tevlin, R., Atashroo, D., Duscher, D., Mc Ardle, A., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2015; 102 (2): e41-55

    Abstract

    Throughout history, surgeons have been prolific innovators, which is hardly surprising as most surgeons innovate daily, tailoring their intervention to the intrinsic uniqueness of each operation, each patient and each disease. Innovation can be defined as the application of better solutions that meet new requirements, unarticulated needs or existing market needs. In the past two decades, surgical innovation has significantly improved patient outcomes, complication rates and length of hospital stay. There is one key area that has great potential to change the face of surgical practice and which is still in its infancy: the realm of regenerative medicine and tissue engineering.A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key surgical innovations influencing regenerative medicine, with a focus on osseous, cutaneous and soft tissue reconstruction.This review describes recent advances in regenerative medicine, documenting key innovations in osseous, cutaneous and soft tissue regeneration that have brought regenerative medicine to the forefront of the surgical imagination.Surgical innovation in the emerging field of regenerative medicine has the ability to make a major impact on surgery on a daily basis.

    View details for DOI 10.1002/bjs.9672

    View details for PubMedID 25627135

  • Isolation and Enrichment of Human Adipose-derived Stromal Cells for Enhanced Osteogenesis. Journal of visualized experiments : JoVE Zielins, E. R., Tevlin, R., Hu, M. S., Chung, M. T., McArdle, A., Paik, K. J., Atashroo, D., Duldulao, C. R., Luan, A., Senarath-Yapa, K., Walmsley, G. G., Wearda, T., Longaker, M. T., Wan, D. C. 2015

    Abstract

    Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are considered the gold standard for stem cell-based tissue engineering applications. However, the process by which they must be harvested can be associated with significant donor site morbidity. In contrast, adipose-derived stromal cells (ASCs) are more readily abundant and more easily harvested, making them an appealing alternative to BM-MSCs. Like BM-MSCs, ASCs can differentiate into osteogenic lineage cells and can be used in tissue engineering applications, such as seeding onto scaffolds for use in craniofacial skeletal defects. ASCs are obtained from the stromal vascular fraction (SVF) of digested adipose tissue, which is a heterogeneous mixture of ASCs, vascular endothelial and mural cells, smooth muscle cells, pericytes, fibroblasts, and circulating cells. Flow cytometric analysis has shown that the surface marker profile for ASCs is similar to that for BM-MSCs. Despite several published reports establishing markers for the ASC phenotype, there is still a lack of consensus over profiles identifying osteoprogenitor cells in this heterogeneous population. This protocol describes how to isolate and use a subpopulation of ASCs with enhanced osteogenic capacity to repair critical-sized calvarial defects.

    View details for DOI 10.3791/52181

    View details for PubMedID 25650785

  • Assessment of viability of human fat injection into nude mice with micro-computed tomography. Journal of visualized experiments : JoVE Atashroo, D. A., Paik, K. J., Chung, M. T., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C. R., Walmsley, G. G., Wearda, T., Marecic, O., Longaker, M. T., Wan, D. C. 2015

    Abstract

    Lipotransfer is a vital tool in the surgeon's armamentarium for the treatment of soft tissue deficits of throughout the body. Fat is the ideal soft tissue filler as it is readily available, easily obtained, inexpensive, and inherently biocompatible.(1) However, despite its burgeoning popularity, fat grafting is hampered by unpredictable results and variable graft survival, with published retention rates ranging anywhere from 10-80%. (1-3) To facilitate investigations on fat grafting, we have therefore developed an animal model that allows for real-time analysis of injected fat volume retention. Briefly, a small cut is made in the scalp of a CD-1 nude mouse and 200-400 µl of processed lipoaspirate is placed over the skull. The scalp is chosen as the recipient site because of its absence of native subcutaneous fat, and because of the excellent background contrast provided by the calvarium, which aids in the analysis process. Micro-computed tomography (micro-CT) is used to scan the graft at baseline and every two weeks thereafter. The CT images are reconstructed, and an imaging software is used to quantify graft volumes. Traditionally, techniques to assess fat graft volume have necessitated euthanizing the study animal to provide just a single assessment of graft weight and volume by physical measurement ex vivo. Biochemical and histological comparisons have likewise required the study animal to be euthanized. This described imaging technique offers the advantage of visualizing and objectively quantifying volume at multiple time points after initial grafting without having to sacrifice the study animal. The technique is limited by the size of the graft able to be injected as larger grafts risk skin and fat necrosis. This method has utility for all studies evaluating fat graft viability and volume retention. It is particularly well-suited to providing a visual representation of fat grafts and following changes in volume over time.

    View details for DOI 10.3791/52217

    View details for PubMedID 25590561

  • Biomaterials for Craniofacial Bone Engineering JOURNAL OF DENTAL RESEARCH Tevlin, R., Mcardle, A., Atashroo, D., Walmsley, G. G., Senarath-Yapa, K., Zielins, E. R., Paik, K. J., Longaker, M. T., Wan, D. C. 2014; 93 (12): 1187-1195
  • The role of stem cells in aesthetic surgery: fact or fiction? Plastic and reconstructive surgery McArdle, A., Senarath-Yapa, K., Walmsley, G. G., Hu, M., Atashroo, D. A., Tevlin, R., Zielins, E., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (2): 193-200

    Abstract

    Stem cells are attractive candidates for the development of novel therapies, targeting indications that involve functional restoration of defective tissue. Although most stem cell therapies are new and highly experimental, there are clinics around the world that exploit vulnerable patients with the hope of offering supposed stem cell therapies, many of which operate without credible scientific merit, oversight, or other patient protection.We review the potential, as well as drawbacks, for incorporation of stem cells in cosmetic procedures. A review of FDA-approved indications and ongoing clinical trials with adipose stem cells is provided. Furthermore, a "snapshot" analysis of websites using the search terms "stem cell therapy" or "stem cell treatment" or "stem cell facelift" was performed.Despite the protective net cast by regulatory agencies such as the FDA and professional societies such as the American Society of Plastic Surgeons, we are witnessing worrying advertisements for procedures such as stem cell facelifts, stem cell breast augmentations, and even stem cell vaginal rejuvenation. The marketing and promotion of stem cell procedures in aesthetic surgery is not adequately supported by clinical evidence in the majority of cases.Stem cells offer tremendous potential, but the marketplace is saturated with unsubstantiated and sometimes fraudulent claims that may place patients at risk. With plastic surgeons at the forefront of stem cell-based regenerative medicine, it is critically important that we provide an example of a rigorous approach to research, data collection, and advertising of stem cell therapies.

    View details for DOI 10.1097/PRS.0000000000000404

    View details for PubMedID 24732654

  • Studies in fat grafting: part I. Effects of injection technique on in vitro fat viability and in vivo volume retention. Plastic and reconstructive surgery Chung, M. T., Paik, K. J., Atashroo, D. A., Hyun, J. S., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Hu, M. S., Walmsley, G. G., Parisi-Amon, A., Momeni, A., Rimsa, J. R., Commons, G. W., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (1): 29-38

    Abstract

    Fat grafting has become increasingly popular for the correction of soft tissue deficits at many sites throughout the body. Long-term outcomes, however, depend on delivery of fat in the least traumatic fashion to optimize viability of the transplanted tissue. In this study, we compare the biologic properties of fat following injection using two methods.Lipoaspiration samples were obtained from five female donors and cellular viability, proliferation, and lipolysis were evaluated following injection using either a modified Coleman technique or an automated, low shear device. Comparisons were made to minimally processed, uninjected fat. Volume retention was also measured over twelve weeks following injection of fat under the scalp of immunodeficient mice using either the modified Coleman technique or the Adipose Tissue Injector. Finally, fat grafts were analyzed histologically.Fat viability and cellular proliferation were both significantly greater with the Adipose Tissue Injector relative to injection with the modified Coleman technique. In contrast, significantly less lipolysis was noted using the automated device. In vivo fat volume retention was significantly greater than with the modified Coleman technique at 4, 6, 8, and 12 week time points. This corresponded with significantly greater histological scores for healthy fat and lower scores for injury following injection with the device.Biological properties of injected tissues reflect how disruptive and harmful techniques for placement of fat may be, and our in vitro and in vivo data both support the use of the automated, low shear devices compared to the modified Coleman technique.

    View details for DOI 10.1097/PRS.0000000000000290

    View details for PubMedID 24622574

  • Studies in Fat Grafting: Part II. Effects of Injection Mechanics on Material Properties of Fat PLASTIC AND RECONSTRUCTIVE SURGERY Atashroo, D., Raphel, J., Chung, M. T., Paik, K. J., Parisi-Amon, A., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Walmsley, G. G., Hu, M. S., Momeni, A., Domecus, B., Rimsa, J. R., Greenberg, L., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 134 (1): 39-46
  • Studies in Fat Grafting: Part II. Effects of Injection Mechanics on Material Properties of Fat. Plastic and reconstructive surgery Atashroo, D., Raphel, J., Chung, M. T., Paik, K. J., Parisi-Amon, A., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Walmsley, G. G., Hu, M. S., Momeni, A., Domecus, B., Rimsa, J. R., Greenberg, L., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 134 (1): 39-46

    Abstract

    Although fat grafting can address many soft-tissue deficits, results remain inconsistent. In this study, the authors compared physical properties of fat following injection using an automated, low-shear device or the modified Coleman technique.Lipoaspirate was obtained from nine patients and processed for injection using either a modified Coleman technique or an automated, low-shear device. Fat was passed through a 2-mm cannula and compared with minimally processed fat. A rheometer was used to measure the storage modulus and shear rate at which tissues began to lose their solid-like properties. Viscosity was also measured, and gross properties of treatment groups were evaluated qualitatively with a glass slide test.Fat injected through an automated, low-shear device closely matched physical properties of minimally processed fat. The storage modulus (G') of fat for the device group was greater than for the modified Coleman group, and the onset of breakdown was delayed. Similarly, viscosity measurement of fat from the automated device closely matched minimally processed fat and was greater than that of othe modified Coleman group.The physical properties of lipoaspirate processed using an automated, low-shear device with a 2-mm cannula preserved the intactness of fat more than the modified Coleman technique. The authors' rheologic data demonstrate less damage using an automated device compared with the modified Coleman technique and potentially support its use for improved fat graft integrity.

    View details for DOI 10.1097/PRS.0000000000000289

    View details for PubMedID 25028817

  • Studies in Fat Grafting: Part I. Effects of Injection Technique on In Vitro Fat Viability and In Vivo Volume Retention PLASTIC AND RECONSTRUCTIVE SURGERY Chung, M. T., Paik, K. J., Atashroo, D. A., Hyun, J. S., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Hu, M. S., Walmsley, G. G., Parisi-Amon, A., Momeni, A., Rimsa, J. R., Commons, G. W., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (1): 29-38
  • Wound healing: an update REGENERATIVE MEDICINE Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Walmsley, G. G., Marecic, O., Hu, M., Senarath-Yapa, K., McArdle, A., Tevlin, R., Wearda, T., Paik, K. J., Duldulao, C., Hong, W. X., Gurtner, G. C., Longaker, M. T. 2014; 9 (6): 817-830

    View details for DOI 10.2217/RME.14.54

    View details for Web of Science ID 000345620600012

  • Osteoclast derivation from mouse bone marrow. Journal of visualized experiments : JoVE Tevlin, R., McArdle, A., Chan, C. K., Pluvinage, J., Walmsley, G. G., Wearda, T., Marecic, O., Hu, M. S., Paik, K. J., Senarath-Yapa, K., Atashroo, D. A., Zielins, E. R., Wan, D. C., Weissman, I. L., Longaker, M. T. 2014

    Abstract

    Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease. As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation. An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

    View details for DOI 10.3791/52056

    View details for PubMedID 25407120

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