Hakan Orbay

University of California, Davis, Davis, California, United States

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Publications (79)188.1 Total impact

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    ABSTRACT: Deep inferior epigastric artery perforator (DIEP) flap breast reconstruction requires complex microsurgical skills. Herein, we examine whether DIEP flap breast reconstruction can be performed safely without microsurgical fellowship training. A total of 28 patients and 34 DIEP flaps were included in the study. We reviewed the medical records of patients for donor site and flap-related complications and analyzed the correlation between the complications and preoperative risk factors. We also performed a literature review to compare complication rates in our series with the literature. We observed total flap necrosis in 1 patient (2.9%), partial flap necrosis in 5 patients (14.7%), infection in 1 patient (2.9%), hematoma/seroma in 3 patients (8.8%), donor site complications in 5 patients (18.5%), venous occlusion in 4 patients (11.7%), and arterial occlusion in 1 patient (2.9%). We did not observe any correlation between complications and preoperative risk factors. Literature review yielded 18 papers that met our inclusion criteria. Partial flap necrosis rate was significantly higher in our series compared with literature (14.7% vs 1.6%, P = 0.003). Venous complication rate was marginally higher in our series compared with literature (11.7% vs 3.3%, P = 0.057). However, total flap loss rate in our series was comparable with the literature (2.9% vs 2.2%, P = 0.759). With proper training during plastic surgery residency, DIEP flap can be performed with acceptable morbidity.
    07/2015; 3(7):e455. DOI:10.1097/GOX.0000000000000428
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    ABSTRACT: The use of undifferentiated cells for cell-based tissue repair and regeneration strategies represents a promising approach for chronic wound healing. Multipotent adult stem cells isolated from adipose tissue, termed adipose-derived stem cells (ASCs), appear to be an ideal population of stem cells because they are autologous, non-immunogenic, plentiful, and easily obtained. Both preclinical and clinical studies have revealed that ASCs have potential for wound healing due to the mechanisms described below. Areas covered: Both in vitro and in vivo studies demonstrated that ASCs not only differentiate into keratinocytes, fibroblasts, and endothelial cells, as evidenced by their morphology, expression of cell surface markers, and gene expression, but also secrete several soluble factors, which positively contribute to wound healing in a paracrine manner. Clinical trials have been conducted using autologous ASCs with great success. Expert opinion: There remain many concerns regarding the use of ASCs, including how these cells act as precursors of keratinocytes, fibroblasts, and endothelial cells, or as a secretion vehicle of soluble factors. Further studies are necessary to establish the optimal strategy for the treatment of chronic wounds in patients with different disease backgrounds.
    Expert opinion on biological therapy 06/2015; DOI:10.1517/14712598.2015.1053867 · 3.65 Impact Factor
  • Plastic and Reconstructive Surgery 05/2015; 135(5S Suppl):75. DOI:10.1097/01.prs.0000465550.83390.3a · 3.33 Impact Factor
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    ABSTRACT: The critical challenge in abdominal aortic aneurysm (AAA) research is the accurate diagnosis and assessment of AAA progression. Angiogenesis is a pathological hallmark of AAA, and CD105 is highly expressed on newly formed vessels. Our goal was to use (64)Cu-labeled anti-CD105 antibody Fab fragment for noninvasive assessment of angiogenesis in the aortic wall in a murine model of AAA. Fab fragment of TRC105, a mAb that specifically binds to CD105, was generated by enzymatic papain digestion and conjugated to NOTA for (64)Cu-labeling. Binding affinity/specificity of NOTA-TRC105-Fab was evaluated by flow cytometry and various ex vivo studies. BALB/c mice were anesthetized and treated with calcium phosphate to induce AAA, which underwent weekly PET scans using (64)Cu-NOTA-TRC105-Fab. Biodistribution and autoradiography studies were also performed to confirm the accuracy of PET results. NOTA-TRC105-Fab exhibited high purity and specifically bound to CD105 in vitro. Uptake of (64)Cu-NOTA-TRC105-Fab increased from a control level of 3.4 ± 0.1 to 9.5 ± 0.4 %ID/g at 6 h p.i. on Day 5, and decreased to 7.2 ± 1.4 %ID/g on Day 12 which correlated well with biodistribution and autoradiography studies (i.e. much higher tracer uptake in AAA than normal aorta). Of note, enhanced AAA contrast was achieved, due to the minimal background in the abdominal area of mice. Degradation of elastic fibers and highly expressed CD105 were observed in ex vivo studies. (64)Cu-NOTA-TRC105-Fab cleared rapidly through kidneys, which enabled noninvasive PET imaging of the aorta with enhanced contrast and showed increased angiogenesis (CD105 expression) during AAA. (64)Cu-NOTA-TRC105-Fab PET may potentially be used for future diagnosis and prognosis of AAA. Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
    Journal of Nuclear Medicine 04/2015; 56(6). DOI:10.2967/jnumed.114.153098 · 5.56 Impact Factor
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    ABSTRACT: Actively targeted theranostic nanomedicine may be the key for future personalized cancer management. Although numerous types of theranostic nanoparticles have been developed in the last decade for cancer treatment, challenges still exist in the engineering of biocompatible theranostic nanoparticles with highly specific in vivo tumor targeting capabilities. Here, we report the design, synthesis, surface engineering, and in vivo active vasculature targeting of a new category of theranostic nanoparticle for future cancer management. Water-soluble photothermally sensitive copper sulfide nanoparticles were encapsulated in biocompatible mesoporous silica shells, followed by multi-step surface engineering to form the final theranostic nanoparticle. Systematic in vitro targeting, an in vivo long-term toxicity study, photothermal ablation evaluation, in vivo vasculature targeted imaging, and biodistribution and histology studies were performed to fully explore the potential of these as-developed new theranostic nanoparticles.
    ACS Nano 04/2015; 9(4). DOI:10.1021/nn507241v · 12.88 Impact Factor
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    ABSTRACT: To date, there is no effective therapy for triple-negative breast cancer (TNBC), which has a dismal clinical outcome. Upregulation of tissue factor (TF) expression leads to increased patient morbidity and mortality in many solid tumor types, including TNBC. Our goal was to employ the Fab fragment of ALT-836, a chimeric anti-human TF mAb, for PET imaging of TNBC, which can be used to guide future TNBC therapy. ALT-836-Fab was generated by enzymatic papain digestion. SDS-PAGE and FACS studies were performed to evaluate the integrity and TF binding affinity of ALT-836-Fab before NOTA conjugation and (64)Cu-labeling. Serial PET imaging and biodistribution studies were carried out to evaluate the tumor targeting efficacy and pharmacokinetics in the MDA-MB-231 TNBC model, which expresses high levels of TF on the tumor cells. Blocking studies, histological assessment, as well as RT-PCR were performed to confirm TF specificity of (64)Cu-NOTA-ALT-836-Fab. ALT-836-Fab was produced with high purity, which exhibited superb TF binding affinity and specificity. Serial PET imaging revealed rapid and persistent tumor uptake of (64)Cu-NOTA-ALT-836-Fab (5.1 ± 0.5 %ID/g at 24 h post-injection; n = 4) and high tumor/muscle ratio (7.0 ± 1.2 at 24 h post-injection; n = 4), several-fold higher than that of the blocking group and tumor models that do not express significant level of TF, which was confirmed by biodistribution studies. TF specificity of the tracer was also validated by histology and RT-PCR. (64)Cu-NOTA-ALT-836-Fab exhibited prominent tissue factor targeting efficiency in MDA-MB-231 TNBC model. The use of a Fab fragment led to fast tumor uptake and good tissue/muscle ratio, which may be translated into same-day immunoPET imaging in the clinical setting to improve TNBC patient management.
    European Journal of Nuclear Medicine 03/2015; 42(8). DOI:10.1007/s00259-015-3038-1 · 5.38 Impact Factor
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    ABSTRACT: Radical oncologic resection can result in large soft tissue defects with exposure of underlying vessels. Unless immediately covered with viable soft tissue, these vessels are vulnerable to desiccation from air exposure and mechanical trauma. Local radiation treatment also contributes to a decline in vessel wall strength. We present an index case of a patient with prolonged exposure of her femoral bone and superficial femoral artery after an initial failed reconstruction of a soft tissue sarcoma resection defect. We provided coverage using a free latissimus dorsi muscle flap. Two weeks after the initial free flap operation, the patient was readmitted to emergency service with profuse bleeding from beneath the free flap. Intraoperative inspection revealed a 2-cm defect of the irradiated superficial femoral artery. The defect was repaired with cryopreserved human arterial graft, and the flap was reset. This case highlights the importance of immediate coverage of soft tissue defects after oncologic resection. If any vessels are left exposed, they should be closely inspected before a delayed flap coverage to rule out future sources of bleeding that may jeopardize the outcomes of an otherwise successful free flap operation.
    Annals of Plastic Surgery 03/2015; 74. DOI:10.1097/SAP.0000000000000432 · 1.46 Impact Factor
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    ABSTRACT: Schwann cell-like cells differentiated from adipose-derived stem cells may have an important role in peripheral nerve regeneration. Herein, we document the individual effects of growth factors in Schwann cell-like differentiation medium. There were 6 groups in the study. In the control group, we supplemented the rat adipose-derived stem cells with normal cell culture medium. In group 1, we fed the cells with Schwann cell-like differentiation medium (normal cell culture medium supplemented with platelet-derived growth factor, basic fibroblast growth factor, forskolin, and glial growth factor). In the other groups, we removed the components of the medium one at a time from the differentiation medium so that group 2 lacked glial growth factor, group 3 lacked forskolin, group 4 lacked basic fibroblast growth factor, and group 5 lacked platelet-derived growth factor. We examined the expression of the Schwann cell-specific genes with quantitative reverse transcription polymerase chain reaction and immunofluorescence staining in each group. Groups 3 and 4, lacking forskolin and basic fibroblast growth factor, respectively, had the highest expression levels of integrin-β4, and p75. Group 1 showed a 3.2-fold increase in the expression of S100, but the expressions of integrin-β4 and p75 were significantly lower compared to groups 3 and 4. Group 2 [glial growth factor (-)] did not express significant levels of Schwann cell-specific genes. The gene expression profile in group 4 most closely resembled Schwann cells. Immunofluorescence staining results were parallel with the quantitative real-time polymerase chain reaction results. Glial growth factor is a key component of Schwann cell-like differentiation medium.
    Annals of Plastic Surgery 01/2015; 74(5). DOI:10.1097/SAP.0000000000000436 · 1.46 Impact Factor
  • Plastic &amp Reconstructive Surgery 01/2015; 135:134. DOI:10.1097/01.prs.0000465640.94173.80 · 3.33 Impact Factor
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    Brittany Busse · Hakan Orbay · David E Sahar
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    ABSTRACT: Prosthetic implants are frequently used for breast augmentation and breast reconstruction following mastectomy. Unfortunately, long-term aesthetic results of prosthetic breast restoration may be hindered by complications such as rippling, capsular contracture, and implant malposition. The advent of use of acellular dermal matrices has greatly improved the outcomes of prosthetic breast reconstruction. We describe a case of rippling deformity of breast that was treated using an acellular dermal matrix product, AlloMax. The patient presented with visible rippling of bilateral prosthetic breast implants as well as significant asymmetry of the breasts after multiple excisional biopsies for right breast ductal carcinoma in situ. A 6 × 10 cm piece of AlloMax was placed on the medial aspect of each breast between the implant and the skin flap. Follow-up was performed at 1 week, 3 months, and 1 year following the procedure. The patient recovered well from the surgery and there were no complications. At her first postoperative follow-up the patient was extremely satisfied with the result. At her 3-month and 1-year follow-up she had no recurrence of her previous deformity and no new deformity.
    12/2014; 2014:876254. DOI:10.1155/2014/876254
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    ABSTRACT: A key goal for successful bone regeneration is to bridge a bone defect using healing procedures that are stable and durable. Adipose-derived stem cells (ASCs) have the potential to differentiate into bone. Meanwhile, platelet-rich plasma (PRP) is an interesting biological means to repair tissue by inducing chemotactic, proliferative, and anabolic cellular responses. This study evaluated bone regeneration using a combination of ASCs and PRP in a rat calvarial defect model. ASCs were isolated from inguinal fat pads of F344 inbred rats, while PRP was prepared from these rats. ASCs were cultured in control medium supplemented with 10% fetal bovine serum or 5% PRP in vitro. After 1 week, levels of growth factors including insulin-like growth factor-1, transforming growth factor-β1, hepatocyte growth factor, and vascular endothelial growth factor in the culture supernatant were measured by enzyme-linked immunosorbent assays. Moreover, the ASC/PRP admixture was transplanted into the rat calvarial defect. Micro-computed tomography, histological, and immunohistochemical (osteopontin and osteocalcin) analyses were performed at 4 and 8 weeks after transplantation. The in vitro study showed that the levels of growth factors secreted by ASCs were significantly increased by the addition of PRP. Transplantation of the ASC/PRP admixture had dramatic effects on bone regeneration overtime in comparison with rats that received other transplants. Furthermore, some ASCs directly differentiated into osteogenic cells in vivo. These findings suggest that the combination of ASCs and PRP has augmentative effects on bone regeneration. The ASC/PRP admixture may be a promising source for the clinical treatment of cranial defects.
    Tissue Engineering Part A 10/2014; 21(5-6). DOI:10.1089/ten.TEA.2014.0336 · 4.70 Impact Factor
  • Plastic and Reconstructive Surgery 03/2014; 133(3S Suppl):148. DOI:10.1097/01.prs.0000444959.44044.c9 · 3.33 Impact Factor
  • Article: Abstract 92
    Plastic &amp Reconstructive Surgery 03/2014; 133:10-99. DOI:10.1097/01.prs.0000445125.90060.8a · 3.33 Impact Factor
  • Hakan Orbay · Jero Bean · Yin Zhang · Weibo Cai
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    ABSTRACT: Over the last several decades, development of various imaging techniques such as computed tomography, magnetic resonance imaging, and positron emission tomography greatly facilitated the early detection of cancer. Another important aspect that is closely related to the survival of cancer patients is complete tumor removal during surgical resection. The major obstacle in achieving this goal is to distinguish between tumor tissue and normal tissue during surgery. Currently, tumor margins are typically assessed by visual assessment and palpation of the tumor intraoperatively. However, the possibility of microinvasion to the surrounding tissues makes it difficult to determine an adequate tumor-free excision margin, often forcing the surgeons to perform wide excisions including the healthy tissue that may contain vital structures. It would be ideal to remove the tumor completely, with minimal safety margins, if surgeons could see precise tumor margins during the operation. Molecular imaging with optical techniques can visualize the tumors via fluorophore conjugated probes targeting tumor markers such as proteins and enzymes that are upregulated during malignant transformation. Intraoperative use of this technique may facilitate complete excision of the tumor and tumor micromasses located beyond the visual capacity of the naked eye, ultimately improving the clinical outcome and survival rates of cancer patients.
    Current pharmaceutical biotechnology 12/2013; DOI:10.2174/1389201014666131226113300 · 2.51 Impact Factor
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    Hakan Orbay · Hao Hong · Yin Zhang · Weibo Cai
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    ABSTRACT: Atherosclerosis-related cardiovascular events are the leading causes of death in the industrialized world. Atherosclerosis develops insidiously and the initial manifestation is usually sudden cardiac death, stroke, or myocardial infarction. Molecular imaging is a valuable tool to identify the disease at an early stage before fatal manifestations occur. Among the various molecular imaging techniques, this review mainly focuses on positron emission tomography (PET) imaging of atherosclerosis. The targets and pathways that have been investigated to date for PET imaging of atherosclerosis include: glycolysis, cell membrane metabolism (phosphatidylcholine synthesis), integrin αvβ3, low density lipoprotein (LDL) receptors (LDLr), natriuretic peptide clearance receptors (NPCRs), fatty acid synthesis, vascular cell adhesion molecule-1 (VCAM-1), macrophages, platelets, etc. Many PET tracers have been investigated clinically for imaging of atherosclerosis. Early diagnosis of atherosclerotic lesions by PET imaging can help to prevent the premature death caused by atherosclerosis, and smooth translation of promising PET tracers into the clinic is critical to the benefit of patients.
    Theranostics 11/2013; 3(11):894-902. DOI:10.7150/thno.5506 · 7.83 Impact Factor
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    ABSTRACT: In conventional tissue-regeneration technologies, stem cells and/or other cells are injected into or incubated on scaffolds. In general, scaffolds can be classified into synthetic and natural polymers and natural matrices. Polymers are generally less suitable than natural matrices in terms of biocompatibility and biodegradability. A highly promising alternative may be the acellular adipose matrix (AAM), which is a natural scaffold that could mediate tissue regeneration without any artefacts. The optimal method for adipose-tissue decellularisation is described in this article. Discarded human adipose tissues harvested from routine operations were used. In experiment 1, four different adipose-tissue-decellularisation methods were compared and modified. In experiment 2, the most effective method was tested by using adipose-tissue blocks from various donor sites (the abdomen, chest and forearm) and of different weights (0.8, 25 and 80 g). Haematoxylin and eosin (H &E) staining, immunohistochemistry (IHC) and scanning electron microscopy were used to determine the efficacy of decellularisation. In experiment 1, a method using an enzymatic digestion solution yielded complete decellularisation after some modifications. In experiment 2, the 0.8-g specimens were completely decellularised by the modified method. However, cell components remained in the 25- and 80-g specimens. The donor site had no effect on the degree of decellularisation. An optimal method for adipose-tissue decellularisation is reported. Because AAM is a natural collagen scaffold that is of human origin, this report describes an important first step in a tissue-engineering innovation that may be suitable for the regeneration of various tissues.
    Journal of Plastic Reconstructive & Aesthetic Surgery 09/2013; 67(1). DOI:10.1016/j.bjps.2013.08.006 · 1.47 Impact Factor
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    ABSTRACT: The goal of this study was to assess ischemia-induced angiogenesis with 64Cu-NOTA-TRC105 positron emission tomography (PET) in a murine hindlimb ischemia model of peripheral artery disease (PAD). CD105 binding affinity/specificity of NOTA-conjugated TRC105 (an anti-CD105 antibody) was evaluated by flow cytometry, which exhibited no difference from unconjugated TRC105. BALB/c mice were anesthetized and the right femoral artery was ligated to induce hindlimb ischemia, with the left hindlimb serving as an internal control. Laser Doppler imaging showed that perfusion in the ischemic hindlimb plummeted to ~20% of the normal level after surgery, and gradually recovered to near normal level on day 24. Ischemia-induced angiogenesis was non-invasively monitored and quantified with 64Cu-NOTA-TRC105 PET on postoperative days 1, 3, 10, 17, & 24. 64Cu-NOTA-TRC105 uptake in the ischemic hindlimb increased significantly from the control level of 1.6±0.2 %ID/g to 14.1±1.9 %ID/g at day 3 (n=3), and gradually decreased with time (3.4±1.9 %ID/g at day 24), which correlated well with biodistribution studies performed on days 3 & 24. Blocking studies confirmed the CD105 specificity of tracer uptake in the ischemic hindlimb. Increased CD105 expression on days 3 and 10 following ischemia was confirmed by histology and RT-PCR. This is the first report of PET imaging of CD105 expression during ischemia-induced angiogenesis. 64Cu-NOTA-TRC105 PET may play multiple roles in future PAD-related research and improve PAD patient management by identifying the optimal timing of treatment and monitoring the efficacy of therapy.
    Molecular Pharmaceutics 06/2013; 10(7). DOI:10.1021/mp400191w · 4.79 Impact Factor
  • Reinier Hernandez · Hakan Orbay · Weibo Cai
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    ABSTRACT: MicroRNAs (miRNAs) are single-stranded non-coding RNAs of ~22 nucleotides, which can negatively regulate gene expression through induction of mRNA degradation and/or post-transcriptional gene silencing. MiRNAs are key factors in the regulation of many biological processes such as cell proliferation, differentiation, and death. Since miRNAs are known to be in close association with cancer development, non-invasive imaging of miRNA expression and/or activity is of critical importance, for which conventional molecular biology techniques are not suitable or applicable. Over the last several years, various molecular imaging techniques have been investigated for imaging of miRNAs. In this review article, we summarize the current state-of-the-art imaging of miRNAs, which are typically based on fluorescent proteins, bioluminescent enzymes, molecular beacons, and/or various nanoparticles. Non-invasive imaging of miRNA expression and/or biological activity is still at its infancy. Future research on more clinically relevant, non-toxic techniques is required to move the field of miRNA imaging into clinical applications. Non-invasive imaging of miRNA is an invaluable method that can not only significantly advance our understandings of a wide range of human diseases, but also lead to new and more effective treatment strategies for these diseases.
    Current Medicinal Chemistry 05/2013; 20. DOI:10.2174/0929867311320290005 · 3.85 Impact Factor
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    Plastic &amp Reconstructive Surgery 05/2013; 131:76. DOI:10.1097/01.prs.0000430038.76356.b7 · 3.33 Impact Factor
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    ABSTRACT: The effect of slow-release basic fibroblast growth factor (bFGF) on ischemia-reperfusion injury was examined using an island skin flap model in rats. Paired rectangular island skin flaps were elevated on the dorsum of 30 Fischer rats. The flaps were subjected to 6 hours of ischemia. Before reperfusion the flaps were injected with acidic gelatin hydrogel microspheres + phosphate-buffered saline (PBS) (group I), 20 μg slow-release bFGF + PBS (group II), 50 μg slow-release bFGF + PBS (group III), and 150 μg slow-release bFGF + PBS (group IV). The mean percent flap survival area and the average number of vessels detected by microangiography were significantly higher in group IV (p < 0.05) than in groups I, II, and III. The immunohistochemical staining for vasculogenic growth factors was quantitatively higher in group IV (p < 0.01). In conclusion, slow-release bFGF prevents ischemia-reperfusion injury by upregulating the secretion of vasculogenic growth factors.
    Journal of Reconstructive Microsurgery 04/2013; 29(5). DOI:10.1055/s-0033-1343830 · 1.01 Impact Factor

Publication Stats

329 Citations
188.10 Total Impact Points


  • 2015
    • University of California, Davis
      • Division of Plastic Surgery
      Davis, California, United States
  • 2013–2015
    • University of Wisconsin–Madison
      Madison, Wisconsin, United States
  • 2007–2013
    • Nippon Medical School
      • Department of Plastic and Reconstructive Surgery
      Edo, Tōkyō, Japan
  • 2007–2008
    • Ankara Numune Training and Research Hospital
      Engüri, Ankara, Turkey
  • 2006–2008
    • Ankara University
      Engüri, Ankara, Turkey