In vitro and in vivo immune assessments of genetically-engineered pig skin grafts in New World (squirrel) monkeys.

Half a million patients in the USA alone require treatment for burns annually. Following an extensive burn, it may not be possible to provide sufficient autografts in a single setting. Genetic manipulations (GM) of pigs offer the possibility of reducing primate humoral and cellular rejection of pig skin xenografts and thus extending graft survival. We compared the survival of skin grafts from pigs with 9-GM with that of autografts and allografts in squirrel monkeys. Monitoring for rejection was by (1) macroscopic examination, (2) histopathological examination of skin biopsies, and (3) measurement of anti-monkey and anti-pig IgM and IgG antibodies. Autografts (n = 5) survived throughout the 28 days of follow-up without histopathological features of rejection. Median survival of allografts (n = 6) was 14 days and of pig xenografts (n = 12) 21 days. Allotransplantation was associated with an increase in anti-monkey IgM, but the anticipated subsequent rise in IgG had not yet occurred at the time of euthanasia. Pig grafts were associated with increases in anti-pig IgM and IgG. In all cases, histopathologic features of rejection were similar. 9-GM pig skin xenografts survive at least as long as monkey skin allografts (and trended to survive longer), suggesting that they are a realistic clinical option for the temporary treatment of burns. Although monkeys with pig skin grafts developed anti-pig IgM and IgG antibodies, these did not cross-react with monkey antigens, indicating that a primary 9-GM pig skin graft would not be detrimental to a subsequent monkey skin allograft.

Changes in United States Residency Program Online Presence Following COVID-19.

PHENOMENON: The 2020-2021 residency application cycle was subject to major alterations following the COVID-19 global pandemic. This study determined the online presence of US-based residency training programs during this time period. APPROACH: An official list of accredited US residency programs for 24 medical specialties was obtained through the Electronic Residency Application Service Programs' online presence and was evaluated for website ownership in addition to Twitter, Instagram, and Facebook account ownership. Date of social media account foundation and virtual opportunities offered were recorded. Doximity Residency Navigator for 2020-2021 was used to determine program rank, and programs were stratified by location using Association of American Medical Colleges regions. Program rank and geographic location were used to determine potential trends in online presence. This study was performed during the residency application cycle from September 2, 2020, to November 29, 2020, during which applications were submitted and the interview cycle began. FINDINGS: Fifty-seven percent of the 4,562 programs had a presence on social media. One-third of all accounts were created after March 1, 2020, and most (58%) were residency program-associated. A total of 1,315 programs offered virtual open houses through Twitter (829), Instagram (792), and Facebook (295). First-quartile programs had significantly more social media accounts per program on average (1.8) than those in subsequent quartiles, and Western region programs had significantly more accounts per program on average (1.3) than the Central (1.0), Northeastern (1.0), and Southern (1.1) regions. INSIGHTS: US residency programs created social media accounts and online opportunities for applicants following March 1, 2020. Online interactions may serve as substitutes at a time when in-person interaction is not possible. Future studies may examine the influence and impact of virtual interactions.Supplemental data for this article is available online at https://doi.org/10.1080/10401334.2022.2047050.

A Systematic Review of Microsurgical Pedicle Lengthening in Free Tissue Transfer.

INTRODUCTION: Traumatic injuries that require free tissue flaps for reconstruction may require vascular pedicle extension between the flap and recipient vessels to form a clear anastomosis. Currently, a variety of techniques are used, each with their own potential benefits and harms. In addition, reports in the literature conflict on the reliability of pedicle extensions of vessels in free flap (FF) surgery. The objective of this study is to systematically assess the available literature about outcomes of pedicle extensions in FF reconstruction. METHODS: A comprehensive search was performed for relevant studies published up to January 2020. Study quality was assessed using the Cochrane Collaboration risk of bias assessment tool and a set of predetermined parameters was extracted by 2 investigators independently for further analysis. The literature review yielded 49 studies investigating pedicled extension of FF. Studies meeting inclusion criteria underwent data extraction focusing on demographics, conduit type, microsurgical technique, and postoperative outcomes. RESULTS: The search yielded 22 retrospective studies totaling 855 procedures from 2007 to 2018 in which 159 complications (17.1%) were reported in patients aged between 39 and 78 years. Overall heterogeneity of articles included in this study was high. Free flap failure and thrombosis were the 2 most prevalent major complications noted: vein graft extension technique had the highest rate of flap failure (11%) in comparison with the arterial graft (9%) and arteriovenous loops (8%). Arteriovenous loops had a rate of thrombosis of 5% versus 6% in arterial grafts and 8% in venous grafts. Bone flaps maintained the highest overall complication rates per tissue type at 21%. The overall success rate of pedicle extensions in FFs was 91%. Arteriovenous loop extension resulted in a 63% decrease in the odds of vascular thrombosis and a 27% decrease in the odds of FF failure when compared with venous graft extensions (P < 0.05). Arterial graft extension resulted in a 25% decrease in the odds of venous thrombosis and a 19% decrease in the odds of FF failure when compared with venous graft extensions (P < 0.05). CONCLUSIONS: This systematic review strongly suggests that pedicle extensions of the FF in a high-risk complex setting are a practical and effective option. There may be a benefit to using arterial versus venous conduits, although further examination is warranted given the small number of reconstructions reported in the literature.

Do Socioeconomic Status and Race Impact the Safety and Efficacy of Breast Reconstruction?

INTRODUCTION: Immediate breast reconstruction after mastectomy has increased in recent years when compared with delayed reconstruction. Despite this encouraging trend, racial and socioeconomic disparities in the receipt of postmastectomy breast reconstruction have been well documented. We sought to assess the effect of race, socioeconomic status, and patient comorbidities on muscle sparing transverse rectus abdominis myocutaneous outcomes at our safety net hospital institution in the southeast. METHODS: The database of a tertiary referral center was queried for patients who received free transverse rectus abdominis myocutaneous flaps for immediate reconstruction after mastectomy meeting inclusion criteria from 2006 to 2020. Patient demographics and outcomes were compared based on socioeconomic status. The primary outcome (reconstructive success) was defined as breast reconstruction without flap loss. Statistical analysis included analysis of variance and χ2 tests were appropriate using Rstudio. RESULTS: Three-hundred fourteen patients were included in the study, with 76% White, 16% Black, and 8% other. Overall complication rate at our institution was 17% and reconstructive success was 94%. Non-White race, older age at time of breast cancer diagnosis, higher body mass index, and presence of comorbid conditions including current smoking and hypertension were all associated with low socioeconomic status. Despite this, surgical complication rates were not predicted by non-White race, older age, or presence of diabetes mellitus. When analyzing major and minor complications based on radiation received or reconstructive success, there was no significant difference regardless of radiation treatment with the group overall achieving a 94% success rate (P = 0.229). CONCLUSIONS: This study aimed to characterize the impact of socioeconomic status and race/ethnic status of patients on breast reconstruction outcomes at an institution in the South. We found that despite the greater morbidity in low income and ethnic/minority patients that when treated by a comprehensive safety net institution, they had excellent reconstructive outcomes due to low complications and minimal reoperations.

Virtual Interactions and the 2020-2021 Residency Application Cycle in General Surgery: A Look Ahead.

INTRODUCTION: General surgery residency training programs adapted to the COVID-19 pandemic by going online instead of in-person, through virtual interviews, social media engagement, and virtual open houses. The impact of these virtual interactions is unknown. We sought to understand their effectiveness as per residency program directors and assistant program directors. MATERIALS AND METHODS: An institutional review board approval was obtained to conduct this anonymous survey. A Qualtrics XM survey containing multiple-choice and short-answer questions was distributed to 590 residency program and assistant program directors through the Association of Program Directors in Surgery (APDS) listserv on July 6, July 13, and July 20. RESULTS: We observed a response rate of approximately 11% across the 590 surgeons contacted. Nearly all (90%) respondents offered virtual preinterview interactions, primarily virtual open houses, virtual facility tours, and virtual question and answer (Q&A) sessions with residents and faculty; 48% of respondents were unsure of the utility of virtual interactions and the majority (54%) felt that virtual interaction limits a program's ability to evaluate applicants. Virtual Q&As were ranked to be the most effective interaction (7.6/10); 80% of respondents felt that visiting rotations were "somewhat important" to "very important," the two highest options available. In addition, 74% felt that applicants missed out on fully experiencing the program by forgoing these rotations. Most respondents (78%) noted that evaluation of applicants' preinterview did not change as a result of virtual interactions. Nearly half (48%) of the respondents offered more interview days due to the virtual format. A fifth (21%) of respondents stated that virtual interactions resulted in a change in the rank position of an applicant. Respondents ranked Twitter and Instagram higher in applicant engagement than Facebook. Factors that impacted interview or rank order list the most were late/absent step two CK scores (33%) and a lack of away rotations (31%), both being limitations largely due to the pandemic. With respect to future application cycles, most (71%) raised concerns regarding disparities between applicants applying in-person and virtually if both or either are offered. CONCLUSIONS: Our study suggests that program directors and associate program directors have reservations about the use of virtual interactions with applicants. Interestingly, these data suggest that visiting subinternships are useful for programs in evaluating applicants. This may encourage students to pursue rotations at other institutions at the expense of already-limited resources. It remains unclear whether virtual interactions will be used in the future, but respondents largely agreed that the virtual means of interacting with and disseminating information to the applicants of the 2020-2021 general surgery Match were a success.

Comorbidity Trends in Patients Requiring Sternectomy and Reconstruction: Updated Data Analysis From 2005 to 2020.

INTRODUCTION: Comorbidity trends after median sternectomy were studied at our institution by Vasconze et al (Comorbidity trends in patients requiring sternectomy and reconstruction. Ann Plast Surg. 2005;54:5). Although techniques for sternal reconstruction have remained unchanged, the patient population has become more complex in recent years. This study offers insight into changing trends in this patient population. METHODS: A retrospective review was performed of patients who underwent median sternectomy followed by flap reconstruction at out institution between 2005 and 2020. Comorbidities, reconstruction method, average laboratory values, and complications were analyzed. RESULTS: A total of 105 patients were identified. Comorbidities noted were diabetes (27%), immunosuppression (16%), hypertension (58%), renal insufficiency (23%), chronic obstructive pulmonary disease (16%), and tobacco utilization (24%). The most common reconstruction methods were omentum (45%) or pectoralis major flaps (34%). Thirty-day mortality rates were 10%, and presence of at least 1 complication was 34% (hematoma, seroma, osteomyelitis, dehiscence, wound infection, flap failure, and graft exposure). Univariate analysis demonstrated that sex (P = 0.048), renal insufficiency, surgical site complication, wound dehiscence, and flap failure (P < 0.05) had statistically significant associations with mortality. In addition, body mass index, creatinine, and albumin had a significant univariate association with mortality (P < 0.05). CONCLUSIONS: Similar to the original study, there is an association between renal insufficiency and mortality. However, the mortality rate is decreased to 10%, likely because of improved medical management of patients with increasing comorbidities (80% with greater than one comorbidity). This has led to the increased use of omentum as a first-line option. Subsequent wound dehiscence and flap failure demonstrate an association with mortality, suggesting that increasingly complex patients are requiring a method of reconstruction once used a last resort as a first-line option.

The Correlation Between Altmetric Score and Traditional Bibliometrics in Orthopaedic Literature.

BACKGROUND: Clinicians and medical researchers increasingly turn to nonformal online platforms to promote research. Altmetric Attention Score (AAS) is a quantitative measurement of online influence of research in real time. The objective of this study is to determine if AAS correlates with traditional bibliometrics in the orthopaedic literature. MATERIALS AND METHODS: From the 15 orthopaedic journals with the highest impact factor, the 10 most cited articles from each journal were reviewed for 2014 -2017. For each article, AAS was collected using the Altmetric Bookmarklet application and citation count from SCOPUS. Journal impact factor was recorded using Journal Citation Reports. Statistical analysis included Pearson's and Spearman's correlation coefficients. RESULTS: A total of 600 articles were analyzed. A significant positive correlation was found between citation count and AAS for 2014 (r = 0.3188, p < 0.0001), and no correlation for 2015 (r = 0.1504, P = 0.0653), 2016 (r = 0.0087, P = 0.9157), and 2017 (r = 0.0061, P = 0.9408). There was no significant correlation between impact factor and AAS in 2014 (r = 0.4312, P = 0.1085), 2015 (r = 0.3850, P = 0.1565), 2016 (r = 0.1460, P = 0.6035) and 2017 (r = 0.0451 P = 0.8732). CONCLUSIONS: AAS and traditional bibliometrics are currently not strongly correlated in orthopaedic literature. Citations take years to accumulate and AAS represents immediate influence of an article. An amalgamation of traditional bibliometrics and AAS may prove useful in determining the short- and long-term impact and influence of publications in orthopaedics.

Ranking United States Plastic Surgery Residency Programs Based on Academic Achievement of Faculty Members.

INTRODUCTION: The Doximity Residency Navigator is currently the only resource that ranks plastic surgery residency programs. Given the paucity of objective program rankings, in this study, we devised a new algorithm to rank plastic surgery programs based on academic achievement of faculty members. METHODS: The Fellowship and Residency Electronic Interactive Database was used to obtain the following information on plastic surgery programs: the amount of 2017 National Institute of Health and Veterans Administration funding, lifetime and 5-year faculty h-indices, and the number of faculty on editorial boards of journals. Based on all of this information, an overall ranking of the top 25 plastic surgery programs was created. RESULTS: The top program for annual National Institutes of Health and Veteran Affairs funding was the University of Southern California (integrated and independent). The top programs for faculty lifetime h-index were the University of Michigan (integrated) and New York University (independent). The top program for faculty 5-year h-index was the University of Pennsylvania (integrated and independent). The top program for the number of faculty members who are on the editorial boards of major journals was Harvard University (integrated and independent). The top program overall was Harvard University (integrated and independent). CONCLUSION: We ranked plastic surgery residency programs based on objective data related to faculty academic achievement. Academic achievement rankings are just one of numerous other factors that medical students should synthesize when making informed decisions when applying to residency.

The Content of US Plastic Surgery Private Practices' Websites.

INTRODUCTION: Connecting patients with healthcare providers continues to grow as the digital era evolves. A successful website has the power to influence patients on choosing a practice and provider. The objectives of this study were to characterize information provided on private practice websites of plastics surgeons in the United States and to assess the relationship among the websites based on the number of years that the physicians have been in practice. METHODS: Newly board-certified plastic surgeons by the American Board of Plastic Surgery in 2005, 2010, and 2015 were identified. A Google search was conducted on all participants, and only those in private practice were included in this study. Each webpage was quantitatively and qualitatively assessed for the presence or absence of 23 criteria that were categorized as practice, physician, patient, or procedure information. χ2 was used for statistical analysis using Microsoft Excel (PSPP 1.2.0). A P value of less than 0.05 was considered statistically significant. RESULTS: Most plastic surgeons in each cohort were currently in private practice. A total of 532 plastic surgery private practice websites were analyzed. The data points found on 100% of the websites were directions to the facility and the contact for any billing questions. Most websites provided information on the practice and its surgeons. The most common web-based data points included online consultations and links to their social media. Information on expenses incurred by patients, such as cancellation policies and consultation fees, was least commonly listed. CONCLUSIONS: Our study shows that the number of years in practice is not associated with comprehensiveness of their website's content. This study provides insight into the content of plastic surgery private practices' websites in the United States in relation to the practice, the physician, the patient, and the procedures. This information may be useful for expanding and optimizing their websites. This has the potential to increase patient satisfaction and visibility of the practice. The success of these businesses is vital as the private sector in plastic surgery continues to grow.

Adaptations in anesthesiology residency programs amid the COVID-19 pandemic: virtual approaches to applicant recruitment.

BACKGROUND: The COVID-19 pandemic significantly impacted residency recruitment in 2020, posing unique challenges for programs and applicants alike. Anesthesiology programs have adopted alternate methods of recruitment, including virtual open houses and social media, due to limiting personal contact rules implemented by AAMC. This study was undertaken to determine the frequency of virtual events hosted and social media accounts created by programs. METHODS: Anesthesiology residency programs and departments were examined for social media presence on Twitter, Instagram, and Facebook. Programs' websites and social media posts were reviewed for virtual open house opportunities. Available sub-internships were collected from the Visiting Student Application Service database. Data was collected after 2020-2021 pre-interview recruitment in October 2020. RESULTS: Of 153 total anesthesiology residency programs, 96 (63%) had some form of social media presence. The platforms of choice for programs with social media accounts included Twitter (71, or 46%), Instagram (67, or 44%), and Facebook (47, or 31%). Forty of seventy-six residency-affiliated accounts were created after March 1, 2020; Instagram accounts (26 of 40) represented most of these. Most Anesthesiology programs (59%) offered virtual open houses for prospective applicants. Twitter (25%), Instagram (22%), and Facebook (8%) were used by programs to advertise these events. CONCLUSIONS: Social media presence of anesthesiology residency programs has grown steadily over the past decade, with exponential growth experienced in 2020. This data suggests that anesthesiology residency programs are employing new, mostly virtual, methods to reach prospective applicants during an unprecedented application cycle amidst the COVID-19 pandemic.

Differences in Highly-Cited and Lowly-Cited Manuscripts in Plastic Surgery.

BACKGROUND: There is a paucity of research comparing journal articles that accrue numerous citations with those that accrue few citations over time. Understanding differences between journal articles can help direct investigators in designing and conducting their research. METHODS: Using advanced bibliometric tools, we queried four plastic surgery journals (Journal of Reconstructive Microsurgery, Annals of Plastic Surgery, Plastic and Reconstructive Surgery, and Microsurgery) for primary research articles published between 1998 and 2008 accruing zero or one citations with at least a 10-y lag time. Forty-seven articles were identified as low citation and were compared with an equal number of articles in the same journals that accrued the highest number of citations in the same period as high citation (HC). The data were analyzed using Student t-tests, Wilcoxon rank sum tests, chi-square tests, and Fisher exact tests. The level of significance was established at P < 0.05. RESULTS: When compared with the HC cohort, the low citation articles were more likely to be nonclinical (P < 0.001), have no plastic surgery authors (P = 0.0026), and focus on the field of microsurgery (P = 0.003). The HC cohort was more likely to have higher sample sizes (P = 0.0339), focus on aesthetic/cosmetic surgery (P = 0.003), have a higher number of other disciplines included on authorship (P < 0.001), references (P = 0.0451), manuscript pages (P < 0.001), and words in the abstract (P < 0.001). CONCLUSIONS: A small number of articles published in four plastic surgery journals were uncited during a 10-y period. There are qualitative and quantitative differences between highly and lowly cited articles in the plastic surgery literature. Investigators should consider these differences when designing and conducting studies.

Impact of COVID-19 on Away Rotations in Surgical Fields.

The COVID-19 pandemic has presented a variety of challenges in the medical education curriculum, one of which is the possible loss of summer and fall away rotations for fourth year students applying into surgical subspecialties. Subsequently, a lack of in-person evaluations may have a major impact on an applicant's perception of the residency and the program's ability to assess the individual applicant. This is especially crucial for applicants without a home program in their specialty of interest, as away rotations are an important opportunity to confirm interest in pursuit of a subspecialty, obtain letters of recommendation, and make positive impressions at programs of interest. The objective of this article is to assess the current COVID-19 pandemic situation in light of away rotations and to provide recommendations for surgical subspecialty programs and applicants to have the best outcome during this upcoming application cycle. In particular, we emphasize the importance of implementing universal processes within each individual subspecialty. This will provide equitable opportunities for all applicants, minimizing potential biases or disadvantages based on geographic location or availability of a program at an applicant's home institution.

Dermal Autografts in Breast Reconstruction: A Review of Past and Current Trends.

Breast cancer affects 1 in 8 women. As the treatment of breast cancer evolves, breast reconstruction does as well. Implant-based reconstructions are increasing, leading to increased use of acellular dermal matrix (ADM) for better implant positioning. Acellular dermal matrices are derived from cadaveric skin and are processed to be immunologically inert. However, ADM can be costly and can have complications such as seroma and infection. This has led to the development of dermal autografts. These were first used in postmastectomy breast reconstruction in women with redundant breast skin that was deepithelialized and used for lower pole coverage of tissue expanders and implants. This evolved into harvesting dermal autografts from the abdomen. Later studies evaluated the use of meshed dermal autografts. Histological analysis of ADM versus dermal autografts shows that there are increased vessels within dermal autografts compared with ADM. This potentially contributes to the decreased complication rate seen with autografts. In addition, one study showed equivalent results in aesthetic outcomes and capsular contracture between ADM and dermal autograft. Analysis of cost has shown that ADM is significantly more costly than harvesting a dermal autograft. Physician reimbursement is also higher for dermal autografts. This review article seeks to summarize key studies that highlight the feasibility of using dermal autografts in breast reconstruction.

The effect of community based-academic partnerships on student knowledge about plastic surgery and interest in medicine.

BACKGROUND: Programs specific to plastic surgery are necessary to dispel common myths and increase interest in the field. In a previous publication by the authors, a community outreach program was developed for these reasons for middle school students. In the current study, we expanded on the previous research and collected objective data to assess students' initial interest in medicine and knowledge about plastic surgery, compared to their interest and knowledge afterward. METHODS: The program previously developed by the authors was modified and performed for the students at various community outreach events and included a PowerPoint presentation, case didactics, and hands-on activities. A test about plastic surgery and questionnaire about interest in the medical field and becoming a doctor was given to each student before and after the program. RESULTS: One hundred seventy-nine students participated in the program from 2009 to 2013. The pretest mean score was 6.50 of 12 questions whereas the posttest mean score was 9.72 (P = <0.001). After participation in the program, 27% of students that answered "no" or "unsure" about interest in the medical field on the pretest changed their answer to "yes," on the posttest, and 17% of students that answered "no" or "unsure" about interest in becoming a doctor on the pretest changed their answer to "yes," on the posttest (P = <0.001). CONCLUSIONS: A plastic surgery community outreach program is beneficial in increasing students' interest in the field of medicine as a whole, and more specifically in the field of plastic surgery.

The Imperative of Academia in the Globalization of Plastic Surgery.

Although vertical health care delivery models certainly will remain a vital component in the provision of surgery in low-and-middle-income countries, it is clear now that the sustainability of global surgery will depend on more than just surgeons operating. Instead, what is needed is a comprehensive approach, that is, a horizontal integration that develops sustainable human resources, physical infrastructure, administrative oversight, and financing mechanisms in the developing world. We propose that such a strategy for development would necessarily involve an active role by academic institutions of high-income countries.

Addressing the Rhino in the Room: ChatGPT Creates "Novel" Patent Ideas for Rhinoplasty.

Background: OpenAI's ChatGPT can generate novel ideas for a number of applications. The aim of this study was to prompt the chatbot to generate possible innovations in aesthetic surgery relating to rhinoplasty. Methods: ChatGPT was prompted to develop rhinoplasty patents. The resulting outputs were tabulated and categorized based on technology domain and anatomic location. A Google Patents search was conducted to find uses of the term "rhinoplasty" between 2021 and 2023. Patents not pertaining to rhinoplasty were excluded. Filed patents were compared with those generated by ChatGPT to determine predictive power. Results: A total of 40 patents resulted from ChatGPT and 42 Google Patents from 2021 to 2023 were included. Patents generated without a detailed description command were related to preoperative planning (35%), intraoperative tools (30%), functional evaluation (15%), and 3D printing and implants (10%). Patents with a detailed description command resulted in the majority being postoperative tools (40%), followed by intraoperative tools (30%), 3D printing and implants (10%), and nonsurgical (10%) categories. The anatomic locations included the airway, dorsum, septum, and nasal tip. ChatGPT's predictive power yielded 45% for the detailed prompting, which was higher than the prompt without the detail command. Conclusions: ChatGPT has reasonable potential to generate ideas for innovations in plastic surgery with the assistance of an experienced surgeon-innovator. With new artificial intelligence generations and updates, chatbots will continue to improve. Determining whether these technologies can assist in the later portions of the patent process beyond idea generation will be crucial.

Epidermal growth factor regulates NIKS keratinocyte proliferation through Notch signaling.

BACKGROUND: Cutaneous wound healing is a significant health issue in the US, often requiring skin grafts. StrataGraft (Stratatech Corporation, Madison, WI), a second-generation living human skin substitute created from NIKS human keratinocyte progenitors, was recently found to be a promising skin graft in phase I/II safety and efficacy clinical trial. NIKS proliferation is optimal in the presence of epidermal growth factor (EGF). Our preliminary data suggested that Notch signaling also plays a role in NIKS keratinocyte proliferation. Therefore, we hypothesized that EGF might stimulate NIKS proliferation by regulating Notch1 signaling. METHOD: Notch1 messenger RNA (mRNA) levels from NIKS cells in monolayer culture were assessed by real-time polymerase chain reaction and Notch1 protein levels were detected by Western blot. To determine the role of EGF on Notch1 regulation, cells were incubated in basal media and then treated with EGF (10 ng/mL). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to test NIKS cell proliferation. Cells were grown in basal media supplemented with EGF for 72 h in the presence or absence of N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) (0-30 µM), an inhibitor of Notch1 signaling. RESULTS: Notch1 mRNA levels were cell confluence-dependent, being more abundant in a subconfluent cell monolayer. We detected a 2-fold decrease in Notch1 mRNA expression and a reduction in active Notch1 protein level in response to EGF. EGF treatment stimulated NIKS cellular proliferation. However, co-treatment with DAPT inhibited NIKS proliferation to basal levels. Blocking Notch1 activation by DAPT alone inhibited NIKS cellular proliferation (P < 0.01%). CONCLUSION: Our results suggest that Notch1 is an essential downstream mediator of NIKS cellular proliferation via the EGF signaling pathway.