About

Richard C. Duncan, DMD, is a Clinical Professor in the Department of Oral Medicine at Penn Dental Medicine. His role involves teaching and clinical responsibilities within the department, contributing to the academic and professional development of students in the field of oral medicine. The department encompasses various specialized programs and research initiatives, indicating his involvement in advancing clinical education and research in oral health sciences.

Research topics

• Pediatrics
• Immunology
• Family medicine
• Medicine

Selected publications

• Retinoic acid signaling guides the efficiency of inner ear organoid-genesis and governs sensory-nonsensory fate specification

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-03-21

  preprintOpen access1st authorCorresponding

  Summary Inner ear organoid development—from germ layer to otocyst formation—relies on timed chemical cues to recapitulate major signals in vivo. In contrast, later stages of differentiation—from otic vesicle (OV) to organoid formation—are self-guided, even though these stages are modulated by several key morphogens in vivo . We sought to elucidate additional morphogens that might improve culture efficiency and influence cell fate decisions. Using a whole-transcriptomic approach, we identified major differences in native and stem cell-derived OVs related to anterior-posterior patterning and retinoic acid (RA) signaling. Increasing the level of RA during OV formation in these cultures modulated organoid efficiency, increased nonsensory markers, decreased sensory markers, and decreased hair cell production. The organoid culture platform mimics the exquisite RA sensitivity found in normal inner ear development and may help identify RA-responsive genes driving organogenesis and cell fate specification.

  PublisherOA PDFDOI

• Teaching developmental neurobiology with inclusion and valuing of neurodivergent learners

  Developmental Biology · 2025-11-18

  articleOpen access

  Developmental biology is one of the fundamental sciences for understanding the basics of life and often intersects with social justice challenges facing society. This article describes an inclusive teaching activity for students and instructors to explore the interface between developmental biology, genetic diversity, and social justice. The instructor and students will choose a recent publication and use it as the basis for exploring the roles of specific genes characterized in autism from educational, emulative, and ethical perspectives. The assignment for students will include a discussion and demonstration of developmental neurobiology and principles of gene function within the nervous system, as well as ethical considerations for how individuals, as well as society as a whole, should consider genetic variations. Two frameworks are introduced for instructors to create an inclusive learning environment, including universal design for learning and multipartiality. Resources and examples are given throughout the article for instructors to use, and a suggested rubric is also provided. A post-activity self-reflection performed by the students will facilitate their own assessment of how the teaching activity has impacted their philosophical and social perspectives on genetic diversity. The short-term goal of the activity is to promote an immediate appreciation of neurodiversity among the participating students, and the long-term goal is to demonstrate the importance of neurodiversity for developing a just society. • Developmental neurobiology can help destigmatize and affirm neurodivergence • Students can learn about neurodiversity through Education, Emulation, and Ethics lenses • Universal design for learning and multipartiality create an inclusive environment • Students can take action based on their learning to propagate social change

  PublisherDOI

• Retinoic acid signaling guides the efficiency of inner ear organoid-genesis and governs sensory-nonsensory fate specification

  Stem Cell Reports · 2025-10-01

  articleOpen access1st authorCorresponding

  Inner ear organoid development-from germ layer to otic vesicle (OV) formation-relies on timed chemical cues to recapitulate major signals in vivo. In contrast, later stages of differentiation-from OV to organoid formation-are self-guided, even though these stages are modulated by several key morphogens in vivo. We sought to elucidate additional morphogens that might improve culture efficiency and influence cell fate decisions. Using a whole-transcriptomic approach, we identified major differences in native and stem-cell-derived OVs related to anterior-posterior patterning and retinoic acid (RA) signaling. Increasing the level of RA during OV formation in these cultures modulated organoid efficiency, increased nonsensory markers, decreased sensory markers, and decreased hair cell production. The organoid culture platform mimics the exquisite RA sensitivity found in normal inner ear development and provides a tunable system for generating sensory and nonsensory cell types in inner ear organoids.

  PublisherDOI

• Mapping the developmental potential of mouse inner ear organoids at single-cell resolution

  iScience · 2024-02-01 · 9 citations

  articleOpen accessSenior author

  <h2>Summary</h2> Inner ear organoids recapitulate development and are intended to generate cell types of the otic lineage for applications such as basic science research and cell replacement strategies. Here, we use single-cell sequencing to study the cellular heterogeneity of late-stage mouse inner ear organoid sensory epithelia, which we validated by comparison with datasets of the mouse cochlea and vestibular epithelia. We resolved supporting cell sub-types, cochlear-like hair cells, and vestibular type I and type II–like hair cells. While cochlear-like hair cells aligned best with an outer hair cell trajectory, vestibular-like hair cells followed developmental trajectories similar to <i>in vivo</i> programs branching into type II and then type I extrastriolar hair cells. These results highlight the transcriptional accuracy of the organoid developmental program but will also inform future strategies to improve synaptic connectivity and regional specification.

  PublisherDOI

• Supplementary tables 1-4 from Risk Stratification System for Oral Cancer Screening

  2023-04-03

  supplementary-materialsOpen access

  &lt;p&gt;Supplementary Table 1. Stage and HPV status by disease site among 150 cases. Supplementary Table 2. SolCD44/Total Protein test by HPV status and stage. Supplementary Table 3. Characteristics of hospital-based cases and controls and community controls. Supplementary Table 4. Prognostic Significance of CD44 and Total Protein Levels.&lt;/p&gt;

  PublisherDOI

• Data from Risk Stratification System for Oral Cancer Screening

  2023-04-03

  preprintOpen access

  &lt;div&gt;Abstract&lt;p&gt;Oral cavity and oropharyngeal cancer (oral cancer) is a deadly disease that is increasing in incidence. Worldwide 5-year survival is only 50% due to delayed intervention with more than half of the diagnoses at stage III and IV, whereas earlier detection (stage I and II) yields survival rates up to 80% to 90%. Salivary soluble CD44 (CD44), a tumor-initiating marker, and total protein levels may facilitate oral cancer risk assessment and early intervention. This study used a hospital-based design with 150 cases and 150 frequency-matched controls to determine whether CD44 and total protein levels in oral rinses were associated with oral cancer independent of age, gender, race, ethnicity, tobacco and alcohol use, and socioeconomic status (SES). High-risk subjects receiving oral cancer prevention interventions as part of a community-based program (&lt;i&gt;n&lt;/i&gt; = 150) were followed over 1 year to determine marker specificity and variation. CD44 ≥5.33 ng/mL was highly associated with case status [adjusted OR 14.489; 95% confidence interval (CI), 5.973–35.145; &lt;i&gt;P&lt;/i&gt; &lt; .0001, vs. reference group CD44 &lt;2.22 ng/mL and protein &lt;1.23 mg/mL]. Total protein aided prediction above CD44 alone. Sensitivity and specificity in the frequency-matched study was 80% and 48.7%, respectively. However, controls were not representative of the target screening population due, in part, to a high rate of prior cancer. In contrast, specificity in the high-risk community was 74% and reached 95% after annual retesting. Simple and inexpensive salivary CD44 and total protein measurements may help identify individuals at heightened risk for oral cancer from the millions who partake in risky behaviors. &lt;i&gt;Cancer Prev Res; 9(6); 445–55. ©2016 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;

  PublisherDOI

• Supplementary tables 1-4 from Risk Stratification System for Oral Cancer Screening

  2023-04-03

  supplementary-materialsOpen access

  &lt;p&gt;Supplementary Table 1. Stage and HPV status by disease site among 150 cases. Supplementary Table 2. SolCD44/Total Protein test by HPV status and stage. Supplementary Table 3. Characteristics of hospital-based cases and controls and community controls. Supplementary Table 4. Prognostic Significance of CD44 and Total Protein Levels.&lt;/p&gt;

  PublisherDOI

• The Genre Switch Game: Tailoring for Audience and Format

  2023-01-01

  book-chapterSenior author
  PublisherDOI

• Data from Risk Stratification System for Oral Cancer Screening

  2023-04-03

  preprintOpen access

  &lt;div&gt;Abstract&lt;p&gt;Oral cavity and oropharyngeal cancer (oral cancer) is a deadly disease that is increasing in incidence. Worldwide 5-year survival is only 50% due to delayed intervention with more than half of the diagnoses at stage III and IV, whereas earlier detection (stage I and II) yields survival rates up to 80% to 90%. Salivary soluble CD44 (CD44), a tumor-initiating marker, and total protein levels may facilitate oral cancer risk assessment and early intervention. This study used a hospital-based design with 150 cases and 150 frequency-matched controls to determine whether CD44 and total protein levels in oral rinses were associated with oral cancer independent of age, gender, race, ethnicity, tobacco and alcohol use, and socioeconomic status (SES). High-risk subjects receiving oral cancer prevention interventions as part of a community-based program (&lt;i&gt;n&lt;/i&gt; = 150) were followed over 1 year to determine marker specificity and variation. CD44 ≥5.33 ng/mL was highly associated with case status [adjusted OR 14.489; 95% confidence interval (CI), 5.973–35.145; &lt;i&gt;P&lt;/i&gt; &lt; .0001, vs. reference group CD44 &lt;2.22 ng/mL and protein &lt;1.23 mg/mL]. Total protein aided prediction above CD44 alone. Sensitivity and specificity in the frequency-matched study was 80% and 48.7%, respectively. However, controls were not representative of the target screening population due, in part, to a high rate of prior cancer. In contrast, specificity in the high-risk community was 74% and reached 95% after annual retesting. Simple and inexpensive salivary CD44 and total protein measurements may help identify individuals at heightened risk for oral cancer from the millions who partake in risky behaviors. &lt;i&gt;Cancer Prev Res; 9(6); 445–55. ©2016 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;

  PublisherDOI

• Mapping the developmental potential of mouse inner ear organoids at single-cell resolution

  bioRxiv (Cold Spring Harbor Laboratory) · 2023-09-09

  preprintOpen accessSenior author

  Summary Inner ear organoids recapitulate development and are intended to generate cell types of the otic lineage for applications such as basic science research and cell replacement strategies. Here, we use single-cell sequencing to study the cellular heterogeneity of late-stage mouse inner ear organoid sensory epithelia, which we validated by comparison with data sets of the mouse cochlea and vestibular epithelia. We resolved supporting cell sub-types, cochlear like hair cells, and vestibular Type I and Type II like hair cells. While cochlear like hair cells aligned best with an outer hair cell trajectory, vestibular like hair cells followed developmental trajectories similar to in vivo programs branching into Type II and then Type I extrastriolar hair cells. These results highlight the transcriptional accuracy of the organoid developmental program but will also inform future strategies to improve synaptic connectivity and regional specification.

  PublisherOA PDFDOI

Recent grants

• NIH Grant R01DC007432

  NIH · $2.1M · 2012

Frequent coauthors

• James B. Polson

  19 shared

• Richard F. Lockey

  17 shared

• Daniel Martín

  Centre d'Estudis Avançats de Blanes

  17 shared

• Liqian Liu

  South China University of Technology

  15 shared

• Tadakazu Shimoda

  Shizuoka Cancer Center

  13 shared

• Joseph J. Krzanowski

  10 shared

• Randy J. Nelson

  West Virginia University

  9 shared

• J KRZANOWSKIJR

  Nagasaki University

  9 shared

Education

• Postdoctoral Fellow, Otolaryngology

  Johns Hopkins University

  2003

• Ph.D., Bioengineering

  University of Pennsylvania

  1999

• M.S., Engineering Science and Mechanics

  Virginia Polytechnic Institute and State University

  1993

• B.S., Engineering Science and Mechanics

  Virginia Polytechnic Institute and State University

  1992

Awards & honors

• Leonard Davis Institute Summer Research Fellowship