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UCLA Vatche & Tamar Manoukian Division of Digestive Diseases


Meet the Team


Daniel Hommes, MD, PhD
Director, Clinical Care & Clinical Research, UCLA Center for Inflammatory Bowel Diseases
Director, GI Quality Program
Professor-In-Residence of Medicine
Vatche and Tamar Manoukian Division of Digestive Diseases
David Geffen School of Medicine at UCLA

Dr. Daniel Hommes is a medical specialist whose professional aims include the improvement of the quality of life of patients suffering from inflammatory bowel diseases (IBD) through basic science, translational research and healthcare delivery innovations.

Dr. Hommes is a certified internist and gastroenterologist specialized in IBD. After completing medical school at the University of Amsterdam, he spend many years working in the Academic Medical Center (Amsterdam) where he qualified as an internist (2000) and later as a gastroenterologist (2002). His PhD thesis (1994) dealt with novel drug targets for IBD, supervised by Prof Dr Sander van Deventer and Prof Dr Guido Tytgat. In 2001, he was appointed Head of the IBD Department in the Academic Medical Center in Amsterdam.

In 2006 he moved to Leiden, the Netherlands, to become Chair of the Department of Gastroenterology and Hepatology at the Leiden University Medical Center (LUMC). In 2007, he was appointed full Professor of Gastroenterology and Hepatology at the University of Leiden. He successfully reorganized the department, focusing on IBD, liver diseases (including liver transplantation) and colorectal cancer. He established a clinical trial center as well as a basic research lab with 4 post-docs and 12 PhD students. In addition, he designed 'CuraRata' (www.curarata.com), a platform for personalized medicine successfully piloted in IBD patients and officially launched by the Dutch Minister of Health.

Nationally, Dr. Hommes was one of the founders of the Dutch Academic IBD Society ICC which he chaired from 2003 until 2007. Also, he initiated the Pearl String Initiative (PSI) in 2006, a national academic biobanking infrastructure between the eight Dutch University Medical Centers for eight disease areas, supported by a € 35 million Dutch Government funding program.  Internationally, he served since 2001 as primary investigator in numerous IBD programs and studies and was invited to act as both a consultant and member of advisory boards on many occasions for a wide variety of biomedical industry. He has authored well over 210 peer-reviewed papers and has lectured all around the globe. His interest and expertise in integrating biobanking into healthcare led to a number of consultancies in Europe and the US. In addition, he serves as reviewer and editor for medical journals. From 2004 to 2008 he chaired the Scientific Committee of the European Crohn´s and Colitis Organisation ECCO, and from 2010 until 2012 he served as ECCO's President.

In 2011, Dr. Hommes moved to Los Angeles where he was appointed as Professor of Medicine at the Division of Digestive Diseases of UCLA. He serves as Director of the Center for Inflammatory Bowel Diseases, being responsible for both the clinical programs as translational research. In addition, he has implemented a quality program across the entire division as the Director of the Quality Initiative. Dr. Hommes designed and successfully piloted a value-based health care delivery program in over 1,300 IBD patients. This program integrates a number of different aspects of modern health care, like home care, biobanking, a mental reinforcement program, patient education and much more. This is demonstrated in two YouTube videos: Vision http://youtu.be/da7dRLSQPEI; Operations: http://youtu.be/HdmsL7GVmMg

Harry Pothoulakis, MD
Director: Basic Research, UCLA Center for Inflammatory Bowel Diseases
Chief for Research Integration
Associate Chief for Training and Education
Professor of Medicine, Pathology and Laboratory Medicine
Eli and Edythe Broad Chair in Medicine
Vatche and Tamar Manoukian Division of Digestive Diseases
David Geffen School of Medicine at UCLA

Dr. Pothoulakis' research program is primarily focused on the role of neuropeptides and hormones in several disease states, including inflammatory bowel diseases, clostridium difficile infection, and irritable bowel syndrome. His recent projects also involve the neuropeptide-dependent mechanisms by which communication between the intestinal mucosa and the fat depots affect the pathogenesis of intestinal inflammation. He is an author of over 157 original articles and numerous reviews and book chapters and served in the Editorial Board of several biomedical journals, including Gastroenterology, and American Journal of Physiology. He has also been a member of Hormones, Transmitters, Growth Factors and Receptors, and Inflammatory Bowel Disease Sections of the American Gastroenterological Association. Dr. Pothoulakis' research projects have been supported by grants from the National Institutes of Health, the Broad Foundation, The Martin Blinder Foundation for Crohn's Disease, and the Knapp Foundation.

Click here to learn more about our research »

Chrisina Ha MD Ulcerative Colitits Crohn's Disease UCLA

Christina Ha, MD
Associate Director, Clinical Affairs, UCLA Center for Inflammatory Bowel Diseases
Health Sciences Assistant Clinical Professor of Medicine
Vatche and Tamar Manoukian Division of Digestive Diseases
David Geffen School of Medicine at UCLA

Dr. Ha graduated from Harvard University and earned her medical degree from Albert Einstein College of Medicine. She completed both her internal medicine residency and gastroenterology fellowship at Washington University in St. Louis School of Medicine. Following GI fellowship, she spent a year as the Present-Levison Inflammatory Bowel Disease Fellow at the Mount Sinai School of Medicine in New York. Subsequently, she joined the faculty at The Johns Hopkins School of Medicine as part of the Meyerhoff Inflammatory Bowel Disease Center prior to joining the UCLA Division of Digestive Diseases in 2013. Her areas of clinical interest are in the inflammatory bowel diseases, Crohn's disease and ulcerative colitis. Her research is also centered around Crohn's disease and ulcerative colitis with a particular focus in the natural history and clinical outcomes of IBD in the elderly.

Daniel Hollander, MD
Director, Fellowship Research Program in Gastroenterology
Professor of Medicine
Vatche and Tamar Manoukian Division of Digestive Diseases
David Geffen School of Medicine at UCLA

Dr. Hollander is a board certified gastroenterologist specializing in diagnosis and therapy of Crohn's disease and ulcerative colitis. He is a professor of medicine at the University of California, Los Angeles (UCLA) School of Medicine. His major research area is intestinal inflammation and intestinal absorption of nutrients.

Before joining UCLA, he was the director of The Broad Foundation medical and scientific initiatives including inflammatory bowel disease research. Before joining the faculty at UCLA, Dr. Hollander has also held several academic leadership positions including dean and professor of medicine at the University of Kansas School of Medicine and head of the Division of Gastroenterology at the University of California, Irvine. At the University of California at Irvine, he also served as associate dean for research and program development, associate dean for academic affairs and senior associate dean for clinical affairs. Dr. Hollander also served as the president of the Los Angeles Biomedical Research Institute.
Dr. Hollander's research has centered on intestinal absorption of nutrients and on paracellular transport and permeability of the intestine. He began his studies of the pathophysiology of inflammatory bowel diseases some 30 years ago by studying the intestinal permeability of patients with Crohn's disease and their family members and spouses. Since then, his studies have centered on the role of the intestinal tight junctions in intestinal inflammation and in the pathogenesis of Crohn's Disease.

Currently, Dr. Hollander is teaching and providing care to patients with Crohn's disease and ulcerative colitis at the Ronald Reagan UCLA Medical Center. 

  Jonathan Sack, MD
Associate Clinical Professor of Surgery, UCLA Department of Surgery

Dr. Sack is a board-certified colon and Rectal Surgeon with over 25 years experience. He has a focused interest in treating patients with inflammatory bowel diseases, with special interest in laparoscopic reconstructive surgery for chronic ulcerative colitis (restorative proctocolectomy with ileal pouch anal anastomosis) and minimally invasive treatment of complicated Crohn's disease with bowel preservation techniques.

Jenny Sauk, MD
Assistant Clinical Professor of Medicine
Vatche and Tamar Manoukian Division of Digestive Diseases
David Geffen School of Medicine at UCLA

Dr. Sauk received her undergraduate degree from Yale University and earned her medical degree from University of Chicago Pritzker School of Medicine. She subsequently completed her internal medicine residency at New York Presbyterian Hospital Weill-Cornell Medical Center and her gastroenterology fellowship at Mount Sinai School of Medicine in New York. After completing her gastroenterology fellowship, she was invited to join the faculty there, where she was appointed as the Gerald and Ruth Crohn Dickler Faculty Scholar in Inflammatory Bowel Disease. Dr. Sauk subsequently accepted a faculty position at the Massachusetts General Hospital (MGH) and developed a specialized practice in IBD at the MGH Crohn's and Colitis Center. 
Her clinical interest remains in the inflammatory bowel diseases, specifically ulcerative colitis and Crohn's disease. She also focuses on treating patients with microscopic colitis and celiac disease. Dr. Sauk's research interests have centered around clinical outcomes in inflammatory bowel disease and the intestinal microbiome. As the translational interface for multiple microbiome projects, she has partnered with investigators from the Infectious Diseases Division at MGH, Massachusetts Institute of Technology (MIT) and the Broad Institute of MIT and Harvard to further understand the significance of intestinal microbiome alterations in inflammatory and infectious gastrointestinal diseases. Dr. Sauk is board-certified in internal medicine and gastroenterology.

David Ziring, MD
Director, UCLA Pediatric IBD Center

Dr. Ziring has dedicated his life to helping children with inflammatory bowel disease (IBD). He received his medical degree from the Chicago Medical School concurrently with earning his master's degree in clinical immunology. His thesis topic was the current state of understanding of the immune system in IBD. Dr. Ziring went on to receive his residency training in Pediatrics at Children's Hospital Orange County. He then pursued subspecialty training in pediatric gastroenterology at UCLA David Geffen School of Medicine with Dr. Marvin Ament and associated faculty, concentrating his research efforts on the regulation of the immune system in IBD with his research mentor, Dr. Jonathan Braun.

Dr. Ziring was instrumental in discovering an IBD-associated gene, working with collaborators at Cedars-Sinai Medical Center. He has since migrated his research interests from working in the laboratory with animal models to studies involving patients with IBD. He was recently awarded a Broad Medical Research Program grant to study the immunomodulatory effects of large doses of vitamin D in children with Crohn's disease.
Besides his research and direct patient care, Dr. Ziring works closely with the IBD community. He serves on the medical advisory board for the IBD Support Foundation, a non-profit organization developed to provide support to patients with IBD. Dr. Ziring is the medical director of the CCFA's national Team Challenge Half-Marathons, with events in Napa, San Antonio, Miami, and Hawaii that have raised more than 30 million dollars to date. He has been a volunteer physician for the last six years with the CCFA's summer program (Camp Oasis) at Paul Newman's Painted Turtle camp, caring for more than 120 children with IBD each summer. Dr. Ziring serves as the primary investigator and UCLA's representative for the CCFA's national Pediatric Research Network (PRO-KIIDS). He is a member of the IBD Committee for the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN). He has given lectures on topics as diverse as skeletal health in children with IBD to the successful transition of care of teens with IBD at regional academic centers.  And he continues to publish extensively, from a recent review on the cutting-edge research being done in pediatric IBD to the discovery of a new IBD-associated gene (CNR2, a gene involved in the endocannabinoid system) and the importance of this system in regulating the immune system in IBD.


Nancee Jaffe, MS, RD
Registered Dietitian
UCLA Digestive Health & Nutrition Clinic
Vatche and Tamar Manoukian Division of Digestive Disease
David Geffen School of Medicine at UCLA

Nancee graduated from California State University, Los Angeles, where she earned her masters of science in nutrition. She completed her dietetic internship at the Cedars-Sinai Medical Center and at the University of California, Los Angeles, where she was mentored by Dr. Lin Chang of the G. Oppenheimer Center for the Neurobiology of Stress and Resilience.

Nancee was invited to join the UCLA Division of Digestive Diseases in 2012, where she is an integral part of the Celiac Disease Program and Digestive Health & Nutrition Clinic. She is involved with direct patient interaction during individual nutrition counseling sessions on such disease states as irritable bowel syndrome, inflammatory bowel disease, celiac disease, short bowel syndrome and idiopathic or functional bowel. 

Nancee was a reviewer for the American Gastroenterological Association patient initiatives for short bowel syndrome and the low fodmap diet in 2016. She also helps mentor the division's fellows and is asked to speak on nutrition and digestive disorders at conferences inclusive of the Southern California Society of Gastroenterology. Nancee is currently working on research regarding the reintroduction phase of the low fodmap diet with Dr. Lin Chang.


Elizabeth Aredas, RN
IBD Clinical Nurse

Elizabeth graduated from California State University, Northridge with a degree in health education and she worked in the community in HIV/AIDS education and prevention. She continued her education and graduated from Los Angeles County School of Nursing. Prior to joining UCLA, she worked at Childrens Hospital Los Angeles with an emphasis in hematology and oncology. She was also an endoscopy nurse at Specialty Surgical Center of Encino which is affiliated with UCLA.


Leticia Gutierrez
Administrative Assistant

Leticia began her employment in the Pediatric Allergy Immunology Division at UCLA as a high school student in 1986 and has made the medical field at UCLA her home. Working in GI the past 12 years, she was told about the exciting plans with the new IBD Program and was honored to become part of the team December 2011.

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