Bio

Bio


I am a physician-scientist in the Division of Gastroenterology at Stanford University. My clinical and research interest has been in neurogastroenterology. Specifically, my research has been exploring the interplay between immune cells and the enteric nervous system, and evaluating how perturbations of this interaction as a result of aging disrupts gastrointestinal neuromuscular function. Ultimately, my hope is that insights from this research provide novel therapies for treating patients with motility disorders like constipation and irritable bowel syndrome.

Clinical Focus


  • Gastroenterology
  • Neurogastroenterology

Academic Appointments


Administrative Appointments


  • Instructor in Medicine, Stanford University (2009 - Present)
  • Clinical and Research Fellow in Gastroenterology, Beth Israel Deaconess, Harvard Medical School (2005 - 2009)

Honors & Awards


  • GEMSSTAR Scholar, NIA/NIH (2013-2015)
  • Neurogastroenterology & Motility Distinguished Abstract Plenary, DDW (2013)
  • Fellowship to Faculty Transition Award, AGA (2012)
  • Albert Einstein College of Medicine Medical Scientist Training Program, MSTP (1994)
  • Golden Key National Honor Society, University of California, Berkeley (1994)
  • Phi Beta Kappa, University of California, Berkeley (1994)

Boards, Advisory Committees, Professional Organizations


  • Member, American Gastroenterologic Association (2005 - Present)

Professional Education


  • Medical Education:Albert Einstein College of Medicine Office of the Registrar (2002) NY
  • Residency:Beth Israel Deaconess Medical Center (2005) MA
  • Board Certification: Gastroenterology, American Board of Internal Medicine (2009)
  • Fellowship:Beth Isreal Deaconess Medical Center (2009) MA
  • Internship:Beth Israel Deaconess Medical Center (2003) MA

Teaching

Graduate and Fellowship Programs


  • Gastroenterology & Hepatology (Fellowship Program)

Publications

All Publications


  • Adult enteric nervous system in health is maintained by a dynamic balance between neuronal apoptosis and neurogenesis PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kulkarni, S., Micci, M., Leser, J., Shin, C., Tang, S., Fu, Y., Liu, L., Li, Q., Saha, M., Li, C., Enikolopov, G., Becker, L., Rakhilin, N., Anderson, M., Shen, X., Dong, X., Butte, M. J., Song, H., Southard-Smith, E. M., Kapur, R. P., Bogunovic, M., Pasricha, P. J. 2017; 114 (18): E3709-E3718

    Abstract

    According to current dogma, there is little or no ongoing neurogenesis in the fully developed adult enteric nervous system. This lack of neurogenesis leaves unanswered the question of how enteric neuronal populations are maintained in adult guts, given previous reports of ongoing neuronal death. Here, we confirm that despite ongoing neuronal cell loss because of apoptosis in the myenteric ganglia of the adult small intestine, total myenteric neuronal numbers remain constant. This observed neuronal homeostasis is maintained by new neurons formed in vivo from dividing precursor cells that are located within myenteric ganglia and express both Nestin and p75NTR, but not the pan-glial marker Sox10. Mutation of the phosphatase and tensin homolog gene in this pool of adult precursors leads to an increase in enteric neuronal number, resulting in ganglioneuromatosis, modeling the corresponding disorder in humans. Taken together, our results show significant turnover and neurogenesis of adult enteric neurons and provide a paradigm for understanding the enteric nervous system in health and disease.

    View details for DOI 10.1073/pnas.1619406114

    View details for Web of Science ID 000400358000016

    View details for PubMedID 28420791

  • Age-dependent shift in macrophage polarisation causes inflammation-mediated degeneration of enteric nervous system. Gut Becker, L., Nguyen, L., Gill, J., Kulkarni, S., Pasricha, P. J., Habtezion, A. 2017

    Abstract

    The enteric nervous system (ENS) undergoes neuronal loss and degenerative changes with age. The cause of this neurodegeneration is poorly understood. Muscularis macrophages residing in close proximity to enteric ganglia maintain neuromuscular function via direct crosstalk with enteric neurons and have been implicated in the pathogenesis of GI motility disorders like gastroparesis and postoperative ileus. The aim of this study was to assess whether ageing causes alterations in macrophage phenotype that contributes to age-related degeneration of the ENS.Longitudinal muscle and myenteric plexus from small intestine of young, mid-aged and old mice were dissected and prepared for whole mount immunostaining, flow cytometry, Luminex immunoassays, western blot analysis, enteric neural stem cell (ENSC) isolation or conditioned media. Bone marrow derived macrophages were prepared and polarised to classic (M1) or alternative (M2) activation states. Markers for macrophage phenotype were measured using quantitative RT-PCR.Ageing causes a shift in macrophage polarisation from anti-inflammatory 'M2' to proinflammatory 'M1' that is associated with a rise in cytokines and immune cells in the ENS. This phenotypic shift is associated with a neural response to inflammatory signals, increase in apoptosis and loss of enteric neurons and ENSCs, and delayed intestinal transit. An age-dependent decrease in expression of the transcription factor FoxO3, a known longevity gene, contributes to the loss of anti-inflammatory behaviour in macrophages of old mice, and FoxO3-deficient mice demonstrate signs of premature ageing of the ENS.A shift by macrophages towards a proinflammatory phenotype with ageing causes inflammation-mediated degeneration of the ENS.

    View details for DOI 10.1136/gutjnl-2016-312940

    View details for PubMedID 28228489

  • Intestinal pseudo-obstruction in patients with systemic sclerosis: an analysis of the Nationwide Inpatient Sample. Rheumatology Valenzuela, A., Li, S., Becker, L., Fernandez-Becker, N., Khanna, D., Nguyen, L., Chung, L. 2016; 55 (4): 654-658

    Abstract

    Intestinal pseudo-obstruction is a rare gastrointestinal complication in patients with SSc without large studies examining its prevalence or outcomes. We aimed to compare outcomes in SSc patients with intestinal pseudo-obstruction to patients with intestinal pseudo-obstruction secondary to other causes, and SSc patients without intestinal pseudo-obstruction.This is a case-control study using the Healthcare Cost and Utilization Project Nationwide Inpatient Sample for the period 2002-2011. We included patients with the previously validated International Classification of Diseases-Clinical Modification-9 code 710.1 for SSc in combination with codes for intestinal pseudo-obstruction, and determined length of hospitalization and the risks for surgical procedures, use of total parenteral nutrition (TPN) and in-hospital mortality.A total of 193 610 SSc hospitalizations occurred in the USA between 2002 and 2011, of which 5.4% (n = 10 386) were associated with a concurrent intestinal pseudo-obstruction diagnosis (cases). In-hospital mortality was 7.3%. In multivariate analyses, cases were more likely to die during the inpatient stay and to receive TPN than patients with idiopathic intestinal pseudo-obstruction (control group 1), patients with intestinal pseudo-obstruction and diabetes (control group 2), and SSc patients without intestinal pseudo-obstruction (control group 3). Cases had longer in-hospital stay than control groups 2 and 3, and were less likely to undergo surgical procedures than control groups 1 and 2.Intestinal pseudo-obstruction is a rare cause of hospitalization in patients with SSc, but is associated with high in-hospital mortality in comparison with other SSc patients and those with intestinal pseudo-obstruction secondary to other causes.

    View details for DOI 10.1093/rheumatology/kev393

    View details for PubMedID 26615031

  • Serum Response Factor Is Essential for Prenatal Gastrointestinal Smooth Muscle Development and Maintenance of Differentiated Phenotype. Journal of neurogastroenterology and motility Park, C., Lee, M. Y., Park, P. J., Ha, S. E., Berent, R. M., Fuchs, R., Miano, J. M., Becker, L. S., Sanders, K. M., Ro, S. 2015; 21 (4): 589-602

    View details for DOI 10.5056/jnm15063

    View details for PubMedID 26424044

  • Ex Vivo Neurogenesis within Enteric Ganglia Occurs in a PTEN Dependent Manner PLOS ONE Becker, L., Peterson, J., Kulkarni, S., Pasricha, P. J. 2013; 8 (3)

    Abstract

    A population of multipotent stem cells capable of differentiating into neurons and glia has been isolated from adult intestine in humans and rodents. While these cells may provide a pool of stem cells for neurogenesis in the enteric nervous system (ENS), such a function has been difficult to demonstrate in vivo. An extensive study by Joseph et al. involving 108 rats and 51 mice submitted to various insults demonstrated neuronal uptake of thymidine analog BrdU in only 1 rat. Here we introduce a novel approach to study neurogenesis in the ENS using an ex vivo organotypic tissue culturing system. Culturing longitudinal muscle and myenteric plexus tissue, we show that the enteric nervous system has tremendous replicative capacity with the majority of neural crest cells demonstrating EdU uptake by 48 hours. EdU(+) cells express both neuronal and glial markers. Proliferation appears dependent on the PTEN/PI3K/Akt pathway with decreased PTEN mRNA expression and increased PTEN phosphorylation (inactivation) corresponding to increased Akt activity and proliferation. Inhibition of PTEN with bpV(phen) augments proliferation while LY294002, a PI3K inhibitor, blocks it. These data suggest that the ENS is capable of neurogenesis in a PTEN dependent manner.

    View details for DOI 10.1371/journal.pone.0059452

    View details for Web of Science ID 000317562100136

    View details for PubMedID 23527198

  • Divergent fate and origin of neurosphere-like bodies from different layers of the gut AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY Becker, L., Kulkarni, S., Tiwari, G., Micci, M., Pasricha, P. J. 2012; 302 (9): G958-G965

    Abstract

    Enteric neural stem cells (ENSCs) are a population of neural crest-derived multipotent stem cells present in postnatal gut that may play an important role in regeneration of the enteric nervous system. In most studies, these cells have been isolated from the layer of the gut containing the myenteric plexus. However, a recent report demonstrated that neurosphere-like bodies (NLBs) containing ENSCs could be isolated from mucosal biopsy specimens from children, suggesting that ENSCs are present in multiple layers of the gut. The aim of our study was to assess whether NLBs isolated from layers of gut containing either myenteric or submucosal plexus are equivalent. We divided the mouse small intestine into two layers, one containing myenteric plexus and the other submucosal plexus, and assessed for NLB formation. Differences in NLB density, proliferation, apoptosis, neural crest origin, and phenotype were investigated. NLBs isolated from the myenteric plexus layer were present at a higher density and demonstrated greater proliferation, lower apoptosis, and higher expression of nestin, p75, Sox10, and Ret than those from submucosal plexus. Additionally, they contained a higher percentage of neural crest-derived cells (99.4 ▒ 1.5 vs. 0.7 ▒ 1.19% of Wnt1-cre:tdTomato cells; P < 0.0001) and produced more neurons and glial cells than those from submucosal plexus. NLBs from the submucosal plexus layer expressed higher CD34 and produced more smooth muscle-like cells. NLBs from the myenteric plexus layer contain more neural crest-derived ENSCs while those from submucosal plexus appear more heterogeneous, likely containing a population of mesenchymal stem cells.

    View details for DOI 10.1152/ajpgi.00511.2011

    View details for Web of Science ID 000303593900007

    View details for PubMedID 22361728

    View details for PubMedCentralID PMC3362075

  • Stem cell transplantation in neurodegenerative disorders of the gastrointestinal tract: future or fiction? GUT Kulkarni, S., Becker, L., Pasricha, P. J. 2012; 61 (4): 613-621

    Abstract

    Current advances in our understanding of stem and precursor cell biology and in the protocols of stem cell isolation and transplantation have opened up the possibility of transplanting neural stem cells for the treatment of gastrointestinal motility disorders. This review summarises the current status of research in this field, identifies the major gaps in our knowledge and discusses the potential opportunities and hurdles for clinical application.

    View details for DOI 10.1136/gut.2010.235614

    View details for Web of Science ID 000300955000020

    View details for PubMedID 21816959

    View details for PubMedCentralID PMC4119942

  • Gut-derived factors promote neurogenesis of CNS-neural stem cells and nudge their differentiation to an enteric-like neuronal phenotype AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY Kulkarni, S., Zou, B., Hanson, J., Micci, M., Tiwari, G., Becker, L., Kaiser, M., Xie, X. (., Pasricha, P. J. 2011; 301 (4): G644-G655

    Abstract

    Recent studies have explored the potential of central nervous system-derived neural stem cells (CNS-NSC) to repopulate the enteric nervous system. However, the exact phenotypic fate of gut-transplanted CNS-NSC has not been characterized. The aim of this study was to investigate the effect of the gut microenvironment on phenotypic fate of CNS-NSC in vitro. With the use of Transwell culture, differentiation of mouse embryonic CNS-NSC was studied when cocultured without direct contact with mouse intestinal longitudinal muscle-myenteric plexus preparations (LM-MP) compared with control noncocultured cells, in a differentiating medium. Differentiated cells were analyzed by immunocytochemistry and quantitative RT-PCR to assess the expression of specific markers and by whole cell patch-clamp studies for functional characterization of their phenotype. We found that LM-MP cocultured cells had a significant increase in the numbers of cells that were immune reactive against the panneuronal marker ?-tubulin, neurotransmitters neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT), and neuropeptide vasoactive intestinal peptide (VIP) and showed an increase in expression of these genes, compared with control cells. Whole cell patch-clamp analysis showed that coculture with LM-MP decreases cell excitability and reduces voltage-gated Na(+) currents but significantly enhances A-current and late afterhyperpolarization (AHP) and increases the expression of the four AHP-generating Ca(2+)-dependent K(+) channel genes (KCNN), compared with control cells. In a separate experiment, differentiation of LM-MP cocultured CNS-NSC produced a significant increase in the numbers of cells that were immune reactive against the neurotransmitters nNOS, ChAT, and the neuropeptide VIP compared with CNS-NSC differentiated similarly in the presence of neonatal brain tissue. Our results show that the gut microenvironment induces CNS-NSC to produce neurons that share some of the characteristics of classical enteric neurons, further supporting the therapeutic use of these cells for gastrointestinal disorders.

    View details for DOI 10.1152/ajpgi.00123.2011

    View details for Web of Science ID 000295253900006

    View details for PubMedID 21817062

    View details for PubMedCentralID PMC3191554

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