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Thomas S. Monahan

Thomas S. Monahan M.D.

Academic Title: Assistant Professor
Primary Appointment: Surgery
Location: BIOPARK 1 N4E40
Phone: 410-328-5840
Fax: 410-328-0717

Personal History:

I am a practicing vascular surgeon with an interest in clinically relevant vascular biology. I graduated from the University of Massachusetts Medical School in 2001. While pursuing my medical degree, I performed research in cardiovascular physiology. Upon completion of my degree, I trained in general surgery at the Beth Israel Deaconess Medical Center in Boston, Massachusetts. I was able to interrupt for two years for a post-doctoral fellowship. It was during this time that I began some of the work on which my lab now focuses. After completion of general surgery residency I matriculated to the University of California, San Francisco for a vascular surgery fellowship. During this fellowship I was able to hone my research questions and begin the framework for future grant applications. I came to the University of Maryland in 2010. I am presently funded by grants through the Veterans Administration and the Vascular Cures Foundation. I have close collaborations with several members of the Center for Vascular and Inflammatory Diseases faculty. Being both a practicing surgeon and a scientist allows me to ask clinically relevant research questions and use technically difficult animal models. The University of Maryland fosters an environment that nurtures the “bench-to-bedside-(to-bench)” concept and supports translational research.

Research Interests:

My research interests are focused on the treatment of peripheral arterial disease (PAD). To this end, one of our long-term goals is to identify differential mechanisms of regulation of vascular smooth muscle cell and endothelial cell proliferation. Proliferation of these two different cell types is a key event in response to arterial injury, such as is observed after angioplasty, stenting, or bypass. Intimal hyperplasia, the vascular response to iatrogenic arterial injury, is characterized by increased vascular smooth muscle cell proliferation. Present strategies to prevent the formation of intimal hyperplasia include the use on antiproliferative agents. However, these agents also inhibit endothelial cell proliferation mandating that the patient receive dual antiplatelet therapy indefinately. An ideal therapeutic agent would exert a differential effect on proliferation of these two cell types. Previously, we have identified a protein kinase C substrate, the myristolated alanine-rich C kinase substrate (MARCKS), that when knocked down in vitro inhibits vascular smooth muscle cell proliferation with minimal effects on endothelial cell proliferation. Our initial experience with MARCKS knockdown suggests that this protein might be important for differential regulation of vascular smooth muscle cell and endothelial cell proliferation. Our present efforts seek to identify the mechanism by which MARCKS knockdown differentially affects vascular smooth muscle cell and endothelial cell proliferation and to determine if the differential effect persists in vivo.

Regardless of the target for therapy, the agent needs to reach the target tissue. Proliferation is a key cellular function in all cell types and consequently administering a potent antiproliferative agent systemically would doubtlessly cause many undesirable side effects. We have been using siRNA to achieve knockdown of MARCKS in vivo in rodent models of intimal hyperplasia. We elected to pursue siRNA-mediated knockdown for two reasons. First, it has a relatively well-defined half-life and duration of effect; the siRNA is divided between each of the daughter cells after each cell division. Second, virtually any sequenced gene or combination of genes can be silenced using this approach. We have developed protocols for in vivo transfection with siRNA in a mouse model. We are anticipating working a method of delivering siRNA in a large animal model using both catheter-based and open surgical techniques.

Finally, there are patients whom do not have a patent distal artery to which to bypass and consequently, these patients are declared non-reconstructable. Several previous trials have evaluated treatment of these limbs with stem cells to induce vasculogenesis. However, the logistics involved with these trials made this approach impractical. We are exploring alternate methods of attracting the stem cell populations that are important in both angiogenesis and arteriogenesis to an ischemic limb. We are presently using a mouse model of hind limb ischemia to test our hypothesis.

Our laboratory is located in the Center for Vascular and Inflammatory Diseases. This location facilitates collaboration with other researchers interested in different aspects of Vascular Biology. We also have access to the many core facilities ad both the CVID and the School of Medicine. This setting is an optimal environment to perform this type of translational research.


Yu D, Makkar G, Dong T, Strickland DK, Sarkar R, and Monahan TS. MARCKS Signaling Differentially Regulates Vascular Smooth Muscle and Endothelial Cell Proliferation through a KIS-, p27kip1-Dependent Mechanism. PLoS One. 2015;10(11):e0141397. PMID: 26528715

Yu D, Makkar G, Strickland DK, Blanpied T, Stumpo DJ, Blackshear PJ, Sarkar R, and Monahan TS. Myristolated Alanine-Rich Protein Kinase C Substrate (MARCKS) Regulates Small GTPase Rac1 and Cdc42 Activity and is a Critical Mediator of Vascular Smooth Muscle Cell Migration in Intima Hyperplasia Formation. Journal of the American Heart Association. 2015;4(10). Pii: e002255. PMID: 26450120.

Chander R, and Monahan TS. Ultrasound evaluation of great saphenous vein insufficiency.  Journal of Vascular Diagnostics 2015;3:25-31.

Monahan TS, Belek K, and Sarkar R. Results of radiofrequency ablation of the lesser saphenous vein in the supine position. Journal of Vascular and Endovascular Surgery 2012;46(1):40-4. PMID: 22156157.

Monahan TS. Nonrecurrent inferior laryngeal nerve. Vascular and Endovascular Surgery 2010;45(1):90-1. PMID: 21193467.

Andersen ND, Chopra A, Monahan TS, Malek JY, Jain M, Pradhan L, Ferran C, and LoGerfo FW. Endothelial cells are susceptible to rapid siRNA transfection and gene silencing ex vivo. Journal of Vascular Surgery 2010;52(6):1608-15. PMID: 20801607.

Monahan TS, Chuter TAM, Reilly LM, Rapp JH, and Hiramoto JS. Long-Term Follow-Up of Neck Expansion after Endovascular Aortic Aneurysm Repair. Journal of Vascular Surgery. 2010;52(2):303-7. PMID: 20670774.

Shrikhande GV, Scali ST, Da Silva CG, Damrauer SM, Csizmadia E, Putheti P, Matthey M, Arjoon R, Patel R, Siracuse JJ, Maccariello ER, Andersen ND, Monahan TS, Kocher O, Usheva A, Veves A, Kaczmarek A, and Christiane Ferran. O-Glycosylation Regulates Ubiquitination and Degradation of the Anti-inflammatory Protein A20 to Accelerate Atherosclerosis in Diabetic ApoE-null Mice. PLoS One 2010;5(12):e14240. PMID: 21151899.

Monahan TS, and Owens CD. Risk factors for vein graft failure. Seminars in Vascular Surgery. 2009;22(4):216-26. PMID: 20006801.

Monahan TS, and Schneider DB. Fenestrated and branched stent grafts for repair of complex aortic aneurysms. Seminars in Vascular Surgery 2009;22(3):132-9. PMID: 19765522.

Monahan TS, Andersen ND, Martin MC, Malek JY, Shrikhande GV, Pradhan L, Ferran C, and LoGerfo FW. MARCKS silencing differentially affects human vascular smooth muscle and endothelial cell phenotypes to inhibit neointimal hyperplasia in saphenous vein. FASEB Journal. 2009 Feb;23(2):557-64.  PMID 18940893.

McIntyre TP, Monahan TS, Villegas L, Doyle J, and Jones D. Telemedicine enhances effective communication and enriches medical education. Surgical Laparoscopy Endoscopy and Percutaneous Techniques.  2008 Feb;8(1):45-48. PMID 18287982

Shrikhande GV, Hamdan AD, Monahan TS, Pomposelli FB, Scovell SS, Logerfo FW, and Schermerhorn ML. Low ejection fraction predicts shortened survival in patients undergoing infrainguinal arterial reconstruction. World Journal of Surgery. 2007 Dec;31(12):2422-6. PMID 17952496.

Monahan TS, Andersen ND, Panossian H, Kalish JA, Contreras MA, Phaneuf MD, Shrikhande GV, Ferran CJ, and LoGerfo FW. A novel function for cadherin 11/OB-cadherin in vascular smooth muscle cells: modulation of cell migration and proliferation. Journal of Vascular Surgery. 2007;45(3):581-9. PMID 17321345.

Andersen ND, Monahan TS, Jain M, Daniel S, Caron LD, Pradhan L, Ferran C, and LoGerfo FW. Gene silencing in human vascular cells using small interfering RNAs. Journal of the American College of Surgeons 2007;204(3):399-408. PMID 17324773.

Monahan TS, Phaneuf MD, Contreras MA, Andersen ND, Popescu-Vladimir A, Bide MJ, Dempsey DJ, Mitchell RN, LoGerfo FW, and Hamdan AD. In vivo testing of an infection-resistant annuloplasty ring. Journal of Surgical Research. 2006 Jan;130(1):140-5. PMID 16154148.

Phaneuf MD, Bide M, Hannel S, Platek M, Monahan TS, Contreras MA, Phaneuf T, LoGerfo FW. Development of an infection-resistant, bioactive wound dressing surface. Journal of Biomedical Materials Research 2005;74A(4):666-676. PMID 16028237.

Monahan TS, Shrikhande GV, Pomposelli FB, Skillman JJ, Campbell DR, Scovell SD, LoGerfo FW, and Hamdan AD. Preoperative cardiac evaluation does not improve or predict perioperative or late survival in asymptomatic diabetic patients undergoing elective lower extremity arterial reconstruction. Journal of Vascular Surgery 2004;41:38-45. PMID 15696041.

Lancey R, and Monahan TS. Correlation of clinical characteristics and outcomes with an injury grading system in blunt cardiac trauma. Journal of Trauma-Injury Infection & Critical Care. 54(3):509-15, 2003. PMID 12634531.

Monahan TS, Sawmiller DR, Fenton RA, Dobson JG. Adenosine A2a receptor activation increases contractility in isolated perfused hearts. American Journal of Physiology. 2000;279: H1472-H1481. PMID 11009431

Text Book Chapters:

Monahan TS. Acute atraumatic lower extremity ischemia. In Vascular emergencies – expert management for the emergency physician. Robert Rogers editor. Cambridge University Press. Publication 2013.

Monahan TS. Microvascular changes in diabetes. In Diabetes and peripheral vascular disease: diagnosis and management. Gautam Shrikhande editor. Springer Science. Publication 2013.

Shrikhande GV, Monahan TS, and Pomposelli FB. Vascular Surgery.  In Pocket Surgery. Goldfarb M editor. Lippincott Williams & Wilkins. Publication 2011.

Monahan TS, LoGerfo FW. Endothelialization of Prosthetic Vascular Grafts. In Endothelial Biomedicine.  William Aird editor. Cambridge University Press. Publication 2007.

Monahan TS, LoGerfo FW. The Healing of Ulceration, Infection, and Minor Amputation Following Revascularization in Patients with Diabetes. Trends in Vascular Surgery William H Pearce and James ST Yao, eds. Publication 2004.