Acupuncture points or acupoints are fundamental to the practice of acupuncture, yet their scientific basis remains unclear. According to traditional explanations of acupuncture, acupoints can become tender or more sensitive to pressure when there is an underlying disease of the body. Findings from recent basic animal studies support this traditional theory. For example, compared to healthy control animals, models of colitis have shown increased skin temperature, blood flow, and pain sensitivity at specific body regions that correspond to the location of acupoints that are commonly used in acupuncture treatment for colitis. However, little is known about whether these findings apply to humans.

Acupuncture is broadly understood as a technique in which practitioners stimulate specific points on the body - most often by inserting thin needles through the skin. Accordingly, acupuncture is theorized to "work" or provide therapeutic benefits through stimulation of specific points, collectively referred to as acupoints. However, to date, there is no clear scientific characterization of acupoints based on an objective, biomedical understanding of the body, which limits our understanding of how acupuncture works in a fundamental way.

Recent findings from basic animal studies suggest that cutaneous neurogenic inflammation may be a potential physiological correlate of acupoints, in the context of visceral diseases. Neurogenic inflammation refers to the role of sensory nerves in promoting inflammation and is mediated by neuropeptides released from the peripheral afferent terminals. Through interactions with nearby immune cells and endothelial cells, these neuropeptides promote increased levels of inflammatory mediators and induce vasodilation and plasma extravasation at the site of their release. In basic animal studies, Evans blue (EB) dye is typically used as a marker for microvascular leakage to assess the location and extent of neurogenic inflammation.

Using EB dye, several studies have provided compelling evidence that experimentally induced visceral diseases (e.g., rodent models of colitis, cystitis, gastritis) cause cutaneous neurogenic inflammation. In many of these studies, neurogenic inflammation was shown to manifest as discrete spots on certain body regions, corresponding to the locations of specific acupoints.

To date, little to no studies have been done to validate the aforementioned preclinical findings in human subjects. To bridge this gap, in this study, we will conduct clinical and translational (C/T) research in human subjects, using inflammatory bowel disease (IBD) as the disease model. We will compare measures of cutaneous sensitization in IBD patients and healthy control participants. Key features of neurogenic inflammation include increased blood flow, increased temperature, and pain sensitivity, so we will assess cutaneous blood perfusion, temperature, and pressure pain threshold (PPT) as proxy measures, using laser speckle contrast imaging (LSCI), infrared thermography, and pressure algometry, respectively.

Inclusion Criteria (Adults with IBD):

• adults (age 18 years or older)
• clinical diagnosis of ulcerative colitis or Crohn's disease

Exclusion Criteria (Adults with IBD):

• any history of serious musculoskeletal or soft tissue injury of the lower and/or upper extremities
• presence of scarring or tattoo on the lower and/or upper extremities
• presence of serious cardiac diseases, severe dermatological conditions, peripheral neuropathy, infectious disease, psychological illnesses, or other serious co-morbidities (e.g., cancer)
• prior history of colostomy or ileostomy
• pregnancy

Inclusion Criteria (Healthy control participants):

- adults (age 18 years or older) in good health conditions

Exclusion Criteria (Healthy control participants):

• history of chronic inflammatory diseases, such as IBD
• severe digestive and/or intestinal conditions, such as irritable bowel syndrome (IBS)
• any history of serious musculoskeletal or soft tissue injury of the lower and/or upper extremities
• presence of scarring or tattoo on the lower and/or upper extremities
• presence of serious cardiac diseases, severe dermatological conditions, peripheral neuropathy, infectious disease, psychological illnesses, or other serious co-morbidities (e.g., cancer)
• pregnancy

Adults with inflammatory bowel disease (IBD) and healthy control participants will be enrolled into the study from the Greater Boston area.