101: Cortical Signatures of Chronic Pain after Rotator Cuff Injury in Mice

Topic: Basic Science
Subtopic: Pain category (ICD-11), Chronic primary musculoskeletal pain, , , , , , Assessment and Measurement of Pain/Nociception, Artificial Intelligence/Machine Learning, Animal imaging (includes Ca2+ imaging, fluorescence microscopy), , ,

Background and Aims: Rotator cuff injury (RCI) is a leading cause of chronic musculoskeletal pain, yet current therapies
remain limited. Surgical repair provides modest benefit, and pharmacologic options such as NSAIDs and
opioids rarely offer durable relief. Because pain is ultimately encoded in the brain, we hypothesized that
persistent pain after RCI reflects altered cortical processing. We focused on the anterior cingulate cortex
(ACC), a region critical for the affective dimension of pain, and sought to link RCI-induced behavioral deficits
with ACC activity.

Methods: Adult male mice (N = 5) underwent supraspinatus and infraspinatus tendon transection with
denervation (TT+DN) to model massive RCI. Pain-related behaviors and gait were recorded at baseline and two
weeks post-injury using the BlackBox One system, which integrates transmitted light imaging and frustrated
total internal reflectance to capture paw pose and weightbearing. Automated gait metrics were extracted with
our AI-enabled Paw Analysis Workflow. Simultaneously, ACC calcium activity was monitored with an Inscopix
miniscope. GCaMP6f was expressed under the CamK2a promoter, and a GRIN lens enabled chronic imaging.
Behavioral and neural data streams were synchronized for analysis.

Results: RCI produced robust behavioral and neural alterations. Injured mice demonstrated a significant
reduction in forelimb weightbearing (baseline ratio: 0.94 ± 0.10; RCI: 0.63 ± 0.08; p ≤ 0.04), consistent with
impaired function and pain-related guarding. ACC imaging revealed fewer active neurons after injury
(baseline: 55 ± 15; RCI: 42 ± 13; p ≤ 0.04), although average firing rates of identified neurons remained
unchanged (baseline: 4.0 ± 0.2 events/min; RCI: 3.8 ± 0.3 events/min; p = 0.57). These findings suggest
reduced ensemble recruitment in the ACC without changes in mean neuronal activity.

Conclusions: Our integrated platform demonstrates sensitive detection of behavioral and cortical correlates of
pain after RCI. Traditional approaches for assessing forelimb pain are laborious and limited, whereas deep
behavioral phenotyping provides rapid, unbiased quantification of functional impairment. Linking these
measures to ACC dynamics offers mechanistic insight into pain chronification. Ongoing work will extend
analyses to later timepoints, female mice, and pharmacologic interventions to determine whether analgesics
restore both behavior and ACC function. These studies establish a framework for developing brain-based
therapeutic strategies for RCI pain and other orthopedic injuries.

References: Milan N, Wague A, Sang L, Youn A, …, Basbaum AI, Davies MR, Kim HT, Feeley BT, Weinrich JAP, Liu X. (2026) Blood flow restriction therapy stimulates intercellular mitochondria transfer and improves muscle regeneration and shoulder function in a murine rotator cuff injury model. American Journal of Sports Medicine. In press.

Layne JE, Snapper DM, Czachor ME, Lam C, …, Motzkin JC, Basbaum AI, Weinrich JAP, Bahney CS. (2025) Deep behavioral phenotyping tracks functional recovery following tibia fracture in mice. Frontiers in Physiology. PMID: 40462932

Presenting Author: Jarret Weinrich
Submitting Author: Jarret Weinrich

Senior Author: Jarret Weinrich

IASP 2026 Global Year theme of Neuropathic Pain: Yes

• Karnika Bhardwaj: MS - UCSF
• Sonali Feeley: NA - UCLA
• Alex Youn: BS - UCSF
• Madison Jewell: BS - UCSF
• Aboubacar Wague: BS - UCSF
• Xuhui Liu: MD - UCSF
• Brian Feeley: MD, PhD - UCSF
• Allan Basbaum: PhD - UCSF
• Jarret Weinrich: PhD - UCSF