Anxious Minds, Broken Shoulders: Brain Circuit Revealed Linking Anxiety to Failed Tendon Healing

Rotator cuff injuries are the most common disorder of the upper extremity and a leading cause of shoulder pain and disability worldwide. Surgeons have long noticed a puzzling pattern: patients who report high levels of anxiety before rotator cuff repair surgery tend to fare worse afterward, with poorer pain relief, weaker function, and lower quality of life, regardless of tear size or surgical technique. Until now, this clinical observation was widely dismissed as a secondary consequence of pain and disability rather than a biological driver of the injury itself. A new study published in Advanced Science turns that assumption on its head, presenting the first patient-level and mechanistic evidence that anxiety and impaired tendon–bone healing are physically wired together through a defined brain–body circuit.

The research team, led by investigators at Central South University’s Xiangya Hospital, began with the human brain. Using resting-state functional MRI in 43 patients with rotator cuff injury and 30 healthy controls, they measured spontaneous neural activity across the whole brain via the amplitude of low-frequency fluctuations. While classic pain and emotion regions — the dorsal anterior cingulate cortex, the amygdala, and the posterior insula — all showed altered activity in patients, only one region tracked symptom severity at the individual level: the hypothalamus. Activity in both the left and right hypothalamus was significantly suppressed in patients, and the degree of suppression correlated inversely with anxiety scores on the Hospital Anxiety and Depression Scale. Notably, anxiety, not depression, was the dominant psychological phenotype in the patient cohort, with 27.9 percent of patients showing moderate to severe anxiety compared with 10 percent of controls.

To pinpoint which hypothalamic compartments were responsible, the team applied a high-resolution human hypothalamic atlas that divides the structure into seven functional subnuclei. The suppression was not diffuse. It concentrated in the paraventricular nucleus, the medial preoptic nucleus, and the superior compartment of the supraoptic nucleus — with the paraventricular nucleus, or PVN, standing out as the most affected. The PVN is a tiny but strategically vital hub: it contains oxytocin-producing neurons that participate in anxiety regulation and send long-range projections to autonomic centers controlling sympathetic nervous system output throughout the body.

The next step was molecular. By integrating the brain-imaging differences with gene expression data from the Allen Human Brain Atlas, and correcting for spatial autocorrelation using BrainSMASH permutation testing, the researchers performed a genome-wide pathway screen. Among all KEGG pathways tested, the oxytocin signaling pathway emerged as one of the most significantly enriched hits spatially concordant with the hypothalamic suppression. This was not a hypothesis the authors brought to the data — it emerged from an unbiased screen, providing a molecular entry point for the circuit-level investigations that followed.

To establish causality, the team turned to mice. Rotator cuff injury in mice produced a time-dependent anxiety-like phenotype that peaked at four weeks post-injury, visible in both the open field test and the elevated plus maze. Strikingly, this behavioral trajectory closely mirrored the dynamics of norepinephrine — the primary sympathetic neurotransmitter — at the tendon–bone interface, which also peaked at four weeks before declining. Central affective disturbance and peripheral sympathetic hyperactivation appeared to be temporally coupled responses to the same injury, not independent sequelae. Whole-brain activity mapping in TRAP2 mice, combined with tissue clearing and light-sheet microscopy, then confirmed that the PVN showed the most significant reduction in activated neurons among all hypothalamic subnuclei, concentrated precisely in the medial and posterior PVN — the same subregions implicated in the human imaging data.

The question became which neuronal population within the PVN could simultaneously regulate emotion and peripheral autonomic tone. Reanalysis of publicly available single-neuron connectome data revealed that PVN clusters concentrated in the medial and posterior subregions contain both long-range spinal-projecting neurons and local intra-hypothalamic projection neurons. Among the 153 spinal-projecting PVN neurons identified, 46.4 percent expressed oxytocin, making oxytocinergic neurons the predominant genotype capable of engaging spinal autonomic circuitry. The team then injected retrograde pseudorabies virus into the subchondral bone of the supraspinatus enthesis — the critical attachment point where tendon meets bone — and found robust labeling in the medial and posterior PVN, with essentially no labeling in the nearby supraoptic nucleus. Spatial transcriptomics and immunofluorescence confirmed that roughly half of all retrogradely labeled PVN neurons were oxytocin-positive, far exceeding the proportions of vasopressinergic or corticotropin-releasing neurons.

With the anatomical map in hand, the researchers manipulated the circuit directly. Using chemogenetic DREADDs targeted to PVN oxytocinergic neurons with nearly 90 percent specificity, they could silence or activate this population at will. Silencing induced robust anxiety-like behavior in injured mice and devastated tendon–bone healing: biomechanical testing revealed reduced stiffness, failure load, and ultimate tensile strength; histology showed disorganized fibrocartilage and reduced proteoglycan deposition; micro-CT revealed deteriorated bone microarchitecture at the humeral greater tuberosity; and molecular markers of cartilage and bone formation — Aggrecan, Sox9, Ocn, and Runx2 — were all suppressed. Activation produced the opposite effects, preserving or even enhancing healing quality. Critically, these manipulations altered norepinephrine levels locally at the tendon–bone interface without changing circulating serum norepinephrine, indicating site-specific autonomic control rather than a generalized shift in systemic sympathetic tone.

The efferent pathway was traced to a classical sympathetic relay: the PVN projects to sympathetic preganglionic neurons in the intermediolateral column of the spinal cord, which in turn drive the superior cervical ganglion. In vivo microelectrode recordings from the superior cervical ganglion showed that silencing PVN oxytocinergic neurons dramatically increased sympathetic firing — elevated spike density, burst rate, and high-frequency local field potential power — while activation suppressed it. When the researchers selectively ablated superior cervical ganglion neurons with diphtheria toxin, the healing deficits caused by PVN silencing were substantially rescued, and ganglion ablation alone improved bone microarchitecture and biomechanical performance in injured mice while lowering local norepinephrine. The peripheral relay was thus established as functionally necessary for translating central oxytocinergic dysregulation into impaired tissue repair.

The model that emerges is a complete brain–body axis: rotator cuff injury suppresses PVN oxytocinergic neuron activity, which couples to anxiety-like affective state and, through disinhibition of the spinal sympathetic relay, drives elevated local norepinephrine at the tendon–bone interface that compromises structural and biomechanical repair. Anxiety, in this framework, is not a secondary psychological burden but a mechanistically coupled component of the healing process itself. The authors caution that the clinical neuroimaging data are cross-sectional and cannot establish whether hypothalamic suppression precedes or follows anxiety onset, and that all mouse experiments were conducted in adult males, leaving generalizability to females an open question. The oxytocin-promoter-driven manipulation also cannot distinguish parvocellular spinal-projecting neurons from magnocellular neuroendocrine cells, and vasopressin and corticotropin-releasing neurons within the PVN may contribute in parallel.

Even with those caveats, the clinical implications are provocative. Interventions that engage hypothalamic oxytocinergic signaling — whether pharmacological, behavioral, or through non-invasive neurostimulation — might concurrently alleviate anxiety and improve healing outcomes after rotator cuff repair. The study suggests a shift away from purely tissue-focused orthopedic treatment toward integrated strategies that address the nervous system as an active participant in musculoskeletal repair. For the millions of patients facing shoulder surgery each year, the mind may matter far more than previously believed — not as a matter of willpower or positive thinking, but as a matter of neuroanatomy, with oxytocinergic neurons in the hypothalamus standing guard over both emotional state and the structural integrity of the healing tendon.

Subject of Research: A hypothalamic oxytocinergic–sympathetic neural axis linking anxiety to impaired tendon–bone healing after rotator cuff injury

Article Title: A Hypothalamic Oxytocinergic–Sympathetic Axis Couples Anxiety Dysregulation With Impaired Tendon–Bone Repair

Article References: Wan, L., Huang, T., Zeng, L., Du, R., Zhang, H., Liu, S., Zhang, T., Hu, J., & Lu, H. (2026). A Hypothalamic Oxytocinergic–Sympathetic Axis Couples Anxiety Dysregulation With Impaired Tendon–Bone Repair. Advanced Science, Article e78190. https://doi.org/10.1002/advs.78190

Image Credits: AI Generated

DOI: 10.1002/advs.78190

Keywords: rotator cuff injury, anxiety, hypothalamus, paraventricular nucleus, oxytocin, sympathetic nervous system, tendon–bone healing, norepinephrine, chemogenetics, superior cervical ganglion, resting-state fMRI, psychological comorbidity