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Updated: Jan 23, 2026
Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays
Published on: July 4, 2018
Mast Cell Degranulation and Fibroblast Activation in the Morphine-induced Spinal Mass: Role of Mas-related G
Tony L Yaksh1, Kelly A Eddinger, Shinichi Kokubu
1From the Laboratory of Anesthesiology Research, Department of Anesthesiology (T.L.Y., K.A.E., S.K., R.R., Y.Z., Y.H., F.W., D.Q., S.A.M., J.J.S.) Department of Dermatology (Z.W., A.D.) Division of Trauma, Department of Surgery (B.P.E.), University of California, San Diego, California the Department of Pharmacology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina (K.L., W.K.K) Montreal Clinical Research Institute and the Department of Pharmacology and Physiology, University of Montreal, Quebec, Canada (P.W.S.) Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nurnberg, Erlangen, Germany (P.G.) Implantables Research and Technology, Medtronic, Inc., Restorative Therapies Group, Minneapolis, Minnesota (L.M.P., K.R.H.).
Background:
As the meningeally derived, fibroblast-rich, mass-produced by intrathecal morphine infusion is not produced by all opiates, but reduced by mast cell stabilizers, the authors hypothesized a role for meningeal mast cell/fibroblast activation. Using the guinea pig, the authors asked: (1) Are intrathecal morphine masses blocked by opiate antagonism?; (2) Do opioid agonists not producing mast cell degranulation or fibroblast activation produce masses?; and (3) Do masses covary with Mas-related G protein-coupled receptor signaling thought to mediate mast cell degranulation?
Methods:
In adult male guinea pigs (N = 66), lumbar intrathecal catheters connected to osmotic minipumps (14 days; 0.5 µl/h) were placed to deliver saline or equianalgesic concentrations of morphine sulfate (33 nmol/h), 2',6'-dimethyl tyrosine-(Tyr-D-Arg-Phe-Lys-NH2) (abbreviated as DMT-DALDA; 10 pmol/h; μ agonist) or PZM21 (27 nmol/h; biased μ agonist). A second pump delivered subcutaneous naltrexone (25 µg/h) in some animals. After 14 to 16 days, animals were anesthetized and perfusion-fixed. Drug effects on degranulation of human cultured mast cells, mouse embryonic fibroblast activation/migration/collagen formation, and Mas-related G protein-coupled receptor activation (PRESTO-Tango assays) were determined.
Results:
Intrathecal infusion of morphine, DMT-DALDA or PZM21, but not saline, comparably increased thermal thresholds for 7 days. Spinal masses proximal to catheter tip, composed of fibroblast/collagen type I (median: interquartile range, 0 to 4 scale), were produced by morphine (2.3: 2.0 to 3.5) and morphine plus naltrexone (2.5: 1.4 to 3.1), but not vehicle (1.2: 1.1 to 1.5), DMT-DALDA (1.0: 0.6 to 1.3), or PZM21 (0.5: 0.4 to 0.8). Morphine in a naloxone-insensitive fashion, but not PZM21 or DMT-DALDA, resulted in mast cell degranulation and fibroblast proliferation/collagen formation. Morphine-induced fibroblast proliferation, as mast cell degranulation, is blocked by cromolyn. Mas-related G protein-coupled receptor activation was produced by morphine and TAN67 (∂-opioid agonist), but not by PZM21, TRV130 (mu biased ligand), or DMT-DALDA.
Conclusions:
Opiates that activate Mas-related G protein-coupled receptor will degranulate mast cells, activate fibroblasts, and result in intrathecal mass formation. Results suggest a mechanistically rational path forward to safer intrathecal opioid therapeutics.
Insights
Intrathecal morphine causes spinal masses by activating mast cells and fibroblasts via Mas-related G protein-coupled receptor signaling. This pathway is key to developing safer intrathecal opioid therapies.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- Intrathecal morphine infusion can cause meningeal masses, a reaction not seen with all opioids.
- Mast cell stabilizers reduce these masses, suggesting a role for mast cell and fibroblast activation.
Purpose of the Study:
- To investigate the role of meningeal mast cell/fibroblast activation in intrathecal morphine-induced mass formation.
- To determine if opioid antagonism blocks mass formation.
- To assess if opioid agonists that do not induce mast cell degranulation or fibroblast activation produce masses.
Main Methods:
- Adult male guinea pigs received intrathecal infusions of morphine, DMT-DALDA, PZM21, or saline for 14 days.
- Effects on thermal thresholds, spinal mass formation, mast cell degranulation, fibroblast activation, and Mas-related G protein-coupled receptor signaling were assessed.
Main Results:
- Morphine, but not DMT-DALDA or PZM21, induced spinal masses, mast cell degranulation, and fibroblast proliferation.
- Morphine-induced effects were naloxone-insensitive and blocked by cromolyn.
- Mas-related G protein-coupled receptor activation correlated with morphine and TAN67, but not PZM21 or DMT-DALDA.
Conclusions:
- Opioids activating Mas-related G protein-coupled receptors can degranulate mast cells, activate fibroblasts, and lead to intrathecal mass formation.
- Findings provide a mechanistic basis for developing safer intrathecal opioid therapeutics.
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