Impact of Severity of Local Soft-Tissue Trauma on Long-Term Manifestation of Microcirculatory and Microlymphatic Dysfunctions

Abstract

The present study aimed at quantitatively evaluating the impact of severity of local trauma on manifestation of soft-tissue injury-associated microcirculatory and microlymphatic dysfunctions in a chronic model that allowed repeated analyses by intravital fluorescence microscopy. C57BL/6 mice were chronically instrumented with dorsal skinfold chambers and subjected to mild (180 J/m2, n = 6), moderate (270 J/m2, n = 6), or severe trauma (450 J/m2, n = 6; 540 J/m2, n = 6). Nontraumatized animals served as controls (sham; n = 8). Intravital microscopy was performed before and at 5 minutes, 1 hour, 8 hours, 24 hours, 3 days, and 5 days after trauma, and included the analysis of (1) blood and lymph microvessel rupture, (2) hematoma formation and lymph leakage, (3) arteriolar and venular constriction, (4) capillary perfusion failure, (5) arteriolar and venular leukocyte adhesion, and (6) interstitial edema formation. Mild trauma did not induce any changes of microcirculatory and microlymphatic functions. Moderate trauma did not affect lymphatics but provoked arteriolar constriction, capillary perfusion failure, leukocyte-endothelial cell interactions, and minor blood vessel ruptures with hematoma formation. These alterations, however, recovered within the first 24 hours after trauma. Severe trauma also did not affect the lymphatic microvasculature, but resulted in massive hematoma formation, arteriolar constriction, and capillary perfusion failure, which was associated with marked arteriolar and venular leukocyte recruitment and edema formation, and which did not recover to normal over a 5-day observation period. Only severe trauma of > 450 J/m2 provokes irreversible microcirculatory dysfunction in soft tissue, however, without affecting the integrity of lymphatic microvessels. Of interest, trauma-induced microcirculatory alterations are neither dominated solely by microcirculatory dysfunction nor by leukocytic inflammation. Instead, both pathologies develop in parallel, generating a vicious circle, which may be responsible for the compromised healing of severely traumatized soft tissue frequently observed in clinical practice.