The Effects of Tissue Preservation Process on the Histology of Human Cerebrovascular Tissue: A Methodology Analysis

Introduction: More precise characterization of arteriovenous malformation rupture risk may be possible through the histologic analysis of intraoperative pathology. Tissue preservation techniques, chiefly cryopreservation, have been demonstrated to alter vascular histology via bulk fluid transport resulting in collagen fiber rearrangement and internal elastic laminae (IEL) microfractures, however this has not yet been evaluated in cerebrovascular tissue. We sought to elucidate the effect of different preservation strategies on the thickness and continuity of the IEL of human cerebrovascular tissue.

Methods: Fresh cerebrovascular tissue was obtained through our institutional cadaver donation program. Donors with prior craniotomy or cerebrovascular disease history were excluded and all dissections were completed within 14 days of patient expiration. Dissected vessels were sectioned into four specimens and randomized to 10% formalin (control), distilled water (dH2O), Dimethyl sulfoxide (DMSO), or -80 degree C DMSO. Specimens treated with dH2O and DMSO were placed into 10% formalin after 24-hours, while -80 degree C DMSO samples were slowly thawed after 14 days and placed in 10% formalin. Specimens were processed into paraffin-embedded sections and treated with Movat staining. Elastin layers were microscopically measured by two blinded evaluators and discontinuities in IEL were tallied. Measurements were compared across treatments using Two-way ANOVA analysis (p < 0.05).

Results: Fifty-six cerebrovascular samples were obtained from the bilateral anterior and posterior circulation and randomized. Average ILE measurements ranged from 3.1μm-10.9 μm. Inter-rater reliability was favorable (MBE= 1.24 µm; 95%CI). We found no significant difference in IEL thickness across tissue preservation methods (p= 0.38). However, there were significant differences in frequency of IEL fractures across tissue treatments (p= 0.003).

Conclusion : This data demonstrates that conventional tissue preservation methods maintain objective IEL thickness in human cerebrovascular tissue. However, with more frequent IEL fractures in the cryopreservation group, the biomechanical properties may be altered.