Proposal of a Safe Transport Protocol and Its Utility of Antigen-Preserving Tissue for Formalin-Fixed Porcine Renal Samples.

Background: Formalin is widely used as a standard fixative in histopathological analysis; however, its high toxicity and strict regulatory restrictions create challenges for the safe transport and external evaluation of specimens. In translational research utilizing large animal models, establishing a reliable transport protocol that preserves both tissue structure and antigenicity remains essential. Objective: This study aimed to develop and validate a protocol for the safe transport of formalin-fixed renal specimens while maintaining their histopathological and immunohistochemical integrity. Methods: Using a porcine model, renal specimens were fixed in formalin and subsequently substituted with physiological saline or 70% ethanol before transport. These were compared with specimens transported in formalin without substitution. Following transportation, hematoxylin and eosin (HE) staining and immunohistochemistry (Nephrin, E-cadherin, CD3) were performed to assess tissue integrity, antigenicity, and structural preservation. Additionally, sample degradation, antigen loss, and potential leakage were evaluated. Results: Specimens substituted with saline or ethanol retained cellular structure and antigenicity comparable to those transported in formalin, with no significant deterioration in histological or immunohistochemical quality. Furthermore, no leakage or sample damage was observed during transport, demonstrating the feasibility of this replacement protocol for routine pathological assessments. Conclusions: These findings suggest that formalin substitution with saline or ethanol provides a viable alternative for specimen transport, ensuring both biosafety and analytical integrity. This protocol may enhance specimen handling in preclinical research, regulatory compliance, and international collaboration in pathology and regenerative medicine.