Preservation solution protects isolated hair micrografts by inhibiting apoptosis of hair bulb.

[AIMS] To investigate the effectiveness of histidine-tryptophan-ketoglutarate (HTK) solution compared to Ringer's (RS) solution for preserving isolated hair follicles (HFs), focusing on structural integrity, cell viability, apoptosis prevention, and identifying the mechanisms of cell death during the preservation period.

[MATERIALS AND METHODS] Isolated human HFs were preserved in HTK or RS solution for periods ranging from 2 to 12 h. Morphological changes were assessed using H&E staining and transmission electron microscopy (TEM). Cell viability, proliferation, and apoptosis were evaluated through Ki-67/TUNEL staining, live/dead cell staining, and immunofluorescence. Quantitative real-time PCR and Western blot analysis were conducted to examine apoptosis-related gene expression, and qPCR array analyses were performed to determine the pathways involved in HF apoptosis.

[KEY FINDINGS] HTK solution preserved the structure of HFs more effectively than RS, maintaining collagen organization, preventing intercellular edema, and sustaining cell membrane integrity. HFs preserved in HTK solution exhibited significantly higher viability and proliferation rates, with a reduced rate of apoptosis compared to RS. Gene expression profiling indicated that HTK group inhibited the activation of the TNF signaling pathway and mitochondrial dysfunction, which were associated with apoptosis in RS-preserved HFs.

[SIGNIFICANCE] This study demonstrates that HTK solution is more effective than RS solution for HF preservation, particularly in extended storage settings required for large-scale hair transplantation. By inhibiting apoptosis pathways and preserving cellular integrity, HTK solution may enhance the success and outcomes of hair transplant procedures, providing insights into optimizing micrograft preservation and reducing ischemia-hypoxia injury in isolated HFs.