Tibial cortex transverse transport surgery improves wound healing in patients with severe type 2 DFUs by activating a systemic immune response: a cross-sectional study
Authors: Yu Lin , Zhang Dingwei , Yin Yuan , Li Xiaoya , Bai Chunxia , Zhou Qian , Liu Xinyi , Tian Xiaojun , Xu Daofei , Yu Xianjun , Zhao Sichun , Hu Rong , Guo Fudie , Yang Yuwei , Ren Yan , Chen Gang , Zeng Jiawei , Feng Jiafu 
Published: July 2024

Background:
Tibial cortex transverse transport (TTT) surgery has become an ideal treatment for patients with type 2 severe diabetic foot ulcerations (DFUs), while conventional treatments are ineffective. Based on our clinical practice experience, the protective immune response from TTT surgery may play a role against infections to promote wound healing in patients with DFUs. Therefore, this research aimed to systematically study the specific clinical efficacy and the mechanism of TTT surgery.

Materials and methods:
Between June 2022 and September 2023, 68 patients with type 2 severe DFUs were enrolled and therapized by TTT surgery in this cross-sectional and experimental study. Major clinical outcomes, including limb salvage rate and antibiotics usage rate, were investigated. Ten clinical characteristics and laboratory features of glucose metabolism and kidney function were statistically analyzed. Blood samples from six key time points of TTT surgery were collected for label-free proteomics and clinical immune biomarker analysis. Besides, tissue samples from three key time points were used for spatially resolved metabolomics and transcriptomics analysis, as well as applied to validate the key TTT-regulated molecules by reverse-transcription quantitative PCR.

Results:
Notably, 64.7% of patients did not use antibiotics during the entire TTT surgery. TTT surgery can achieve a high limb salvage rate of 92.6% in patients with unilateral or bilateral DFUs. Pathway analysis of a total of 252 differentially expressed proteins from the proteomic revealed that the immune response induced by TTT surgery at different stages was first comprehensively verified through multiomics combined with immune biomarker analysis. The function of upward transport was activating the systemic immune response, and wound healing occurs with downward transport. The spatial metabolic characteristics of skin tissue from patients with DFUs indicated downregulated levels of stearoylcarnitine and the glycerophospholipid metabolism pathway in skin tissue from patients with severe DFUs. Finally, the expressions of PRNP (prion protein) to activate the immune response, PLCB3 (phospholipase C beta 3) and VE-cadherin play roles in neovascularization, and PPDPF (pancreatic progenitor cell differentiation and proliferation factor), LAMC2 (laminin subunit gamma 2), and SPRR2G (small proline-rich protein 2G) to facilitate the developmental process mainly keratinocyte differentiation were statistically significant in skin tissues through transcriptomic and reverse-transcription quantitative PCR analysis.

Conclusion:
TTT surgery demonstrates favorable outcomes for patients with severe type 2 DFUs by activating a systemic immune response, contributing to anti-infection, ulcer recurrence, and the limb salvage for unilateral or bilateral DFUs. The specific clinical immune responses, candidate proteins, genes, and metabolic characteristics provide directions for in-depth mechanistic research on TTT surgery. Further research and public awareness are needed to optimize TTT surgery in patients with severe type 2 DFUs.