Microvascular integrity plays an important role for graft survival after experimental skin transplantation

Skin graft surgery and its impact on platelet counts in Iranian burn patients: a non-randomized clinical trial

BACKGROUND

Platelets are critical in maintaining homeostasis and immune response in burn patients. The concentration of platelets decreases in burn patients, and any intervention that increases serum platelet concentration can prevent serious consequences and patient death. The present study aimed to assess the impact of skin graft surgery on burn patients' platelet counts.

METHODS

In this non-randomized clinical trial, 200 burn patients were investigated. The patients were recruited from the surgical ward of Imam Khomeini Teaching Hospital during the first six months of 2021. After completing the checklist, patients underwent skin graft surgery. Blood was taken from the patients during surgery in the operating room and on the third and fifth day after the surgery to check platelets. Data analysis was conducted using SPSS software (ver. 22.0).

RESULTS

Most patients (63.5%) were male, and 73 (36.5%) were female. One hundred eighty-one patients (90.5%) had deep burns, and 19 (9.5%) had superficial burns. The mean burns percentage in the patients was 19.3 ± 15.4%, the lowest was 2%, and the highest was 90%. The most common burns were caused by flame (42%) and boiling water (30.5%). The patients' outcomes revealed that 6% gained complete recovery, 86.5% partial recovery, 2.5% showed transplant rejection, and 5% died. Mean platelet levels in deceased patients had an upward trend. The mean platelet counts of patients were elevated during surgery (289,855 ± 165,378), decreased three days after surgery (282,778 ± 317,310), and elevated again five days after surgery (330,375 ± 208,571). However, no significant difference was found between the mean platelet counts during surgery, the third and fifth days after surgery in patients undergoing skin grafts (P = 0.057).

CONCLUSIONS

This study suggests that skin graft positively increases the patient's platelets. Further studies are needed to confirm the findings and elucidate the mechanism. Iranian Registry of Clinical Trial approval code (IRCT# IRCT20131112015390N8 & 06/01/2024).

3-D tissue-engineered epidermis against human primary keratinocytes apoptosis via relieving mitochondrial oxidative stress in wound healing

The tissue-engineered epidermal (TEE), composed of biocompatible vectors and autogenous functional cells, is a novel strategy to solve the problem of shortage of donor skin sources. The human primary keratinocyte (HPK), the major skin components, are self-evident vital in wound healing and was considered as one of the preferred seed cells for TEEs. Since the process of separating HPKs from the skin triggers a stress state of the cells, achieving its rapid adhesion and proliferation on biomaterials remains challenging. The key to the clinical application is to ensure the normal function of cells while improving the proliferation ability in vitro, and to complete the complex mesenchymal epithelialization to achieve tissue remodeling after vivo implantation. Herein, in order to aid HPKs adhesion and proliferation in vitro and promoting wound healing, we developed a three dimensional collagen scaffold with Y-27632 sustainedly released from the nanoplatform, hollow mesoporous organosilica nanoparticles (HMON). The results showed that the porous structure within the TEE supports the implanted HPKs expanding in a three-dimensional mode to jointly construct the tissue-engineered epidermis in vitro and inhibited the mitochondria-mediated cell apoptosis. It was confirmed that the TEEs with suitable degradation rate could maintain drug release after implantation and could accelerate vascularization of wound base and further revealed the involvement of mesenchymal transformation of transplanted HPKs during skin regeneration in a nude mouse model with full-thickness skin resection. In conclusion, our study highlights the great potential of constructing TEE using a nanoparticle platform for the treatment of large-area skin defects.

Microvasculature in murine tracheal allografts after combined therapy with clopidogrel and everolimus

OBJECTIVES

Survival after lung transplantation is mainly limited by the development of chronic lung allograft dysfunction. Previous studies have suggested T-cell mediated proliferation and microvascular changes in experimental small airways models as potential therapeutic targets. The aim of this study was to assess microvascular changes in murine orthotopic tracheal allografts after treatment with everolimus alone or in combination with clopidogrel.

METHODS

C57Bl/6 (H-2b) donor tracheas were orthotopically transplanted into CBA (H-2k) recipients. Mice received daily injections of everolimus (0.05 mg/kg) alone or combined with clopidogrel (1 mg/kg). Twenty-eight days after transplantation, ratio of the thickness of tracheal epithelium and lamina propria was measured as an indicator for chronic rejection. Additionally, graft oxygenation and graft perfusion were detected on postoperative days 4, 10 and 28. Quantitative reverse transcription polymerase chain reaction analysis was used for gene expression analysis.

RESULTS

While syngeneic grafts showed a stable tissue pO2 and undisturbed microvascular perfusion, rejecting allografts had a drastic decline in both parameters as well as a flattened epithelium and an increased thickness of the lamina propria. Treatment with everolimus reduced allogeneic fibroproliferation, but had no protective effects on the microvasculature; polymerase chain reaction analysis indicated hypoxic stress and inflammation. Combining everolimus with clopidogrel improved microvascular integrity in the tracheal grafts, but had no synergistic effect in preventing obliterative bronchiolitis development.

CONCLUSIONS

These data demonstrate that the ability of everolimus to reduce the development of post-transplant obliterative bronchiolitis is not caused by microvascular protection and has no synergistic effects with clopidogrel in acute airway rejection.

Microvascular injury after lung transplantation

PURPOSE OF REVIEW

Airway microvessel injury following transplantation has been implicated in the development of chronic rejection. This review focuses on the most recent developments in the field describing preclinical and clinical findings that further implicate the loss of microvascular integrity as an important pathological event in the evolution of irreversible fibrotic remodeling.

RECENT FINDINGS

When lungs are transplanted, the airways appear vulnerable from the perspective of perfusion. Two vascular systems are lost, the bronchial artery and the lymphatic circulations, and the remaining vasculature in the airways expresses donor antigens susceptible to alloimmune-mediated injury via innate and adaptive immune mechanisms. Preclinical studies indicate the importance of hypoxia-inducible factor-1α in mediating microvascular repair and that hypoxia-inducible factor-1α can be upregulated to bolster endogenous repair.

SUMMARY

Airway microvascular injury is a feature of lung transplantation that limits short-term and long-term organ health. Although some problems are attributable to a missing bronchial artery circulation, another significant issue involves alloimmune-mediated injury to transplant airway microvessels. For a variety of reasons, bronchial artery revascularization surgery at the time of transplantation has not been widely adopted, and the current best hope for this era may be new medical approaches that offer protection against immune-mediated vascular injury or that promote microvascular repair.

Pre-vascularization Enhances Therapeutic Effects of Human Mesenchymal Stem Cell Sheets in Full Thickness Skin Wound Repair

Split thickness skin graft (STSG) implantation is one of the standard therapies for full thickness wound repair when full thickness autologous skin grafts (FTG) or skin flap transplants are inapplicable. Combined transplantation of STSG with dermal substitute could enhance its therapeutic effects but the results remain unsatisfactory due to insufficient blood supply at early stages, which causes graft necrosis and fibrosis. Human mesenchymal stem cell (hMSC) sheets are capable of accelerating the wound healing process. We hypothesized that pre-vascularized hMSC sheets would further improve regeneration by providing more versatile angiogenic factors and pre-formed microvessels. In this work, in vitro cultured hMSC cell sheets (HCS) and pre-vascularized hMSC cell sheets (PHCS) were implanted in a rat full thickness skin wound model covered with an autologous STSG. Results demonstrated that the HCS and the PHCS implantations significantly reduced skin contraction and improved cosmetic appearance relative to the STSG control group. The PHCS group experienced the least hemorrhage and necrosis, and lowest inflammatory cell infiltration. It also induced the highest neovascularization in early stages, which established a robust blood micro-circulation to support grafts survival and tissue regeneration. Moreover, the PHCS grafts preserved the largest amount of skin appendages, including hair follicles and sebaceous glands, and developed the smallest epidermal thickness. The superior therapeutic effects seen in PHCS groups were attributed to the elevated presence of growth factors and cytokines in the pre-vascularized cell sheet, which exerted a beneficial paracrine signaling during wound repair. Hence, the strategy of combining STSG with PHCS implantation appears to be a promising approach in regenerative treatment of full thickness skin wounds.