Effetti biologici delle forze meccaniche esterne sui tessuti molli: ottimizzazione preclinica per l'applicazione translazionale in chirurgia rigenerativa.Biological effects of external mechanical forces on soft tissues: preclinical optimization for translational application in regenerative surgery

In reconstructive surgery, tissues are routinely transferred to repair a defect caused by trauma, cancer, chronic diseases, or congenital malformations. Surgical transfer intrinsically impairs metabolic supply to tissues placing a risk for ischemic complications such as necrosis, impaired healing, or infection. Pre-surgical induction of angiogenesis in tissues (preconditioning) limits ischemic complications and improves outcomes but very few preconditioning strategies have successfully been translated to clinical practice. The first goal of our research was to improve current standard of care in reconstructive surgery by developing a translational technique that can effectively and safely increase the vascularization of soft tissues. To achieve this goal, we optimized, using preclinical animal models resembling clinical needs and scenarios in a controlled setting, a method that adopts non-invasive external suction (External Volume Expansion, EVE) to precondition tissues through the induction of hypoxia-mediated angiogenesis. Using a sequential approach in a rodent model we determined the parameters of application (frequency, suction levels, duration, and interfaces) that fine-tune the balance of enhanced angiogenesis, attenuation of hypoxic tissue damage, and length of treatment. The optimized parameters of application (short, cyclical stimulations at moderate suction) almost doubled tissue vascular density after only 5 days of treatment. Our outcomes also showed that the use of micro-deformational interfaces of treatment retain the biological effectiveness of EVE while further reducing the cutaneous damage by distributing forces across the stimulated tissue. Our model confirmed that the optimized technique significantly improves the survival of transferred soft tissues (+20-30%), such as adipose tissue grafts, and can achieve the same beneficial outcomes in animal models of pathologic cutaneous vascularization, such as the one occurring in the skin of patients affected type-2 diabetes. We assessed that EVE retains a beneficial effect on the vascularization and proliferation (adipogenesis) of soft tissues when used both as a pre-conditioning method (before surgeries) and as a post-conditioning method (after surgeries) As a second goal of our research we integrated the knowledge on the application of EVE on soft tissues, to the use of a shelf-ready, bio-mimetic, decellularized allograft adipose matrix (AAM) with the aim of developing an innovative and minimally-invasive strategy for in vivo regeneration of soft tissues. In an animal model we tested the potential of a human-derived, injectable AAM to regenerate soft tissues when used in combination with EVE. This strategy significantly improved long-term volume retention (50-80% higher) and histological quality of reconstructed tissues compared to current standard of care (adipose grafts). The AAM induced both adipogenesis and angiogenesis. Combined use of the AAM and adipose grafts mitigated efficacy. Our studies suggest that EVE can improve the outcomes of reconstructive surgeries by safely and promptly enhance vascularity of soft tissues, in addition to its edema-/mechanically-induced adipogenic effect (confirmed by our study). EVE's use with an AAM, instead, can synergistically and effectively induce in vivo soft tissue regeneration. These translational principles are ready to be translated to clinical trials and, if outcomes will be confirmed, they could establish the basis for a novel therapeutic paradigm in reconstructive and regenerative surgery for the benefit of a large number of patients.