Background

Delayed bone healing and nonunion are complications of long bone fractures, with prolonged pain and disability. Regenerative therapies employing mesenchymal stromal cells (MSC) and/or bone substitutes are increasingly applied to enhance bone consolidation. Within the REBORNE project, a multi-center orthopaedic clinical trial was focused on the evaluation of efficacy of expanded autologous bone marrow (BM) derived MSC combined with a CaP-biomaterial to enhance bone healing in patients with nonunion of diaphyseal fractures. To complement the clinical and radiological examination of patients, bone turnover markers (BTM) were assayed as potential predictors of bone healing or non-union.

For unrepairable nerve defects, to date autogenous nerves are considered the golden standard, but donor site morbidity, limited availability and operation time prolongation are relevant problem. Acellular nerves from cadaveric donor, introduced since more than one decade ago, represent a novel promising alternative to bridge unrepairable nerve gaps.

Aim of this study is to provide a new tool to ameliorate the assistance of the numerous patients suffering from traumatic, oncological and jatrogenic nerve lesions. For this purpose, our project is promoting a progress beyond the state of the art of nerve gaps bridging surgery by developing a new technique to obtain acellular nerve allografts (ANAs).

Several methods to examine the effect of detergents on nerve tissue morphology and protein composition have been previously reported. Most of them are too expensive and time consuming. The presented novel decellularization technique is a modification of the Michigan detergent-based organic material removal, to speed up myelin and cellular debris detachment. The previously published Hudson's method¹has been chosen as control of the decellularization process). To validate the new nerve decellularization method, in terms of histological characteristics, outcomes were estimated through morphological and immunohistochemical studies in vitro and in vivo. The in vivo study consisted of a 1 cm defect in the tibial nerve of 3 new Zealand rabbits. This nerve defect was microsurgically replaced with a “Rizzoli” acellular nerve allograft. Rabbits were sacrificed 12 weeks after surgery. Endpoints were nerve conduction studies and histology.

Histological analysis of processed acellular nerve have been performed to evaluate the preservation of the structure and almost complete clearance of donor cells and cellular debris. Immunostaining analysis confirmed absence of Schwann cells and the maintenance of basal lamina. In vivo studies showed an effective and abundant nerve regeneration through the microsurgically reconstructed nerve defects. This was histologically proven. However no electophysiological return of function was showed.

The novel method will allow the storing of acellular nerve allografts. First results obtained by morphological analysis and immunofluorescence experiments and in vivo studies indicate that the internal structure of native nerve is maintained. It is then possible to decellularize nerves with the novel technique reducing both manufacturing times and costs. The relatively inexpensive method of decellularization will facilitate the number of patients that will benefit from reconstruction of nerve defects with ANAs.

Summary

Reciprocal metabolic reprogramming of MSCs and osteosarcoma cells influences tumor-stroma cross talk. Drugs targeting Warburg metabolism may define innovative therapeutic approaches in osteosarcoma.