The cell-assembled extracellular matrix: A focus on the storage stability and terminal sterilization of this human "bio" material.

The Cell-Assembled extracellular Matrix (CAM) is an attractive biomaterial because it provided the backbone of vascular grafts that were successfully implanted in patients, and because it can now be assembled in "human textiles". For future clinical development, it is important to consider key manufacturing questions. In this study, the impact of various storage conditions and sterilization methods were evaluated. After 1 year of dry frozen storage, no change in mechanical nor physicochemical properties were detected. However, storage at 4 °C and room temperature resulted in some mechanical changes, especially for dry CAM, but physicochemical changes were minor. Sterilization modified CAM mechanical and physicochemical properties marginally except for hydrated gamma treatment. All sterilized CAM supported cell proliferation. CAM ribbons were implanted subcutaneously in immunodeficient rats to assess the impact of sterilization on the innate immune response. Sterilization accelerated strength loss but no significant difference could be shown at 10 months. Very mild and transient inflammatory responses were observed. Supercritical CO2 sterilization had the least effect. In conclusion, the CAM is a promising biomaterial since it is unaffected by long-term storage in conditions available in hospitals (hydrated at 4 °C), and can be sterilized terminally (scCO2) without compromising in vitro nor in vivo performance. STATEMENT OF SIGNIFICANCE: In the field of tissue engineering, the use of extracellular matrix (ECM) proteins as a scaffolding biomaterial has become very popular. Recently, many investigators have focused on ECM produced by cells in vitro to produce unprocessed biological scaffolds. As this new kind of "biomaterial" becomes more and more relevant, it is critical to consider key manufacturing questions to facilitate future transition to the clinic. This article presents an extensive evaluation of long-term storage stability and terminal sterilization effects on an extracellular matrix assembled by cells in vitro. We believe that this article will be of great interest to help tissue engineers involved in so-called scaffold-free approaches to better prepare the translation from benchtop to bedside.

Development of a vascular substitute produced by weaving yarn made from human amniotic membrane.

Because synthetic vascular prostheses perform poorly in small-diameter revascularization, biological vascular substitutes are being developed as an alternative. Although theirin vivoresults are promising, their production involves long, complex, and expensive tissue engineering methods. To overcome these limitations, we propose an innovative approach that combines the human amniotic membrane (HAM), which is a widely available and cost-effective biological raw material, with a rapid and robust textile-inspired assembly strategy. Fetal membranes were collected after cesarean deliveries at term. Once isolated by dissection, HAM sheets were cut into ribbons that could be further processed by twisting into threads. Characterization of the HAM yarns (both ribbons and threads) showed that their physical and mechanical properties could be easily tuned. Since our clinical strategy will be to provide an off-the-shelf allogeneic implant, we studied the effects of decellularization and/or gamma sterilization on the histological, mechanical, and biological properties of HAM ribbons. Gamma irradiation of hydrated HAMs, with or without decellularization, did not interfere with the ability of the matrix to support endothelium formationin vitro. Finally, our HAM-based, woven tissue-engineered vascular grafts (TEVGs) exhibited clinically relevant mechanical properties. Thus, this study demonstrates that human, completely biological, allogeneic, small-diameter TEVGs can be produced from HAM, thereby avoiding costly cell culture and bioreactors.

Near infrared spectroscopy for measuring changes in bone hemoglobin content after exercise in individuals with spinal cord injury.

Bone blood perfusion has an essential role in maintaining a healthy bone. However, current methods for measuring bone blood perfusion are expensive and highly invasive. This study presents a custom built near-infrared spectroscopy (NIRS) instrument to measure changes in bone blood perfusion. We demonstrated the efficacy of this device by monitoring oxygenated and deoxygenated hemoglobin changes in the human tibia during and after exercise in able-bodied and in individuals with spinal cord injury (SCI), a population with known impaired peripheral blood perfusion. Nine able-bodied individuals and six volunteers with SCI performed a 10 min rowing exercise (functional electrical stimulation rowing for those with SCI). With exercise, during rowing, able-bodied showed an increase in deoxygenated hemoglobin in the tibia. Post rowing, able-bodied showed an increase in total blood content, characterized by an increase in total hemoglobin content due primarily to an increase in deoxygenated hemoglobin. During rowing and post-rowing, those with SCI showed no change in total blood content in the tibia. The current study demonstrates that NIRS can non-invasively detect changes in hemoglobin concentration in the tibia. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:183-191, 2018.