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Studies evaluating fat grafting in mice have frequently used micro-computed tomography (micro-CT) as an accurate radiographic tool to measure longitudinal volume retention without killing the animal. Over the past decade, however, microultrasonography has emerged as an equally powerful preclinical imaging tool. Given their respective strengths in 3-dimensional reconstruction, there is no study to our knowledge that directly compares micro-CT with microultrasound in volumetric analysis. In this study, we compared the performance of micro-CT with microultrasound in the evaluation of adipose tissue graft volume in a murine model. Fifteen immunodeficient mice were given 200 μL of adipose tissue grafts. In vivo volumetric analysis of the grafts by micro-CT and microultrasound was conducted at discrete time points up to postoperative day 105. Three mice were killed at multiple time points, and explanted grafts were reimaged by CT and ultrasound, as mentioned previously. Analysis revealed that in vivo graft volumes measured by micro-CT do not differ significantly from those of microultrasound. Furthermore, both micro-CT and microultrasound were capable of accurately measuring fat grafts as in vivo volumes closely correlated with explanted volumes. Finally, ultrasound was found to yield improved soft tissue contrast compared with micro-CT. Therefore, either modality may be used, depending on experimental needs.

Background: Renevia is a hyaluronin-gelatin crosslinked matrix scaffold that has been studied as an alternative to adipose transfer in soft tissue reconstruction. It is designed to emulate the native extracellular matrix environment by supporting stromal vascular fraction (SVF) cell attachment, survival, and proliferation, thus promoting cell-based volume restoration. However, the concentration of incorporated cells for a clinically relevant result has yet to be determined., Methods: Five experimental groups of seven CD-1 nude immunodeficient mice were given 250 μL grafts of the following composition: 1 million human SVF cells per mL of Renevia scaffold, 6 million human SVF cells per mL scaffold, 12 million human SVF cells per mL scaffold, Renevia scaffold-alone or human adipose tissue-alone. Volumetric analysis was conducted at discrete time points over 16 weeks using 3-dimensional ultrasound, after which time the grafts were explanted for histologic analysis., Results: At the conclusion of the study at week 16, the Renevia scaffold group incorporating the highest concentration of human SVF cells (12 million cells per mL scaffold) had significantly greater volume retention compared with the 2 lower concentrations, scaffold-alone and fat-alone groups. Histology of the 12 million scaffold group revealed abundant adipocyte formation within the scaffold, exceeding that observed in the 6 million, 1 million, and scaffold-alone groups. The 12 million group also demonstrated significantly increased vascularity per CD31 staining., Conclusions: Stromal vascular fraction cells coupled with Renevia hydrogel scaffold can enhance soft tissue volume reconstruction. In this study, we observed the greatest effect with 12 million cells per mL. From the perspective of volume retention, incorporation of higher concentrations of SVF cells with Renevia may be an alternative to conventional adipose tissue grafting.

Bone has the capacity to regenerate and repair itself. However, this capacity may be impaired or lost depending on the size of the defect or the presence of certain disease states. In this review, we discuss the key principles underlying bone healing, efforts to characterize bone stem and progenitor cell populations, and the current status of translational and clinical studies in cell-based bone tissue engineering. Though barriers to clinical implementation still exist, the application of stem and progenitor cell populations to bone engineering strategies has the potential to profoundly impact regenerative medicine., Competing Interests: The authors indicate no potential conflicts of interest