John Flacco

Stem Cells in Bone Regeneration.

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.

Magnetic Nanoparticle‐Based Upregulation of B‐Cell Lymphoma 2 Enhances Bone Regeneration

Clinical translation of cell‐based strategies for tissue regeneration remains challenging because survival of implanted cells within hostile, hypoxic wound environments is uncertain. Overexpression of B‐cell lymphoma 2 (Bcl‐2) has been shown to inhibit apoptosis in implanted cells. The present study describes an “off the shelf” prefabricated scaffold integrated with magnetic nanoparticles (MNPs) used to upregulate Bcl‐2 expression in implanted adipose‐derived stromal cells for bone regeneration. Iron oxide cores were sequentially coated with branched polyethyleneimine, minicircle plasmid encoding green fluorescent protein and Bcl‐2, and poly‐β‐amino ester. Through in vitro assays, increased osteogenic potential and biological resilience were demonstrated in the magnetofected group over control and nucleofected groups. Similarly, our in vivo calvarial defect study showed that magnetofection had an efficiency rate of 30%, which in turn resulted in significantly more healing compared with control group and nucleofected group. Our novel, prefabricated MNP‐integrated scaffold allows for in situ postimplant temporospatial control of cell transfection to augment bone regeneration. Stem Cells Translational Medicine 2017;6:151–160

Dynamic Rheology for the Prediction of Surgical Outcomes in Autologous Fat Grafting

Background: Because of the abundance and biocompatibility of fat, lipotransfer has become an attractive method for treating soft-tissue deficits. However, it is limited by unpredictable graft survival and retention. Currently, little is known about the viscoelastic properties of fat after various injection methods. Here, the authors assess the effects of cannula diameter, length, and shape on the viscoelastic properties, structure, and retention of fat. Methods: Human lipoaspirate was harvested using suction-assisted liposuction and prepared for grafting. A syringe pump was used to inject fat at a controlled flow rate through cannulas of varying gauges, lengths, and shapes. Processed samples were tested in triplicate on an oscillatory rheometer to measure their viscoelastic properties. Fat grafts from each group were placed into the scalps of immunocompromised mice. After 8 weeks, graft retention was measured using micro–computed tomography and grafts were explanted for histologic analysis. Results: Lipoaspirate injected through narrower, longer, and bent cannulas exhibited more shear thinning with diminished quality. The storage modulus (G′) of fat processed with 18-gauge cannulas was significantly lower than when processed with 14-gauge or larger cannulas, which also corresponded with inferior in vivo histologic structure. Similarly, the longer cannula group had a significantly lower storage modulus than the shorter cannula, and was associated with decreased graft retention. Conclusions: Discrete modifications in the methods used for fat placement can have a significant impact on immediate graft integrity, and ultimately on graft survival and quality. Respecting these biomechanical influences during the placement phase of lipotransfer may allow surgeons to optimize outcomes. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Biomimetics of Bone Implants: The Regenerative Road

Abstract The current strategies for healing bone defects are numerous and varied. At the core of each bone healing therapy is a biomimetic mechanism, which works to enhance bone growth. These range from porous scaffolds, bone mineral usage, collagen, and glycosaminoglycan substitutes to transplanted cell populations. Bone defects face a range of difficulty in their healing, given the composite of dense outer compact bone and blood-rich inner trabecular bone. As such, the tissue possesses a number of inherent characteristics, which may be clinically harnessed as promoters of bone healing. These include mechanical characteristics, mineral composition, native collagen content, and cellular fraction of bone. This review charts multiple biomimetic strategies to help heal bony defects in large and small osseous injury sites, with a special focus on cell transplantation.

Abstract 68: Deferoxamine Preconditioning of Irradiated Tissue Increases Fat Graft Volume Retention

PURPOSE: Inflammatory breast cancer (IBC) is an aggressive disease characterized by the formation of tumor emboli, rapid local invasion, and lymphatic dissemination. Furthermore, IBC rapidly develops therapeutic resistance and evades immune surveillance and attack. For these reasons, the treatment of inflammatory breast cancer is extremely challenging and new therapeutic approaches are needed. Numerous studies have shown that adipose derived stem cells (ASCs), which are abundant in breast tissue, are recruited to the tumor microenvironment where they influence tumor progression. We have previously demonstrated the feasibility of using nanoparticles in conjunction with ASCs in treatmentresistant breast cancer. In this study, we show that ASCs localize to IBC tumor emboli and can be used as a targeted delivery vehicle for cancer nanotherapeutics.

Cell-Based Soft Tissue Reconstruction in a Hydrogel Scaffold.

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 &mgr;L 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.