Yunjun Liao

Hypoxia preconditioned human adipose derived mesenchymal stem cells enhance angiogenic potential via secretion of increased VEGF and bFGF.

Mesenchymal stem cells (MSCs) are adult multipotent cells found in bone marrow, adipose tissue, and other adult tissues. MSCs improve regeneration of injured tissues in vivo, but the mechanisms remain unclear. Typically, MSCs are cultured under ambient or normoxic conditions (21% O2). However, the physiological niches of MSCs have much lower oxygen tension. When used as a therapeutic tool to repair tissue injuries, MSCs cultured in standard conditions must adapt from 21% O2 in culture to <1% O2 in ischemic tissue. We have examined the effects of hypoxia preconditioning (1% O2) in human adipose derived mesenchymal stem cells (AD‐MSCs) to discover the conditions that best enhance their tissue regenerative potential. We demonstrate that AD‐MSCs respond positively to hypoxia compared with normoxia preconditioning, show decreased apoptosis even in severe microenvironmental conditions (such as a low‐serum medium), and an increased expression of the angiogenic factors, vascular endothelial growth factor and basic fibroblast growth factor. Human umbilical vein endothelial cells have higher vitality and lower apoptosis when cultured in medium taken from hypoxia‐preconditioned AD‐MSCs, as well as significantly increased capillary‐like structures with this medium on Matrigel. The data suggest that hypoxia preconditioned AD‐MSCs can improve tissue regeneration.

Supplementing fat grafts with adipose stromal cells for cosmetic facial contouring.

Background Numerous methods have been proposed to enhance the survival of fat grafts, but no definitive treatment is available. Stromal vascular fraction (SVF)‐assisted cell therapy offers new perspectives for improving fat graft survival. Objectives To determine whether SVF supplementation could improve graft retention in patients undergoing autologous fat grafting for cosmetic improvement of facial contour. Methods We retrospectively analyzed data from 38 women who underwent fat transplantation with SVF (n = 26) or fat grafting alone (n = 12) between October 2010 and January 2012. Each patient underwent computed tomography, and photographs were taken before and 6 months after surgery. The Philips Extended Brilliance Workspace was used for analysis of volume augmentation. Results All patients showed cosmetic improvements, but the degree varied. No complications were evidenced during follow‐up. Fat survival was higher with SVF (64.8 ± 10.2%) than fat grafting alone (46.4 ± 9.3%) (p < .01). SVF supplementation resulted in better clinical improvement than fat grafting alone. Conclusion Supplementing fat grafts with SVF for cosmetic facial contouring can improve the survival of fat grafts over fat grafting alone and provides satisfactory outcomes without major complications. Autologous fat grafting has been used for various cosmetic treatments and difficult reconstructive indications such as temporal depression, wrinkles of nasolabial folds, and hemifacial atrophy, with no incisional scar or complications associated with foreign materials, although problems such as a low rate of graft survival because of early resorption remain. (Aesthet Plast Surg, 14, 1990 and 127) Despite many innovations to overcome these problems, (Dermatol Surg, 26, 2000 and 1159); (Ann Plast Surg, 60, 2008 and 594); (Dermatol Surg, 27, 2001 and 819); (Dermatol Surg, 28, 2002 and 987) we lack a definitive method of fat processing that ensures maximal graft take and viability. (Plast Reconstr Surg, 115, 2005 and 197); (Dermatol Surg, 37, 2011 and 619)

Adipocyte regeneration after free fat transplantation: promotion by stromal vascular fraction cells.

Our objective was to explore the mechanism of cell-assisted adipose transplantation by using freshly isolated human stromal vascular fraction (SVF) cells and to observe the dynamic changes of the graft after transplantation. The SVF was isolated from human liposuction aspirates, and 0.5 ml adipose tissue was mixed with 1 × 106 SVF cells or culture medium then injected to nude mice subcutaneously. At 1, 4, 7, 14, 30, 60, and 90 days after transplantation, samples were harvested for 1) general observation and retention rate; 2) whole-mount stain; 3) H&E stain; 4) immunohistochemical staining for S100, CD68, and CD34; 5) ELISA for VEGF and bFGF; 6) peroxisome proliferator-activated receptor-γ (PPARγ) fluorescence in situ hybridization. The retention rate in the experiment group was markedly higher than that in the control group. Whole-mount stain shows most of the cells in the center of the graft could not survive the ischemia until day 14. Histology showed new vessels on the surface of the graft at 3 days. However, in the control group, fewer newly formed vessels were detected until day 7. In the late stage of transplantation, gradual fibrosis was found in the graft, and the tissue was divided into a grid-like structure. A large number of round neonatal adipocytes with big nuclei in the center were found surrounding the new vessels, which were S100 and CD34 positive and CD68 negative. In the late stage of transplantation, most of the neonatal adipocytes were human PPARγ positive. Moreover, the SVF group showed a higher level of VEGF and bFGF. SVF assisting adipose transplantation could increase the retention rate of the graft through promoting adipose tissue regeneration via secretion of growth factors, promotion of angiogenesis, and increasing the density of mesenchymal stem cells.

Adipose Extracellular Matrix/Stromal Vascular Fraction Gel: A Novel Adipose Tissue-Derived Injectable for Stem Cell Therapy.

Background: Adipose-derived stem cells and other stromal vascular fraction cells were used more often for stem cell therapy, even though limitations such as poor cell retention rate, complicated and expensive isolation processes, and the use of specific laboratory equipment need to be overcome. Methods: Here, the authors developed a novel but simple method for generating an injectable mixture of stromal vascular fraction cells and native adipose extracellular matrix. It is a purely mechanical process in which lipoaspirate is processed into an extracellular matrix/stromal vascular fraction gel. The standard processing procedure was established using quantized tests. The therapeutic potential of the product for wound healing was then tested. Results: Extracellular matrix/stromal vascular fraction gel derived from lipoaspirate and processed using a standard Coleman technique, followed by 1 minute of mechanical processing by passage back and forth between two 10-ml syringes at a flow rate of 10 ml/second, showed the highest adipose-derived stem cell and endothelial cell density. The stromal vascular fraction cells within the product also showed potential for multipotent differentiation similar to that of normal fat samples. In addition, the product showed better therapeutic results than stromal vascular fraction cell suspension when used to treat a nude mouse model of wound healing. Conclusions: Extracellular matrix/stromal vascular fraction gel is an autologous injectable derived from native extracellular matrix and is a functional cellular component generated using a simple mechanical process. As such, it may offer a novel mode of tissue repair suitable for clinical application in stem cell therapies.

In Vivo Dedifferentiation of Adult Adipose Cells

Introduction Adipocytes can dedifferentiate into fibroblast-like cells in vitro and thereby acquire proliferation and multipotent capacities to participate in the repair of various organs and tissues. Whether dedifferentiation occurs under physiological or pathological conditions in vivo is unknown. Methods A tissue expander was placed under the inguinal fat pads of rats and gradually expanded by injection of water. Samples were collected at various time points, and morphological, histological, cytological, ultrastructural, and gene expression analyses were conducted. In a separate experiment, purified green fluorescent protein+ adipocytes were transplanted into C57 mice and collected at various time points. The transplanted adipocytes were assessed by bioluminescence imaging and whole-mount staining. Results The expanded fat pad was obviously thinner than the untreated fat pad on the opposite side. It was also tougher in texture and with more blood vessels attached. Hematoxylin and eosin staining and transmission electron microscopy indicated there were fewer monolocular adipocytes in the expanded fat pad and the morphology of these cells was altered, most notably their lipid content was discarded. Immunohistochemistry showed that the expanded fat pad contained an increased number of proliferative cells, which may have been derived from adipocytes. Following removal of the tissue expander, many small adipocytes were observed. Bioluminescence imaging suggested that some adipocytes survived when transplanted into an ischemic-hypoxic environment. Whole-mount staining revealed that surviving adipocytes underwent a process similar to adipocyte dedifferentiation in vitro. Monolocular adipocytes became multilocular adipocytes and then fibroblast-like cells. Conclusions Mature adipocytes may be able to dedifferentiate in vivo, and this may be an adipose tissue self-repair mechanism. The capacity of adipocytes to dedifferentiate into stem cell-like cells may also have a more general role in the regeneration of many tissues, notably in fat grafting.

Daily Suction Provided by External Volume Expansion Inducing Regeneration of Grafted Fat in a Murine Model.

Background: Fat grafting has variable and sometimes poor outcomes, and therefore new methods are needed. Multiple studies have demonstrated the excellent performance of external volume expansion and focused only on preexpansion with emphasis on the recipient. Methods: Two mouse models (a suction model and a fat-exchange transplantation model) were established to investigate changes in the origins and biological behaviors of regeneration-related cells in grafted fat under daily suction provided by external volume expansion. Results: Blood supply increased from new host-derived capillaries or macrophage infiltration under suction. CD34-positive cells showed increased migration from the host into the grafts under suction. At week 12, nearly half of the mature adipocytes regenerated in the grafts in the suction group were derived from the host. Peroxisome proliferator-activated receptor &ggr; expression of the suction group was significantly higher than that of controls at weeks 2 and 4 during adipogenesis. The normalized sample weight of the grafted fat was significantly greater than that of controls at 1 (0.081 ± 0.001 versus 0.072 ± 0.005; p < 0.001), 4 (0.060 ± 0.002 versus 0.048 ± 0.001; p = 0.002), 8 (0.060 ± 0.001 versus 0.046 ± 0.001; p < 0.001), and 12 weeks (0.060 ± 0.001 versus 0.046 ± 0.001; p = 0.002). Conclusions: The mechanical effect of daily suction provided by external volume expansion favors the regeneration of grafted fat and improves retention by promoting the migration of regeneration-related cells and the differentiation of adipocytes. Thus, more mature fat tissue with a well-organized structure was formed under suction.

Pre-expanded Intercostal Perforator Super-Thin Skin Flap

This article introduces pre-expanded super-thin intercostal perforator flaps, particularly the flap that has a perforator from the first to second intercostal spaces. The key techniques, advantages and disadvantages, and complications and management of this flap are described. At present, the thinnest possible flap is achieved by thinning the pre-expanded flap that has a perforator from the first to second intercostal spaces. It is used to reconstruct large defects on the face and neck, thus restoring function and cosmetic appearance.