Sudheer Ravuri

Prevalence of endogenous CD34+ adipose stem cells predicts human fat graft retention in a xenograft model.

Background: Fat grafting is a promising technique for soft-tissue augmentation, although graft retention is highly unpredictable and factors that affect graft survival have not been well defined. Because of their capacity for differentiation and growth factor release, adipose-derived stem cells may have a key role in graft healing. The authors’ objective was to determine whether biological properties of adipose-derived stem cells present within human fat would correlate with in vivo outcomes of graft volume retention. Methods: Lipoaspirate from eight human subjects was processed using a standardized centrifugation technique and then injected subcutaneously into the flanks of 6-week-old athymic nude mice. Graft masses and volumes were measured, and histologic evaluation, including CD31+ staining for vessels, was performed 8 weeks after transplantation. Stromal vascular fraction isolated at the time of harvest from each subject was analyzed for surface markers by multiparameter flow cytometry, and also assessed for proliferation, differentiation capacity, and normoxic/hypoxic vascular endothelial growth factor secretion. Results: Wide variation in percentage of CD34+ progenitors within the stromal vascular fraction was noted among subjects and averaged 21.3 ± 15 percent (mean ± SD). Proliferation rates and adipogenic potential among stromal vascular fraction cells demonstrated moderate interpatient variability. In mouse xenograft studies, retention volumes ranged from approximately 36 to 68 percent after 8 weeks, with an overall average of 52 ± 11 percent. A strong correlation (r = 0.78, slope = 0.76, p < 0.05) existed between stromal vascular fraction percentage of CD34+ progenitors and high graft retention. Conclusion: Inherent biological differences in adipose tissue exist between patients. In particular, concentration of CD34+ progenitor cells within the stromal vascular fraction may be one of the factors used to predict human fat graft retention.

Adipose- and Bone Marrow-Derived Mesenchymal Stem Cells Prolong Graft Survival in Vascularized Composite Allotransplantation

Background Strategies aiming at minimization or elimination of systemic immunosuppression are key immediate goals for clinical expansion of vascularized composite allotransplantation (VCA). We compared the in vitro and in vivo immunomodulatory efficacy of adipose-derived mesenchymal stem cells (AD-MSCs) and bone marrow (BM)–derived MSCs in a rat VCA model. Methods Both cell types were tested in vitro for suppressor function using mixed lymphocyte reactivity assays. AD-MSCs or BM-MSCs were administered intravenously (1 × 106 or 5 × 106 cells/animal) to Lewis rat recipients of mismatched Brown Norway hindlimb transplants. Short course tacrolimus (FK-506) monotherapy was withdrawn at postoperative day 21. In vivo regulatory T-cell induction, peripheral blood chimerism, and microchimerism in lymphatic organs were analyzed. Results AD-MSCs and BM-MSCs exhibited strong dose-dependent suppressor function in vitro, which was significantly more pronounced for AD cells. In vivo, all animals revealed peripheral multi-lineage chimerism at four weeks (P < 0.01) independent of cell type and dosage. Regulatory T-cell levels were increased with both cell types, the most in AD-MSC groups. These immunomodulatory effects were only transient. MSC treatment resulted in long-term (>120 day) allograft survival in 47% of the animals, which correlated with durable microchimerism in BM and spleen. Conclusions AD-MSCs and BM-MSCs exert immunomodulatory effects that prolong survival of immunogenic skin-bearing VCA grafts with short course (21 day) tacrolimus induction therapy. The in vivo findings in terms of allograft survival did not reflect superior immunomodulatory characteristics of AD-MSCs found in vitro.

Estrogen Sulfotransferase/SULT1E1 Promotes Human Adipogenesis

ABSTRACT Estrogen sulfotransferase (EST/SULT1E1) is known to catalyze the sulfoconjugation and deactivation of estrogens. The goal of this study is to determine whether and how EST plays a role in human adipogenesis. By using human primary adipose-derived stem cells (ASCs) and whole-fat tissues from the abdominal subcutaneous fat of obese and nonobese subjects, we showed that the expression of EST was low in preadipocytes but increased upon differentiation. Overexpression and knockdown of EST in ASCs promoted and inhibited differentiation, respectively. The proadipogenic activity of EST in humans was opposite to the antiadipogenic effect of the same enzyme in rodents. Mechanistically, EST promoted adipogenesis by deactivating estrogens. The proadipogenic effect of EST can be recapitulated by using an estrogen receptor (ER) antagonist or ERα knockdown. In contrast, activation of ER in ASCs inhibited adipogenesis by decreasing the recruitment of the adipogenic peroxisome proliferator-activated receptor γ (PPARγ) onto its target gene promoters, whereas ER antagonism increased the recruitment of PPARγ to its target gene promoters. Linear regression analysis revealed a positive correlation between the expression of EST and body mass index (BMI), as well as a negative correlation between ERα expression and BMI. We conclude that EST is a proadipogenic factor which may serve as a druggable target to inhibit the turnover and accumulation of adipocytes in obese patients.

A review of adipocyte lineage cells and dermal papilla cells in hair follicle regeneration.

Alopecia is an exceedingly prevalent problem effecting men and women of all ages. The standard of care for alopecia involves either transplanting existing hair follicles to bald areas or attempting to stimulate existing follicles with topical and/or oral medication. Yet, these treatment options are fraught with problems of cost, side effects, and, most importantly, inadequate long-term hair coverage. Innovative cell-based therapies have focused on the dermal papilla cell as a way to grow new hair in previously bald areas. However, despite this attention, many obstacles exist, including retention of dermal papilla inducing ability and maintenance of dermal papilla productivity after several passages of culture. The use of adipocyte lineage cells, including adipose-derived stem cells, has shown promise as a cell-based solution to regulate hair regeneration and may help in maintaining or increasing dermal papilla cells inducing hair ability. In this review, we highlight recent advances in the understanding of the cellular contribution and regulation of dermal papilla cells and summarize adipocyte lineage cells in hair regeneration.

Differential inflammatory networks distinguish responses to bone marrow-derived versus adipose-derived mesenchymal stem cell therapies in vascularized composite allotransplantation

BACKGROUND Vascularized composite allotransplantation (VCA) is aimed at enabling injured individuals to return to their previous lifestyles. Unfortunately, VCA induces an immune/inflammatory response, which mandates lifelong, systemic immunosuppression, with attendant detrimental effects. Mesenchymal stem cells (MSC)—both adipose-derived (AD-MSC) and bone marrow–derived (BM-MSC)—can reprogram inflammation and have been suggested as an alternative to immunosuppression, but their mechanism of action is as yet not fully elucidated. We sought to gain insights into these mechanisms using a systems biology approach. METHODS PKH26 (red) dye-labeled AD-MSC or BM-MSC were administered intravenously to Lewis rat recipients of mismatched Brown-Norway hindlimb transplants. Short course tacrolimus (FK-506) monotherapy was withdrawn at postoperative day 21. Sera were collected at 4 weeks, 6 weeks, and 18 weeks; assayed for 29 inflammatory/immune mediators; and the resultant data were analyzed using Dynamic Network Analysis (DyNA), Dynamic Bayesian Network (DyBN) inference, and Principal Component Analysis. RESULTS DyNA network complexity decreased with time in AD-MSC rats, but increased in BM-MSC rats. DyBN and Principal Component Analysis suggested mostly different central nodes and principal characteristics, respectively, in AD-MSC versus BM-MSC rats. CONCLUSION AD-MSC and BM-MSC are associated with both overlapping and distinct dynamic networks and principal characteristics of inflammatory/immune mediators in VCA grafts with short-course tacrolimus induction therapy. The decreasing inflammatory complexity of dynamic networks in the presence of AD-MSC supports the previously suggested role for T regulatory cells induced by AD-MSC. The finding of some overlapping and some distinct central nodes and principal characteristics suggests the role of key mediators in the response to VCA in general, as well as potentially differential roles for other mediators ascribed to the actions of the different MSC populations. Thus, combined in vivo/in silico strategies may yield novel means of optimizing MSC therapy for VCA.

Mesenchymal and Adipose Stem Cell Strategies for Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) is a common sequela of soft tissue and bony trauma. The morbidity and loss of function secondary to PNI significantly limit patient quality of life. Strategies that restore or augment nerve regeneration and enable motor/sensory recovery after injury can help patients to return to functional/employable status while improving performance, morale, mobility, agility and capability. Suboptimal nerve regeneration after reconstructive transplantation remains one of the key obstacles to functional outcomes. Distal denervated muscles have impaired/no function and will undergo denervation atrophy if the nerves do not reach the motor end plates in time. Several drugs/biologics/growth factors (tacrolimus, chondroitinase, insulin-like growth factor-1, IGF1) as well as cellular therapies (Schwann cells (SC), mesenchymal stromal cells (MSC) of adipose, or bone marrow origin) have shown promise and potential in enhancing nerve regeneration via different mechanisms and distinct biochemical pathways. Combinations of these treatments may also provide an additive or even synergistic effect on the neuroregenerative process. Undifferentiated MSCs have inherent advantages over SCs or other cell types. These include higher yield, superior expansion characteristics and innate self-renewal, angiogeneic and immunomodulatory properties. Here in, we focus on the current experimental evidence for MSCs as promising potential therapies in accelerating or maximizing peripheral nerve regeneration and subsequent functional outcomes in reconstructive transplant indications.

Immunomodulation with Adipose and Bone Marrow-derived Mesenchymal Stem Cells in Vascularized Composite Allotransplantation

Reconstructive transplantation is a clinical reality. Graft sustenance requires life-long immunosuppression with coincident adverse effects. Therapies incorporating adipose tissueand bone marrow-derived mesenchymal stem cells (AD-MSC/BM-MSCs) have shown promising effects in experimental autoimmune diseases, solid organ transplantation and vascularized composite allotransplantation (VCA). Clinical translation of these therapies must consider collateral effects of depletional conditioning protocols. For the first time, we compare AD-MSCs versus BM-MSCs in VCA.

Abstract P31: Immunomodulatory Effects of Adipose-Derived Stem Cells and Bone Marrow-Derived Stem Cells in Rat Hind-limb Composite Tissue Allotransplantation

BaCkground: Mesenchymal stem cells (MSCs) have broad range of applications in nerve repair. In vitro and local administration in vivo studies had well demonstrated enhanced nerve regeneration. However there is unmet need to develop and study systemic application of MSCs for immunomodulation and/or immunosuppression for improving functional outcomes after CTA. Hence this study was intended to investigate whether donor adipose-derived stem cells (ASCs) and bone marrow derived stem cells (BMSCs) have immunomodulatory effects, such as modulation of related cytokines and prolongation of allograft survival in a rodent hind limb model.