Subcutaneous fat tissue engineering using autologous adipose-derived stem cells seeded onto a collagen scaffold

Evaluation of the regenerative capacity of stem cells combined with bone graft material and collagen matrix using a rabbit calvarial defect model

PURPOSE

The purpose of this study was to evaluate the regenerative capacity of stem cells combined with bone graft material and a collagen matrix in rabbit calvarial defect models according to the type and form of the scaffolds, which included type I collagen matrix and synthetic bone.

METHODS

Mesenchymal stem cells (MSCs) were obtained from the periosteum of participants. Four symmetrical 6-mm-diameter circular defects were made in New Zealand white rabbits using a trephine drill. The defects were grafted with (1) group 1: synthetic bone (β-tricalcium phosphate/hydroxyapatite [β-TCP/HA]) and 1×105 MSCs; (2) group 2: collagen matrix and 1×105 MSCs; (3) group 3: β-TCP/HA, collagen matrix covering β-TCP/HA, and 1×105 MSCs; or (4) group 4: β-TCP/HA, chipped collagen matrix mixed with β-TCP/HA, and 1×105 MSCs. Cellular viability and cell migration rates were analyzed.

RESULTS

Uneventful healing was achieved in all areas where the defects were made at 4 weeks, and no signs of infection were identified during the healing period or at the time of retrieval. New bone formation was more evident in groups 3 and 4 than in the other groups. A densitometric analysis of the calvarium at 8 weeks post-surgery showed the highest values in group 3.

CONCLUSIONS

This study showed that the highest regeneration was found when the stem cells were applied to synthetic bone along with a collagen matrix.

Innovations in Skin and Soft Tissue Aging-A Systematic Literature Review and Market Analysis of Therapeutics and Associated Outcomes

PURPOSE

Skin and soft tissue aging has been an important topic of discussion among plastic surgeons and their patients. While botulinum toxin, facial fillers, chemical peels, and surgical lifts preside as the mainstay of treatment to restore appearance of youth, emergent technologies, such as CRISPR-Cas9, proteostasis, flap biology, and stem cell therapies, have gained traction in addressing the aging process of skin and soft tissue. Several studies have introduced these advancements, but it remains unclear how safe and effective these therapeutics are in facial rejuvenation, and how they may fit in the existent treatment workflow for soft tissue aging.

MATERIALS/METHODS

A systematic literature review was conducted to identify and assess therapeutics utilized in addressing skin and soft tissue aging. Variables collected included year of publication, journal, article title, organization of study, patient sample, treatment modality, associated outcomes. In addition, we performed a market analysis of companies involved in promoting technologies and therapeutics within this space. PitchBook (Seattle, WA), a public market database, was utilized to classify companies, and record the amount of venture capital funding allocated to these categories.

RESULTS

Initial review yielded four hundred and two papers. Of these, thirty-five were extracted after applying inclusion and exclusion criteria. Though previous literature regards CRISPR-Cas9 technology as the most favorable anti-aging innovation, after reviewing the current literature, stem cell therapies utilizing recipient chimerism appeared to be the superior skin anti-aging technique when accounting for possible disadvantages of various techniques. The psychosocial and cosmetic outcomes from using cell therapy to modulate allograft survival and tolerance may confer more long-term proposed benefits than the technologies in CRISPR-Cas9, flap biology innovations, and autologous platelet-rich plasma use. Market analysis yielded a total of 87 companies, which promoted innovations in technology, biotechnology, biopharmaceuticals, cell-based therapies, and genetic therapy.

CONCLUSION

This review provides physicians and patients with relevant, usable information regarding how therapeutics can impact treatment regimen for facial aesthetics and skin rejuvenation. Furthermore, the goal of this research is to elucidate the varying therapeutics to restore appearance of youth, present associated outcomes, and in doing so, present plastic surgeons and their colleagues with greater insight on the role of these therapeutics and technologies in clinical practice. Future studies can further assess the safety and efficacy of these innovations and discuss how these may fit within surgical plans among patients seeking rejuvenation procedures.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Effect of Human Umbilical Cord-Derived Lyophilized Stem Cells on Fat Graft Viability: An Experimental Study

OBJECTIVE

The extended use of autologous adipose tissue has increased the importance of the viability of fat graft cells. This experimental animal study assesses the effects of lyophilized mesenchymal stem cells on the viability and survival of autologous fat grafts.

METHODS

For this prospective treatment control study, 27 male Wistar albino rats were divided into three groups, each containing nine animals. In Group 1 (control), an incision was made in the right inguinal region, and the skin was closed with 4/0 prolene sutures. In Groups 2 and 3, fat pads collected from the right groin of the rats were lipoaspirated and placed on the sternum as a subcutaneous fat graft. The skin was then closed with 4/0 prolene sutures. Saline was added to the fat grafts of the Group 2 (sham) rats, and placenta-derived mesenchymal stem cell lyophilizate (MSC-L) was administered to the fat graft in the Group 3 (treatment) rats. After three months of treatment, the adipose tissue harvested from Group 1 and the fat grafts taken from Groups 2 and 3 were assessed histopathologically, stereologically and biochemically.

RESULTS

Adipose tissue volume was lower in Group 2 than in Groups 1 and 3, and the adipose tissue treated with MSC-L in Group 3 was better preserved than that in Group 1. Connective tissue and vascular volumes were greater in Group 3 than those in the other groups. The normal structures of adipocytes, fibrous tissues and vessels were better preserved in Group 3 than in Group 2, and a large number of new blood vessels were noted to have formed in Group 3. Damaged cystic cells, areas of calcification and degenerated adipocytes were noted in Group 2, while the G3PDH levels increased significantly more in Group 3 than in Group 2.

CONCLUSION

It was shown that MSC-L treatment plays an active role in maintaining the volume and survival of fat grafts by promoting neovascularization in this animal experimental study.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Protective roles of mesenchymal stem cells on skin photoaging: A narrative review

Skin is a natural barrier of human body and a visual indicator of aging process. Exposure to ultraviolet (UV) radiation in the sunlight may injure the skin tissues and cause local damage. Besides, it is reported that repetitive or long-term exposure to UV radiation may reduce the collagen production, change the normal skin structure and cause premature skin aging. This is termed "photoaging". The classical symptoms of photoaging include increased roughness, wrinkle formation, mottled pigmentation or even precancerous changes. Mesenchymal stem cells (MSCs) are a kind of cells with the ability of self-renewal and multidirectional differentiation into many types of cells, like adipocytes, osteoblasts and chondrocytes. Researchers have explored diverse pharmacological actions of MSCs because of their migratory activity, paracrine actions and immunoregulation effects. In recent years, the huge potential of MSCs in preventing skin from photoaging has gained wide attention. MSCs exert their beneficial effects on skin photoaging via antioxidant effect, anti-apoptotic/anti-inflammatory effect, reduction of matrix metalloproteinases (MMPs) and activation of dermal fibroblasts proliferation. MSCs and MSC related products have demonstrated huge potential in the treatment of skin photoaging. This narrative review concisely sums up the recent research developments on the roles of MSCs in protection against photoaging and highlights the enormous potential of MSCs in skin photoaging treatment.

Construction of adipose tissue using a silica expander capsule and cell sheet-assembled of decellularized adipose tissue

Delayed neovascularization and unstable adipose formation are major confounding factors in adipose tissue engineering. A system using decellularized adipose tissue (DAT), adipose-derived stem cells (ADSCs), and human umbilical vein endothelial cells (HUVECs) has been preliminarily studied, but it requires optimization, as adipogenic and angiogenic capabilities for maintaining a stable construct shape are limited. The current study aimed to address these limitations. Our initial modification involved the addition of exogenous chemokine (C-C motif) ligand 2 (CCL2), which resulted in enhanced adipogenesis and angiogenesis. However, further improvement was required due to delayed blood recanalization. To further optimize the system, a vascularized fibrous capsule derived from an implanted silica expander was utilized as a second modification. We hypothesized this would function as both a microbioreactor to fix the seed cells and exogenous CCL2 locally and as a vascular bed to promote neovascularization. Compared with that of the CCL2 loaded ADSC-HUVECs cell sheet assembled DAT system, adding the silica expander capsule resulted in significantly increased construct stability, new vessel intensity, a greater number of Oil Red O-positive lipid droplets, more enhanced tissue remodeling, and upregulated peroxisome proliferator-activated receptor gamma (PPARγ) & leptin expression. Thus, these two modifications helped optimize the currently available ADSC-HUVEC cell sheet assembled DAT system, providing an adipose tissue construction strategy with enhanced adipogenesis and angiogenesis to reconstruct soft tissue defects. Moreover, close-to-normal leptin expression provided the engineered adipose tissue with a glucometabolic function, in addition to remodeling capabilities. STATEMENT OF SIGNIFICANCE: Delayed neovascularization and unstable adipose formation are the two major problems in tissue engineering adipose. Here, we introduced an adipose tissue engineering construction strategy using a silica expander capsule along with hADSCs-HUVECs cell sheet-assembled DAT in a CCL2-rich microenvironment. Our data suggested that CCL2 could improve angiogenesis and adipogenesis in vitro and in vivo. The addition of tissue expander capsule could further improve the stability of construction and fabricated adipose tissue with increased new vessel intensity, greater numbers of Oil Red O-positive lipid droplets, more enhanced tissue remodeling, and upregulated leptin expression. CCL2 and expander capsule can have clinical utility for soft tissue defects repair, and these two factors can be useful in other tissue engineering.

New insight of immuno-engineering in osteoimmunomodulation for bone regeneration

With the continuous development of bone tissue engineering, the importance of immune response in bone tissue regeneration is gradually recognized. The new bone tissue engineering products should possess immunoregulatory functions, harmonizing the interactions between the bone's immune defense and regeneration systems, and promoting tissue regeneration. This article will interpret the relationship between the bone immune system, bone tissue regeneration, as well as the immunoregulatory function of bone biomaterials and seed stem cells in bone tissue engineering. This review locates arears for foucusing efforts at providing novel designs ideas about the development of immune-mediation targeted bone tissue engineering products and the evaluation strategy for the osteoimmunomodulation property of bone biomaterials.

Adipose tissue-derived mesenchymal stem cells for breast tissue regeneration

With an escalating incidence of breast cancer cases all over the world and the deleterious psychological impact that mastectomy has on patients along with several limitations of the currently applied modalities, it's plausible to seek unconventional approaches to encounter such a burgeoning issue. Breast tissue engineering may allow that chance via providing more personalized solutions which are able to regenerate, mimicking natural tissues also facing the witnessed limitations. This review is dedicated to explore the utilization of adipose tissue-derived mesenchymal stem cells for breast tissue regeneration among postmastectomy cases focusing on biomaterials and cellular aspects in terms of harvesting, isolation, differentiation and new tissue formation as well as scaffolds types, properties, material-host interaction and an in vitro breast tissue modeling.

Application of adipose-derived stem cells in photoaging: basic science and literature review

Photoaging is mainly induced by continuous exposure to sun light, causing multiple unwanted skin characters and accelerating skin aging. Adipose-derived stem cells(ADSCs) are promising in supporting skin repair because of their significant antioxidant capacity and strong proliferation, differentiation, and migration ability, as well as their enriched secretome containing various growth factors and cytokines. The identification of the mechanisms by which ADSCs perform these functions for photoaging has great potential to explore therapeutic applications and combat skin aging. We also review the basic mechanisms of UV-induced skin aging and recent improvement in pre-clinical applications of ADSCs associated with photoaging. Results showed that ADSCs are potential to address photoaging problem and might treat skin cancer. Compared with ADSCs alone, the secretome-based approaches and different preconditionings of ADSCs are more promising to overcome the current limitations and enhance the anti-photoaging capacity.

Epidural hemostasis by autologous fat graft in minimally invasive surgery for lumbar spinal stenosis: In vivo experimental study

BACKGROUND

Epidural hemostasis needs to use small, adapted material in minimally invasive surgery, including bilateral decompression via a unilateral approach for lumbar spinal stenosis. Most surgeons avoid external material for hemostasis because of possible neural tissue damage or complications. We compared epidural hemostasis in minimally invasive surgery by fat graft versus gelatin sponge.

METHODS

The design was a prospective randomized controlled in-vivo human experimental study. The 24 levels operated on for lumbar spinal stenosis were evaluated in two groups: Group A (control group: gelatin sponge) and Group B (experimental group: fat graft). International Normalized Ratio and Prothrombin Time were assessed preoperatively. Number of cotton hemostats and systolic and diastolic blood pressure were assessed intraoperatively. Epidural hemorrhage area, spinal cord size and ratio of epidural hemorrhage area to spinal cord size were evaluated on early postoperative lumbar MRI.

RESULTS

Mean epidural hemorrhage area in groups A and B was respectively 1.3±0.5 and 1.2±0.6cm², and mean spinal cord size 1.2±0.6 and 1.8±0.6cm² on early postoperative axial lumbar MRI. The two groups did not significantly differ in ratio of epidural hemorrhage/spinal cord size or number of intraoperative hemostats (P=0.36, and P=0.71).

CONCLUSIONS

The autologous fat graft ensured sufficient and safe epidural hemostasis without serious adverse events in minimally invasive spinal surgery, and is preferable as autologous tissue is easily and quickly harvested. The surgeon feels safe with this technique and does not need external hemostatic agents.

Growing a backbone - functional biomaterials and structures for intervertebral disc (IVD) repair and regeneration: challenges, innovations, and future directions

Back pain and associated maladies can account for an immense amount of healthcare cost and loss of productivity in the workplace. In particular, spine related injuries in the US affect upwards of 5.7 million people each year. The degenerative disc disease treatment almost always arises due to a clinical presentation of pain and/or discomfort. Preferred conservative treatment modalities include the use of non-steroidal anti-inflammatory medications, physical therapy, massage, acupuncture, chiropractic work, and dietary supplements like glucosamine and chondroitin. Artificial disc replacement, also known as total disc replacement, is a treatment alternative to spinal fusion. The goal of artificial disc prostheses is to replicate the normal biomechanics of the spine segment, thereby preventing further damage to neighboring sections. Artificial functional disc replacement through permanent metal and polymer-based components continues to evolve, but is far from recapitulating native disc structure and function, and suffers from the risk of unsuccessful tissue integration and device failure. Tissue engineering and regenerative medicine strategies combine novel material structures, bioactive factors and stem cells alone or in combination to repair and regenerate the IVD. These efforts are at very early stages and a more in-depth understanding of IVD metabolism and cellular environment will also lead to a clearer understanding of the native environment which the tissue engineering scaffold should mimic. The current review focusses on the strategies for a successful regenerative scaffold for IVD regeneration and the need for defining new materials, environments, and factors that are so finely tuned in the healthy human intervertebral disc in hopes of treating such a prevalent degenerative process.

Fat Graft Enrichment Strategies: A Systematic Review

BACKGROUND

Autologous fat grafting is a dynamic modality used in plastic surgery as an adjunct to improve functional and aesthetic form. However, current practices in fat grafting for soft-tissue augmentation are plagued by tremendous variability in long-term graft retention, resulting in suboptimal outcomes and repetitive procedures. This systematic review identifies and critically appraises the evidence for various enrichment strategies that can be used to augment and improve the viability of fat grafts.

METHODS

A comprehensive literature search of the Medline and PubMed databases was conducted for animal and human studies published through October of 2017 with multiple search terms related to adipose graft enrichment agents encompassing growth factors, platelet-rich plasma, adipose-derived and bone marrow stem cells, gene therapy, tissue engineering, and other strategies. Data on level of evidence, techniques, complications, and outcomes were collected.

RESULTS

A total of 1382 articles were identified, of which 147 met inclusion criteria. The majority of enrichment strategies demonstrated positive benefit for fat graft survival, particularly with growth factors and adipose-derived stem cell enrichment. Platelet-rich plasma and adipose-derived stem cells had the strongest evidence to support efficacy in human studies and may demonstrate a dose-dependent effect.

CONCLUSIONS

Improved understanding of enrichment strategies contributing to fat graft survival can help to optimize safety and outcomes. Controlled clinical studies are lacking, and future studies should examine factors influencing graft survival through controlled clinical trials in order to establish safety and to obtain consistent outcomes.

Tissue engineering applications in breast cancer

In Iran, breast cancer (BC) is the most prevalent cancer among women. The standard treatment for this cancer is partial or total removal of breast tissue, followed by chemotherapy and radiation. Tissue engineering (TE) has made new treatments for tissue loss in these patients by creating functional substitutes in the laboratory. In addition, cancer biology combined with TE provides a new strategy for evaluation of anti-BC therapy. Several innovations in TE have led to the design of scaffold or matrix based culture systems that more closely mimic the native extracellular matrix (ECM). Currently, engineered three-dimensional (3D) cultures are being developed for modelling of the tumour microenvironment. These 3D cultures fulfil the need for in vitro approaches that allow an accurate study of the molecular mechanisms and a better analysis of the drugs effect. In the present study, we review recent developments in utilising of TE in BC. Moreover, this review describes achievements of Iranian researchers in the field of breast TE.

Transplantation of Adipose-Derived Stem Cells Before Flap Expansion and After Expanded Flap Elevation Result in Different Effects

BACKGROUND

Studies of using mesenchymal stem cells to assist skin and soft tissue expansion have shown that stem cells can improve expansion efficiency through promoting tissue regeneration. However, the issue that whether the flap viability is also improved is unknown.

METHODS

Sixteen pigs were equally divided into 2 groups. A pair of 150 mL expanders was symmetrically inserted into each pig's dorsum. Group 1 received adipose-derived stem cells (ADSCs) injection before expansion, and group 2 received ADSCs grafting after flap elevation. After 4 weeks' expansion, a random flap measuring 2 cm × 16 cm was elevated along the long axis of each expanded flap on the pigs' back. Flap viability was measured at postoperative day 7. Histological analysis and cell tracking were performed. The expression of vascular endothelial growth factor was determined.

RESULTS

The flap viability of the ADSCs-grafted expanded flap (75.5 ± 6.6%) was similar to the control (69.4 ± 8.4%) in group 1 (transplantation before expansion). However, in group 2 (transplantation after flap elevation), the ADSCs-grafted expanded flap had a higher flap viability (92.6 ± 5.7%) compared with control (66.2 ± 7.4%). Moreover, the ADSCs-grafted expanded flap in group 1 showed increased skin thickness, collagen content, cells proliferation, vascularization, and vascular endothelial growth factor expression. Cell tracking showed that the positively stained cell differentiating into an endotheliocyte could be seen in group 2.

CONCLUSIONS

Transplantation of ADSCs before tissue expansion does not improve flap viability but can promote tissue regeneration. Injection of ADSCs after flap elevation can increase the surviving rate of the expanded flap.

Conventional Nanofat and SVF/ADSC-Concentrated Nanofat: A Comparative Study on Improving Photoaging of Nude Mice Skin

BACKGROUND

Nanofats could improve photoaging. Stromal vascular fraction (SVF) and adipose-derived stem cells (ADSCs) may play pivotal roles. However, SVFs and ADSCs in nanofats processed by conventional methods cannot be enriched. Some researchers have found that after centrifugation, the SVF/ADSC density increases from top to bottom.

OBJECTIVES

The authors hypothesized that centrifugation can be used to obtain SVF/ADSC-concentrated nanofats that are superior to conventional nanofats in improving the photoaging of skin.

METHODS

After a photoaging model was successfully established in nude mice, the back of each mouse was divided into 4 areas and randomly injected with conventional nanofat, centrifuged nanofat (either the middle or lower layer of centrifuged nanofat), or normal saline. Wrinkles, dermis thickness, dermal collagen content, and elastic fiber morphology were measured and compared at weeks 4 and 8.

RESULTS

Compared with the wrinkles in the physiological saline injection areas, the wrinkles in the areas injected with the 3 nanofats (lower and middle layers of centrifuged nanofat and conventional nanofat) were significantly reduced. All 3 nanofat groups showed increased dermal thickness, increased collagen content, and a more regular distribution of elastic fibers compared with the saline injection areas.

CONCLUSIONS

The study established the efficacy of nanofats in improving photoaging by reducing wrinkles and increasing the thickness of dermal collagen, making nanofats a promising novel treatment for photoaging. The SVF/ADSC-concentrated nanofats exhibited the most improvement.

Biological Morphogenetic Surgery: A Minimally Invasive Procedure to Address Different Biological Mechanisms

We present a methodology called biological morphogenetic surgery (BMS) that can recover (enlarge or reduce) the shape/volume of anatomic structures/tissues affected by congenital or acquired malformations based on a minimally invasive procedure. This emerges as a new concept in which the main task of surgery is the biological modulation of different remodeling and repair mechanisms. When applied, for example, to a tuberous breast deformity, the "enlarging BMS" expands the retracted tissue surrounding the gland through a cutting tip of a needle being inserted through small incisions percutaneously, accounting for the biological activity of the grafted fat. The obtained spaces might be spontaneously occupied and later filled with autologous grafted fat, which promotes tissue expansion by eliciting adipogenesis and preventing fibrosis. The "reducing BMS" creates an interruption of the contact between the derma and the hypoderma of the abnormally large areola and then promotes adipocytes to induce a fibrotic reaction, leading to areola reduction. Current evidence suggests that BMS might induce a bivalent mesenchymalization of the adipocyte, which promotes either new adipogenesis and angiogenesis of local fat (expanding BMS) or the granulation tissue/fibrotic response (reducing BMS), thus leading to the physiological recovery of the affected structures/tissues to normality. Level of Evidence: 4.

Assisting Rapid Soft-Tissue Expansion with Adipose-Derived Stem Cells: An Experimental Study in a Pig Model

BACKGROUND

Rapid tissue expansion has been attempted, aiming at shortening the period of conventional expansion. However, it has scarcely been clinically applied because of its drawbacks such as low expansion efficiency and tissue destruction. Adipose-derived stem cell transplantation is a promising therapeutic method in regenerative medicine. However, its effects on rapid expansion remain poorly understood.

METHODS

Twenty-four expanders were implanted in the dorsum of 12 pigs. Rapid expansion persisted for 1 week with 20 ml of saline daily. The increased area of the expanded skin was measured. Histologic and ultrastructural analysis and cell tracking were performed. The expression of vascular endothelial growth factor, fibroblast growth factor-2, and epidermal growth factor was also determined.

RESULTS

The increased area of adipose-derived stem cell-grafted expanded skin (0.91 ± 0.06 cm) was significantly more than the non-adipose-derived stem cell-treated control (0.51 ± 0.05 cm) (p < 0.01). Enhanced tissue regeneration in the adipose-derived stem cell-grafted expanded skin was evidenced by increased skin thickness, proliferating cells, extracellular matrix, and vascularization (113 ± 19/mm versus control 59 ± 14/mm) (all p < 0.05). Higher expression of vascular endothelial growth factor and epidermal growth factor was observed in the adipose-derived stem cell-transplanted expanded skin (p < 0.01 and p < 0.05, respectively), whereas the expression of fibroblast growth factor-2 was higher in the non-adipose-derived stem cell-treated control (p < 0.05). Transmission electron microscopy showed that a high density of collagen fibers could be seen in the adipose-derived stem cell-treated expanded skin. Cell tracking showed that the positively stained cells could be seen.

CONCLUSION

For rapid tissue expansion, adipose-derived stem cell transplantation may limit tissue destruction and improve the expansion efficiency by promoting tissue regeneration.

A Thin Layer of Decellularized Porcine Myocardium for Cell Delivery

Decellularized porcine myocardium has shown many benefits as a cell delivery scaffold for cardiac therapy. However, using full thickness decellularized myocardium as cardiac patch may lead to poor viability and inhomogeneous distribution of delivered cells, due to perfusion limitations. In this study, we explored the feasibility of decellularized porcine myocardial slice (dPMS) to construct a vascularized cardiac patch for cell delivery. Decellularized porcine myocardium was sliced into thin layers (thickness~300 µm). Adipose-derived Stem cells (ASCs) obtained from rat and pig were seeded on dPMS. The viability, infiltration, and differentiation of seeded ASCs were examined. The mechanical properties of dPMSs of various thickness and native myocardium were tested. We noticed dPMS supported attachment and growth of rat and pig ASCs. Both rat and pig ASCs showed high viability, similar patterns of proliferation and infiltration within dPMS. Rat ASCs showed expression of early-endothelial markers followed by mature-endothelial marker without any additional inducers on dPMS. Using rat myocardial infarction model, we delivered ASCs using dPMS patched to the infarcted myocardium. After 1 week, a higher number of transplanted cells were present in the infarcted area when cells were delivered using dPMS versus direct injection. Compared with MI group, increased vascular formation was also observed.

Characterization of Adipose-Derived Stem Cells Following Burn Injury

Severe burns induce a prolonged inflammatory response in subcutaneous adipose tissue that modulates signaling in adipose-derived stem cells (ASCs), which hold potential for healing burn wounds or generating skin substitutes. Using a 60% rat scald burn model, we conducted a series of experiments to determine which cells isolated from the adipose tissue produced inflammatory mediators and how these changes affect ASC fate and function. The stromal vascular fraction (SVF), adipocytes, and ASCs were isolated from adipose tissue at varying times up to 4 weeks postburn and from non-injured controls. Endpoints included inflammatory marker expression, expression of ASC-specific cell-surface markers, DNA damage, differentiation potential, and proliferation. Inflammatory marker expression was induced in adipocytes and the SVF at 24 and 48 h postburn; expression of inflammatory marker mRNA transcripts and protein returned to normal in the SVF isolated 1 week postburn. In enriched ASCs, burns did not alter cell-surface expression of stem cell markers, markers of inflammation, differentiation potential, or proliferative ability. These results suggest that adipocytes and the SVF produce large quantities of inflammatory mediators, but that ASCs do not, after burns and that ASCs are unaffected by burn injury or culturing procedures.. They also suggest that cells isolated over 48 h after injury are best for cell culture or tissue engineering purposes.

CD54+ rabbit adipose-derived stem cells overexpressing HIF-1α facilitate vascularized fat flap regeneration

Fat flap transplantation is frequently performed in patients suffering from soft tissue defects resulting from disease or trauma. This study explored the feasibility of constructing vascularized fat flaps using rabbit adipose-derived stem cells (rASCs) and collagen scaffolds in a rabbit model. We evaluated rASCs proliferation, paracrine function, adipogenesis, vascularization, and CD54 expression, with or without HIF-1α transfection in vitro and in vivo. We observed that adipogenic differentiation potential was greater in rASCs with high CD54 expression (CD54⁺rASCs) than in those with low expression (CD54^–rASCs), both in vitro and in vivo. HIF-1α overexpression not only augmented this effect, but also enhanced cell proliferation and paracrine function in vitro. We also demonstrated that HIF-1α-transfected CD54⁺rASCs showed enhanced paracrine function and adipogenic capacity, and that paracrine function increases expression of angiogenesis-related markers. Thus, CD54⁺rASCs overexpressing HIF-1α enhanced large volume vascularized fat flap regeneration in rabbits, suggesting CD54 may be an ideal candidate marker for ASCs adipogenic differentiation.

Stem Cells and Engineered Scaffolds for Regenerative Wound Healing

The normal wound healing process involves a well-organized cascade of biological pathways and any failure in this process leads to wounds becoming chronic. Non-healing wounds are a burden on healthcare systems and set to increase with aging population and growing incidences of obesity and diabetes. Stem cell-based therapies have the potential to heal chronic wounds but have so far seen little success in the clinic. Current research has been focused on using polymeric biomaterial systems that can act as a niche for these stem cells to improve their survival and paracrine activity that would eventually promote wound healing. Furthermore, different modification strategies have been developed to improve stem cell survival and differentiation, ultimately promoting regenerative wound healing. This review focuses on advanced polymeric scaffolds that have been used to deliver stem cells and have been tested for their efficiency in preclinical animal models of wounds.

Treatment of Vesicovaginal Fistulas With Autologous Cell Injections—A Randomized Study in an Animal Model

Purpose:

Materials and Methods:

Results:

Conclusion:

Experimental In-Vivo Models Used in Fat Grafting Research for Volume Augmentation in Soft Tissue Reconstruction

As the popularity of fat grafting research increases, animal models are being used as the source of pre-clinical experimental information for discovery and to enhance techniques. To date, animal models used in this research have not been compared to provide a standardized model. We analyzed publications from 1968–2015 to compare published accounts of animal models in fat grafting research. Data collected included: species used, graft characteristics (donor tissue, recipient area, amount injected, injection technique), time of sacrifice and quantification methods. Mice were most commonly used (56% of studies), with the “athymic nude” strain utilized most frequently (44%). Autologous fat was the most common source of grafted tissue (52%). Subcutaneous dorsum was the most common recipient site (51%). On average, 0.80±0.60 mL of fat was grafted. A single bolus technique was used in 57% of studies. Fat volume assessment was typically completed at the end of the study, occurring at less than 1 week to one year. Graft volume was quantified by weight (63%), usually in conjunction with another analysis. The results demonstrate the current heterogeneity of animal models in this research. We propose that the research community reach a consensus to allow better comparison of techniques and results. One example is the model used in our laboratory and others; this model is described in detail. Eventually, larger animal models may better translate to the human condition but, given increased financial costs and animal facility capability, should be explored when data obtained from small animal studies is exhausted or inconclusive.

Breast Augmentation and Reconstruction from a Regenerative Medicine Point of View: State of the Art and Future Perspectives

Breast reconstruction and augmentation are very common procedures, yet the prevailing current methods utilize silicone implants that may have significant local complications requiring reoperation. Lipofillling is increasingly used to contour and is considered safe, however, its utility is limited by significant volume loss. A new approach could offer an alternative and increase the scope of patient choice. A small number of teams around the world are investigating a breast tissue engineering (TE) paradigm. Conventional breast TE concepts are based on seeding a scaffold with the patients' own stem cells. However, the clinical viability of many of these approaches is limited by their costs in relevant volumes. In this article the state of the art of tissue-engineered breast reconstruction is reviewed and future perspectives are presented and discussed.

Stem Cells and Tissue Engineering: Regeneration of the Skin and Its Contents

In this review, the authors discuss the stages of skin wound healing, the role of stem cells in accelerating skin wound healing, and the mechanism by which these stem cells may reconstitute the skin in the context of tissue engineering.

The regenerative role of adipose-derived stem cells (ADSC) in plastic and reconstructive surgery

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs offers a paradigm shift in plastic and reconstructive surgery. The use of either embryonic stem cells (ESC) or induced pluripotent stem cells (iPSC) in clinical situations is limited because of regulations and ethical considerations even though these cells are theoretically highly beneficial. Adult mesenchymal stem cells appear to be an ideal stem cell population for practical regenerative medicine. Among these cells, adipose-derived stem cells (ADSC) have the potential to differentiate the mesenchymal, ectodermal and endodermal lineages and are easy to harvest. Additionally, adipose tissue yields a high number of ADSC per volume of tissue. Based on this background knowledge, the purpose of this review is to summarise and describe the proliferation and differentiation capacities of ADSC together with current preclinical data regarding the use of ADSC as regenerative tools in plastic and reconstructive surgery.

Winner of the Young Investigator Award of the Society for Biomaterials at the 10th World Biomaterials Congress, May 17-22, 2016, Montreal QC, Canada: Microribbon-based hydrogels accelerate stem cell-based bone regeneration in a mouse critical-size cranial defect model

Stem cell-based therapies hold great promise for enhancing tissue regeneration. However, the majority of cells die shortly after transplantation, which greatly diminishes the efficacy of stem cell-based therapies. Poor cell engraftment and survival remain a major bottleneck to fully exploiting the power of stem cells for regenerative medicine. Biomaterials such as hydrogels can serve as artificial matrices to protect cells during delivery and guide desirable cell fates. However, conventional hydrogels often lack macroporosity, which restricts cell proliferation and delays matrix deposition. Here we report the use of injectable, macroporous microribbon (μRB) hydrogels as stem cell carriers for bone repair, which supports direct cell encapsulation into a macroporous scaffold with rapid spreading. When transplanted in a critical-sized, mouse cranial defect model, μRB-based hydrogels significantly enhanced the survival of transplanted adipose-derived stromal cells (ADSCs) (81%) and enabled up to three-fold cell proliferation after 7 days. In contrast, conventional hydrogels only led to 27% cell survival, which continued to decrease over time. MicroCT imaging showed μRBs enhanced and accelerated mineralized bone repair compared to hydrogels (61% vs. 34% by week 6), and stem cells were required for bone repair to occur. These results suggest that paracrine signaling of transplanted stem cells are responsible for the observed bone repair, and enhancing cell survival and proliferation using μRBs further promoted the paracrine-signaling effects of ADSCs for stimulating endogenous bone repair. We envision μRB-based scaffolds can be broadly useful as a novel scaffold for enhancing stem cell survival and regeneration of other tissue types. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1321-1331, 2016.

Injectable SVF-loaded porcine extracellular matrix powders for adipose tissue engineering

This study provides a novel method in injectable tissue engineering which contains porcine extracellular matrix (ECM) powder scaffolds and stromal-vascular fraction (SVF) cells.

Engineering vascularized soft tissue flaps in an animal model using human adipose-derived stem cells and VEGF+PLGA/PEG microspheres on a collagen-chitosan scaffold with a flow-through vascular pedicle

Insufficient neovascularization is associated with high levels of resorption and necrosis in autologous and engineered fat grafts. We tested the hypothesis that incorporating angiogenic growth factor into a scaffold-stem cell construct and implanting this construct around a vascular pedicle improves neovascularization and adipogenesis for engineering soft tissue flaps. Poly(lactic-co-glycolic-acid/polyethylene glycol (PLGA/PEG) microspheres containing vascular endothelial growth factor (VEGF) were impregnated into collagen-chitosan scaffolds seeded with human adipose-derived stem cells (hASCs). This setup was analyzed in vitro and then implanted into isolated chambers around a discrete vascular pedicle in nude rats. Engineered tissue samples within the chambers were harvested and analyzed for differences in vascularization and adipose tissue growth. In vitro testing showed that the collagen-chitosan scaffold provided a supportive environment for hASC integration and proliferation. PLGA/PEG microspheres with slow-release VEGF had no negative effect on cell survival in collagen-chitosan scaffolds. In vivo, the system resulted in a statistically significant increase in neovascularization that in turn led to a significant increase in adipose tissue persistence after 8 weeks versus control constructs. These data indicate that our model-hASCs integrated with a collagen-chitosan scaffold incorporated with VEGF-containing PLGA/PEG microspheres supported by a predominant vascular vessel inside a chamber-provides a promising, clinically translatable platform for engineering vascularized soft tissue flap. The engineered adipose tissue with a vascular pedicle could conceivably be transferred as a vascularized soft tissue pedicle flap or free flap to a recipient site for the repair of soft-tissue defects.

Methacrylated gelatin and mature adipocytes are promising components for adipose tissue engineering

In vitro engineering of autologous fatty tissue constructs is still a major challenge for the treatment of congenital deformities, tumor resections or high-graded burns. In this study, we evaluated the suitability of photo-crosslinkable methacrylated gelatin (GM) and mature adipocytes as components for the composition of three-dimensional fatty tissue constructs. Cytocompatibility evaluations of the GM and the photoinitiator Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) showed no cytotoxicity in the relevant range of concentrations. Matrix stiffness of cell-laden hydrogels was adjusted to native fatty tissue by tuning the degree of crosslinking and was shown to be comparable to that of native fatty tissue. Mature adipocytes were then cultured for 14 days within the GM resulting in a fatty tissue construct loaded with viable cells expressing cell markers perilipin A and laminin. This work demonstrates that mature adipocytes are a highly valuable cell source for the composition of fatty tissue equivalents in vitro. Photo-crosslinkable methacrylated gelatin is an excellent tissue scaffold and a promising bioink for new printing techniques due to its biocompatibility and tunable properties.

Combining decellularized human adipose tissue extracellular matrix and adipose-derived stem cells for adipose tissue engineering

Repair of soft tissue defects resulting from lumpectomy or mastectomy has become an important rehabilitation process for breast cancer patients. This study aimed to provide an adipose tissue engineering platform for soft tissue defect repair by combining decellularized human adipose tissue extracellular matrix (hDAM) and human adipose-derived stem cells (hASCs). To derive hDAM incised human adipose tissues underwent a decellularization process. Effective cell removal and lipid removal were proved by immunohistochemical analysis and DNA quantification. Scanning electron microscopic examination showed a three-dimensional nanofibrous architecture in hDAM. The hDAM included collagen, sulfated glycosaminoglycan, and vascular endothelial growth factor, but lacked major histocompatibility complex antigen I. hASC viability and proliferation on hDAM were proven in vitro. hDAM implanted subcutaneously in Fischer rats did not cause an immunogenic response, and it underwent remodeling, as indicated by host cell infiltration, neovascularization, and adipose tissue formation. Fresh fat grafts (Coleman technique) and engineered fat grafts (hDAM combined with hASCs) were implanted subcutaneously in nude rats. The implanted engineered fat grafts maintained their volume for 8 weeks, and the hASCs contributed to adipose tissue formation. In summary, the combination of hDAM and hASCs provides not only a clinically translatable platform for adipose tissue engineering, but also a vehicle for elucidating fat grafting mechanisms.

Mesenchymal stem cells and nano-structured surfaces

Mesenchymal stem cells (MSCs) represent multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage cells), and adipocytes (fat cells). Their multi-potency provides a great promise as a cell source for tissue engineering and cell-based therapy for many diseases, particularly bone diseases and bone formation. To be able to direct and modulate the differentiation of MSCs into the desired cell types in situ in the tissue, nanotechnology is introduced and used to facilitate or promote cell growth and differentiation. These nano-materials can provide a fine structure and tuneable surface in nanoscales to help the cell adhesion and promote the cell growth and differentiation of MSCs. This could be a dominant direction in future for stem cells based therapy or tissue engineering for various diseases. Therefore, the isolation, manipulation, and differentiation of MSCs are very important steps to make meaningful use of MSCs for disease treatments. In this chapter, we have described a method of isolating MSC from human bone marrow, and how to culture and differentiate them in vitro. We have also provided research methods on how to use MSCs in an in vitro model and how to observe MSC biological response on the surface of nano-scaled materials.