Synergistic angiogenesis promoting effects of extracellular matrix scaffolds and adipose-derived stem cells during wound repair

Fabrication and characterization of a hydrocolloid wound dressing functionalized with human placental derived extracellular matrix for management of skin wounds: An animal study

BACKGROUND

Functionalization of wound dressing is one of the main approaches for promoting wound healing in skin wound management. In this study, our aim is to fabricate a bio-functionalized hydrocolloid wound dressing.

METHODS

The extracellular matrix (ECM) was extracted from human placental tissue. A hydrocolloid film was fabricated using Na-CMC, pectin, gelatin, styrene-isoprene-styrene adhesive, glycerol, and 0.5%-2.5% powdered ECM. A polyurethane film and a release liner were used in the hydrocolloid/ECM films. The mechanical, adhesion, swelling rate, and integrity of the films were investigated. Cell proliferation, adhesion, and migration assays, as well as, SEM and FTIR spectroscopy were also conducted. Macroscopic and microscopic evaluations of wound healing process and formation of blood vessels were conducted in mouse animal models.

RESULTS

We successfully fabricated a three-layered ECM-functionalized hydrocolloid dressing with a water vapor transmission rate of 371 g/m2 /day and an adhesion peel strength of 176 KPa. Cellular adhesion, proliferation and migration were promoted by ECM. In the animal tests, ECM-functionalized hydrocolloids significantly improved wound closure and re-epithelialization at days 14 and 21. Also, ECM-functionalized hydrocolloids promoted the formation of hair follicles.

CONCLUSIONS

Our findings suggest that ECM could enhance the wound healing properties of hydrocolloid wound dressings. This wound dressing could be considered for application in hard-to-heal acute wounds.

Experimental study on the effect and mechanism of adipose stem cell-derived exosomes combined with botulinum toxin A on skin trauma in rats

BACKGROUND

Adipose stem cell-derived exosomes (ADSC-EXO) and botulinum toxin type A (BTX-A) individually showed a therapeutic effect on skin wound repair.

AIMS

This study investigated their synergistic effect on promoting skin wound healing in vitro and in vivo and the underlying molecular events.

METHODS

ADSCs were isolated from Sprague-Dawley (SD) rats to obtain ADSC-EXO by ultrafiltration and ultracentrifugation and were confirmed using nanoparticle tracking analysis and transmission electron microscopy. Human skin fibroblasts (HSF) were cultured and treated with or without ADSC-EXO, BTX-A, or their combination. Changes in cell phenotypes and protein expression were analyzed using different in vitro assays, and a rat skin wound model was used to assess their in vivo effects.

RESULTS

The isolated ADSC-EXO from primarily cultured ADSCs had a circular vesicle shape with a 30-180 nm diameter. Treatment of HSF with ADSC-EXO and/or BTX-A significantly accelerated HSF migration in vitro and skin wound healing in a rat model. Moreover, ADSC-EXO plus BTX-A treatment dramatically induced VEGFA expression but reduced COL III and COL I levels in vivo. ADSC-EXO and/or BTX-A treatment significantly upregulated TGF-β3 expression on Day 16 after surgery but downregulated TGF-β1 expression, suggesting that ADSC-EXO plus BTX-A promoted skin wound healing and reduced inflammatory cell infiltration.

CONCLUSIONS

The ADSC-EXO plus BTX-A treatment demonstrated a synergistic effect on skin wound healing through upregulation of VEGF expression and the TGF-β3/TGF-β1 and COL III/COL I ratio.

Development of a Self-Assembled Dermal Substitute from Human Fibroblasts Using Long-term Three-Dimensional Culture

Skin substitutes have emerged as an alternative to autografts for the treatment of skin defects. Among them, scaffold-based dermal substitutes have been extensively studied; however, they have certain limitations, such as delayed vascularization, limited elasticity, and the inability to achieve permanent engraftment. Self-assembled, cell-based dermal substitutes are a promising alternative that may overcome these shortcomings but have not yet been developed. In this study, we successfully developed a cell-based dermal substitute (cultured dermis) through the long-term culture of human dermal fibroblasts using the net-mold method, which enables three-dimensional cell culture without the use of a scaffold. Spheroids prepared from human dermal fibroblasts were poured into a net-shaped mold and cultured for 2, 4, or 6 months. The dry weight, tensile strength, collagen and glycosaminoglycan levels, and cell proliferation capacity were assessed and compared among the 2-, 4-, and 6-month culture periods. We found that collagen and glycosaminoglycan levels decreased over time, while the dry weight remained unchanged. Tensile strength increased at 4 months, suggesting that remodeling had progressed. In addition, the cell proliferation capacity was maintained, even after a 6-month culture period. Unexpectedly, the internal part of the cultured dermis became fragile, resulting in the division of the cultured dermis into two collagen-rich tissues, each of which had a thickness of 400 μm and sufficient strength to be sutured during in vivo analysis. The divided 4-month cultured dermis was transplanted to skin defects of immunocompromised mice and its wound healing effects were compared to those of a clinically available collagen-based artificial dermis. The cultured dermis promoted epithelialization and angiogenesis more effectively than the collagen-based artificial dermis. Although further improvements are needed, such as the shortening of the culture period and increasing the size of the cultured dermis, we believe that the cultured dermis presented in this study has the potential to be an innovative material for permanent skin coverage.

Biomaterials / bioinks and extrusion bioprinting

Bioinks are formulations of biomaterials and living cells, sometimes with growth factors or other biomolecules, while extrusion bioprinting is an emerging technique to apply or deposit these bioinks or biomaterial solutions to create three-dimensional (3D) constructs with architectures and mechanical/biological properties that mimic those of native human tissue or organs. Printed constructs have found wide applications in tissue engineering for repairing or treating tissue/organ injuries, as well as in vitro tissue modelling for testing or validating newly developed therapeutics and vaccines prior to their use in humans. Successful printing of constructs and their subsequent applications rely on the properties of the formulated bioinks, including the rheological, mechanical, and biological properties, as well as the printing process. This article critically reviews the latest developments in bioinks and biomaterial solutions for extrusion bioprinting, focusing on bioink synthesis and characterization, as well as the influence of bioink properties on the printing process. Key issues and challenges are also discussed along with recommendations for future research.

The Effects of Tissue Healing Factors in Wound Repair Involving Absorbable Meshes: A Narrative Review

Wound healing is a complex and meticulously orchestrated process involving multiple phases and cellular interactions. This narrative review explores the intricate mechanisms behind wound healing, emphasizing the significance of cellular processes and molecular factors. The phases of wound healing are discussed, focusing on the roles of immune cells, growth factors, and extracellular matrix components. Cellular shape alterations driven by cytoskeletal modulation and the influence of the 'Formin' protein family are highlighted for their impact on wound healing processes. This review delves into the use of absorbable meshes in wound repair, discussing their categories and applications in different surgical scenarios. Interleukins (IL-2 and IL-6), CD31, CD34, platelet rich plasma (PRP), and adipose tissue-derived mesenchymal stem cells (ADSCs) are discussed in their respective roles in wound healing. The interactions between these factors and their potential synergies with absorbable meshes are explored, shedding light on how these combinations might enhance the healing process. Recent advances and challenges in the field are also presented, including insights into mesh integration, biocompatibility, infection prevention, and postoperative complications. This review underscores the importance of patient-specific factors and surgical techniques in optimizing mesh placement and healing outcomes. As wound healing remains a dynamic field, this narrative review provides a comprehensive overview of the current understanding and potential avenues for future research and clinical applications.

Efficacy of Supercritical Fluid Decellularized Porcine Acellular Dermal Matrix in the Post-Repair of Full-Thickness Abdominal Wall Defects in the Rabbit Hernia Model

Damage to abdominal wall integrity occurs in accidents, infection and herniation. Repairing the hernia remains to be one of the most recurrent common surgical techniques. Supercritical carbon dioxide (SCCO2) was used to decellularize porcine skin to manufacture acellular dermal matrix (ADM) for the reparation of full-thickness abdominal wall defects and hernia. The ADM produced by SCCO2 is chemically equivalent and biocompatible with human skin. The ADM was characterized by hematoxylin and eosin (H&E) staining, 4,6-Diamidino-2-phenylindole, dihydrochloride (DAPI) staining, residual deoxyribonucleic acid (DNA) contents and alpha-galactosidase (α-gal staining), to ensure the complete decellularization of ADM. The ADM mechanical strength was tested following the repair of full-thickness abdominal wall defects (4 × 4 cm) created on the left and right sides in the anterior abdominal wall of New Zealand White rabbits. The ADM produced by SCCO2 technology revealed complete decellularization, as characterized by H&E, DAPI staining, DNA contents (average of 26.92 ng/mg) and α-gal staining. In addition, ADM exhibited excellent performance in the repair of full-thickness abdominal wall defects. Furthermore, the mechanical strength of the reconstructed abdominal wall after using ADM was significantly (p < 0.05) increased in suture retention strength (30.42 ± 1.23 N), tear strength (63.45 ± 7.64 N and 37.34 ± 11.72 N) and burst strength (153.92 ± 20.39 N) as compared to the suture retention (13.33 ± 5.05 N), tear strength (6.83 ± 0.40 N and 15.27 ± 3.46 N) and burst strength (71.77 ± 18.09 N) when the predicate device materials were concomitantly tested. However, the efficacy in hernia reconstruction of ADM is substantially equivalent to that of predicate material in both macroscopic and microscopic observations. To conclude, ADM manufactured by SCCO2 technology revealed good biocompatibility and excellent mechanical strength in post-repair of full-thickness abdominal wall defects in the rabbit hernia model.

Human adipose-derived stem cell-loaded small intestinal submucosa as a bioactive wound dressing for the treatment of diabetic wounds in rats

Chronic nonhealing wounds are one of the most common and serious complications of diabetes, which can lead to disability of patients. Adipose-derived stem cells (ADSCs) have emerged as a promising tool for skin wound healing, but the therapeutic potential depends considerably on the cell delivery system. Small intestinal submucosa (SIS) is an extracellular matrix-based membranous scaffold with outstanding repair potential for skin wounds. In this study, we first fabricated a bioactive wound dressing, termed the SIS+ADSCs composite, by using human ADSCs as the seed cell and porcine SIS as the cell delivery vehicle. Then, we systematically investigated, for the first time, the healing potential of this wound dressing in a rat model of type 2 diabetes. In vitro studies revealed that SIS provided a favorable microenvironment for ADSCs and significantly promoted the expression of growth factors critical for chronic wound healing. After implantation in the full-thickness skin wounds of diabetic rats, the SIS+ADSCs composite showed a higher wound healing rate and wound healing quality than those in the PBS, ADSCs, and SIS groups. Along with the ability to modulate the polarization of macrophages in vivo, the SIS+ADSCs composite was potent at promoting wound angiogenesis, reepithelialization, and skin appendage regeneration. Taken together, these results indicate that the SIS+ADSCs composite has good therapeutic potential and high translational value for diabetic wound treatment.

Cell-Seeded Biomaterial Scaffolds: The Urgent Need for Unanswered Accelerated Angiogenesis

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular to cellular, some other promising stimulatory factors have been underdeveloped (such as electrical, topographical, and magnetic). When it comes to choosing biomaterial scaffolds in tissue engineering for angiogenesis, key traits rush to mind including biocompatibility, appropriate physical and mechanical properties (adhesion strength, shear stress, and malleability), as well as identifying the appropriate biomaterial in terms of stability and degradation profile, all of which may leave essential trace materials behind adversely influencing angiogenesis. Nevertheless, the selection of the best biomaterial and cells still remains an area of hot dispute as such previous studies have not sufficiently classified, integrated, or compared approaches. To address the aforementioned need, this review article summarizes a variety of natural and synthetic scaffolds including hydrogels that support angiogenesis. Furthermore, we review a variety of cell sources utilized for cell seeding and influential factors used for angiogenesis with a concentrated focus on biomechanical factors, with unique stimulatory factors. Lastly, we provide a bottom-to-up overview of angiogenic biomaterials and cell selection, highlighting parameters that need to be addressed in future studies.

Use of confocal microscopy imaging for in vitro assessment of adipose-derived mesenchymal stromal cells seeding on acellular dermal matrices: 3D reconstruction based on collagen autofluorescence

Background

Both mesenchymal stromal cells (MSCs) and acellular dermal matrices (ADMs) represent fascinating therapeutic tools in the wound healing scenario. Strategies aimed at combining these two treatment modalities are currently under investigation. Moreover, scarcity of quantitative, nondestructive techniques for quality assessment of engineered tissues poses great limitations in regenerative medicine and collagen autofluorescence‐based imaging techniques are acquiring great importance in this setting.

Objective

Our goals were to assess the in vitro interactions between ADSCs and ADMs and to analyze extracellular‐matrix production.

Methods

Adipose‐derived MSCs (ADSC) were plated on 8‐mm punch biopsies of a commercially available ADM (Integra®). Conventional histology with hematoxylin‐eosin staining, environmental scanning electron microscopy, and confocal‐laser scanning microscopy were used to obtain imaging of ADSC‐seeded ADMs. Collagen production by ADSCs was quantified by mean fluorescence intensity (MFI), expressed in terms of positive pixels/field, obtained through ImageJ software processing of three‐dimensional projections from confocal scanning images. Control conditions included: fibroblast‐seeded ADM, ADSC‐ and fibroblast‐induced scaffolds, and Integra® alone.

Results

ADSCs were efficiently seeded on Integra® and were perfectly incorporated in the pores of the scaffold. Collagen production was revealed to be significantly higher when ADSCs were seeded on ADM rather than in all other control conditions. Collagen autofluorescence was efficiently used as a surrogate marker of ECM production.

Conclusions

Combined therapies based on MSCs and collagenic ADMs are promising therapeutic options for chronic wounds. Not only ADSCs can be efficiently seeded on ADMs, but ADMs also seem to potentiate their regenerative properties, as highlightable from fluorescence confocal imaging.

Investigating the vascularization capacity of a decellularized dental pulp matrix seeded with human dental pulp stem cells: in vitro and preliminary in vivo evaluations

AIM

To investigate the vascularization capacity of a decellularized dental pulp matrix (DDP) of bovine origin seeded with human dental pulp stem cells (hDPSCs) in vitro and to present preliminary in vivo findings.

METHODOLOGY

Bovine dental pulps were decellularized and then analysed using histological staining and DNA quantification. The resultant DDPs were characterized using immunohistochemical staining for the retention of vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor 2 (FGF-2). Furthermore, DDPs were recellularized with hDPSCs and analysed histologically. The expression of markers involved in angiogenesis by hDPSCs colonizing the DDPs was assessed in vitro. A preliminary in vivo study was then conducted in which hDPSCs-seeded and unseeded DDPs were inserted in debrided human premolars root slices and implanted subcutaneously in immunodeficient mice. Samples were retrieved after 30 days and analysed using histological and immunohistochemical staining. The independent samples t-test, analysis of variance and a Kruskal-Wallis test were used to analyse the quantitative data statistically depending on the group numbers and normality of data distribution. The difference between the groups was considered significant when the P-value was less than 0.05.

RESULTS

Acellular dental pulp matrices were generated following bovine dental pulp decellularization. Evaluation of the developed DDPs revealed a significant DNA reduction (P < 0.0001) with preservation of the native histoarchitecture and vasculature and retention of VEGF-A and FGF-2. Upon recellularization of the DDPs with hDPSCs, the in vitro analyses revealed cell engraftment with progressive repopulation of DDPs' matrices and vasculature and with enhanced expression of markers involved in angiogenesis. In vivo implantation of root slices with hDPSCs-seeded DDPs revealed apparent vascularization enhancement as compared to the unseeded DDP group (P < 0.0001).

CONCLUSIONS

The developed decellularized dental pulp matrix had pro-angiogenic properties characterized by the retention of native vasculature and angiogenic growth factors. Seeding of hDPSCs into the DDP led to progressive repopulation of the vasculature, enhanced expression of markers involved in angiogenesis in hDPSCs and improved in vivo vascularization capacity. The se suggest that a combination of DDP and hDPSCs have the potential to provide a promising vascularization promoting strategy for dental pulp regeneration.

SDF-1α gene-activated collagen scaffold enhances provasculogenic response in a coculture of human endothelial cells with human adipose-derived stromal cells

Novel biomaterials can be used to provide a better environment for cross talk between vessel forming endothelial cells and wound healing instructor stem cells for tissue regeneration. This study seeks to investigate if a collagen scaffold containing a proangiogenic gene encoding for the chemokine stromal-derived factor-1 alpha (SDF-1α GAS) could be used to enhance functional responses in a coculture of human umbilical vein endothelial cells (HUVECs) and human adipose-derived stem/stromal cells (ADSCs). Functional responses were determined by (1) monitoring the amount of junctional adhesion molecule VE-cadherin released during 14 days culture, (2) expression of provasculogenic genes on the 14th day, and (3) the bioactivity of secreted factors on neurogenic human Schwann cells. When we compared our SDF-1α GAS with a gene-free scaffold, the results showed positive proangiogenic determination characterized by a transient yet controlled release of the VE-cadherin. On the 14th day, the coculture on the SDF-1α GAS showed enhanced maturation than its gene-free equivalent through the elevation of provasculogenic genes (SDF-1α-7.4-fold, CXCR4-1.5-fold, eNOS-1.5-fold). Furthermore, we also found that the coculture on SDF-1α GAS secretes bioactive factors that significantly (p < 0.01) enhanced human Schwann cells' clustering to develop toward Bünger band-like structures. Conclusively, this study reports that SDF-1α GAS could be used to produce a bioactive vascularized construct through the enhancement of the cooperative effects between endothelial cells and ADSCs.

Acellular dermal matrix in skin wound healing in rabbits - histological and histomorphometric analyses

OBJECTIVES

To analyze the histology and histomorphometry of healing associated with acellular dermal matrix in skin wounds in rabbits.

METHODS

Twelve male rabbits were divided into two groups: the control group (CG) and the matrix group (MG). Three skin wounds with a total area of 20 × 20 mm were created on the dorsal region of each animal. Photographic records of the lesions taken over a 21-day period and use of the ImageJ program allowed calculation of the wound contraction rate. The lesions were biopsied on days 3, 14 and 21 for histomorphometric analysis to define the thicknesses of the dermis and epidermis (hematoxylin-eosin) and calculate the densities of type I and type III collagen (picrosirius).

RESULTS

No significant difference in the healing rate was found between the groups (p>0.05). The MG presented greater epidermal thickness on day 3 (p<0.05) and on days 14 and 21 (p<0.001). The MG presented greater dermal thickness throughout the study period (p<0.05). The type I collagen density was higher in the MG throughout the study period (p<0.05), and the type III collagen density was higher in the MG on days 3 and 14 (p<0.05) and on day 21 (p<0.001).

CONCLUSION

The use of acellular dermal matrix increased the thickness of the dermal and epidermal layers and the amount of type I and III collagen during skin wound healing and did not alter the rate of wound contraction.

Extracellular matrix-based biomaterials as adipose-derived stem cell delivery vehicles in wound healing: a comparative study between a collagen scaffold and two xenografts

BACKGROUND

Stem cell therapies represent a promising tool in regenerative medicine. Considering the drawbacks of direct stem cell injections (e.g. poor cell localisation), extracellular matrix-based biomaterials (e.g. scaffolds and tissue grafts), due to their compositional biofunctionality and cytocompatibility, are under investigation as potential stem cell carriers.

METHODS

The present study assessed the potential of three commercially available extracellular matrix-based biomaterials [a collagen/glycosaminoglycan scaffold (Integra™ Matrix Wound Dressing), a decellularised porcine peritoneum (XenoMEM™) and a porcine urinary bladder (MatriStem™)] as human adipose-derived stem cell delivery vehicles.

RESULTS

Both tissue grafts induced significantly (p < 0.01) higher human adipose-derived stem cell proliferation in vitro over the collagen scaffold, especially when the cells were seeded on the basement membrane side. Human adipose-derived stem cell phenotype and trilineage differentiation potential was preserved in all biomaterials. In a splinted wound healing nude mouse model, in comparison to sham, biomaterials alone and cells alone groups, all biomaterials seeded with human adipose-derived stem cells showed a moderate improvement of wound closure, a significantly (p < 0.05) lower wound gap and scar index and a significantly (p < 0.05) higher proportion of mature collagen deposition and angiogenesis (the highest, p < 0.01, was observed for the cell loaded at the basement membrane XenoMEM™ group). All cell-loaded biomaterial groups retained more cells at the implantation side than the direct injection group, even though they were loaded with half of the cells than the cell injection group.

CONCLUSIONS

This study further advocates the use of extracellular matrix-based biomaterials (in particular porcine peritoneum) as human adipose-derived stem cell delivery vehicles. Comparative analysis of a collagen scaffold (Integra™ Matrix Wound Dressing) and two tissue grafts [decellularised porcine peritoneum (XenoMEM™) and porcine urinary bladder (MatriStem™)] as human adipose-derived stem cells carriers.

Effect of Mineral Pitch on the Proliferation of Human Adipose Derived Stem Cells on Acellular Scaffold

Purpose: Acellular scaffold extracted from extracellular matrix (ECM) have been used for constructive and regenerative medicine. Adipose derived stem cells (ADSCs) can enhance the vascularization capacity of scaffolds. High mobility group box 1 (HMGB1) and stromal derived factor1 (SDF1) are considered as two important factors in vascularization and immunologic system. In this study, the effect of mineral pitch on the proliferation of human ADSCs was evaluated. In addition to HMGB1 and SDF1, factors expression in acellular scaffold was also assessed.

Methods: To determine acellular scaffold morphology and the degree of decellularization, hematoxylin & eosin (H&amp;E), 6-diamidino-2-phenylindole (DAPI), and Masson’s trichrome staining were applied. The scaffolds were treated with mineral pitch. Also, ADSCs were seeded on the scaffolds, and adhesion of the cells to the scaffolds were assessed using field emission scanning electron microscopy (FE-SEM). In addition, the efficiency of mineral pitch to induce the proliferation of ADSCs on the scaffolds was evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. To measure HMGB1 and SDF1 mRNA expression, real-time polymerase chain reactions (RT-PCR) was used.

Results: FE-SEM showed that decellularized matrix possesses similar matrix morphology with a randomly oriented fibrillar structure and interconnecting pores. No toxicity was observed in all treatments, and cell proliferation were supported in scaffolds. The important point is that, the proliferation capacity of ADSCs on Mineral pitch loaded scaffolds significantly increased after 48 h incubation time compared to the unloaded scaffold (P<0.001).

Conclusion: The results of this study suggest that mineral pitch has potentials to accelerate proliferation of ADSCs on the acellular scaffolds.

Adipose Stromal Cells Enhance Decellularized Adipose Tissue Remodeling Through Multimodal Mechanisms

Decellularized adipose tissue (DAT) scaffolds represent a promising cell-instructive platform for soft tissue engineering. While recent work has highlighted that mesenchymal stromal cells, including adipose-derived stromal cells (ASCs), can be combined with decellularized scaffolds to augment tissue regeneration, the mechanisms involved require further study. The objective of this work was to probe the roles of syngeneic donor ASCs and host-derived macrophages in tissue remodeling of DAT scaffolds within an immunocompetent mouse model. Dual transgenic reporter mouse strains were employed to track and characterize the donor ASCs and host macrophages within the DAT implants. More specifically, ASCs isolated from dsRed mice were seeded on DAT scaffolds, and the seeded and unseeded control scaffolds were implanted subcutaneously into MacGreen transgenic mice for up to 8 weeks. ASC seeding was shown to augment cell infiltration into the DAT implants at 8 weeks, and this was linked to significantly enhanced angiogenesis relative to the unseeded controls. Immunohistochemical staining demonstrated long-term retention of the syngeneic donor ASCs over the duration of the 8-week study, providing evidence that the DAT scaffolds are a cell-supportive delivery platform. Notably, newly formed adipocytes within the DAT implants were not dsRed⁺, indicating that the donor ASCs supported fat formation through indirect mechanisms. Immunohistochemical tracking of host macrophages through costaining for enhanced green fluorescent protein with the macrophage marker Iba1 revealed that ASC seeding significantly increased the number of infiltrating macrophages within the DAT implants at 3 weeks, while the fraction of macrophages relative to the total cellular infiltrate was similar between the groups at 1, 3, and 8 weeks. Consistent with the tissue remodeling response that was observed, western blotting demonstrated that there was significantly augmented expression of CD163 and CD206, markers of constructive M2-like macrophages, within the ASC-seeded DAT implants. Overall, our results demonstrate that exogenous ASCs enhance tissue regeneration within DAT scaffolds indirectly through multimodal mechanisms that include host cell recruitment and immunomodulation. These data provide further evidence to support the use of decellularized scaffolds as a delivery platform for ASCs in tissue engineering.

Harnessing Stem Cell Potential for the Treatment of Erectile Function in Men with Diabetes Mellitus: From Preclinical/Clinical Perspectives to Penile Tissue Engineering

Background::

According to the World Health Organization, more than 150 million people are diabetic, and this number will increase twofold by the year 2025. Diabetes-related complications affect all body organ systems, including the penis. Diabetes-induced Erectile Dysfunction (ED) is caused by neuropathy of the penile nerves and vasculopathy involving the smooth muscle and endothelium of the corpus cavernosum.

Objective::

This study aims to present an overview of Stem Cell (SC) research in diabetic animal models of ED, focusing on the function, signaling, and niches that have a prominent role in the regeneration of cavernosal cells and penile tissues. We highlight common erectile pathologies caused by diabetes and review relevant preclinical trials. We also discuss paracrine mechanisms of various SC therapies involved in the repair of endothelial cells and cavernous nerves in these diabetic models.

Method::

A PubMed search was performed, with dates ranging from inception until Mar 31, 2019.

Results::

This review provides a comprehensive evaluation of the various strategies that have been investigated for improving SC delivery methods, through preclinical literature and published clinical trials regarding ED in men with diabetes. Various cell-type applications have benefited erectile function in diabetic models of ED.

Conclusion::

This review examines the progress and remaining challenges in diabetes-related SC research regarding ED. Moving forward, it is only with a combined effort of basic biology and translational work that the potential of SC-based therapies in diabetes in ED can be realized.

Adipose tissue and the vascularization of biomaterials: Stem cells, microvascular fragments and nanofat-a review

Tissue defects in the human body after trauma and injury require precise reconstruction to regain function. Hence, there is a great demand for clinically translatable approaches with materials that are both biocompatible and biodegradable. They should also be able to adequately integrate within the tissue through sufficient vascularization. Adipose tissue is abundant and easily accessible. It is a valuable tissue source in regenerative medicine and tissue engineering, especially with regard to its angiogenic potential. Derivatives of adipose tissue, such as microfat, nanofat, microvascular fragments, stromal vascular fraction and stem cells, are commonly used in research, but also clinically to enhance the vascularization of implants and grafts at defect sites. In plastic surgery, adipose tissue is harvested via liposuction and can be manipulated in three ways (macro-, micro- and nanofat) in the operating room, depending on its ultimate use. Whereas macro- and microfat are used as a filling material for soft tissue injuries, nanofat is an injectable viscous extract that primarily induces tissue remodeling because it is rich in growth factors and stem cells. In contrast to microfat that adds volume to a defect site, nanofat has the potential to be easily combined with scaffold materials due to its liquid and homogenous consistency and is particularly attractive for blood vessel formation. The same is true for microvascular fragments that are easily isolated from adipose tissue through collagenase digestion. In preclinical animal models, it has been convincingly shown that these vascular fragments inosculate with host vessels and subsequently accelerate scaffold perfusion and host tissue integration. Adipose tissue is also an ideal source of stem cells. It yields larger quantities of cells than any other source and is easier to access for both the patient and doctor compared with other sources such as bone marrow. They are often used for tissue regeneration in combination with biomaterials. Adipose-derived stem cells can be applied unmodified or as single cell suspensions. However, certain pretreatments, such as cultivation under hypoxic conditions or three-dimensional spheroids production, may provide substantial benefit with regard to subsequent vascularization in vivo due to induced growth factor production. In this narrative review, derivatives of adipose tissue and the vascularization of biomaterials are addressed in a comprehensive approach, including several sizes of derivatives, such as whole fat flaps for soft tissue engineering, nanofat or stem cells, their secretome and exosomes. Taken together, it can be concluded that adipose tissue and its fractions down to the molecular level promote, enhance and support vascularization of biomaterials. Therefore, there is a high potential of the individual fat component to be used in regenerative medicine.

In vivo evaluation of an electrospun and 3D printed cellular delivery device for dermal wound healing

Burns and chronic wounds are especially challenging wounds to heal. In efforts to heal these wounds, physicians often use autologous skin grafts to help restore mechanical and barrier functionality to the wound area. These grafts are, by nature, limited in availability. In an effort to provide an alternative, we have developed an electrospun wound dressing designed to incorporate into the wound with the option to deliver a cellular payload. Here, a blend of poly(glycolic acid) and poly(ethylene glycol) was electrospun as part of a custom fabrication method that incorporated 3D printed poly(vinyl alcohol) sacrificial elements. This preparation is unique compared to traditional electrospinning as sacrificial elements provide an internal void space for an injectable payload to be delivered to the wound site. When the construct was tested in vivo (full thickness excisional skin wounds), wound closure was slightly delayed by the presence of the scaffold in both normal and challenged wounds. Quality of healing was improved in normal wounds as measured by histomorphometrics when treated with the construct and exhibited increased neovascularization. Our results demonstrate that the extracellular matrix-like scaffold developed in this study is beneficial to healing of full thickness skin defects and may benefit challenged wounds.

The Role of Adipose-Derived Stem Cells, Dermal Regenerative Templates, and Platelet-Rich Plasma in Tissue Engineering-Based Treatments of Chronic Skin Wounds

The continuous improvements in the field of both regenerative medicine and tissue engineering have allowed the design of new and more efficacious strategies for the treatment of chronic or hard-to-heal skin wounds, which represent heavy burden, from a medical and economic point of view. These novel approaches are based on the usage of three key methodologies: stem cells, growth factors, and biomimetic scaffolds. These days, the adipose tissue can be considered the main source of multipotent mesenchymal stem cells, especially adipose-derived stem cells (ASCs). ASCs are easily accessible from various fat depots and show an intrinsic plasticity in giving rise to cell types involved in wound healing and angiogenesis. ASCs can be found in fat grafts, historically used in the treatment of chronic wounds, and have been evaluated as such in both animal models and human trials, to exploit their capability of accelerating wound closure and inducing a correct remodeling of the newly formed fibrovascular tissue. Since survival and fitness of ASCs need to be improved, they are now employed in conjunction with advanced wound dressings, together with dermal regenerative templates and platelet-rich plasma (as a source of growth and healing factors). In this work, we provide an overview of the current knowledge on the topic, based on existing studies and on our own experience.

Self-assembled cell sheets composed of mesenchymal stem cells and gelatin nanofibers for the treatment of full-thickness wounds

Gelatin-layered PCL nanofibrils for 3D cell sheet formation were composed with adipocyte-derived stem cells for wound healing.

Design of hydrogel-based scaffolds for the treatment of spinal cord injuries

Hydrogel-based scaffold design approaches for the treatment of spinal cord injuries.

Bone Tissue Regeneration in the Oral and Maxillofacial Region: A Review on the Application of Stem Cells and New Strategies to Improve Vascularization

Bone tissue engineering techniques are a promising alternative for the use of autologous bone grafts to reconstruct bone defects in the oral and maxillofacial region. However, for successful bone regeneration, adequate vascularization is a prerequisite. This review presents and discusses the application of stem cells and new strategies to improve vascularization, which may lead to feasible clinical applications. Multiple sources of stem cells have been investigated for bone tissue engineering. The stromal vascular fraction (SVF) of human adipose tissue is considered a promising single source for a heterogeneous population of essential cells with, amongst others, osteogenic and angiogenic potential. Enhanced vascularization of tissue-engineered grafts can be achieved by different mechanisms: vascular ingrowth directed from the surrounding host tissue to the implanted graft, vice versa, or concomitantly. Vascular ingrowth into the implanted graft can be enhanced by (i) optimizing the material properties of scaffolds and (ii) their bioactivation by incorporation of growth factors or cell seeding. Vascular ingrowth directed from the implanted graft towards the host tissue can be achieved by incorporating the graft with either (i) preformed microvascular networks or (ii) microvascular fragments (MF). The latter may have stimulating actions on both vascular ingrowth and outgrowth, since they contain angiogenic stem cells like SVF, as well as vascularized matrix fragments. Both adipose tissue-derived SVF and MF are cell sources with clinical feasibility due to their large quantities that can be harvested and applied in a one-step surgical procedure. During the past years, important advancements of stem cell application and vascularization in bone tissue regeneration have been made. The development of engineered in vitro 3D models mimicking the bone defect environment would facilitate new strategies in bone tissue engineering. Successful clinical application requires innovative future investigations enhancing vascularization.

Immune responses towards bioengineered tissues and strategies to control them

PURPOSE OF REVIEW

Research into development of artificial tissues and bioengineered organs to replace physiological functions of injured counterparts has highlighted a previously underestimated challenge for its clinical translatability: the immune response against biomaterials. Herein, we will provide an update and review current knowledge regarding this important barrier to regenerative medicine.

RECENT FINDINGS

Although a clear understanding of the immune reactivity against biomaterials remains elusive, accumulating evidence indicates that innate immune cells, primarily neutrophils and macrophages, play a key role in the initial phases of the immune response. More recently, data have shown that in later phases, T and B cells are also involved. The use of physicochemical modifications of biomaterials and cell-based strategies to modulate the host inflammatory response is being actively investigated for effective biomaterial integration.

SUMMARY

The immune response towards biomaterials and bioengineered organs plays a crucial role in determining their utility as transplantable grafts. Expanding our understanding of these responses is necessary for developing protolerogenic strategies and delivering on the ultimate promise of regenerative medicine.

Bioprinting Approaches to Engineering Vascularized 3D Cardiac Tissues

PURPOSE OF REVIEW

3D bioprinting technologies hold significant promise for the generation of engineered cardiac tissue and translational applications in medicine. To generate a clinically relevant sized tissue, the provisioning of a perfusable vascular network that provides nutrients to cells in the tissue is a major challenge. This review summarizes the recent vascularization strategies for engineering 3D cardiac tissues.

RECENT FINDINGS

Considerable steps towards the generation of macroscopic sizes for engineered cardiac tissue with efficient vascular networks have been made within the past few years. Achieving a compact tissue with enough cardiomyocytes to provide functionality remains a challenging task. Achieving perfusion in engineered constructs with media that contain oxygen and nutrients at a clinically relevant tissue sizes remains the next frontier in tissue engineering. The provisioning of a functional vasculature is necessary for maintaining a high cell viability and functionality in engineered cardiac tissues. Several recent studies have shown the ability to generate tissues up to a centimeter scale with a perfusable vascular network. Future challenges include improving cell density and tissue size. This requires the close collaboration of a multidisciplinary teams of investigators to overcome complex challenges in order to achieve success.

In vitro Engineering of a Skin Substitute Based on Adipose-Derived Stem Cells

In the field of wound healing, stem cell-based strategies are gaining importance for their regenerative potential. Adipose-derived stem cells (ADSCs) are a particular subset of mesenchymal stem cells present in the stromal-vascular fraction of the adipose tissue, today considered very attractive for their relative abundance and accessibility in the human body. However, ADSCs are still not routinely used in normal clinical practice. Several studies have also reported ADSC transplantation in association with biomaterials in an attempt to enhance the local retention and growth rate of the cells. The aim of our study was to evaluate the ability of ADSCs to build a dermal scaffold to be potentially used as a dermal substitute in the field of wound healing, with optimal biocompatibility and mechanical properties. ADSCs were defined as CD90-, CD73-, and CD105-positive cells. ADSCs turned out to be capable of secreting all the main components of the extracellular matrix (ECM) upon stimulation, thus efficiently producing a collagen and fibronectin-containing dermal matrix. We also checked whether the ADSC-produced dermal scaffold could be seeded with keratinocytes. The scaffolding material directly produced by ADSCs has several advantages when compared to the commercially available ones: it is easily obtained from the patients and it is 100% biocompatible and supports cell-ECM interaction. Moreover, it represents a possible powerful therapeutic tool for patients with chronic ulcers since it appears to be potentially grafted with keratinocytes layers, thus bypassing the classical two-step grafting procedure.

Harnessing the secretome of adipose-derived stem cells in the treatment of ischemic heart diseases

Adipose-derived stem cells (ASCs) are promising therapeutic cells for ischemic heart diseases, due to the ease and efficiency of acquisition, the potential of myocardial lineage differentiation, and the paracrine effects. Recently, many researchers have claimed that the ASC-based myocardial repair is mainly attributed to its paracrine effects, including the anti-apoptosis, pro-angiogenesis, anti-inflammation effects, and the inhibition of fibrosis, rather than the direct differentiation into cardiovascular lineage cells. However, the usage of ASCs comes with the problems of low cardiac retention and survival after transplantation, like other stem cells, which compromises the effectiveness of the therapy. To overcome these drawbacks, researchers have proposed various strategies for improving survival rate and ensuring sustained paracrine secretion. They also investigated the safety and efficacy of phase I and II clinical trials of ASC-based therapy for cardiovascular diseases. In this review, we will discuss the characterization and paracrine effects of ASCs on myocardial repair, followed by the strategies for stimulating the paracrine secretion of ASCs, and finally their clinical usage.

Epithelial defect repair in the auricle and auditory meatus by grafting with cultured adipose-derived mesenchymal stem cell aggregate-extracellular matrix

Background:

Several patients experience persistent otorrhea after a flawless surgical procedure because of insufficient epithelial healing. Several efforts, such as autologous tissue allograft and xenograft, have been made to halt otorrhea. However, a stable technology to induce temporal epithelial repair is yet to be established. Therefore, this study aims to investigate whether implantation of seeding adipose-derived mesenchymal stem cell (ADMSC) aggregates on extracellular matrix (ECM; herein, ADMSC aggregate-ECM) into damaged skin wound promotes skin regeneration.

Methods:

ADMSC aggregate-ECM was prepared using a previously described procedure that isolated ADMSCs from rabbits and applied to the auricle and auditory meatus wound beds of New Zealand white rabbits. Wound healing was assessed by general observation and hematoxylin and eosin (H&E) staining. Secretion of growth factor of the tissue was evaluated by western blotting. Two other groups, namely, ECM and control, were used. Comparisons of three groups were conducted by one-way analysis of variance analysis.

Results:

ADMSCs adhered tightly to the ECM and quickly formed cell sheets. At 2 weeks, general observation and H&E staining indicated that the wound healing rates in the ADMSC aggregate-ECM (69.02 ± 6.36%) and ECM (59.32 ± 4.10%) groups were higher than that in the control group (43.74 ± 12.15%; P = 0.005, P < 0.001, respectively) in ear auricle excisional wounds. At 7 weeks, The scar elevation index was evidently reduced in the ADMSC aggregate-ECM (2.08 ± 0.87) and ECM (2.31 ± 0.33) groups compared with the control group (4.06 ± 0.45; P < 0.001, P < 0.001, respectively). In addition, the scar elevation index of the ADMSC aggregate-ECM group reached the lowest rate 4 weeks in advance. In auditory meatus excisional wounds, the ADMSC aggregate-ECM group had the largest range of normal skin-like structure at 4 weeks. The ADMSC aggregate–ECM and ECM groups secreted increased amounts of growth factors that contributed to skin regeneration at weeks 1 and 2, respectively.

Conclusions:

ADMSC aggregate-ECM and ECM are effective repair materials for wound healing, especially ADMSC aggregate-ECM. This approach will provide a meaningful experimental basis for mastoid epithelium repair in subsequent clinical trials.

COL4A2 in the tissue-specific extracellular matrix plays important role on osteogenic differentiation of periodontal ligament stem cells

Periodontal ligament stem cells (PDLSCs) can repair alveolar bone defects in periodontitis in a microenvironment context-dependent manner. This study aimed to determine whether different extracellular matrices (ECMs) exert diverse effects on osteogenic differentiation of PDLSCs and accurately control alveolar bone defect repair. Methods: The characteristics of PDLSCs and bone marrow mesenchymal stem cells (BMSCs) with respect to surface markers and multi-differentiation ability were determined. Then, we prepared periodontal ligament cells (PDLCs)-derived and bone marrow cells (BMCs)-derived ECMs (P-ECM and B-ECM) and the related decellularized ECMs (dECMs). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and protein mass spectrometry were used to distinguish the ECMs. The expression of Type IV collagen A2 (COL4A2) in the ECMs was inhibited by siRNA or activated by lentiviral transduction of relevant cells. The stemness, proliferation, and differentiation of PDLSCs were determined in vitro in different dECMs. For the in vivo analysis, different dECMs under the regulation of COL4A2 mixed with PDLSCs and Bio-Oss bone powder were subcutaneously implanted into immunocompromised mice or in defects in rat alveolar bone. The repair effects were identified by histological or immunohistochemical staining and micro-CT. Results: B-dECM exhibited more compact fibers than P-dECM, as revealed by TEM, SEM, and AFM. Protein mass spectrometry showed that COL4A2 was significantly increased in B-dECM compared with P-dECM. PDLSCs displayed stronger proliferation, stemness, and osteogenic differentiation ability when cultured on B-dECM than P-dECM. Interestingly, B-dECM enhanced the osteogenic differentiation of PDLSCs to a greater extent than P-dECM both in vitro and in vivo, whereas downregulation of COL4A2 in B-dECM showed the opposite results. Furthermore, the classical Wnt/β-catenin pathway was found to play an important role in the negative regulation of osteogenesis through COL4A2, confirmed by experiments with the Wnt inhibitor DKK-1 and the Wnt activator Wnt3a. Conclusion: These findings indicate that COL4A2 in the ECM promotes osteogenic differentiation of PDLSCs through negative regulation of the Wnt/β-catenin pathway, which can be used as a potential therapeutic strategy to repair bone defects.

Transition metal-doped cryogels as bioactive materials for wound healing applications

Transition metals (TM) are essential microelements with various biological functions demanded in tissue regeneration applications. Little is known about therapeutic potential of TM within soft hydrogel biomaterials. The soluble divalent TM, such as Zn, Cu, Mn and Co, were stably incorporated into gelatin network during cryogelation. TM content in the resultant cryogels varied from 0.1 × 10³ to 11.8 × 10³ ppm, depending on the TM type and concentration in the reaction solution. Zn component was uniformly complexed with the gelatin scaffold according to elemental imaging, increasing the swelling of polymer walls and the G'/G″ values and also decreasing the size of cryogel macro-pores. Zn-doped cryogels supported migration of human skin fibroblasts (HSF); only upper Zn content of 11.8 × 10³ ppm in the scaffold caused c.a. 50% inhibition of cell growth. Zn ions solubilized in culture medium were more active towards HSF (IC₅₀ ≈ 0.3 mM). Treatment of splinted full-skin excisional wounds in rats with the Zn-doped and non-doped cryogels showed that Zn considerably promoted passing inflammatory/proliferation phases of healing process, inducing more intense dermis formation and structuration. The results show the feasibility of development of cryogel based formulations with different TM and support high phase-specific ability of the Zn-gelatin cryogels to repair acute wounds.

Autologous adipose-derived stem cell transplantation enhances healing of wound with exposed bone in a rat model

OBJECTIVES

Soft tissue wounds with exposed bone often require extended healing times and can be associated with severe complications. We describe the ability of artificial dermis with autogenic adipose-derived stem cells (ADSCs) to promote the healing of wounds with exposed bone in a rat model.

METHODS

Adipose tissues harvested from the bilateral inguinal regions of Wistar rats were used as ADSCs. Rats were randomly divided into control and ADSC groups to investigate the efficacy of ADSC transplantation for wound healing (n = 20 per group). Soft tissue defects were created on the heads of the rats and were covered with artificial dermis with or without the seeded ADSCs. Specimens from these rats were evaluated using digital image analysis, histology, immunohistochemistry, cell labeling, and real-time reverse-transcription polymerase chain reaction (real-time RT-PCR).

RESULTS

The average global wound area was significantly smaller in the ADSC group than in the control group on days 3, 7, and 14 after surgery (p<0.05). After 14 days, the blood vessel density in the wound increased by 1.6-fold in the ADSC group compared with that in the control group (p<0.01). Real-time RT-PCR results showed higher Fgfb and Vegf expression levels at all time points, and higher Tgfb1 and Tgfb3 expression levels until 14 days after surgery in the ADSC group than in the control group (p<0.05).

CONCLUSIONS

In wounds with exposed bone, autogenic ADSCs can promote vascularization and wound healing. Use of this cell source has multiple benefits, including convenient clinical application and lack of ethical concerns.

In-vitro cytocompatibility and growth factor content of GBR/GTR membranes

OBJECTIVE

To assess the cytocompatibility of five commercially available xenogenic barrier membranes used for oral regenerative procedures and to determine the growth factor content of these membranes in-vitro.

METHODS

Human mesenchymal stem cells (hMSCs) and immortalized periodontal ligament stem cells (PDL-hTERTs) were used to determine the cytocompatibility of xenogenic barrier membranes made of collagen (Biogide, BG, Geistlich Pharma AG, Switzerland; Biomend, BM, Zimmer Biomet, USA; Osseoguard OG, Zimmer Biomet, USA; OssixPlus, OX, Datum Dental, Israel) or extracellular matrix (ECM) (Dynamatrix, DM, Keystone Dental, USA) and of their eluates obtained by washing. Cells were cultured with previously washed and unwashed membranes (n=4) and in the medium used for washing (eluate). Cell proliferation at 3 days (eluates) and at 7 days (membranes) was assessed using the WST-1 cell proliferation kit. Growth factor content of the membranes was measured using multiplex ELISA.

RESULTS

The eluate of BG and BM significantly inhibited proliferation of hMSCs, whereas DM and OX showed stimulating effects. The highest impact was observed for DM, its eluate doubled the cell proliferation of adherent cells when compared to the control (p<0.001). The eluate of OG did not influence eluate cell cultures (p>0.05). The presence of membranes had different impact on hMSCs and PDLs. hMSCs seem to be more resistant to the inhibitory effects of BG, OG and BM. hMSCs are only affected by OX, which actually stimulates hMSCs when the specimens are not washed previously. PDLs however proliferate significantly less once they are placed into culture with BM and OG as well as BG-not washed. Once BG is washed no inhibitory effect on PDLs was observed, however overall the washing of membrane samples prior to the placement into the cell culture did hardly have any effect on the outcome. The strongest inhibition of proliferation was shown with the BM and OG membrane in PDL-hTERTs (p<0.001). Growth factor contents were quite similar quantitatively and qualitatively among the tested membranes with concentrations in the range of 50-500 pg/ml. Intriguingly DM contained considerably higher amounts of bFGF with up to 8000 pg/ml.

SIGNIFICANCE

The collagen membranes cross-linked with aldehydes show poor outcomes in PDLs while the collagen membrane cross-linked with polysaccharides generally shows promising results similar to the ECM-membrane DM in both membrane and eluate tests. The findings may be due to various factors, especially differences observed in composition, processing and bFGF content.

The use of fat grafting and platelet-rich plasma for wound healing: A review of the current evidence

Fat grafting is becoming a common procedure in regenerative medicine because of its high content of growth factors and adipose derived stem cells (ADSCs) and the ease of harvest, safety, and low cost. The high concentration of ADSCs found in fat has the potential to differentiate into a wide range of wound-healing cells including fibroblasts and keratinocytes as well as demonstrating proangiogenic qualities. This suggests that fat could play an important role in wound healing. However retention rates of fat grafts are highly variable due in part to inconsistent vascularisation of the transplanted fat. Furthermore, conditions such as diabetes, which have a high prevalence of chronic wounds, reduce the potency and regenerative potential of ADSCs. Platelet-rich plasma (PRP) is an autologous blood product rich in growth factors, cell adhesion molecules, and cytokines. It has been hypothesised that PRP may have a positive effect on the survival and retention of fat grafts because of improved proliferation and differentiations of ADSCs, reduced inflammation, and improved vascularisation. There is also increasing interest in a possible synergistic effect that PRP may have on the healing potential of fat, although the evidence for this is very limited. In this review, we evaluate the evidence in both in vitro and animal studies on the mechanistic relationship between fat and PRP and how this translates to a benefit in wound healing. We also discuss future directions for both research and clinical practice on how to enhance the regenerative potential of the combination of PRP and fat.

Hydrogel from Acellular Porcine Adipose Tissue Accelerates Wound Healing by Inducing Intradermal Adipocyte Regeneration

As an important component of the skin, intradermal adipocytes are closely associated with skin homeostasis and wound healing. Although studies have focused on the role of fibroblasts, keratinocytes, and inflammatory cells in wound healing, the role of adipocytes has not been fully investigated. Here, we verified whether the induction of adipocyte regeneration in a wound bed can effectively promote wound healing, finding that the hydrogel from acellular porcine adipose tissue in combination with adipose-derived stem cells can induce in situ adipogenesis in the wound microenvironment. The newly regenerated adipocytes enhanced fibroblast migration, accelerated wound closing, and enhanced wound epithelialization. More importantly, newly formed intact skin structure was observed after treating the wound with adipose-derived stem cell-loaded hydrogel from acellular porcine adipose tissue. These results show that hydrogel from acellular porcine adipose tissue might substantially improve re-epithelialization, angiogenesis, and skin-appendage regeneration, making it a promising therapeutic biomaterial for skin wound healing.

Mesenchymal stem cells and extracellular matrix scaffold promote muscle regeneration by synergistically regulating macrophage polarization toward the M2 phenotype

Background

Skeletal muscle plays an important role in the body’s physiology but there are still no effective treatments for volumetric muscle loss (VML) resulting from severe traumatic injury or tumor excision. Recent studies show that a tissue engineering strategy using a compound containing mesenchymal stem cells (MSCs) and decellularized extracellular matrix (ECM) scaffold generates significant regenerative effects on VML injury, but the underlying mechanisms are not fully understood.

Methods

The characteristics of human umbilical cord MSCs, including multiplication capacity and multidifferentiation ability, were determined. We constructed a compound containing MSCs and decellularized ECM scaffold which was used for tissue regeneration in a VML model.

Results

We found that MSCs and decellularized ECM scaffold generated synergistic effects on promoting skeletal muscle tissue regeneration. Interestingly, both MSCs and decellularized ECM scaffold could promote macrophage polarization toward the M2 phenotype and suppress macrophage polarization toward the M1 phenotype, which is widely regarded as an important promoting factor in tissue regeneration. More importantly, MSCs and decellularized ECM scaffold generate synergistic promoting effects on macrophage polarization toward the M2 phenotype, not just an additive effect.

Conclusions

Our findings uncover a previously unknown mechanism that MSCs and decellularized ECM scaffold promote tissue regeneration via collaboratively regulating macrophage polarization.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0821-5) contains supplementary material, which is available to authorized users.

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.

Autophagy promotes MSC-mediated vascularization in cutaneous wound healing via regulation of VEGF secretion

Vascularization deficiency caused a lot of diseases, such as diabetes ulcer and myocardial infarction. Mesenchymal stem cells (MSCs), with the self-renewal and multipotent differentiation capacities, have been used for many diseases treatment through regulation microenvironment. Numerous studies reported that MSCs transplantation could largely improve cutaneous wound healing via paracrine secretion of growth factors. However, whether MSCs take part in the angiogenesis process directly remains elusive. Previous study proved that autophagy inhibited immunosuppressive function of MSCs and prevented the degradation of MSCs function in inflammatory and senescent microenvironment. Here, we proved that autophagy determines the therapeutic effect of MSCs in cutaneous wound healing through promoting endothelial cells angiogenesis and demonstrated that the paracrine of vascular endothelial growth factor (VEGF) in MSCs was required in wound site. We further revealed that autophagy enhanced the VEGF secretion from MSCs through ERK phosphorylation directly. Collectively, we put forward that autophagy mediated paracrine of VEGF plays a central role in MSCs cured cutaneous wound healing and may provide a new therapeutic method for angiogenesis-related diseases.

Decellularized Matrices As Cell-Instructive Scaffolds to Guide Tissue-Specific Regeneration

Decellularized scaffolds are promising clinically translational biomaterials that can be applied to direct cell responses and promote tissue regeneration. Bioscaffolds derived from the extracellular matrix (ECM) of decellularized tissues can naturally mimic the complex extracellular microenvironment through the retention of compositional, biomechanical, and structural properties specific to the native ECM. Increasingly, studies have investigated the use of ECM-derived scaffolds as instructive substrates to recapitulate properties of the stem cell niche and guide cell proliferation, paracrine factor production, and differentiation in a tissue-specific manner. Here, we review the application of decellularized tissue scaffolds as instructive matrices for stem or progenitor cells, with a focus on the mechanisms through which ECM-derived scaffolds can mediate cell behavior to promote tissue-specific regeneration. We conclude that although additional preclinical studies are required, ECM-derived scaffolds are a promising platform to guide cell behavior and may have widespread clinical applications in the field of regenerative medicine.

Biologic Scaffolds

Biologic scaffold materials composed of allogeneic or xenogeneic extracellular matrix are commonly used for the repair and functional reconstruction of injured and missing tissues. These naturally occurring bioscaffolds are manufactured by the removal of the cellular content from source tissues while preserving the structural and functional molecular units of the remaining extracellular matrix (ECM). The mechanisms by which these bioscaffolds facilitate constructive remodeling and favorable clinical outcomes include release or creation of effector molecules that recruit endogenous stem/progenitor cells to the site of scaffold placement and modulation of the innate immune response, specifically the activation of an anti-inflammatory macrophage phenotype. The methods by which ECM biologic scaffolds are prepared, the current understanding of in vivo scaffold remodeling, and the associated clinical outcomes are discussed in this article.

Human umbilical cord blood-derived mesenchymal stromal cells and small intestinal submucosa hydrogel composite promotes combined radiation-wound healing of mice

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are a promising agent for treating impaired wound healing, and their therapeutic potential may be enhanced by employing extracellular matrix scaffolds as cell culture scaffolds or transplant cell carriers. Here, we evaluated the effect of human umbilical cord blood-derived (hUCB)-MSCs and a porcine small intestinal submucosa (SIS)-derived extracellular matrix scaffold in a combined radiation-wound mouse model of impaired wound healing.

METHODS

hUCB-MSCs and SIS hydrogel composite was applied to the excisional wound of whole-body irradiated mice. Assessment of wound closing and histological evaluation were performed in vivo. We also cultured hUCB-MSCs on SIS gel and examined the angiogenic effect of conditioned medium on irradiated human umbilical vein endothelial cells (HUVECs) in vitro.

RESULTS

hUCB-MSCs and SIS hydrogel composite treatment enhanced wound healing and angiogenesis in the wound site of mice. Conditioned medium from hUCB-MSCs cultured on SIS hydrogel promoted the chemotaxis of irradiated HUVECs more than their proliferation. The secretion of angiogenic growth factors hepatocyte growth factor, vascular endothelial growth factor-A and angiopoietin-1 from hUCB-MSCs was significantly increased by SIS hydrogel, with HGF being the predominant angiogenic factor of irradiated HUVECs.

CONCLUSIONS

Our results suggest that the wound healing effect of hUCB-MSCs is enhanced by SIS hydrogel via a paracrine factor-mediated recruitment of vascular endothelial cells in a combined radiation-wound mouse model.

Manufacture and preparation of human placenta-derived mesenchymal stromal cells for local tissue delivery

BACKGROUND

In this study we describe the development of a Current Good Manufacturing Practice (CGMP)-compliant process to isolate, expand and bank placenta-derived mesenchymal stromal cells (PMSCs) for use as stem cell therapy. We characterize the viability, proliferation and neuroprotective secretory profile of PMSCs seeded on clinical-grade porcine small intestine submucosa extracellular matrix (SIS-ECM; Cook Biotech).

METHODS

PMSCs were isolated from early gestation placenta chorionic villus tissue via explant culture. Cells were expanded, banked and screened. Purity and expression of markers of pluripotency were determined using flow cytometry. Optimal loading density and viability of PMSCs on SIS-ECM were determined using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) cell proliferation and fluorescent live/dead assays, respectively. Growth factors secretion was analyzed using enzyme-linked immunosorbent assays (ELISA).

RESULTS

PMSCs were rapidly expanded and banked. Viable Master and Working Cell Banks were stable with minimal decrease in viability at 6 months. All PMSCs were sterile, free from Mycoplasma species, karyotypically normal and had low endotoxin levels. PMSCs were homogeneous by immunophenotyping and expressed little to no pluripotency markers. Optimal loading density on SIS-ECM was 3-5 × 10⁵ cells/cm², and seeded cells were >95% viable. Neurotrophic factor secretion was detectable from PMSCs seeded on plastic and SIS-ECM with variability between donor lots.

DISCUSSION

PMSCs from early gestation placental tissues can be rapidly expanded and banked in stable, viable cell banks that are free from contaminating agents, genetically normal and pure. PMSC delivery can be accomplished by using SIS-ECM, which maintains cell viability and protein secretion. Future work in vivo is necessary to optimize cell seeding and transplantation to maximize therapeutic capabilities.

Effect of 2-octylcyanoacrylate on placenta derived mesenchymal stromal cells on extracellular matrix

PURPOSE

Determine the effect of 2-octylcyanoacrylate on placenta derived mesenchymal stromal cells (PMSCs) seeded onto extracellular matrix (ECM) in order to assess its biocompatibility as a potential adhesive for in-vivo fetal cell delivery.

METHODS

PMSCs isolated from chorionic villus tissue were seeded onto ECM. A MTS proliferation assay assessed cellular metabolic activity at various time points in PMSC-ECM with direct, indirect, and no glue contact. Conditioned media collected prior to and 24 hours after glue exposure was analyzed for secretion of human brain-derived neurotrophic factor, hepatocyte growth factor, and vascular endothelial growth factor.

RESULTS

Direct and indirect contact with 2-octylcyanoacrylate results in progressively decreased cellular metabolic activity over 24 hours compared to no glue controls. Cells with direct contact are less metabolically active than cells with indirect contact. 24 hours of glue exposure resulted in suppression of growth factor secretion that is near complete with direct contact.

DISCUSSION

Exposure to 2-octylcyanoacrylate results in decreased metabolic activity and decreased measurable secretion of growth factors by PMSCs seeded onto ECM. Thus, the application of 2-octylcyanoacrylate glue should be limited when working with cell-engineered scaffolds as its inhibitory effects on cell growth and secretory function can limit the therapeutic potential of cell-based interventions.

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.

Perivascular extracellular matrix hydrogels mimic native matrix microarchitecture and promote angiogenesis via basic fibroblast growth factor

Extracellular matrix (ECM)-derived bioscaffolds have been shown to elicit tissue repair through retention of bioactive signals. Given that the adventitia of large blood vessels is a richly vascularized microenvironment, we hypothesized that perivascular ECM contains bioactive signals that influence cells of blood vessel lineages. ECM bioscaffolds were derived from decellularized human and porcine aortic adventitia (hAdv and pAdv, respectively) and then shown have minimal DNA content and retain elastin and collagen proteins. Hydrogel formulations of hAdv and pAdv ECM bioscaffolds exhibited gelation kinetics similar to ECM hydrogels derived from porcine small intestinal submucosa (pSIS). hAdv and pAdv ECM hydrogels displayed thinner, less undulated, and fibrous microarchitecture reminiscent of native adventitia, with slight differences in ultrastructure visible in comparison to pSIS ECM hydrogels. Pepsin-digested pAdv and pSIS ECM bioscaffolds increased proliferation of human adventitia-derived endothelial cells and this effect was mediated in part by basic fibroblast growth factor (FGF2). Human endothelial cells cultured on Matrigel substrates formed more numerous and longer tube-like structures when supplemented with pAdv ECM bioscaffolds, and FGF2 mediated this matrix signaling. ECM bioscaffolds derived from pAdv promoted FGF2-dependent in vivo angiogenesis in the chick chorioallantoic membrane model. Using an angiogenesis-focused protein array, we detected 55 angiogenesis-related proteins, including FGF2 in hAdv, pAdv and pSIS ECMs. Interestingly, 19 of these factors were less abundant in ECMs bioscaffolds derived from aneurysmal specimens of human aorta when compared with non-aneurysmal (normal) specimens. This study reveals that Adv ECM hydrogels recapitulate matrix fiber microarchitecture of native adventitia, and retain angiogenesis-related actors and bioactive properties such as FGF2 signaling capable of influencing processes important for angiogenesis. This work supports the use of Adv ECM bioscaffolds for both discovery biology and potential translation towards microvascular regeneration in clinical applications.

Biomaterial-mediated strategies targeting vascularization for bone repair

Repair of non-healing bone defects through tissue engineering strategies remains a challenging feat in the clinic due to the aversive microenvironment surrounding the injured tissue. The vascular damage that occurs following a bone injury causes extreme ischemia and a loss of circulating cells that contribute to regeneration. Tissue-engineered constructs aimed at regenerating the injured bone suffer from complications based on the slow progression of endogenous vascular repair and often fail at bridging the bone defect. To that end, various strategies have been explored to increase blood vessel regeneration within defects to facilitate both tissue-engineered and natural repair processes. Developments that induce robust vascularization will need to consolidate various parameters including optimization of embedded therapeutics, scaffold characteristics, and successful integration between the construct and the biological tissue. This review provides an overview of current strategies as well as new developments in engineering biomaterials to induce reparation of a functional vascular supply in the context of bone repair.

Use of Adipose-Derived Stem Cells to Support Topical Skin Adhesive for Wound Closure: A Preliminary Report from Animal In Vivo Study

The aim of this study was to determine the local and systemic effects of adipose-derived stem cells (ADSCs) as a component of topical skin adhesive in an animal artificial wound closure model. In presented study the cosmetic effects, histological analysis, mechanical properties, and cell migration have been assessed to evaluate the usefulness of ADSCs as supporting factor for octyl blend cyanoacrylate adhesive. The total of 40 rats were used and divided into six groups. In the Study Group, ADSCs were administered by multipoint injection of the six surrounding intrawound areas with additional freely leaving procedure of the cells between the skin flaps just before applying adhesive to close the wound. Five control groups without using ADSCs, utilizing different types of standard wound closure, were created in order to check efficiency of experimental stem cell therapy. In our study, we proved that ADSCs could be used effectively also as a supportive tool in topical skin adhesive for wound closure. However we did not achieve any spectacular differences related to such aspects as better mechanical properties or special biological breakthroughs in wound healing properties. The use of stem cells, especially ADSCs for wound closure can provide an inspiring development in plastic and dermatologic surgery.