Co-culture of human adipose-derived stem cells with tenocytes increases proliferation and induces differentiation into a tenogenic lineage

Therapeutic Potential of Mesenchymal Stem Cell and Tenocyte Secretomes for Tendon Repair: Proteomic Profiling and Functional Characterization In Vitro and In Ovo

Tendon ruptures and tendinopathies represent a major part of musculoskeletal injuries. Due to the hypovascular and hypocellular nature of tendons, the natural healing capacity is slow and limited. Cell-free approaches for tendon injuries are being investigated as the next generation of therapeutic treatments. The aim of this study was to compare the proteomic profiles and biological activities of two different secretomes, obtained from New Zealand white rabbit adipose-tissue-derived mesenchymal stem cells (ADSCs) or a 3:1 mixed culture of ADSCs and rabbit tenocytes. The secretomes were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and their functional properties, such as gene expression, migration and angiogenesis, were investigated in vitro in rabbit tenocytes and in ovo using the chicken chorioallantoic membrane (CAM) assay after stimulation with secretomes or medium control. Both secretomes had a positive effect on angiogenesis and showed similar changes in relative gene expression levels associated with extracellular matrix (ECM) remodeling. Proteomic data showed that the two secretomes were clearly distinguishable, with 182 proteins significantly differentially expressed. The ADSC secretome was more effective in enhancing tenocyte migration under both healthy and inflammatory conditions. In the upregulated protein fraction of the mixed secretome, the tendon-related protein biglycan (BGN) and tenascin C (TNC) were increased. Based on our results, the mixed secretome shows great potential for promoting tendon healing as its composition is more effective in enhancing ECM-related processes and tendon development than the secretome of ADSCs.

State-of the-art and future perspective in co-culture systems for tendon engineering

Tendon is a connective tissue that links bone to muscle, allowing for maintenance of skeleton posture, joint movement, energy storage and transmission of muscle force to bone. Tendon is a hypocellular and hypovascular tissue of poor self-regeneration capacity. Current surgical treatments are of limited success, frequently resulting in reinjury. Upcoming cell therapies are primarily based on tenocytes, a cell population of limited self-renewal capacity in vitro or mesenchymal stromal cells, a cell population prone to ectopic bone formation in vivo. Over the years mono- or multi- factorial cell culture technologies have failed to effectively maintain tenocyte phenotype in culture during expansion or to prime mesenchymal stromal cells towards tenogenic lineage prior to implantation. Upon these limitations the concept of co-culture was conceived. Here, we comprehensively review and discuss tenogenic differentiation of mesenchymal stromal cells through direct or indirect culture with tenocytes in an attempt to generate a tenocyte or a tendon-like cell population for regenerative medicine purposes.

The Application of Photobiomodulation on Mesenchymal Stem Cells and its Potential Use for Tenocyte Differentiation

Tendinopathy is a prevalent and debilitating musculoskeletal disorder. Uncertainty remains regarding its pathophysiology, but it is believed to be a combination of inflammation, damage, degenerative changes, and unsuccessful repair mechanisms. Cell-based therapy is an emerging regenerative medicine modality that uses mesenchymal stem cells (MSCs), their progeny or exosomes to promote tendon healing and regeneration. It is based on the fact that MSCs can be differentiated into tenocytes, the major cell type within tendons, and facilitate tendon repair. Photobiomodulation (PBM) is a non-invasive and potentially promising therapeutic technique that utilizes low-level light to alter intracellular processes and promote tissue healing and regeneration. Recent studies have examined the potential for PBM to improve MSC therapy use in tendinopathy by promoting viability, proliferation, and differentiation. As well as enhance tendon regeneration. This review focuses on Photobiomodulation and MSC therapy applications in regenerative medicine and their potential for tendon tissue engineering.

Effects of Conditioned Media From Human Umbilical Cord-Derived Mesenchymal Stem Cells on Tenocytes From Degenerative Rotator Cuff Tears in an Interleukin 1β-Induced Tendinopathic Condition

Background

Evidence suggests that mesenchymal stem cells (MSCs) are safe for treating different tendinopathies. Synovial fluid is a pooled environment of biomarkers from the inflammatory and degenerative joint cavity. Understanding the effects of synovial fluid on MSCs is important, as it is the first microenvironment that administered MSCs encounter. Several studies have reported that exposure to osteoarthritic synovial fluid-activated MSCs increased the release of soluble factors; however, the paracrine effects of shoulder synovial fluid-stimulated umbilical cord-derived MSCs (SF-UC-MSCs) on tendinopathy have yet to be investigated.

Purpose

To assess the effects of the conditioned media from SF-UC-MSCs on tenocytes from degenerative rotator cuff tears in an interleukin-1β (IL-1β)-induced tendinopathic condition.

Study Design

Controlled laboratory study.

Methods

UC-MSCs were isolated and cultured from healthy, full-term deliveries by cesarean section. Tenocytes were isolated and cultured from patients with degenerative rotator cuff tears. Conditioned media were obtained from UC-MSCs stimulated with synovial fluid. To evaluate the gene expression of proinflammatory and anti-inflammatory cytokines, enzymes and their inhibitors, matrix molecules, and growth factors, the tenocytes were cultured with IL-1β and 50% of the conditioned media from the SF-UC-MSCs; quantitative, real-time, reverse transcriptase polymerase chain reaction was also performed. A prostaglandin E2 (PGE2) assay was performed to investigate the PGE2 level secreted by the tenocytes. Western blotting was performed to examine protein synthesis of collagen type I and III. Cell viability, senescence, and apoptosis assays were also performed.

Results

The conditioned media from the SF-UC-MSCs interfered with the inflammatory gene expression on tenocytes induced by IL-1β, but it increased the gene expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-3. Meanwhile, the conditioned media decreased the PGE2 level on cells induced by IL-1β. It did increase the type I/III ratio of gene expression and protein synthesis, mainly through the induction of type I collagen. Conditioned media of SF-UC-MSCs reversed senescence and apoptosis induced by IL-1β.

Conclusion

Study findings indicated that the conditioned media from SF-UC-MSCs had anti-inflammatory effects and cytoprotective effects on IL-1β-treated tenocytes from degenerative rotator cuff tears.

Clinical Relevance

UC-MSCs have useful potential for the treatment of tendinopathy in practice.

Why Use Adipose-Derived Mesenchymal Stem Cells in Tendinopathic Patients: A Systematic Review

The aim of the present systematic review was to provide a clear overview of the clinical current research progress in the use of adipose-derived mesenchymal stem cells (ASCs) as an effective therapeutic option for the management of tendinopathies, pathologies clinically characterized by persistent mechanical pain and structural alteration of the tendons. The review was carried out using three databases (Scopus, ISI Web of Science and PubMed) and analyzed records from 2013 to 2021. Only English-language papers describing the isolation and manipulation of adipose tissue as source of ASCs and presenting ASCs as treatment for clinical tendinopathies were included. Overall, seven clinical studies met the inclusion criteria and met the minimum quality inclusion threshold. Data extraction and quality assessment were performed by groups of three reviewers. The available evidence showed the efficacy and safety of ASCs treatment for tendinopathies, although it lacked a clear description of the biomolecular mechanisms underlying the beneficial properties of ASCs.

Engineering a Mechanoactive Fibrous Substrate with Enhanced Efficiency in Regulating Stem Cell Tenodifferentiation

Electrospun-aligned fibers in ultrathin fineness have previously demonstrated a limited capacity in driving stem cells to differentiate into tendon-like cells. In view of the tendon's mechanoactive nature, endowing such aligned fibrous structure with mechanoactivity to exert in situ mechanical stimulus by itself, namely, without any forces externally applied, is likely to potentiate its efficiency of tenogenic induction. To test this hypothesis, in this study, a shape-memory-capable poly(l-lactide-co-caprolactone) (PLCL) copolymer was electrospun into aligned fibrous form followed by a "stretching-recovery" shape-programming procedure to impart shape memory capability. Thereafter, in the absence of tenogenic supplements, human adipose-derived stem cells (ADSCs) were cultured on the programmed fibrous substrates for a duration of 7 days, and the effects of constrained recovery resultant stress-stiffening on cell morphology, proliferation, and tenogenic differentiation were examined. The results indicate that the in situ enacted mechanical stimulus due to shape memory effect (SME) did not have adverse influence on cell viability and proliferation, but significantly promoted cellular elongation along the direction of fiber alignment. Moreover, it revealed that tendon-specific protein markers such as tenomodulin (TNMD) and tenascin-C (TNC) and gene expression of scleraxis (SCX), TNMD, TNC, and collagen I (COL I) were significantly upregulated on the mechanoactive fibrous substrate with higher recovery stress compared to the counterparts. Mechanistically, the Rho/ROCK signaling pathway was identified to be involved in the substrate self-actuation-induced enhancement in tenodifferentiation. Together, these results suggest that constrained shape recovery stress may be employed as an innovative loading modality to regulate the stem cell tenodifferentiation by presenting the fibrous substrate with an aligned tendon-like topographical cue and an additional mechanoactivity. This newly demonstrated paradigm in modulating stem cell tenodifferentiation may improve the efficacy of tendon tissue engineering strategy for tendon healing and regeneration.

Influence of mechanical and TGF-β3 stimulation on the tenogenic differentiation of tonsil-derived mesenchymal stem cells

Background

Organogenesis from tonsil-derived mesenchymal cells (TMSCs) has been reported, wherein tenogenic markers are expressed depending on the chemical stimulation during tenogenesis. However, there are insufficient studies on the mechanical strain stimulation for tenogenic cell differentiation of TMSCs, although these cells possess advantages as a cell source for generating tendinous tissue. The purpose of this study was to investigate the effects of mechanical strain and transforming growth factor-beta 3 (TGF-β3) on the tenogenic differentiation of TMSCs and evaluate the expression of tendon-related genes and extracellular matrix (ECM) components, such as collagen.

Results

mRNA expression of tenogenic genes was significantly higher when the mechanical strain was applied than under static conditions. Moreover, mRNA expression of tenogenic genes was significantly higher with TGF-β3 treatment than without. mRNA expression of osteogenic and chondrogenic genes was not significantly different among different mechanical strain intensities. In cells without TGF-β3 treatment, double-stranded DNA concentration decreased, while the amount of normalized collagen increased as the intensity of mechanical strain increased.

Conclusions

Mechanical strain and TGF-β3 have significant effects on TMSC differentiation into tenocytes. Mechanical strain stimulates the differentiation of TMSCs, particularly into tenocytes, and cell differentiation, rather than proliferation. However, a combination of these two did not have a synergistic effect on differentiation. In other words, mechanical loading did not stimulate the differentiation of TMSCs with TGF-β3 supplementation. The effect of mechanical loading with TGF-β3 treatment on TMSC differentiation can be manipulated according to the differentiation stage of TMSCs. Moreover, TMSCs have the potential to be used for cell banking, and compared to other mesenchymal stem cells, they can be procured from patients via less invasive procedures.

Autograft Long Head Biceps Tendon Can Be Used as a Scaffold for Biologically Augmenting Rotator Cuff Repairs

PURPOSE

We create a viable, mechanically expanded autograft long head biceps tendon (LHBT) scaffold for biologically augmenting the repair of torn rotator cuffs.

METHODS

The proximal aspect of the tenotomized LHBTs was harvested from patients during rotator cuff repair surgery and was mechanically formed into porous scaffolds using a surgical graft expander. LHBT scaffolds were evaluated for change in area, tensile properties, and tenocyte viability before and after expansion. The ability of endogenous tenocytes derived from the LHBT scaffold to promote tenogenic differentiation of human adipose-derived mesenchymal stromal cells (ADMSCs) was also determined.

RESULTS

Autograft LHBTs were successfully expanded using a modified surgical graft expander to create a porous scaffold containing viable resident tenoctyes from patients undergoing rotator cuff repair. LHBT scaffolds had significantly increased area (length: 24.91 mm [13.91, 35.90] × width: 22.69 mm [1.87, 34.50]; P = .011) compared with the native LHBT tendon (length: 27.16 mm [2.70, 33.62] × width: 6.68 mm [5.62, 7.74]). The structural properties of the autograft were altered, including the ultimate tensile strength (LHBT scaffold: .56 MPa [.06, 1.06] vs. native LHBT: 2.35 MPa [1.36, 3.33]; P = .002) and tensile modulus (LHBT scaffold: 4.72 MPa [-.80, 1.24] versus native LHBT: 37.17 MPa [24.56, 49.78]; P = .001). There was also a reduction in resident tenocyte percent viability (LHBT scaffold: 38.52% [17.94, 59.09] vs. native LHBT: 68.87% [63.67, 74.37]; P =.004). Tenocytes derived from the LHBT scaffold produced soluble signals that initiated ADMSC differentiation into an immature tenocyte-like phenotype, as indicated by an 8.7× increase in scleraxis (P = .040) and a 3.6× increase in collagen type III mRNA expression (P = .050) compared with undifferentiated ADMSC controls.

CONCLUSIONS

The ability to produce a viable autologous scaffold from the proximal biceps tendon having dimensions, porosity, mechanical characteristics, native ECM components, and viable tenocytes that produce bioactive signals conducive to supporting the biologic augmentation of rotator cuff repair surgery has been demonstrated.

CLINICAL RELEVANCE

This biologically active construct may help to improve the quality of healing and regeneration at the repair site of rotator cuff tears, especially those at high risk for retear.

Adipose-Derived Stem Cell Sheets Improve Early Biomechanical Graft Strength in Rabbits After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Although various reconstruction techniques are available for anterior cruciate ligament (ACL) injuries, a long recovery time is required before patients return to sports activities, as the reconstructed ACL requires time to regain strength. To date, several studies have reported use of mesenchymal stem cells in orthopaedic surgery; however, no studies have used adipose-derived stem cell (ADSC) sheets in ACL reconstruction (ACLR).

HYPOTHESIS

ADSC sheet transplantation can improve biomechanical strength of the autograft used in ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 68 healthy Japanese white rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into a control group (no sheet; n = 34) and a sheet group (ADSC sheet; n = 34). At 2, 4, 8, 16, and 24 weeks after surgery, rabbits in each group were sacrificed to evaluate tendon-bone healing using histological staining, micro-computed tomography, and biomechanical testing. At 24 weeks, scanning transmission electron microscopy of the graft midsubstance was performed.

RESULTS

The ultimate failure load for the control and sheet groups, respectively, was as follows: 17.2 ± 5.5 versus 37.3 ± 10.3 (P = .01) at 2 weeks, 28.6 ± 1.9 versus 47.4 ± 10.4 (P = .003) at 4 weeks, 53.0 ± 14.3 versus 48.1 ± 9.3 (P = .59) at 8 weeks, 66.2 ± 9.3 versus 95.2 ± 43.1 (P = .24) at 16 weeks, and 66.7 ± 27.3 versus 85.3 ± 29.5 (P = .39) at 24 weeks. The histological score was also significantly higher in the sheet group compared with the control group at early stages up to 8 weeks. On micro-computed tomography, relative to the control group, the bone tunnel area was significantly narrower in the sheet group at 4 weeks, and the bone volume/tissue volume of the tendon-bone interface was significantly greater at 24 weeks. Scanning transmission electron microscopy at 24 weeks indicated that the mean collagen fiber diameter in the midsubstance was significantly greater, as was the occupation ratio of collagen fibers per field of view, in the sheet group.

CONCLUSION

ADSC sheets improved biomechanical strength, prevented bone tunnel enlargement, and promoted tendon-bone interface healing and graft midsubstance healing in an in vivo rabbit model.

CLINICAL RELEVANCE

ADSC sheets may be useful for early tendon-bone healing and graft maturation in ACLR.

Engineering multi-tissue units for regenerative Medicine: Bone-tendon-muscle units of the rotator cuff

Our body systems are comprised of numerous multi-tissue units. For the musculoskeletal system, one of the predominant functional units is comprised of bone, tendon/ligament, and muscle tissues working in tandem to facilitate locomotion. To successfully treat musculoskeletal injuries and diseases, critical consideration and thoughtful integration of clinical, biological, and engineering aspects are necessary to achieve translational bench-to-bedside research. In particular, identifying ideal biomaterial design specifications, understanding prior and recent tissue engineering advances, and judicious application of biomaterial and fabrication technologies will be crucial for addressing current clinical challenges in engineering multi-tissue units. Using rotator cuff tears as an example, insights relevant for engineering a bone-tendon-muscle multi-tissue unit are presented. This review highlights the tissue engineering strategies for musculoskeletal repair and regeneration with implications for other bone-tendon-muscle units, their derivatives, and analogous non-musculoskeletal tissue structures.

In Vitro Innovation of Tendon Tissue Engineering Strategies

Tendinopathy is the term used to refer to tendon disorders. Spontaneous adult tendon healing results in scar tissue formation and fibrosis with suboptimal biomechanical properties, often resulting in poor and painful mobility. The biomechanical properties of the tissue are negatively affected. Adult tendons have a limited natural healing capacity, and often respond poorly to current treatments that frequently are focused on exercise, drug delivery, and surgical procedures. Therefore, it is of great importance to identify key molecular and cellular processes involved in the progression of tendinopathies to develop effective therapeutic strategies and drive the tissue toward regeneration. To treat tendon diseases and support tendon regeneration, cell-based therapy as well as tissue engineering approaches are considered options, though none can yet be considered conclusive in their reproduction of a safe and successful long-term solution for full microarchitecture and biomechanical tissue recovery. In vitro differentiation techniques are not yet fully validated. This review aims to compare different available tendon in vitro differentiation strategies to clarify the state of art regarding the differentiation process.

The Impact of Lidocaine on Adipose-Derived Stem Cells in Human Adipose Tissue Harvested by Liposuction and Used for Lipotransfer

The local anesthetic lidocaine, which has been used extensively during liposuction, has been reported to have cytotoxic effects and therefore would be unsuitable for use in autologous lipotransfer. We evaluated the effect of lidocaine on the distribution, number, and viability of adipose-derived stem cells (ASCs), preadipocytes, mature adipocytes, and leukocytes in the fatty and fluid portion of the lipoaspirate using antibody staining and flow cytometry analyses. Adipose tissue was harvested from 11 female patients who underwent liposuction. Abdominal subcutaneous fat tissue was infiltrated with tumescent local anesthesia, containing lidocaine on the left and lacking lidocaine on the right side of the abdomen, and harvested subsequently. Lidocaine had no influence on the relative distribution, cell number, or viability of ASCs, preadipocytes, mature adipocytes, or leukocytes in the stromal-vascular fraction. Assessing the fatty and fluid portions of the lipoaspirate, the fatty portions contained significantly more ASCs (p < 0.05), stem cells expressing the preadipocyte marker Pref-1 (p < 0.01 w/lidocaine, p < 0.05 w/o lidocaine), and mature adipocytes (p < 0.05 w/lidocaine, p < 0.01 w/o lidocaine) than the fluid portions. Only the fatty portion should be used for transplantation. This study found no evidence that would contraindicate the use of lidocaine in lipotransfer. Limitations of the study include the small sample size and the inclusion of only female patients.

Tissue Engineering for Musculoskeletal Regeneration and Disease Modeling

Musculoskeletal injuries and associated conditions are the leading cause of physical disability worldwide. The concept of tissue engineering has opened up novel approaches to repair musculoskeletal defects in a fast and/or efficient manner. Biomaterials, cells, and signaling molecules constitute the tissue engineering triad. In the past 40 years, significant progress has been made in developing and optimizing all three components, but only a very limited number of technologies have been successfully translated into clinical applications. A major limiting factor of this barrier to translation is the insufficiency of two-dimensional cell cultures and traditional animal models in informing the safety and efficacy of in-human applications. In recent years, microphysiological systems, often referred to as organ or tissue chips, generated according to tissue engineering principles, have been proposed as the next-generation drug testing models. This chapter aims to first review the current tissue engineering-based approaches that are being applied to fabricate and develop the individual critical elements involved in musculoskeletal organ/tissue chips. We next highlight the general strategy of generating musculoskeletal tissue chips and their potential in future regenerative medicine research. Exemplary microphysiological systems mimicking musculoskeletal tissues are described. With sufficient physiological accuracy and relevance, the human cell-derived, three-dimensional, multi-tissue systems have been used to model a number of orthopedic disorders and to test new treatments. We anticipate that the novel emerging tissue chip technology will continually reshape and improve our understanding of human musculoskeletal pathophysiology, ultimately accelerating the development of advanced pharmaceutics and regenerative therapies.

Novel Assay Analyzing Tropism between Adipose-Derived Stem Cells and Breast Cancer Cells Reveals a Low Oncogenic Response

Introduction

In the surgical world of breast cancer reconstruction, fat grafting is commonly viewed as an oncogenic risk. Scientific studies add confusion, given the stark lack of clinical evidence suggesting pro-oncogenic links. Typically, classic migration assays (e.g., Boyden chamber) between adipose-derived stem cells and breast cancer cells define this cell relationship as pro-oncogenic.

Objective

We sought to develop a new migration model which better explains existing clinical data.

Methods

Silicon chambers were used to seed isolated populations of cells simultaneously in culture dish. Once cells had adhered, chambers were removed and cells were allowed to follow natural trophic cues. Multiple permutations of MDA-MB-231, MCF-7, HS-27, and ASCs were engineered. Cells were stained with MitoTracker for fluorescent visualization. A human cytokine array (RayBiotech) was performed on the media of migrating assays. Cellular tropism and blot intensity were quantitatively measured in Image J.

Results

An in vitro model was successfully constructed where ASCs reproducibly and freely migrated. Cytokine arrays reveal higher levels of IL-6 and CCL2 in the media of Boyden chambers containing ASCs and MDA-MB-231, compared to the novel assay, comprised of the same cell numbers, types, and incubation times.

Conclusion

These data collectively show for the first time the attraction of ASCs to malignant breast cancer cells; a phenomenon which many ASC studies infer. The cytokine profile of the novel system described is less oncogenic than the commonly described Boyden chamber. These data integrate better into the clinical data, which fail to link cancer recurrence with fat grafting.

Application of Cell Therapy for Anti-Aging Facial Skin

The human skin undergoes the complex process of aging which is prompted by the interplay of intrinsic mechanisms and extrinsic influences. Aging is unavoidable but can be somewhat delayed. Numerous approaches have been developed to slow down facial skin aging process as it is of interest to stake holders in the beauty and fashion world as well as to plastic surgeons. Adipose-derived stem cell [ADSC] and mesenchymal stem cell [MSC] as potential anti-aging agents to some extent have provided a promising and effective alternative in managing skin and facial skin aging. Furthermore, bone marrow-derived mesenchymal stem cells [BMMSC] have exhibited similar ability to rejuvenate aged skin. This review is aimed at giving a comprehensive account of the application of stem cells especially ADSCs and MSCs to reduce or slow down the rate of facial skin aging process.

Tenocyte-derived exosomes induce the tenogenic differentiation of mesenchymal stem cells through TGF-β

Mesenchymal stem cells (MSCs) hold great potential to treat tissue damage based on their multipotent property, and are also considered as suitable cell resources to create tissue-engineered grafts for tendon repair. However, the clinical application of MSCs is still limited by the lack of efficient methods to induce tenogenic differentiation. In this study, by performing the experiments in transwell system, we found that paracrine factors from tenocytes could induce MSCs to undergo the tenogenic differentiation. We further verified that tenocytes could secrete exosomes and these tenocyte-derived exosomes efficiently initiated the tenogenic differentiation of MSCs. Finally, we revealed that the TGF-β existing in tenocyte-derived exosomes mediated the process, as the inhibition of TGF-β signaling abolished the effects of tenocyte-derived exosomes on MSCs. By investigating the effects of tenocytes on MSCs, we found that tenocytes-derived exosomes can induce tenogenic differentiation of MSCs in a TGF-β dependent manner. These studies provided critical information about the multipotency of MSCs and suggested potential strategies for clinical translation.

Real-Time Monitoring of Ascorbic Acid-Mediated Reduction of Cytotoxic Effects of Analgesics and NSAIDs on Tenocytes Proliferation

Tendinopathy is a common painful musculoskeletal disorder treated by injection of analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs), which are believed to have cytotoxicity toward tenocytes. Ascorbic acid is an antioxidant that promotes collagen biosynthesis and prevents free radical formation. It is believed to protect tenocytes from oxidative stress. The optimal concentration of ascorbic acid, especially when used in conjunction with anesthetics and NSAIDs injection, to treat different stages of tendinopathies is unknown. Human tenocytes were isolated from a torn edge of the supraspinatus tendon of a 51-year-old male patient during arthroscopic repair. We monitored real-time changes in human tenocyte proliferation upon exposure to different concentrations of ascorbic acid, bupivacaine, and ketorolac tromethamine using the xCELLigence system. No significant changes in cell index were observed between the control group and tenocytes treated with the 3 concentrations of ascorbic acid. Tenocytes exposed to 0.5% bupivacaine and 30 or 15 mg/mL ketorolac tromethamine revealed significant reduction in tenocytes proliferation. Bupivacaine 0.5% with 250 μg/mL ascorbic acid and 15 mg/mL ketorolac tromethamine with 250 μg/mL ascorbic acid showed the least cytotoxicity against tenocytes. The optimal ascorbic acid concentration required to reduce the cytotoxic effects of bupivacaine and ketorolac tromethamine was demonstrated using this platform.

Extracorporeal shock waves trigger tenogenic differentiation of human adipose-derived stem cells

PURPOSES

Incomplete tendon healing impairs the outcome of tendon ruptures and tendinopathies. Human Adipose-derived Stem Cells (hASCs) are promising for tissue engineering applications. Extracorporeal Shock Waves (ESW) are a leading choice for the treatment of several tendinopathies. In this study, we investigated the effects of ESW treatment and tenogenic medium on the differentiation of hASCs into tenoblast-like cells.

MATERIALS AND METHODS

hASCs were treated with ESW generated by a piezoelectric device and tenogenic medium. Quantitative real-time PCR was used to check the mRNA expression levels of tenogenic transcription factors, extracellular matrix proteins, and integrins. Western blot and immunofluorescence were used to detect collagen 1 and fibronectin. Collagen fibers were evaluated by Masson staining. Calcium deposition was assessed by Alizarin Red staining.

RESULTS

The combined treatment improved the expression of the tendon transcription factors scleraxis and eyes absent 2, and of the extracellular matrix proteins fibronectin, collagen I, and tenomodulin. Cells acquired elongated and spindle shaped fibroblastic morphology; Masson staining revealed the appearance of collagen fibers. Finally, the combined treatment induced the expression of alpha 2, alpha 6, and beta 1 integrin subunits, suggesting a possible role in mediating ESW effects.

CONCLUSIONS

ESW in combination with tenogenic medium improved the differentiation of hASCs toward tenoblast-like cells, providing the basis for ESW and hASCs to be used in tendon tissue engineering.

[Repair effects of rat adipose-derived stem cells on DNA damage induced by ultraviolet in chondrocytes]

Objective

To explore the DNA repair effect of rat adipose-derived stem cells (ADSCs) on chond-rocytes exposed to ultraviolet (UV) radiation.

Methods

ADSCs were isolated and cultured from the inguinal adipose tissue of Sprague Dawley rat by digestion with collagenase type I. ADSCs cell phenotype was assayed with flow cytometry. Multiple differentiation capability of ADSCs at passage 3 was identified with osteogenic and adipogenic induction. The chondrocytes were obtained from rat articular cartilage by digestion with collagenase type II and were identified with toluidine blue staining. The chondrocytes at passage 3 were irradiated with 40 J/m ² UV and cultured with normal medium (irradiated group), and medium containing the ADSCs supernatant (ADSCs supernatant group) or ADSCs was used for co-culture (ADSCs group) for 24 hours; no irradiation chondrocytes served as control group. The cell proliferation was estimated by MTS method. The expression of phosphorylated histone family 2A variant (γH2AX) was detected by immunofluorescence and Western blot.

Results

ADSCs presented CD29(+), CD44(+), CD106(-), and CD34(-); and results of the alizarin red staining and oil red O staining were positive after osteogenic and adipogenic induction. Cell proliferation assay demonstrated the absorbance ( A) values were 2.20±0.10 (control group), 1.34±0.04 (irradiated group), and 1.57±0.06 (ADSCs supernatant group), showing significant difference between groups ( P<0.05). Immunofluorescence and Western blot showed that the γH2AX protein expression was significantly increased in irradiated group, ADSCs supernatant group, and ADSCs group when compared with control group ( P<0.05), and the expression was significantly decreased in ADSCs supernatant group and ADSCs group when compared with irradiated group ( P<0.05), but no significant difference was found between ADSCs supernatant group and ADSCs group ( P>0.05).

Conclusion

ADSCs can increase the cell proliferation and down-regulate the γH2AX protein expression of irradiated cells, indicating ADSCs contribute to the repair of irradiated chondrocyte.

Tendon Tissue Engineering: Mechanism and Effects of Human Tenocyte Coculture With Adipose-Derived Stem Cells

PURPOSE

Adipose-derived stem cells (ASCs) are a potential candidate for cell-based therapy targeting tendon injury; however, their therapeutic benefit relies on their ability to interact with native tenocytes. This study examines the mechanism and effects of coculturing human tenocytes and ASCs.

METHODS

Tenocytes (T) were directly cocultured with either ASCs (A) or fibroblasts (F) (negative control) in the following ratios: 50% T/50% A or F; 25% T/75% A or F; and 75% T/25% A or F. Cells were indirectly cocultured using a transwell insert that allowed for exchange of soluble factors only. Proliferation and collagen I production were measured and compared with monoculture controls. Synergy was quantified using the interaction index (II), which normalizes measured values by the expected values assuming no interaction (no synergy when II = 1). The ability of ASCs to elicit tenocyte migration was examined in vitro using a transwell migration assay and ex vivo using decellularized human flexor tendon explants.

RESULTS

Compared with monoculture controls, II of proliferation was greater than 1 for all tenocyte and ASC direct coculture ratios, but not for tenocyte and fibroblast direct coculture ratios or for tenocyte and ASC indirect coculture. The ASCs elicited greater tenocyte migration in vitro and ex vivo. The II of collagen I production was greater than 1 for direct coculture groups with 25% T/75% A and 75% T/25% A.

CONCLUSIONS

Direct coculture of ASCs and tenocytes demonstrated synergistic proliferation and collagen I production, and ASCs elicited tenocyte migration in vitro and ex vivo. These interactions play a key role in tendon healing and were absent when ASCs were replaced with fibroblasts, supporting the use of ASCs for cell-based therapy targeting tendon injuries.

CLINICAL RELEVANCE

When ASCs are delivered for cell-based therapy, they directly interact with native tenocytes to increase cell proliferation, collagen I production, and tenocyte migration, which may enhance tendon healing.

Crosstalk between adipose stem cells and tendon cells reveals a temporal regulation of tenogenesis by matrix deposition and remodeling

Tendon injuries constitute an unmet clinical challenge owing to the limited intrinsic regenerative ability of this tissue. Cell-based therapies aim at improving tendon healing through the delicate orchestration of tissue rebuilding and regain of function. Hence, human adipose-derived stem cells (hASCs) have been proposed as a promising cell source for boosting tendon regeneration. In this work, we investigated the influence of hASCs on native human tendon-derived cells (hTDCs) through the establishment of a direct contact co-culture system. Results demonstrated that direct interactions between these cell types resulted in controlled proliferation and spontaneous cell elongation. ECM-related genes, particularly COL1A1 and TNC, and genes involved in ECM remodeling, such as MMP1, MMP2, MMP3, and TIMP1, were expressed in co-culture in a temporally regulated manner. In addition, deposition of collagen type I was accelerated in co-culture systems and favored over the production of collagen type III, resulting in an enhanced COL1/COL3 ratio as soon as 7 days. In conclusion, hASCs seem to be good candidates in modulating the behavior of native tendon cells, particularly through a balanced process of ECM synthesis and degradation.

Spheroid formation and modulation of tenocyte-specific gene expression under simulated microgravity

Background

For tendon tissue engineering, tenocyte-seeded scaffolds are a promising approach. Under conventional 2D culture however, tenocytes show rapid senescene and phenotype loss. We hypothesized that phenotype loss could be counteracted by simulated microgravity conditions.

Methods

Human tenocytes were exposed to microgravity for 9 days on a Random Positioning Machine (RPM). Formation of 3D-structures (spheroids) was observed under light microscopy, gene expression was measured by real-time PCR. Cells under conventional 2D-culture served as control group.

Results

Simulated microgravity reached a value of as low as 0.003g. Spheroid formation was observed after 4 days, and spheroids showed stable existance to the end of the observation period. After 9 days, spheroids showed a significantly higher gene expression of collagen 1 (Col1A1) compared to adherent cells under microgravity (4.4x, p=0.04) and compared to the control group (5.6x, p=0.02). Gene expression of collagen 3 (COL3A1) was significantly increased in spheroids compared to the control group (2.3x, p=0.03). Gene expressions of the extracellular matrix genes Tenascin C und Fibronectin (TNC and FN) were increased in adherent cells under microgravity compared to the 1g-control group, not reaching statistical significance (p=0.1 and p=0.3). For the gene expression of vimentin, no significant alteration was observed both in the adherent cells and in the spheroids compared to the 1g control group. Gene expression of the tenocyte-specific transcription factor scleraxis (SCX) was significantly increased in spheroids compared to the control group (3.7x, p=0.03).

Conclusion

Simulated microgravity could counteract tenocyte senescence in vitro and serve as a promising model for scaffold-free 3D cell culturing and tissue engineering.

Level of evidence

V (laboratory study).

Tissue Engineering in Hand Surgery: A Technology Update

The field of hand surgery is constantly evolving to meet the challenges of repairing intricate anatomical structures with limited availability of donor tissue. The past 10 years have seen an exponential growth in tissue engineering, which has broadened the perspectives of tackling these age-old problems. Various fabrication techniques such as melt electrospinning and fused deposition modelling have been employed to synthesize 3-dimensional bioscaffolds that can be used to replace lost tissue. These bioscaffolds with strategic biomimicry have been shown to allow for integrative and functional repair of tissue injuries. This review article summarizes the most current advances in tissue engineering and its applications in the field of hand surgery. It outlines the current tissue engineering techniques commonly used for tackling musculoskeletal problems and highlights the most promising approaches according to clinical evidence. In particular, the paper explores regenerative medicine concepts applied to specific tissues including nerve, bone, cartilage, tendon, ligament, and vessels. In the face of innovative and pioneering research, tissue engineering will undoubtedly play a key role in reconstructive hand surgery in the not too distant future.

Current concepts on tenogenic differentiation and clinical applications

Tendon is a tissue that transmits force from muscle to bone. Chronic or acute tendon injuries are very common, and are always accompanied by pain and a limited range of motion in patients. In clinical settings, management of tendon injuries still remains a big challenge. Cell therapies, such as the application of stem cells for tenogenic differentiation, were suggested to be an ideal strategy for clinical translation. However, there is still a lack of specific methods for tenogenic differentiation due to the limited understanding of tendon biology currently. This review focuses on the summary of current published strategies for tenogenic differentiation, such as the application of growth factors, mechanical stimulation, biomaterials, coculture, or induced pluripotent stem cells. Current clinical applications of stem cells for treatment of tendon injuries and their limitations have also been discussed in this review.

Adult Cells Combined With Platelet-Rich Plasma for Tendon Healing: Cell Source Options

Background:

The combination of cells with platelet-rich plasma (PRP) may fulfill tendon deficits and help overcome the limited ability of tendons to heal.

Purpose:

To examine the suitability of 3 human cell types in combination with PRP and the potential impact of the tenocyte-conditioned media (CM) to enhance tendon healing.

Study Design:

Controlled laboratory study.

Methods:

Tenocytes, bone marrow–derived mesenchymal stem cells, and skin fibroblasts were cultured in 3-dimensional PRP hydrogels supplemented or not with CM, and cell proliferation and migration were examined. The effect of tendon-derived CM on matrix-forming phenotype and secretion of inflammatory proteins was determined through their administration to mesenchymal stem cells, tendon, and skin fibroblasts by reverse transcription quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

Results:

Differences were found in the matrix-forming phenotype between each of the cell types. The ratio of collagen I:collagen III was greater in bone marrow–derived mesenchymal stem cells than in skin fibroblasts and tenocytes. The bone marrow–derived mesenchymal stem cells expressed increased levels of cartilage-related genes than tenocytes or skin fibroblasts. The presence of the tenocyte-CM stimulated basic healing mechanisms including proliferation and chemotaxis in all cell types. In addition, the tenocyte-CM modified the matrix-forming phenotype of every cell type when cultured in PRP hydrogels. Each cell type secreted interleukin-6, interleukin-8, and monocyte chemotactic protein-1 in PRP hydrogels, but mesenchymal stem cells secreted less interleukin-8 and monocyte chemotactic protein-1 than tenocytes or skin fibroblasts.

Conclusion:

The tenocyte-CM combined with PRP stimulated tenogenesis in mesenchymal stem cells and in skin fibroblasts and reduced the secretion of inflammatory proteins.

Clinical Relevance:

Modifying the target tissue with PRP prior to cell implantation may optimize the effect of cell therapies. Skin fibroblasts and bone marrow–derived mesenchymal stem cells combined with PRP could be used to regenerate tendons.

Tenogenesis of bone marrow-, adipose-, and tendon-derived stem cells in a dynamic bioreactor

Tendons are frequently damaged and fail to regenerate, leading to pain, loss of function, and reduced quality of life. Mesenchymal stem cells (MSCs) possess clinically useful tissue-regenerative properties and have been exploited for use in tendon tissue engineering and cell therapy. However, MSCs exhibit phenotypic heterogeneity based on the donor tissue used, and the efficacy of cell-based treatment modalities may be improved by optimizing cell source based on relative differentiation capacity. Equine MSCs were isolated from bone marrow (BM), adipose (AD), and tendon (TN), expanded in monolayer prior to seeding on decellularized tendon scaffolds (DTS), and cell-laden constructs were placed in a bioreactor designed to mimic the biophysical environment of the tendon. It was hypothesized that TN MSCs would differentiate toward a tendon cell phenotype better than BM and AD MSCs in response to a conditioning period involving cyclic mechanical stimulation for 1 hour per day at 3% strain and 0.33 Hz. All cell types integrated into DTS adopted an elongated morphology similar to tenocytes, expressed tendon marker genes, and improved tissue mechanical properties after 11 days. TN MSCs expressed the greatest levels of scleraxis, collagen type-I, and cartilage oligomeric matrix protein. Major histocompatibility class-II protein mRNA expression was not detected in any of the MSC types, suggesting low immunogenicity for allogeneic transplantation. The results suggest that TN MSCs are the ideal cell type for regenerative medicine therapies for tendinopathies, exhibiting the most mature tendon-like phenotype in vitro. When TN MSCs are unavailable, BM or AD MSCs may serve as robust alternatives.

Adipose-Derived Stem Cells Improve Collagenase-Induced Tendinopathy in a Rat Model

BACKGROUND

Tendinopathy is a common and highly prevalent musculoskeletal disorder characterized by repetitive activity-related pain and focal tendon tenderness. Histopathologically, tendinopathic tissue mainly shows degenerative changes. Therefore, tendinopathy is not affected by anti-inflammatory therapies. A novel approach, including a stem cell-based therapy, may be beneficial for its treatment.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate the effects of adipose-derived stem cells (ASCs) on tendon healing in a rat tendinopathy model. The hypothesis was that ASC transplantation would improve degeneration in collagenase-induced tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen F344/NSlc rats underwent collagenase injection into the Achilles tendon to induce tendinopathy. At 1 week after collagenase injection, 8 rats received ASCs (ASC group) and 8 received phosphate-buffered saline alone (PBS group). Animals were sacrificed at 4 or 12 weeks after ASC administration, and the degree of degeneration in each tendon was histologically evaluated according to the Bonar scale. The microstructure of healing tendons was observed by scanning electron microscopy. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to measure the ratio of type III collagen messenger RNA (mRNA) to type I collagen mRNA in tendons.

RESULTS

The median Bonar scale score in the ASC and PBS groups was 2.5 and 5.33 at 4 weeks after treatment and 1.0 and 4.0 at 12 weeks after treatment, respectively. Histologically, the ASC group showed a significantly lower degree of tendon degeneration than the PBS group at both time points. In the RT-PCR analysis, the ratio of type III collagen to type I collagen was significantly lower in the ASC group than in the PBS group at 12 weeks after treatment. Moreover, this ratio decreased over time in the ASC group, whereas it increased over time in the PBS group.

CONCLUSION

The study findings demonstrate that the application of ASCs results in significant improvement in the pathological findings associated with tendinopathy and the normalization of collagen ratios within the affected tendon.

CLINICAL RELEVANCE

Subcutaneous adipose tissue can be harvested easily, and ASC administration might have the potential to rapidly treat tendinopathy.

Tissue Engineering of Tendons: A Comparison of Muscle-Derived Cells, Tenocytes, and Dermal Fibroblasts as Cell Sources

BACKGROUND

The rapid development of tendon tissue-engineering technology may offer an alternative graft for reconstruction of severe tendon losses. One critical factor for tendon tissue engineering is the optimization of seed cells. Little is known about the optimal cell source for engineered tendons. The aim of this study was to compare mouse muscle-derived cells, dermal fibroblasts, and tenocytes and determine the optimal cell source for tendon tissue engineering.

METHODS

Mouse muscle-derived cells, dermal fibroblasts, and tenocytes were isolated and cultured in vitro. At passage 1, cellular morphology, cell proliferation, and tenogenic marker expression were evaluated. After seeding on the polyglycolic acid scaffolds for 2 weeks in vitro and 12 weeks in vivo, histologic qualities, ultrastructure, and biomechanical characteristics were evaluated.

RESULTS

Proliferation and cellular morphology were similar for dermal fibroblasts and tenocytes, whereas muscle-derived cells proliferated faster than the other two groups. With regard to the phenotype difference between them, muscle-derived cells and tenocytes shared the gene expression of SCX, TNMD, GDF-8, and Col-I, but with MyoD gene expression only in muscle-derived cells. In contrast to dermal fibroblast and tenocyte constructed tendons, neotendon with muscle-derived cells exhibited better aligned collagen fibers, more mature collagen fibril structure, and stronger mechanical properties, whereas no significant difference in the dermal fibroblast and tenocyte groups was observed.

CONCLUSION

Although dermal fibroblasts are candidates for tendon tissue engineering because they are similar to tenocytes in proliferation and neotendon formation, muscle-derived cells appear to be the most suitable cells for further study and development of engineered tendon.

Hypoxia enhances tenocyte differentiation of adipose-derived mesenchymal stem cells by inducing hypoxia-inducible factor-1α in a co-culture system

OBJECTIVES

Tissue engineering is a promising approach for repair of tendon injuries. Adipose-derived mesenchymal stem cells (ADMSCs) have gained increasing research interest for their potential in improving healing and regeneration of injured tendons. The present study aimed to investigate effects of O2 tension and potential signalling pathways on AMDSC differentiation into tenocytes, in an indirect co-culture system.

MATERIALS AND METHODS

Human ADMSCs were co-cultured under normoxia (20% O2 ) and also under hypoxia (2% O2 ). Tenocyte differentiation of AMDSCs and expression of hypoxia-inducible factor-1 (HIF-1α) were analysed by reverse transcription-PCR, Western blotting and immunohistochemistry. Furthermore, HIF-1α inhibitor and inducer (FG-4592) effects on differentiation of AMDSCs were studied using qPCR, immunofluorescence and Western blotting.

RESULTS

Indirect co-culture with tenocytes increased differentiation of ADMSCs into tenocytes; furthermore, hypoxia further enhanced tenocyte differentiation of AMDSCs, accompanied by increased expression of HIF-1α. HIF-1α inhibitor attenuated effects of hypoxia on differentiation of ADMSCs; in contrast, FG-4592 increased differentiation of ADMSCs under both hypoxia and normoxia.

CONCLUSIONS

Taken together, we found that growing ADMSCs under hypoxia, or activating expression of HIF-1α to be important in differentiation of ADMSCs, which provides a foundation for application of ADMSCs in vivo for tendon regeneration.

Human Adipose Stem Cells Differentiated on Braided Polylactide Scaffolds Is a Potential Approach for Tendon Tissue Engineering

Growing number of musculoskeletal defects increases the demand for engineered tendon. Our aim was to find an efficient strategy to produce tendon-like matrix in vitro. To allow efficient differentiation of human adipose stem cells (hASCs) toward tendon tissue, we tested different medium compositions, biomaterials, and scaffold structures in preliminary tests. This is the first study to report that medium supplementation with 50 ng/mL of growth and differentiation factor-5 (GDF-5) and 280 μM l-ascorbic acid are essential for tenogenic differentiation of hASCs. Tenogenic medium (TM) was shown to significantly enhance tendon-like matrix production of hASCs compared to other tested media groups. Cell adhesion, proliferation, and tenogenic differentiation of hASCs were supported on braided poly(l/d)lactide (PLA) 96l/4d copolymer filament scaffolds in TM condition compared to foamed poly(l-lactide-co-ɛ-caprolactone) (PLCL) 70L/30CL scaffolds. A uniform cell layer formed on braided PLA 96/4 scaffolds when hASCs were cultured in TM compared to maintenance medium (MM) condition after 14 days of culture. Furthermore, total collagen content and gene expression of tenogenic marker genes were significantly higher in TM condition after 2 weeks of culture. The elastic modulus of PLA 96/4 scaffold was more similar to the elastic modulus reported for native Achilles tendon. Our study showed that the optimized TM is needed for efficient and rapid in vitro tenogenic extracellular matrix production of hASCs. PLA 96/4 scaffolds together with TM significantly stimulated hASCs, thus demonstrating the potential clinical relevance of this novel and emerging approach to tendon injury treatments in the future.

Strategies to engineer tendon/ligament-to-bone interface: Biomaterials, cells and growth factors

Integration between tendon/ligament and bone occurs through a specialized tissue interface called enthesis. The complex and heterogeneous structure of the enthesis is essential to ensure smooth mechanical stress transfer between bone and soft tissues. Following injury, the interface is not regenerated, resulting in high rupture recurrence rates. Tissue engineering is a promising strategy for the regeneration of a functional enthesis. However, the complex structural and cellular composition of the native interface makes enthesis tissue engineering particularly challenging. Thus, it is likely that a combination of biomaterials and cells stimulated with appropriate biochemical and mechanical cues will be needed. The objective of this review is to describe the current state-of-the-art, challenges and future directions in the field of enthesis tissue engineering focusing on four key parameters: (1) scaffold and biomaterials, (2) cells, (3) growth factors and (4) mechanical stimuli.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

A review on the use of cell therapy in the treatment of tendon disease and injuries

Tendon disease and injuries carry significant morbidity worldwide in both athletic and non-athletic populations. It is estimated that tendon injuries account for 30%−50% of all musculoskeletal injuries globally. Current treatments have been inadequate in providing an accelerated process of repair resulting in high relapse rates. Modern concepts in tissue engineering and regenerative medicine have led to increasing interest in the application of cell therapy for the treatment of tendon disease. This review will explore the use of cell therapy, by bringing together up-to-date evidence from in vivo human and animal studies, and discuss the issues surrounding the safety and efficacy of its use in the treatment of tendon disease.

The biophysical, biochemical, and biological toolbox for tenogenic phenotype maintenance in vitro

Tendon injuries constitute an unmet clinical need, with 3 to 5 million new incidents occurring annually worldwide. Tissue grafting and biomaterial-based approaches fail to provide environments that are conducive to regeneration; instead they lead to nonspecific cell adhesion and scar tissue formation, which collectively impair functionality. Cell based therapies may potentially recover native tendon function, if tenocyte trans-differentiation can be evaded and stem cell differentiation towards tenogenic lineage is attained. To this end, recreating an artificial in vivo tendon niche by engineering functional in vitro microenvironments is a research priority. Clinically relevant cell based therapies for tendon repair and regeneration could be created using tools that harness biophysical beacons (surface topography, mechanical loading), biochemical cues (oxygen tension), and biological signals (growth factors).

Anti-aging effect of adipose-derived stem cells in a mouse model of skin aging induced by D-galactose

Introduction

Glycation products accumulate during aging of slowly renewing tissue, including skin, and are suggested as an important mechanism underlying the skin aging process. Adipose-derived cells are widely used in the clinic to treat ischemic diseases and enhance wound healing. Interestingly, adipose-derived stem cells (ASCs) are also effective in anti-aging therapy, although the mechanism underlying their effects remains unknown. The purpose of the present study was to examine the anti-aging effect of ASCs in a D-galactose-induced aging animal model and to clarify the underlying mechanism.

Materials and Methods

Six-week-old nude mice were subcutaneously injected with D-gal daily for 8 weeks. Two weeks after completion of treatment, mice were randomized to receive subcutaneous injections of 10⁶ green fluorescent protein (GFP)-expressing ASCs, aminoguanidine (AG) or phosphate-buffered saline (PBS). Control mice received no treatment. We examined tissue histology and determined the activity of senescence-associated molecular markers such as superoxide dismutase (SOD) and malondialdehyde (MDA).

Results

Transplanted ASCs were detectable for 14 days and their GFP signal disappeared at day 28 after injection. ASCs inhibited advanced glycation end product (AGE) levels in our animal model as well as increased the SOD level and decreased the MDA level, all of which act to reverse the aging phenotype in a similar way to AG, an inhibitor of AGE formation. Furthermore, ASCs released angiogenic factors in vivo such as vascular endothelial growth factor, suggesting a skin trophic effect.

Conclusions

These results demonstrate that ASCs may contribute to the regeneration of skin during aging. In addition, the data shows that ASCs provide a functional benefit by glycation suppression, antioxidation, and trophic effects in a mouse model of aging.