Human Adipose-Derived Mesenchymal Stromal/Stem Cells Remain Viable and Metabolically Active Following Needle Passage

Adipose-derived stem cells in diabetic foot care: Bridging clinical trials and practical application

Diabetic foot ulcers (DFUs) pose a critical medical challenge, significantly im-pairing the quality of life of patients. Adipose-derived stem cells (ADSCs) have been identified as a promising therapeutic approach for improving wound healing in DFUs. Despite extensive exploration of the mechanical aspects of ADSC therapy against DFU, its clinical applications remain elusive. In this review, we aimed to bridge this gap by evaluating the use and advancements of ADSCs in the clinical management of DFUs. The review begins with a discussion of the classification and clinical management of diabetic foot conditions. It then discusses the current landscape of clinical trials, focusing on their geographic distribution, reported efficacy, safety profiles, treatment timing, administration techniques, and dosing considerations. Finally, the review discusses the preclinical strategies to enhance ADSC efficacy. This review shows that many trials exhibit biases in study design, unclear inclusion criteria, and intervention protocols. In conclusion, this review underscores the potential of ADSCs in DFU treatment and emphasizes the critical need for further research and refinement of therapeutic approaches, with a focus on improving the quality of future clinical trials to enhance treatment outcomes and advance the field of diabetic wound care.

Cellular Enhancement of Frozen Meniscus Allograft Combining Native Meniscus and Mesenchymal Stromal Cell Injections

OBJECTIVE

This proof-of-concept study investigated an improved cell-based injection therapy combining mesenchymal stem cells (MSCs) and meniscus cells (MCs) to support superior meniscus allograft repopulation and early revival compared to injecting MSCs alone.

DESIGN

In this controlled laboratory study, frozen meniscus allograft samples were injected vertically with a cell suspension containing different ratios of MSCs and MCs or control (lactated ringers) and cultured for 28 days. Samples were analyzed weekly for cell viability, migration, and metabolism using histological and biochemical assays. Tissue medium was analyzed for matrix metalloproteinase (MMP) expression using zymography.

RESULTS

Cellular repopulation of frozen allografts injected with different cell suspensions was validated by immunohistochemistry. Significant higher DNA content was evidenced in grafts treated with suspensions of MCs or MC:MSC (1:4 ratio). Cell metabolic activity was significantly different between all treated groups and control group after 1 week. Allografts injected with MCs showed significantly more cell proliferation than injections with MSCs. MMP2 activity was detected in medium of all grafts cellularized with MCs with or without MSCs. Scanning electron microscopy (SEM) analysis showed resolution of the needle puncture, but not in the control group. Cell labeling of MCs upon injection of mixed MC:MSC suspensions revealed a gradual increase in the cell ratio.

CONCLUSIONS

The findings of this study establish that injection of MCs with or without MSCs enhances the cellularity of meniscus allograft to support early graft revival and remodeling.

Dynamic Seeding versus Microinjection of Adipose-Derived Mesenchymal Stem Cells to Acellular Nerve Allograft Reconstructions

BACKGROUND

Functional recovery following acellular nerve allograft (ANA) reconstructions remains inferior to autologous nerve grafting, but have demonstrated improved outcomes with the addition of adipose-derived mesenchymal stem cells (MSC). Controversy exists regarding the optimal cell delivery method to enhance ANA reconstructions. We investigated the functional recovery of ANAs after dynamic seeding versus microinjection of MSCs.

METHODS

Forty Lewis rats underwent reconstruction of a 10-mm sciatic nerve defect. Animals were divided into four groups: reversed autograft, ANA alone, ANA dynamically seeded, or ANA injected with MSCs. During the survival period, ultrasound measurements of the tibialis anterior (TA) muscle cross-sectional area were performed. At 12 weeks, functional recovery was evaluated using measurements of ankle contracture, compound muscle action potential (CMAP), maximum isometric tetanic force (ITF), muscle mass, histomorphometry, and immunofluorescence.

RESULTS

The dynamic seeding and microinjection groups demonstrated higher cross-sectional TA muscle area recovery than autografts and ANAs alone at week 8 and week 4 and 8, respectively. The ankle contracture and CMAP amplitude recovery were superior in autografts and both seeding methods compared to ANAs alone. The microinjection group demonstrated significantly higher ITF, muscle mass, and number of axons compared to ANAs alone. Both seeding methods showed higher CD34 densities compared to ANAs alone. No significant differences between dynamic seeding and microinjection were observed for both functional and histological outcomes.

CONCLUSIONS

The addition of MSCs to ANAs demonstrated earlier motor regeneration compared to autografts and ANAs alone. Both seeding methods improved functional outcomes in the rat sciatic nerve defect model.

CLINICAL RELEVANCE STATEMENT

Future clinical applications of stem cell-based nerve reconstructions are dependent on determining optimum delivery methods, which are technically feasible, reproducible, cost-efficient, and timely.

Optimal Intravenous Administration Procedure for Efficient Delivery of Canine Adipose-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) are currently being investigated for their therapeutic applications in a wide range of diseases. Although many studies examined peripheral venous administration of MSC, few have investigated the detailed intravenous administration procedures of MSC from their preparation until they enter the body. The current study therefore aimed to explore the most efficient infusion procedure for MSC delivery by preparing and infusing them under various conditions. Canine adipose-derived mesenchymal stem cells (cADSC) were infused using different infusion apparatuses, suspension solutions, allogenic serum supplementation, infusion time and rates, and cell densities, respectively. Live and dead cell counts were then assessed by manual measurements and flow cytometry. Efficiency of live- and dead-cell infusion and cell viability were calculated from the measured cell counts and compared under each condition. Efficiency of live-cell infusion differed significantly according to the infusion apparatus, infusion rate, and combination of cell density and serum supplementation. Cell viability after infusion differed significantly between the infusion apparatuses. The optimal infusion procedure resulting in the highest cell delivery and viability involved suspending cADSC in normal saline supplemented with 5% allogenic serum at a density of 5 × 10⁵ cells/mL, and infusing them using an automatic infusion device for 15 min. This procedure is therefore recommended as the standard procedure for the intravenous administration of ADSC in terms of cell-delivery efficiency.

Dynamic seeding versus microinjection of mesenchymal stem cells for acellular nerve allograft: an in vitro comparison

BACKGROUND

Mesenchymal stem cell (MSC)-supplemented acellular nerve allografts (ANA) are a potential strategy to improve the treatment of segmental nerve defects. Prior to clinical translation, optimal cell delivery methods must be defined. While two techniques, dynamic seeding and microinjection, have been described, the seeding efficiency, cell viability, and distribution of MSCs in ANAs are yet to be compared.

METHODS

Sciatic nerve segments of Sprague-Dawley rats were decellularized, and MSCs were harvested from the adipose tissue of Lewis rats. Cell viability was evaluated after injection of MSCs through a 27-gauge needle at different flow rates (10, 5, and 1 µL/min). MSCs were dynamically seeded or longitudinally injected into ANAs. Cell viability, seeding efficiency, and distribution were evaluated using LIVE/DEAD and MTS assays, scanning electron microscopy, and Hoechst staining.

RESULTS

No statistically significant difference in cell viability after injection at different flow rates was seen. After cell delivery, 84.1 ± 3.7% and 87.8 ± 2.8% of MSCs remained viable in the dynamic seeding and microinjection group, respectively (p = 0.41). The seeding efficiency of microinjection (100.4%±5.6) was significantly higher than dynamic seeding (48.1%±8.6) on day 1 (p = 0.001). Dynamic seeding demonstrated a significantly more uniform cell distribution over the course of the ANA compared to microinjection (p = 0.02).

CONCLUSION

MSCs remain viable after both dynamic seeding and microinjection in ANAs. Higher seeding efficiency was observed with microinjection, but dynamic seeding resulted in a more uniform distribution. In vivo studies are required to assess the effect on gene expression profiles and functional motor outcomes.

Human meniscus allograft augmentation by allogeneic mesenchymal stromal/stem cell injections

Meniscus allograft transplantations (MATs) represent established surgical procedures with proven outcomes. Yet, storage as frozen specimens and limited cellular repopulation may impair graft viability. This proof-of-concept study tests the feasibility of injecting allogeneic mesenchymal stromal/stem cells (MSCs) in meniscus allograft tissue. We investigated the injectable cell quantity, survival rate, migration, and proliferation ability of MSCs up to 28 days of incubation. In this controlled laboratory study, seven fresh-frozen human allografts were injected with human allogeneic MSCs. Cells were labeled and histological characteristics were microscopically imaged up to 28 days. Mock-injected menisci were included as negative controls in each experiment. Toluidine blue staining demonstrated that a 100-µl volume can be injected while retracting and rotating the inserted needle. Immediately after injection, labeled MSCs were distributed throughout the injection channel and eventually migrated into the surrounding tissues. Histological assessment revealed that MSCs cluster in disc-like shapes, parallel to the intrinsic lamination of the meniscus and around the vascular network. Quantification showed that more than 60% of cells were present in horizontally injected grafts and more than 30% were observed in vertically injected samples. On Day 14, cells adopted a spindle-shaped morphology and exhibited proliferative and migratory behaviors. On Day 28, live/dead ratio assessment revealed an approximately 80% cell survival. The study demonstrated the feasibility of injecting doses of MSCs (>0.1 million) in meniscus allograft tissue with active cell proliferation, migration, and robust cell survival.

Differences in Cytotoxicity of Lidocaine, Ropivacaine, and Bupivacaine on the Viability and Metabolic Activity of Human Adipose-Derived Mesenchymal Stem Cells

PURPOSE

We evaluated biological effects of distinct local anesthetics on human adipose-derived mesenchymal stem cells when applied to reduce periprocedural pain during mesenchymal stem cell injections.

METHODS AND MATERIALS

Metabolic activity (MTS assay), viability (Live/Dead stain), and gene expression (quantitative real-time reverse-transcriptase polymerase chain reaction) were measured in mesenchymal stem cells incubated with various concentrations of lidocaine, ropivacaine, or bupivacaine during a 12-hr time course.

RESULTS

Cell viability and metabolic activity decreased in a dose, time, and substance-specific manner after exposure to lidocaine, ropivacaine, and bupivacaine, with ropivacaine being the least cytotoxic. Cell viability decreases after brief exposure (<1.5 hrs) at clinically relevant concentrations (eg, 8 mg/ml of lidocaine, 2.5 mg/ml of ropivacaine or bupivacaine). Mesenchymal stem cells exposed to local anesthetics change their expression of mRNA biomarkers for stress response (EGR1, EGR2), proliferation (MKI67, HIST2H4A), ECM (COL1A1, COL3A1), and cell surface marker (CD105).

CONCLUSIONS

Local anesthetics are cytotoxic to clinical-grade human mesenchymal stem cells in a dose-, time-, and agent-dependent manner and change expression of ECM, proliferation, and cell surface markers. Lidocaine and bupivacaine are more cytotoxic than ropivacaine. Single-dose injections of local anesthetics may affect the biological properties of mesenchymal stem cells in vitro but may not affect the effective dose of MSCs in a clinical setting.

Introducing human adipose-derived mesenchymal stem cells to AvanceⓇ nerve grafts and NeuraGenⓇ nerve guides

BACKGROUND

When direct nerve coaptation is impossible after peripheral nerve injury, autografts, processed allografts, or conduits are used to bridge the nerve gap. The purpose of this study was to examine if human adipose-derived Mesenchymal Stromal/Stem Cells (MSCs) could be introduced to commercially available nerve graft substitutes and to determine cell distribution and the seeding efficiency of a dynamic seeding strategy.

METHODS

MTS assays examined the viability of human MSCs after introduction to the Avance^Ⓡ Nerve Graft and the NeuraGen^Ⓡ Nerve Guide. MSCs were dynamically seeded on nerve substitutes for either 6, 12, or 24 h. Cell counts, live/dead stains, Hoechst stains, and Scanning Electron Microscopy (SEM) revealed the seeding efficiency and the distribution of MSCs after seeding.

RESULTS

The viability of MSCs was not affected by nerve substitutes. Dynamic seeding led to uniformly distributed MSCs over the surface of both nerve substitutes and revealed MSCs on the inner surface of the NeuraGen^Ⓡ Nerve Guides. The maximal seeding efficiency of NeuraGen^Ⓡ Nerve Guides (94%), obtained after 12 h was significantly higher than that of Avance^Ⓡ Nerve Grafts (66%) (p = 0.010).

CONCLUSION

Human MSCs can be dynamically seeded on Avance^Ⓡ Nerve Grafts and NeuraGen^Ⓡ Nerve Guides. The optimal seeding duration was 12 h. MSCs were distributed in a uniform fashion on exposed surfaces. This study demonstrates that human MSCs can be effectively and efficiently seeded onto commercially available nerve autograft substitutes in a timely fashion and sets the stage for the clinical application of MSC-seeded nerve graft substitutes clinically.

Hypothermia and nutrient deprivation alter viability of human adipose-derived mesenchymal stem cells

PURPOSE

Adipose-derived mesenchymal stem cells (MSCs) are attractive biological agents in regenerative medicine. To optimize cell therapies, it is necessary to determine the most effective delivery method for MSCs. Therefore, we evaluated the biological properties of MSCs after exposure to various temperatures to define optimal storage conditions prior to therapeutic delivery of MSCs.

DESIGN

Prospective observational study.

METHODS AND MATERIALS

Adherent and non-adherent MSCs were incubated at multiple temperatures (i.e., 4, 23 and 37 °C) in Lactated Ringers (LR) solution lacking essential cell growth ingredients, or in culture media which is optimized for cell growth. Cells were assessed either after the temperature changes (4 h) or after recovery (24 h). Metabolic activity of MSCs, cell number and expression of representative mRNA biomarkers were evaluated to assess the biological effects of temperature. We monitored changes in mRNAs expression related to cytoprotective- or stress-related responses (e.g., FOS, JUN, ATF1, ATF4, EGR1, EGR2, MYC), proliferation (e.g., HIST2H4, CCNB2), and extracellular matrix production (ECM; e.g., COL3A1, COL1A1) by quantitative real time reverse-transcriptase polymerase chain reaction (RT-qPCR) analysis.

RESULTS

Our study demonstrates that storing MSCs in Lactated Ringers (LR) solution for 4 h decreases cell number and metabolic activity. The number of viable MSCs decreased significantly when cultured at physiological temperature (37 °C) and severe hypothermia (4 °C), while cells grown at ambient temperature (23 °C) exhibited the least detrimental effects. There were no appreciable biological differences in mRNA markers for proliferation or ECM deposition at any of the temperatures. However, biomarkers related to cytoprotective- or stress-responses were selectively elevated depending on temperature or media type (i.e., LR versus standard media).

CONCLUSION

The biological impact of nutrient-free media and temperature changes after 4 h exposure persists after a 24 h recovery period. Hence, storage temperature and media conditions should be optimized to improve effective dosing of MSCs.

Effect of Lidocaine on Viability and Gene Expression of Human Adipose-derived Mesenchymal Stem Cells: An in vitro Study

OBJECTIVE

To assess the biologic effects of lidocaine on the viability, proliferation, and function of human adipose tissue-derived mesenchymal stromal/stem cells (MSCs) in vitro.

METHODS

Adipose-derived MSCs from three donors were exposed to lidocaine at various dilutions (2 mg/mL to 8 mg/mL) and exposure times (0.5 to 4 hours). Cell number and viability, mitochondrial activity, and real-time reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) were analyzed at 0 (immediate effects) or 24 and 48 hours (recovery effects) after treatment with lidocaine.

RESULTS

Trypan blue staining showed that increasing concentrations of lidocaine decreased the number of observable viable cells. 3-[4,5,dimethylthiazol-2-yl]-5-[3-carboxymethoxy-phenyl]-2-[4-sulfophenyl]-2H-tetrazolium (MTS) assays revealed a concentration- and time- dependent decline of mitochondrial activity and proliferative ability. Gene expression analysis by RT-qPCR revealed that adipose-derived MSCs exposed to lidocaine express robust levels of stress response/cytoprotective genes. However, higher concentrations of lidocaine caused a significant downregulation of these genes. No significant differences were observed in expression of extracellular matrix (ECM) markers COL1A1 and DCN except for COL3A1 (P < .05). Levels of messenger RNA (mRNA) for proliferation markers (CCNB2, HIST2H4A, P < .001) and MKI67 (P < .001) increased at 24 and 48 hours. Expression levels of several transcription factors- including SP1, PRRX1, and ATF1-were modulated in the same manner. MSC surface markers CD44 and CD105 demonstrated decreased expression immediately after treatment, but at 24 and 48 hours postexposure, the MSC markers showed no significant difference among groups.

CONCLUSION

Lidocaine is toxic to MSCs in a dose- and time- dependent manner. MSC exposure to high (4-8 mg/mL) concentrations of lidocaine for prolonged periods can affect their biologic functions. Although the exposure time in vivo is short, it is essential to choose safe concentrations when applying lidocaine along with MSCs to avoid compromising the viability and potency of the stem cell therapy.

Efficacy of Platelet-Rich Plasma Containing Xenogenic Adipose Tissue-Derived Stromal Cells on Restoring Intervertebral Disc Degeneration: A Preclinical Study in a Rabbit Model

Objective

Platelet-rich plasma (PRP) containing multiple growth factors is a promising strategy for disc degeneration. Thus, this study hypothesizes that the combination of PRP and adipose tissue-derived stromal cells (ADSCs) may repair degenerative disc more effectively than using each one of them alone.

Methods

The model of early intervertebral disc degeneration was induced by annular puncture in the New Zealand rabbit. Autologous PRP was extracted from fresh arterial blood by using two centrifugation techniques. ADSC was offered by the Center for Clinic Stem Cell Research. Four weeks after the first experiment, PRP or ADSCs or a combination of PRP and ADSCs was injected into the punctured intervertebral disc. Four weeks later, disc height and signal intensity on T2-weighted magnetic resonance imaging (MRI) were assessed.

Results

One month after puncture, we detected relatively narrow discs and lower signal intensity in MRI T2-weighted images. At four weeks after injection, the PRP-ADSC group statistically significantly restored discs, compared with PRP, ADSCs, or negative control group.

Conclusions

The combination of PRP and ADSCs shows an effective potential to restore degenerated intervertebral discs in the rabbit.

Targeted stimulation of MSCs in peripheral nerve repair

Mesenchymal stem cells (MSCs) have considerable translational potential in a wide variety of clinical disciplines and are the cellular foundation of individualized treatments of auto-immune, cardiac, neurologic and musculoskeletal diseases and disorders. While the cellular mechanisms by which MSCs exert their biological effects remain to be ascertained, it has been hypothesized that MSCs are supportive of local tissue repair through secretion of essential growth factors. Therapeutic applications of MSCs in peripheral nerve repair have recently been reported. This review focuses on how MSCs can promote nerve regeneration by conversion into Schwann-like cells, and discusses differentiation methods including delivery and dosing of naive or differentiated MSCs, as well as in vitro and in vivo outcomes. While MSC-based therapies for nerve repair are still in early stages of development, current progress in the field provides encouragement that MSCs may have utility in the treatment of patients with peripheral nerve injury.

Cell density, dimethylsulfoxide concentration and needle gauge affect hydrogel-induced bone marrow mesenchymal stromal cell viability

Mesenchymal stromal cells (MSCs) have shown potential therapeutic benefits for a range of medical disorders and continue to be a focus of intense scientific investigation. Transplantation of MSCs into injured tissue can improve wound healing, tissue regeneration and functional recovery. However, implanted cells rapidly lose their viability or fail to integrate into host tissue. Hydrogel-seeded bone marrow (BM)-MSCs offer improved viability in response to mechanical forces caused by syringe needles, cell density and dimethylsulfoxide (DMSO) concentration, which in turn, will help to clarify which factors are important for enhancing biomaterial-induced cell transplantation efficiency and provide much needed guidance for clinical trials. In this study, under the control of cell density (<2 × 107 cells/mL) and final DMSO concentration (<0.5%), hydrogel-induced BM-MSC viability remained >82% following syringe needle passage by 25- or 27-gauge needles, providing improved cell therapeutic approaches for regenerative medicine.