Cryopreserved human adipose-derived stromal vascular fraction maintains fracture healing potential via angiogenesis and osteogenesis in an immunodeficient rat model

Intrathecal Fumagillin Alleviates Chronic Neuropathy-Induced Nociceptive Sensitization and Modulates Spinal Astrocyte-Neuronal Glycolytic and Angiogenic Proteins

Nociceptive sensitization is accompanied by the upregulation of glycolysis in the central nervous system in neuropathic pain. Growing evidence has demonstrated glycolysis and angiogenesis to be related to the inflammatory processes. This study investigated whether fumagillin inhibits neuropathic pain by regulating glycolysis and angiogenesis. Fumagillin was administered through an intrathecal catheter implanted in rats with chronic constriction injury (CCI) of the sciatic nerve. Nociceptive, behavioral, and immunohistochemical analyses were performed to evaluate the effects of the inhibition of spinal glycolysis-related enzymes and angiogenic factors on CCI-induced neuropathic pain. Fumagillin reduced CCI-induced thermal hyperalgesia and mechanical allodynia from postoperative days (POD) 7 to 14. The expression of angiogenic factors, vascular endothelial growth factor (VEGF) and angiopoietin 2 (ANG2), increased in the ipsilateral lumbar spinal cord dorsal horn (SCDH) following CCI. The glycolysis-related enzymes, pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) significantly increased in the ipsilateral lumbar SCDH following CCI on POD 7 and 14 compared to those in the control rats. Double immunofluorescence staining indicated that VEGF and PKM2 were predominantly expressed in the astrocytes, whereas ANG2 and LDHA were predominantly expressed in the neurons. Intrathecal infusion of fumagillin significantly reduced the expression of angiogenic factors and glycolytic enzymes upregulated by CCI. The expression of hypoxia-inducible factor-1α (HIF-1α), a crucial transcription factor that regulates angiogenesis and glycolysis, was also upregulated after CCI and inhibited by fumagillin. We concluded that intrathecal fumagillin may reduce the expression of ANG2 and LDHA in neurons and VEGF and PKM2 in the astrocytes of the SCDH, further attenuating spinal angiogenesis in neuropathy-induced nociceptive sensitization. Hence, fumagillin may play a role in the inhibition of peripheral neuropathy-induced neuropathic pain by modulating glycolysis and angiogenesis.

Comparative Analysis of Stromal Vascular Fraction and Alternative Mechanisms in Bone Fracture Stimulation to Bridge the Gap between Nature and Technological Advancement: A Systematic Review

BACKGROUND

Various stimulation methods, including electrical, ultrasound, mechanical, and biological interventions, are explored, each leveraging intricate cellular and molecular dynamics to expedite healing. The advent of stromal vascular fraction (SVF) marks a significant stride, offering multifarious benefits in bone healing, from enhanced bone formation to optimal vascular integration, drawing a harmonious balance between innate mechanisms and scientific advancements.

METHODS

This systematic review was conducted focusing on literature from 2016 to 2023 and encompassing various bone healing stimulation mechanisms like SVF, electrical, ultrasound, and mechanical stimulation. The extracted data underwent meticulous synthesis and analysis, emphasizing comparative evaluations of mechanisms, applications, and outcomes of each intervention.

RESULTS

The reviewed studies reveal the potential of SVF in bone fracture healing, with its regenerative and anti-inflammatory effects. The purification of SVF is crucial for safe therapeutic use. Characterization involves flow cytometry and microscopy. Studies show SVF's efficacy in bone regeneration, versatility in various contexts, and potential for clinical use. SVF appears superior to electrical, ultrasound, and mechanical stimulation, with low complications.

CONCLUSIONS

This review compares bone healing methods, including SVF. It provides valuable insights into SVF's potential for bone regeneration. However, due to limited human studies and potential bias, cautious interpretation is necessary. Further research is essential to validate these findings and determine the optimal SVF applications in bone healing.

Measuring Bone Healing: Parameters and Scores in Comparison

(1) Background: Bone healing is a complex process that can not be replicated in its entirety in vitro. Research on bone healing still requires the animal model. The critical size femur defect (CSFD) in rats is a well-established model for fractures in humans that exceed the self-healing potential. New therapeutic approaches can be tested here in vivo. Histological, biomechanical, and radiological parameters are usually collected and interpreted. However, it is not yet clear to what extent they correlate with each other and how necessary it is to record all parameters. (2) Methods: The basis for this study was data from three animal model studies evaluating bone healing. The µCT and histological (Movat pentachrome, osteocalcin) datasets/images were reevaluated and correlation analyses were then performed. Two image processing procedures were compared in the analysis of the image data. (3) Results: There was a significant correlation between the histologically determined bone fraction (Movat pentachrome staining) and bending stiffness. Bone fraction determined by osteocalcin showed no prognostic value. (4) Conclusions: The evaluation of the image datasets using ImageJ is sufficient and simpler than the combination of both programs. Determination of the bone fraction using Movat pentachrome staining allows conclusions to be drawn about the biomechanics of the bone. A standardized procedure with the ImageJ software is recommended for determining the bone proportion.

Clinical and Radiological Comparison of Single and Double Intra-articular Injection of Adipose-Derived Stromal Vascular Fraction for Knee Osteoarthritis

The aim of the article is to compare the clinical and radiological outcomes between single and double stromal vascular fraction (SVF) cell injections in patients with knee osteoarthritis (OA). We included 54 patients treated for varus knee OA with intra-articular SVF cell injection. They were divided into two groups: those who received one injection and those who received two. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, knee range of motion, and knee muscle force were assessed at baseline and 3, 6, 12, and 24 months after the first injection. The preoperative hip-knee-ankle (HKA) angle was evaluated using plain radiographs, and T2 mapping values were assessed. The total WOMAC score improved significantly in the single injection group from 3 to 24 months, but the total WOMAC score in the double injection group improved significantly at 24 months. The T2 mapping values in both the groups improved, with a significant difference at 12 months. The preoperative mean HKA angle and the correlation coefficients between the HKA angle and the total WOMAC score and between the HKA angle and the T2 mapping value of the medial femur were significant. In conclusion, double injections may provide more satisfactory treatment outcomes in patients with severe varus knee alignment. This clinical trial is registered in the Japanese Ministry of Health, Labour and Welfare (URL: https://saiseiiryo.mhlw.go.jp/published_plan/index/2) with the registration name "Cell transplantation therapy for osteoarthritis using autologous subcutaneous adipose tissue-derived regenerative (stem) cells (ADRCs)," and the registration number was "PB5160012."

Autologous Adipose-Derived Tissue Stromal Vascular Fraction (AD-tSVF) for Knee Osteoarthritis

Adipose tissue contains adult mesenchymal stem cells that may modulate the metabolism when applied to other tissues. Stromal vascular fraction (SVF) can be isolated from adipose tissue mechanically and/or enzymatically. SVF was recently used to decrease the pain and improve the function of knee osteoarthritis (OA) patients. Primary and/or secondary OA causes inflammation and degeneration in joints, and regenerative approaches that may modify the natural course of the disease are limited. SVF may modulate inflammation and initiate regeneration in joint tissues by initiating a paracrine effect. Chemokines released from SVF may slow down degeneration and stimulate regeneration in joints. In this review, we overviewed articular joint cartilage structures and functions, OA, and macro-, micro-, and nano-fat isolation techniques. Mechanic and enzymatic SVF processing techniques were summarized. Clinical outcomes of adipose tissue derived tissue SVF (AD-tSVF) were evaluated. Medical devices that can mechanically isolate AD-tSVF were listed, and publications referring to such devices were summarized. Recent review manuscripts were also systematically evaluated and included. Transferring adipose tissues and cells has its roots in plastic, reconstructive, and aesthetic surgery. Micro- and nano-fat is also transferred to other organs and tissues to stimulate regeneration as it contains regenerative cells. Minimal manipulation of the adipose tissue is recently preferred to isolate the regenerative cells without disrupting them from their natural environment. The number of patients in the follow-up studies are recently increasing. The duration of follow up is also increasing with favorable outcomes from the short- to mid-term. There are however variations for mean age and the severity of knee OA patients between studies. Positive outcomes are related to the higher number of cells in the AD-tSVF. Repetition of injections and concomitant treatments such as combining the AD-tSVF with platelet rich plasma or hyaluronan are not solidified. Good results were obtained when combined with arthroscopic debridement and micro- or nano-fracture techniques for small-sized cartilage defects. The optimum pressure applied to the tissues and cells during filtration and purification of the AD-tSVF is not specified yet. Quantitative monitoring of articular joint cartilage regeneration by ultrasound, MR, and synovial fluid analysis as well as with second-look arthroscopy could improve our current knowledge on AD-tSVF treatment in knee OA. AD-tSVF isolation techniques and technologies have the potential to improve knee OA treatment. The duration of centrifugation, filtration, washing, and purification should however be standardized. Using gravity-only for isolation and filtration could be a reasonable approach to avoid possible complications of other methodologies.

Stromal Vascular Fraction Reverses the Age-Related Impairment in Revascularization following Injury

Adipose-derived stromal vascular fraction (SVF) has emerged as a potential regenerative therapy, but few studies utilize SVF in a setting of advanced age. Additionally, the specific cell population in SVF providing therapeutic benefit is unknown. We hypothesized that aging would alter the composition of cell populations present in SVF and its ability to promote angiogenesis following injury, a mechanism that is T cell-mediated. SVF isolated from young and old Fischer 344 rats was examined with flow cytometry for cell composition. Mesenteric windows from old rats were isolated following exteriorization-induced (EI) hypoxic injury and intravenous injection of one of four cell therapies: (1) SVF from young or (2) old donors, (3) SVF from old donors depleted of or (4) enriched for T cells. Advancing age increased the SVF T-cell population but reduced revascularization following injury. Both young and aged SVF incorporated throughout the host mesenteric microvessels, but only young SVF significantly increased vascular area following EI. This study highlights the effect of donor age on SVF angiogenic efficacy and demonstrates how the ex vivo mesenteric-window model can be used in conjunction with SVF therapy to investigate its contribution to angiogenesis.

Paracrine effect of the stromal vascular fraction containing M2 macrophages on human chondrocytes through the Smad2/3 signaling pathway

The adipose-derived stromal vascular fraction (SVF) is composed of a heterogeneous mix of adipose-derived stem cells (ADSCs), macrophages, pericytes, fibroblasts, blood, and other cells. Previous studies have found that the paracrine effects of SVF cells may be therapeutic, but their role in osteoarthritis treatment remains unclear. This study aimed to investigate the therapeutic effect of SVF cells on chondrocytes. Chondrocytes were seeded on culture plates alone (control) or cocultured with SVF or ADSCs on cell culture inserts. After 48 h of coculture, chondrocyte collagen II, tissue inhibitors of metalloproteinases-3 (TIMP-3), and matrix metalloproteinases-13 (MMP-13) messenger RNA (mRNA) expression levels were evaluated using reverse-transcription polymerase chain reaction, and the transforming growth factor-β (TGF-β) levels in the supernatant were measured using ELISA. Immunohistochemical staining and flow cytometry were used to evaluate the macrophages in the SVF. These macrophages were characterized according to phenotype using the F4/80, CD86, and CD163 markers. To determine whether the Smad2/3 signaling pathways were involved, the chondrocytes were pre-treated with a Smad2/3 phosphorylation inhibitor and stimulated with the SVF, and then Smad2/3 phosphorylation levels were analyzed using western blot. The mRNA expression levels of various paracrine factors and chondrocyte pellet size were also assessed. Collagen II and TIMP-3 expression were higher in the SVF group than in the ADSC group and controls, while MMP-13 expression was the highest in the ADSC group and the lowest in the controls. TGF-β levels in the SVF group were also elevated. Immunohistochemical staining and flow cytometry revealed that the macrophages in the SVF were of the anti-inflammatory phenotype. Western blot analysis showed that the SVF increased Smad2/3 phosphorylation, while Smad2/3 inhibitors decreased phosphorylation. Smad2/3 inhibitors also reduced the expression of various other paracrine factors and decreased chondrocyte pellet size. These findings suggested that the paracrine effect of heterogeneous cells, such as anti-inflammatory macrophages, in the SVF partly supports chondrocyte regeneration through TGF-β-induced Smad2/3 phosphorylation.

Osteogenic Induction with Silicon Hydroxyapatite Using Modified Autologous Adipose Tissue-Derived Stromal Vascular Fraction: In Vitro and Qualitative Histomorphometric Analysis

Large bone defects requiring invasive surgical procedures have long been a problem for orthopedic surgeons. Despite the use of autologous bone grafting, satisfactory results are often not achieved due to associated limitations. Biomaterials are viable alternatives and have lately been used in association with Stromal Vascular Fraction (SVF), stem cells, and signaling factors for bone tissue engineering (BTE). The objective of the current study was to assess the biocompatibility of Silicon Hydroxyapatite (Si-HA) and to improve osteogenic potential by using autologous adipose-derived SVF with Si-HA in a rabbit bone defect model. Si-HA granules synthesized using a wet precipitation method were used. They were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). A hemolysis assay was used to assess the hemolytic effects of Si-HA, while cell viability was assessed through Alamar Blue assay using MC3T3 mouse osteoblasts. The osteogenic potential of Si-HA both alone and with enzymatically/non-enzymatically-derived SVF (modified) was performed by implantation in a rabbit tibia model followed by histomorphometric analysis and SEM of dissected bone after six weeks. The results showed that Si-HA granules were microporous and phase pure and that the addition of Silicon did not influence Si-HA phase composition. Si-HA granules were found to be non-hemolytic on the hemolysis assay and non-toxic to MC3T3 mouse osteoblasts on the Alamar Blue assay. Six weeks following implantation Si-HA showed high biocompatibility, with increased bone formation in all groups compared to control. Histologically more mature bone was formed in the Si-HA implanted along with non-enzymatically-derived modified SVF. Bone formation was observed on and around Si-HA, reflecting osseointegration. In conclusion, Si-HA is osteoconductive and promotes osteogenesis, and its use with SVF enhances osteogenesis.

Microvascular fragments in microcirculation research and regenerative medicine

Adipose tissue-derived microvascular fragments (MVF) are functional vessel segments, which rapidly reassemble into new microvasculatures under experimental in vitro and in vivo conditions. Accordingly, they have been used for many years in microcirculation research to study basic mechanisms of endothelial cell function, angiogenesis and microvascular network formation in two- and three-dimensional environments. Moreover, they serve as vascularization units for musculoskeletal regeneration and implanted biomaterials as well as for the treatment of myocardial infarction and the generation of prevascularized tissue organoids. Besides, multiple factors determining the vascularization capacity of MVF have been identified, including their tissue origin and cellular composition, the conditions for their short- and long-term storage as well as their implantation site and the general health status and medication of the recipient. The next challenging step is now the successful translation of all these promising experimental findings into clinical practice. If this succeeds, a multitude of future therapeutic applications may significantly benefit from the remarkable properties of MVF.