Vascular Endothelial Growth Factor Induction of Muscle-Derived Stem Cells Enhances Vascular Phenotype While Preserving Myogenic Potential.

BACKGROUND: Previous work by our group and other laboratories have revealed that muscle-derived stem cells (MDSCs) may contain both myogenic and endothelial progenitors, making MDSCs a promising option for skeletal muscle regeneration. The purpose of this study was to investigate the impact of vascular endothelial growth factor (VEGF) induction on the vascular and myogenic potential of MDSCs. METHODS: Muscle-derived stem cells were isolated from 4- to 8-week-old C57BL/6J mice using a preplate technique and recombinant human VEGFa was used as the induction agent. Cellular proliferation and migration were assessed using serial imaging and wound healing assays, respectively. Myosin heavy chain staining was performed to assess MDSC myotube formation. Vascular potential of MDSCs was measured by expression of CD31 and in vitro capillary tube formation. RESULTS: Vascular endothelial growth factor stimulation led to a dose-dependent increase in MDSC proliferation (P < 0.05) and migration kinetics (P < 0.01). Control MDSCs had low levels of baseline expression of CD31, which was significantly upregulated by VEGF stimulation. Similarly, MDSCs demonstrated a basal capability for capillary tube formation, which was significantly increased after VEGF induction as evidenced by increased branches (5.91 ± 0.58 vs 9.23 ± 0.67, P < 0.01) and total tube length (11.73 ± 0.97 vs 18.62 ± 1.57 mm, P < 0.01). Additionally, the myogenic potential of MDSCs as measured by fusion index remained unchanged with increasing concentration of VEGF up to 250 ng/mL (P = 0.77). CONCLUSIONS: Vascular endothelial growth factor induction enhances MDSC proliferation, migration, and endothelial phenotypes without negatively impacting myogenic potential. These results suggest that VEGF stimulation may improve vascularization of MDSC-based strategies for skeletal muscle regeneration.

Is Continuing Anticoagulation or Antiplatelet Therapy Safe Prior to Kidney Transplantation?

BACKGROUND Patients undergoing kidney transplantation are often placed on anticoagulation or antiplatelet therapy, and their perioperative management is often challenging. This study aimed to determine the safety of continuing anticoagulation or antiplatelet therapy prior to kidney transplantation. The primary outcome was bleeding after transplantation. MATERIAL AND METHODS Patients who underwent kidney transplantation between January 2017 and July 2019 were included and divided into 3 groups: pretransplant anticoagulation with warfarin (WARF; n=23); pretransplant antiplatelet therapy with clopidogrel/aspirin (ASA/CLOP; n=32); and control (CTL; n=197). Patients received kidneys from live or deceased donors. Preoperative INRs and platelet counts were compared to ensure therapeutic anticoagulation in the warfarin group and no significant platelet count variation among groups. The primary outcome was graft exploration for bleeding at 3 and 6 months after transplantation. Secondary outcomes included perioperative transfusion requirements, prolonged length of stay (>7 days), and outcomes at 3 and 6 months after transplantation, including hemodialysis and rejection rates and creatinine levels. RESULTS Pretransplant INR was significantly greater in the warfarin group (CTL 1.1, WARF 2.2, ASA/CLOP 1.2; P<0.01). There were no differences in pretransplant platelet count (CTL 202×10³, WARF 186×10³, ASA/CLOP 194×10³; P=0.31), graft exploration for bleeding at 3 (CTL 3%, WARF 0%, ASA/CLOP 3%; P=0.69) and 6 months after transplantation (CTL 1%, WARF 4%, ASA/CLOP 0%; P=0.12), or perioperative blood transfusion requirements (CTL 4%, WARF 4%, ASA/CLOP 14%; P=0.13). Prolonged length of stay was similar (CTL 24%, WARF 26%, ASA/CLOP 44%; P=0.08). There were no significant differences among groups at 3 months in dialysis (CTL 2%, WARF 0%, ASA/CLOP 0%; P=0.71), creatinine (CTL 1.5 mg/dL, WARF 1.7 mg/dL, ASA/CLOP 1.7; P=0.13), or rejection (CTL 6%, WARF 0%, ASA/CLOP 0%) or at 6 months in dialysis (CTL 3%, WARF 0%, ASA/CLOP 0%; P=0.49), creatinine (CTL 1.5 mg/dL, WARF 1.7 mg/dL, ASA/CLOP 1.5; P=0.49), or rejection (CTL 1%, WARF 0%, ASA/CLOP 3%). CONCLUSIONS Continuing anticoagulation or antiplatelet was safe in not increasing bleeding complications or perioperative transfusion requirements. Outcomes were similar at 3 and 6 months among groups. This strategy avoids exposing patients to risk of thrombosis if treatment is held and simplifies proceeding to transplantation.

The Efficacy of Schwann-Like Differentiated Muscle-Derived Stem Cells in Treating Rodent Upper Extremity Peripheral Nerve Injury.

BACKGROUND: There is a pressing need to identify alternative mesenchymal stem cell sources for Schwann cell cellular replacement therapy, to improve peripheral nerve regeneration. This study assessed the efficacy of Schwann cell-like cells (induced muscle-derived stem cells) differentiated from muscle-derived stem cells (MDSCs) in augmenting nerve regeneration and improving muscle function after nerve trauma. METHODS: The Schwann cell-like nature of induced MDSCs was characterized in vitro using immunofluorescence, flow cytometry, microarray, and reverse-transcription polymerase chain reaction. In vivo, four groups (n = 5 per group) of rats with median nerve injuries were examined: group 1 animals were treated with intraneural phosphate-buffered saline after cold and crush axonotmesis (negative control); group 2 animals were no-injury controls; group 3 animals were treated with intraneural green fluorescent protein-positive MDSCs; and group 4 animals were treated with green fluorescent protein-positive induced MDSCs. All animals underwent weekly upper extremity functional testing. Rats were euthanized 5 weeks after treatment. The median nerve and extrinsic finger flexors were harvested for nerve histomorphometry, myelination, muscle weight, and atrophy analyses. RESULTS: In vitro, induced MDSCs recapitulated native Schwann cell gene expression patterns and up-regulated pathways involved in neuronal growth/signaling. In vivo, green fluorescent protein-positive induced MDSCs remained stably transformed 5 weeks after injection. Induced MDSC therapy decreased muscle atrophy after median nerve injury (p = 0.0143). Induced MDSC- and MDSC-treated animals demonstrated greater functional muscle recovery when compared to untreated controls (hand grip after induced MDSC treatment: group 1, 0.91 N; group 4, 3.38 N); p < 0.0001) at 5 weeks after treatment. This may demonstrate the potential beneficial effects of MDSC therapy, regardless of differentiation stage. CONCLUSION: Both MDSCs and induced MDSCs decrease denervation muscle atrophy and improve subsequent functional outcomes after upper extremity nerve trauma in rodents.

Versatility of Free Cutaneous Flaps for Upper Extremity Soft Tissue Reconstruction.

The goals of upper extremity soft tissue reconstruction should go well beyond providing coverage and restoring function. As the field of reconstructive microsurgery has evolved, free cutaneous flaps (FCFs) are gaining wider application. The advantages of FCF include minimizing donor-site morbidity by preserving the muscle and fascia, improving versatility of flap design, and superior aesthetic results. This review highlights the application of anterolateral thigh, superficial circumflex iliac artery, deep inferior epigastric perforator, superficial inferior epigastric artery, and flow-through flaps for reconstruction of upper extremity defects. These flaps share several qualities in common: well-concealed donor sites, preservation of major arteries responsible of providing inflow to distal extremity, and potential for a two-team approach (donor and recipient sites). While the choice of flaps should be decided based on individual patient and defect characteristics, FCF should be considered as excellent options to achieve the goals of upper extremity reconstruction.