Behfar, Atta

Soft tissue defects are common following trauma and tumor extirpation. These injuries can result in poor functional recovery and lead to a diminished quality of life. The healing of skin and muscle is a complex process that, at present, leads to incomplete recovery and scarring. Regenerative medicine may offer the opportunity to improve the healing process and functional outcomes. Barriers to regenerative strategies have included cost, regulatory hurdles, and the need for cell-based therapies. In recent years, exosomes, or extracellular vesicles, have gained tremendous attention in the field of soft tissue repair and regeneration. These nanosized extracellular particles (30–140 nm) can break the cellular boundaries, as well as facilitate intracellular signal delivery in various regenerative physiologic and pathologic processes. Existing studies have established the potential of exosomes in regenerating tendons, skeletal muscles, and peripheral nerves through different mechanisms, including promoting myogenesis, increasing tenocyte differentiation and enhancing neurite outgrowth, and the proliferation of Schwann cells. These exosomes can be stored for immediate use in the operating room, and can be produced cost efficiently. In this article, we critically review the current advances of exosomes in soft tissue (tendons, skeletal muscles, and peripheral nerves) healing. Additionally, new directions for clinical applications in the future will be discussed.

Background: Tendons are primarily acellular, limiting their intrinsic regenerative capabilities. This limited regenerative potential contributes to delayed healing, rupture, and adhesion formation after tendon injury. Purpose: To determine if a tendon’s intrinsic regenerative potential could be improved after the application of a purified exosome product (PEP) when loaded onto a collagen scaffold. Study Design: Controlled laboratory study. Methods: An in vivo rabbit Achilles tendon model was used and consisted of 3 groups: (1) Achilles tenotomy with suture repair, (2) Achilles tenotomy with suture repair and collagen scaffold, and (3) Achilles tenotomy with suture repair and collagen scaffold loaded with PEP at 1 × 10 12 exosomes/mL. Each group consisted of 15 rabbits for a total of 45 specimens. Mechanical and histologic analyses were performed at both 3 and 6 weeks. Results: The load to failure and ultimate tensile stress were found to be similar across all groups ( P ≥ .15). The tendon cross-sectional area was significantly smaller for tendons treated with PEP compared with the control groups at 6 weeks, which was primarily related to an absence of external adhesions ( P = .04). Histologic analysis confirmed these findings, demonstrating significantly lower adhesion grade both macroscopically ( P = .0006) and microscopically ( P = .0062) when tendons were treated with PEP. Immunohistochemical staining showed a greater intensity for type 1 collagen for PEP-treated tendons compared with collagen-only or control tendons. Conclusion: Mechanical and histologic results suggested that healing in the PEP-treated group favored intrinsic healing (absence of adhesions) while control animals and animals treated with collagen only healed primarily via extrinsic scar formation. Despite a smaller cross-sectional area, treated tendons had the same ultimate tensile stress. This pilot investigation shows promise for PEP as a means of effectively treating tendon injuries and enhancing intrinsic healing. Clinical Relevance: The production of a cell-free, off-the-shelf product that can promote tendon regeneration would provide a viable solution for physicians and patients to enhance tendon healing and decrease adhesions as well as shorten the time required to return to work or sports.

Aims Bone marrow-derived mesenchymal stem cells obtained from bone marrow aspirate concentrate (BMAC) with platelet-rich plasma (PRP), has been used as an adjuvant to hip decompression. Early results have shown promise for hip preservation in patients with osteonecrosis (ON) of the femoral head. The purpose of the current study is to examine the mid-term outcome of this treatment in patients with precollapse corticosteroid-induced ON of the femoral head. Methods In all, 22 patients (35 hips; 11 males and 11 females) with precollapse corticosteroid-induced ON of the femoral head underwent hip decompression combined with BMAC and PRP. Mean age and BMI were 43 years (SD 12) and 31 kg/m² (SD 6), respectively, at the time of surgery. Survivorship free from femoral head collapse and total hip arthroplasty (THA) and risk factors for progression were evaluated at minimum five-years of clinical follow-up with a mean follow-up of seven years (5 to 8). Results Survivorship free from femoral head collapse and THA for any reason was 84% and 67% at seven years postoperatively, respectively. Risk factors for conversion to THA included a high preoperative modified Kerboul angle (grade 3 or 4) based on preoperative MRI (hazard ratio (HR) 3.96; p = 0.047) and corticosteroid use at the time of decompression (HR 4.15; p = 0.039). The seven-year survivorship for patients with grade 1 or 2 Kerboul angles for conversion to THA for articular collapse, and THA for any reason, were 96% and 72%, respectively, versus THA for articular collapse and THA for any reason in patients with grade 3 or 4 Kerboul angles of 40% (p = 0.003) and 40% (p = 0.032). Conclusion At seven years, hip decompression augmented with BMAC and PRP provided a 67% survivorship free from THA in patients with corticosteroid-induced ON. Ideal candidates for this procedure are patients with low preoperative Kerboul angles and can stop corticosteroid treatment prior to decompression. Cite this article: Bone Jt Open 2021;2(11):926–931.

Heart failure pathobiology is permissive to reparative intent. Regenerative therapies exemplify an emerging disruptive innovation aimed at achieving structural and functional organ restitution. However, mixed outcomes, complexity in use, and unsustainable cost have curtailed broader adoption, mandating the development of novel cardio-regenerative approaches. Lineage guidance offers a standardized path to customize stem cell fitness for therapy. A case in point is the molecular induction of the cardiopoiesis program in adult stem cells to yield cardiopoietic cell derivatives designed for heart failure treatment. Tested in early and advanced clinical trials in patients with ischemic heart failure, clinical grade cardiopoietic cells were safe and revealed therapeutic improvement within a window of treatment intensity and pre-treatment disease severity. With the prospect of mass customization, cardiopoietic guidance has been streamlined from the demanding, recombinant protein cocktail-based to a protein-free, messenger RNA-based single gene protocol to engineer affordable cardiac repair competent cells. Clinical trial biobanked stem cells enabled a systems biology deconvolution of the cardiopoietic cell secretome linked to therapeutic benefit, exposing a paracrine mode of action. Collectively, this new knowledge informs next generation regenerative therapeutics manufactured as engineered cellular or secretome mimicking cell-free platforms. Launching biotherapeutics tailored for optimal outcome and offered at mass production cost would contribute to advancing equitable regenerative care that addresses population health needs.

Data on pre-implant hemodynamic optimization before continuous flow left ventricular assist device placement (CF-LVAD) with respect to patient-centered outcomes remain limited. Consecutive patients undergoing CF-LVAD implant between 2007 and 2017 were identified. Hemodynamic variables, trends, and laboratory studies were evaluated pre-LVAD implant in a logistic regression model to identify predictors of the primary composite endpoint: the need for right ventricular assist device therapy, the requirement for hemodialysis at 90 days, and 30-day mortality. Multivariate modeling identified three variables significantly associated with the primary endpoint: right ventricular stroke work index (RVSWI), right atrial pressure (RAP), and blood urea nitrogen (BUN); all immediately pre-LVAD, p < 0.01. Optimal dichotomization points were 500 mmHg*ml*m−2, 12 mmHg, and 40 mg/dL. The three-component model identified an AUC of 0.77 (p < 0.0001) for the composite endpoint. Optimization of 2/3 parameters, 1/3, and 0/3 was associated with odds ratios of 3.5 (95% CI, 1.1−11.7), 7.2 (95% CI, 2.1−24.2), and 20.6 (95% CI, 5.3−80.6), respectively, relative to those patients who were fully optimized (3/3 parameters). The number of optimized parameters was also associated with 1-year overall survival (p = 0.02). Low RVSWI, high RAP, and high BUN were independently associated with adverse outcomes after the CF-LVAD implant, demonstrating a stepwise association with severe postimplant adverse events.

Abstract Stem cell paracrine activity is implicated in cardiac repair. Linkage between secretome functionality and therapeutic outcome was here interrogated by systems analytics of biobanked human cardiopoietic cells, a regenerative biologic in advanced clinical trials. Protein chip array identified 155 proteins differentially secreted by cardiopoietic cells with clinical benefit, expanded into a 520 node network, collectively revealing inherent vasculogenic properties along with cardiac and smooth muscle differentiation and development. Next generation RNA sequencing, refined by pathway analysis, pinpointed miR-146 dependent regulation upstream of the decoded secretome. Intracellular and extracellular integration unmasked commonality across cardio-vasculogenic processes. Mirroring the secretome pattern, infarcted hearts benefiting from cardiopoietic cell therapy restored the disease proteome engaging cardiovascular system functions. The cardiopoietic cell secretome thus confers a therapeutic molecular imprint on recipient hearts, with response informed by predictive systems profiling.

Introduction: Counteracting the pandemic of peripheral vascular disease necessitates development of proangiogenic treatments. As stem cell benefit has increasingly been associated with paracrine influence on diseased tissue, a purified extracellular vesicle population (PEP) was established to promote tissue regeneration and neovascularization. The mechanistic basis for PEP-induced proangiogenic effects was here probed and validated in two separate in vivo models of vascular ischemia. Hypothesis: PEP drives pro-angiogenic effects though donation of VEGFR. Methods: Nanosight and immunoblotting were utilized to characterize PEP purity and identity. OMICs profiling identified VEGFR as highly prioritized, with downstream signaling was tested in human umbilical vascular endothelial cells using Matrigel assay, qPCR and immunoblotting. In vivo, blood perfusion (Fluorescent imaging - SPY) was quantified in a rodent model of hind-limb ischemia and in a rabbit model of critical ischemic ear, each treated with sham or PEP. Rabbit tissues were next examined by whole transcriptome analysis to assess PEP-induced proangiogenic signaling. Immunohistochemical staining with smooth muscle actin and von Willebrand factor probed de novo blood vessel formation. Results: PEP was characterized by size (mean: 128.6 +/-1 nm) and VEGFR expression. VEGFR knock-down diminished endothelial cell angiogenic activity in vitro, rescued with PEP (5.3x1010+/-109 vesicles/ml) was sufficient enhance total and phosphor-VEGFR expression, along with amplification of downstream VEGFR targets (MAPK, AKT, CXCL8, NOTCH4, MMP9) and enhanced tube formation. In both hind-limb (n=5) and critical ear (n=4) ischemia models, local delivery of PEP to ischemic tissue resulted in restoration of blood perfusion and prioritized proangiogenic signaling in tissue transcriptome pathway analysis, further confirmed by immunohistochemistry. Conclusions: Taken together, our study establishes a new regenerative paradigm documenting exosome-based delivery of VEGFR as a key driver for angiogenesis. This PEP-based platform broadens potential options available for treatment of peripheral vascular disease and may have therapeutic implications in restoration of microvasculature.