S100b treatment overcomes RAGE signaling deficits in myoblasts on advanced glycation end-product cross-linked collagen and promotes myogenic differentiation

Advanced glycation end-products (AGEs) stochastically accrue in skeletal muscle and on collagen over an individual's lifespan, stiffening the muscle and modifying the stem cell (MuSC) microenvironment while promoting proinflammatory, antiregenerative signaling via the receptor for advanced glycation end-products (RAGEs). In the present study, a novel in vitro model was developed of this phenomenon by cross linking a 3-D collagen scaffold with AGEs and investigating how myoblasts responded to such an environment. Briefly, collagen scaffolds were incubated with d-ribose (0, 25, 40, 100, or 250 mM) for 5 days at 37°C. C2C12 immortalized mouse myoblasts were grown on the scaffolds for 6 days in growth conditions for proliferation, and 12 days for differentiation and fusion. Human primary myoblasts were also used to confirm the C2C12 data. AGEs aberrantly extended the DNA production stage of C2C12s (but not in human primary myoblasts) which is known to delay differentiation in myogenesis, and this effect was prevented by RAGE inhibition. Furthermore, the differentiation and fusion of myoblasts were disrupted by AGEs, which were associated with reductions in integrins and suppression of RAGE. The addition of S100b (RAGE agonist) recovered the differentiation and fusion of myoblasts, and the addition of RAGE inhibitors (FPS-ZM1 and Azeliragon) inhibited the differentiation and fusion of myoblasts. Our results provide novel insights into the role of the AGE-RAGE axis in skeletal muscle aging, and future work is warranted on the potential application of S100b as a proregenerative factor in aged skeletal muscle.NEW & NOTEWORTHY Collagen cross-linked by advanced glycation end-products (AGEs) induced myoblast proliferation but prevented differentiation, myotube formation, and RAGE upregulation. RAGE inhibition occluded AGE-induced myoblast proliferation, while the delivery of S100b, a RAGE ligand, recovered fusion deficits.

Prospective Clinical Trial Evaluating the Outcomes Associated with the Use of Fresh Frozen Allograft Cartilage in Rhinoplasty

Background

There are different types of grafts for rhinoplasty, each with certain advantages and disadvantages. Fresh frozen cadaveric costal allograft (CCA) provides an alternative to rhinoplasties. The aim of this study was to compare the outcomes of fresh frozen CCA and traditional autologous costal cartilage in cosmetic and reconstructive rhinoplasty procedures.

Methods

This is a prospective, single-center, nonrandomized, open-label clinical trial. Objective assessment to evaluate warping, resorption, and displacement of the cartilage was achieved by measuring the differences of standardized values (deviation angle, nasofrontal angle, total facial convexity, nasofacial angle, and nasolabial angle) obtained at 6-months and 12-months postoperative follow-up on standard two-dimensional photographs (Δ = ∣measurement6 - measurement12∣). Subjective assessment was measured by the FACE-Q assessment.

Results

Fifty eligible patients between March 2017 and October 2020 were included. The average age was 43.9 ± 16.6 years and the mean follow-up period was 14.8 months. In the control group, the changes (Δ) in the deviation angle and nasolabial angle were greater than in the CCA group (P < 0.05). In the CCA group, the mean score of satisfaction with nose improved at 6 months and 1 year postoperatively (P < 0.05). The mean score of satisfaction with nostrils and overall facial appearance also increased in the CCA group at 6 months postoperatively (P < 0.05). Six patients from the CCA group and 10 patients from the control group experienced postoperative complications.

Conclusions

Fresh frozen CCA is a safe and reliable source of rhinoplasty grafts. It is aseptic, readily available, and free of donor site complications.

A Prospective Multicenter Study of a Weekly Application Regimen of Viable Human Amnion Membrane Allograft in the Management of Nonhealing Diabetic Foot Ulcers

Background

Diabetic foot ulcers (DFUs) pose a significant clinical challenge for providers and patients, and often precede devastating complications such as infection, hospitalization, and amputation. Therefore, advanced treatment options are needed to facilitate the healing of chronic DFUs and improve outcomes in this high-risk population. Cryopreserved viable human amnion membrane allograft (vHAMA) has shown great promise in the treatment of recalcitrant DFUs as a supplement to standard of care (SOC). Placental grafts are rich in extracellular matrix proteins, growth factors, and cytokines, which can induce angiogenesis and dermal fibroblast proliferation, resulting in accelerated healing.

Methods

In this prospective, multicenter single arm trial, 20 patients with nonhealing DFUs received weekly application of vHAMA, in addition to SOC, for up to 12 weeks. The primary study endpoint was proportion of healed wounds at 12 weeks. Secondary endpoints included proportion of wounds healed at 6 weeks, time to heal, and percentage area wound reduction. Subjects were evaluated for ulcer healing and assessed for adverse events at every treatment visit.

Results

At study conclusion, 85% of patients receiving vHAMA healed. Ten wounds healed (50%) by 6 weeks, and 17 wounds (85%) healed by 12 weeks. The mean time to heal was 46.6 days (95% CI: 35.1-58.0), and the average number of vHAMAs used was 5.4 (SD: 3.25). The mean PAR was 86.3% (SD: 40.51).

Conclusions

Aseptically processed, cryopreserved vHAMA should be considered as a safe and effective option for DFUs refractory to SOC therapy.

Lysosomal protein surface expression discriminates fat- from bone-forming human mesenchymal precursor cells

Tissue resident mesenchymal stem/stromal cells (MSCs) occupy perivascular spaces. Profiling human adipose perivascular mesenchyme with antibody arrays identified 16 novel surface antigens, including endolysosomal protein CD107a. Surface CD107a expression segregates MSCs into functionally distinct subsets. In culture, CD107alow cells demonstrate high colony formation, osteoprogenitor cell frequency, and osteogenic potential. Conversely, CD107ahigh cells include almost exclusively adipocyte progenitor cells. Accordingly, human CD107alow cells drove dramatic bone formation after intramuscular transplantation in mice, and induced spine fusion in rats, whereas CD107ahigh cells did not. CD107a protein trafficking to the cell surface is associated with exocytosis during early adipogenic differentiation. RNA sequencing also suggested that CD107alow cells are precursors of CD107ahigh cells. These results document the molecular and functional diversity of perivascular regenerative cells, and show that relocation to cell surface of a lysosomal protein marks the transition from osteo- to adipogenic potential in native human MSCs, a population of substantial therapeutic interest.

Smoothened agonist sterosome immobilized hybrid scaffold for bone regeneration

Biomaterial delivery of bioactive agents and manipulation of stem cell fate are an attractive approach to promote tissue regeneration. Here, smoothened agonist sterosome is developed using small-molecule activators [20S-hydroxycholesterol (OHC) and purmorphamine (PUR)] of the smoothened protein in the hedgehog pathway as carrier and cargo. Sterosome presents inherent osteoinductive property even without drug loading. Sterosome is covalently immobilized onto three-dimensional scaffolds via a bioinspired polydopamine intermediate to fabricate a hybrid scaffold for bone regeneration. Sterosome-immobilized hybrid scaffold not only provides a favorable substrate for cell adhesion and proliferation but also delivers bioactive agents in a sustained and spatially targeted manner. Furthermore, this scaffold significantly improves osteogenic differentiation of bone marrow stem cells through OHC/PUR-mediated synergistic activation of the hedgehog pathway and also enhances bone repair in a mouse calvarial defect model. This system serves as a versatile biomaterial platform for many applications, including therapeutic delivery and endogenous regenerative medicine.