Metformin alleviates bone loss in ovariectomized mice through inhibition of autophagy of osteoclast precursors mediated by E2F1.

BACKGROUND: Postmenopausal bone loss, mainly caused by excessive bone resorption mediated by osteoclasts, has become a global public health burden. Metformin, a hypoglycemic drug, has been reported to have beneficial effects on maintaining bone health. However, the role and underlying mechanism of metformin in ovariectomized (OVX)-induced bone loss is still vague. RESULTS: In this study, we demonstrated for the first time that metformin administration alleviated bone loss in postmenopausal women and ovariectomized mice, based on reduced bone resorption markers, increased bone mineral density (BMD) and improvement of bone microstructure. Then, osteoclast precursors administered metformin in vitro and in vivo were collected to examine the differentiation potential and autophagical level. The mechanism was investigated by infection with lentivirus-mediated BNIP3 or E2F1 overexpression. We observed a dramatical inhibition of autophagosome synthesis and osteoclast formation and activity. Treatment with RAPA, an autophagy activator, abrogated the metformin-mediated autophagy downregulation and inhibition of osteoclastogenesis. Additionally, overexpression of E2F1 demonstrated that reduction of OVX-upregulated autophagy mediated by metformin was E2F1 dependent. Mechanistically, metformin-mediated downregulation of E2F1 in ovariectomized mice could downregulate BECN1 and BNIP3 levels, which subsequently perturbed the binding of BECN1 to BCL2. Furthermore, the disconnect between BECN1 and BCL2 was shown by BNIP3 overexpression. CONCLUSION: In summary, we demonstrated the effect and underlying mechanism of metformin on OVX-induced bone loss, which could be, at least in part, ascribed to its role in downregulating autophagy during osteoclastogenesis via E2F1-dependent BECN1 and BCL2 downregulation, suggesting that metformin or E2F1 inhibitor is a potential agent against postmenopausal bone loss. Video abstract.

Exercise-induced gene expression changes in skeletal muscle of old mice.

Exercise is believed to be beneficial for skeletal muscle functions across all ages. Regimented exercise is often prescribed as an effective treatment/prophylaxis for age-related loss of muscle mass and function, known as sarcopenia, and plays an important role in the maintenance of mobility and functional independence in the elderly. However, response to exercise declines with aging, resulting in limited gain of muscle strength and endurance. These changes likely reflect age-dependent alterations in transcriptional response underlying the muscular adaptation to exercise. The exact changes in gene expression accompanying exercise, however, are largely unknown, and elucidating them is of a great clinical interest for understanding and optimizing the exercise-based therapies for sarcopenia. In order to characterize the exercise-induced transcriptomic changes in aged muscle, a paired-end RNA sequencing was performed on rRNA-depleted total RNA extracted from the gastrocnemius muscles of 24 months-old mice after 8 weeks of regimented exercise (exercise group) or no formal exercise program (sedentary group). Differential gene expression analysis of aged skeletal muscle revealed upregulations in the group of genes involved in neurotransmission and neuroexcitation, as well as equally notable absence of anabolic gene upregulations in the exercise group. In particular, genes encoding the transporters and receptor components of glutaminergic transmission were significantly upregulated in exercised muscles, as exemplified by Gria 1, Gria 2 and Grin2c encoding glutamate receptor 1, 2 and 2C respectively, Grin1 and Grin2b encoding N-methyl-d-aspartate receptors (NMDARs), Nptx1 responsible for glutaminergic receptor clustering, and Slc1a2 and Slc17a7 regulating synaptic uptake of glutamate. These changes were accompanied by an increase in the post-synaptic density of NMDARs and acetylcholine receptors (AChRs), as well as their innervation at neuromuscular junctions (NMJs). These results suggest that neural responses predominate the adaptive response of aged skeletal muscle to exercise, and indicate a possibility that glutaminergic transmission at NMJs may be present and responsible for synaptic protection and neural remodeling accompanying the exercise-induced functional enhancement in aged skeletal muscle. In addition, the absence of upregulations in the anabolic pathways highlights them as the area of potential pharmacological targeting for optimizing exercise-led sarcopenia therapy.

The Three-Dimensional Structure of Porcine Bladder Scaffolds Alters the Biology of Murine Diabetic Wound Healing.

OBJECTIVE: To determine if the various three-dimensional structures of bioscaffolds affect wound healing by investigating the efficacy of different porcine-derived urinary bladder matrix (UBM) structures in treating murine diabetic wound healing. METHODS: The authors studied three different UBM structures: particulate (pUBM), one-layer freeze-dried sheet (fdUBM), and three-layer laminated sheet (lmUBM). Scanning electron microscopy images of the structures were used to calculate a wound-exposed surface-area-to-volume ratio. A 1.0 × 1.0-cm full-thickness dorsal wound was excised on 90 db/db mice. Mice were either untreated (blank, n = 15), treated with one UBM structure (pUBM, n = 15; fdUBM, n = 15; lmUBM, n = 15), or treated with a combination of either the one- or three-layer sheet over the particulate matrix (fdUBM + pUBM, n = 15; lmUBM + pUBM, n = 15). The authors obtained macroscopic images of the wounds and harvested tissues for analyses at multiple time points. RESULTS: The surface area available to interact with the wound was highest in the pUBM group and lowest in the lmUBM group. Greater wound bed thickness was noted in the fdUBM, fdUBM + pUBM, and lmUBM groups compared with the blank group. Cellular proliferation was significantly higher in the fdUBM and fdUBM + pUBM groups than in the blank group. The lmUBM + pUBM group had the highest collagen deposition. The pUBM group induced significantly higher leukocyte infiltration compared with the lmUBM, lmUBM + pUBM, and blank groups. Microvessel density was highest in the fdUBM + pUBM group. Significant differences in the wound closure rate were noted between the blank group and the fdUBM and fdUBM + pUBM groups. CONCLUSIONS: Assessment of the three UBM bioscaffold structures highlighted differences in the wound-exposed surface area. Variations in wound healing effects, including collagen deposition, cellular proliferation, and angiogenesis, were identified, with combinations of the structures displaying synergistic effects. This study serves as a platform for future scaffold design and offers promising evidence of the benefits of combining various structures of scaffolds.

LncRNA KCNQ1OT1 accelerates fracture healing via modulating miR-701-3p/FGFR3 axis.

Emerging evidence highlights the role of the long noncoding RNA (lncRNA) KCNQ1OT1 in fracture healing. Osteoblast proliferation, migration, and survival are pivotal during this process. In this study, we aimed to improve our understanding of the regulatory role of lncRNA KCNQ1OT1 during osteoblast proliferation, migration, and survival. We searched the gene expression omnibus databases and LncBase Experimental V.2 to identify key microRNAs (miRNAs) targets of KCNQ1OT1. MiR-701-3p was selected as a differentially expressed miRNA and RNA immunoprecipitation assays were performed to verify its interaction with KCNQ1OT1. Fibroblast growth factor receptor 3 (FGFR3) was also identified as a target of miR-701-3p. We further identified KCNQ1OT1 as a competing endogenous RNA of miR-701-3p that could influence osteoblast proliferation, migration, and apoptosis in vitro and in vivo. Taken together, our results indicate that the KCNQ1OT1/miR-701-3p/FGFR3 axis is an important regulator of osteoblast proliferation, migration, and apoptosis, and provide a new therapeutic avenue for fracture healing.

Loss of ARNT in skeletal muscle limits muscle regeneration in aging.

The ability of skeletal muscle to regenerate declines significantly with aging. The expression of aryl hydrocarbon receptor nuclear translocator (ARNT), a critical component of the hypoxia signaling pathway, was less abundant in skeletal muscle of old (23-25 months old) mice. This loss of ARNT was associated with decreased levels of Notch1 intracellular domain (N1ICD) and impaired regenerative response to injury in comparison to young (2-3 months old) mice. Knockdown of ARNT in a primary muscle cell line impaired differentiation in vitro. Skeletal muscle-specific ARNT deletion in young mice resulted in decreased levels of whole muscle N1ICD and limited muscle regeneration. Administration of a systemic hypoxia pathway activator (ML228), which simulates the actions of ARNT, rescued skeletal muscle regeneration in both old and ARNT-deleted mice. These results suggest that the loss of ARNT in skeletal muscle is partially responsible for diminished myogenic potential in aging and activation of hypoxia signaling holds promise for rescuing regenerative activity in old muscle.

Incised urethral diversion reduces the rate of fistula after one-stage hypospadias repair: a single-center retrospective controlled study.

OBJECTIVE: Urethrocutaneous fistula is the most prevalent complication after hypospadias repair. The aim of this study was to evaluate whether incised urethral diversion was superior to traditional transurethral diversion in minimizing complications. PATIENTS AND METHODS: We retrospectively collected and analyzed 113 cases with proximal penile or penoscrotal hypospadias that were repaired by one-stage transverse preputial island flap urethroplasty between January 2016 and January 2020. Of those cases, 60 used incised urethral diversion (group A), whereas the remaining 53 were managed by transurethral diversion (group B) for urinary drainage after surgery. Postoperative complications in both groups were assessed for fistula, urethral diverticulum, meatal stenosis, wound infection, and distal urethral breakdown. RESULTS: Fistula was reported in 2 patients (3.3%) in group A, while it was observed in 15 patients (28.3%) in group B (p < 0.001). Wound infection occurred in one patient (1.7%) in group A, compared with six patients (11.3%) in group B (p < 0.05). The incidence rates of distal urethral breakdown were 1.7% (1/60) and 11.3% (6/53) for group A and group B, respectively (p < 0.05). One patient (1.7%) in group A and three patients (5.7%) in group B had a meatal stenosis (p > 0.05). There were two patients who developed urethral diverticulum in either group (p > 0.05). CONCLUSIONS: The use of incised urethral diversion for urinary drainage had an advantage over transurethral diversion in one-stage hypospadias repair with respect to the post-operational fistula occurrence, wound infection, and distal urethral breakdown.

Use of venous couplers in microsurgical lower extremity reconstruction: A systematic review and meta-analysis.

BACKGROUND: Free tissue transfer for lower limb reconstruction has become a workhorse procedure for limb-salvage. Compared with other recipient sites, the lower extremity has a higher risk of microvascular complications, in particular with venous anastomosis. The study's objective is to evaluate the evidence, safety, and efficacy of venous coupler use in microsurgical anastomosis in lower limb reconstruction to provide objective appraisal of the surgical techniques. METHODS: A systematic review (SR) and meta-analysis (MA) were performed analyzing articles from PubMed, Cochrane, Embase, and Web of Science from January 1990, to August 2018. Abstracts and titles were screened and assessed for eligibility by independent reviewers. Following full-text review, articles were included in the SR and MA. Case reports were excluded. Cochrane Collaboration and the Quality of Reporting of Meta-analyses (QUOROM) guidelines were followed. RESULTS: Out of 15 included studies that met the inclusion criteria for the SR, 9 were included in MA. Patients treated with venous couplers did not experience more surgical complications (risk ratio (RR) 0.79; 95% confidence interval (CI) 0.48-1.33; p = .38), total failure (RR 0.61; 95% CI 0.22-1.70; p = .34), venous compromise (RR 0.72; 95% CI 0.23-2.27; p = .57), arterial compromise (RR 0.85; 95% CI 0.25-2.88; p = .80), partial failure (RR 0.77; 95% CI 0.33-1.77; p = .54), or reoperation (RR 11.79; 95% CI 0.49-286.55; p = .13) in comparison with hand-sewn anastomosis. CONCLUSIONS: Outcomes of venous couplers in lower limb reconstruction are comparable to those of hand-sewn anastomosis. However, this study was limited by the quality of the available literature. Additional prospective studies should aim to directly compare both techniques and potential further benefits in clinical trials.

The Effect of Arm Position on Breast Volume Measurement Using Three-dimensional Imaging.

BACKGROUND: Three-dimensional (3D) imaging offers an objective and quantitative way to evaluate the breast volume. In this study, we aimed to investigate whether arm position can be a factor influencing the measurement of breast volume and which arm position is more stable when using 3D breast imaging in evaluating the fat volume retention rate in autologous fat grafting for breast augmentation. METHODS: Patients undergoing breast augmentation with autologous fat grafting in our department were selected for the first part of this study. Preoperative 3D breast imaging was performed at three different arm positions: at the sides, akimbo and with hands on the head. Scans on each arm position were repeated on the first day after surgery, taking six scans in total. Breast volume change (BVC) was compared before and after surgery. The patients planning to receive bilateral mammaplasty in our department were selected for the second part of this study. Two repeated 3D scans were performed at the sides, akimbo and hands on the head, and then, the breast volume change error (BVCE) was compared. RESULTS: Twenty-five patients (n = 50 breasts) were included in the first part of study. For the patients who received 100-200 ml fat injection, compared with hands on the head, a statistically significant difference in the average BVC was found at the sides and akimbo (p = 0.02). For the patients receiving more than 200 ml fat injection, there was no statistically significant difference between the groups (p > 0.05). Twenty-six patients (n = 52 breasts) were enrolled in the second part. For the average BVCE, there was no significant difference between the groups (p = 0.11). CONCLUSIONS: The arm position during 3D breast imaging, to some extent, affects the evaluation of BVC after breast augmentation using autologous fat grafting, particularly for patients receiving less fat grafting. The arm position should be kept consistent when using 3D breast imaging in evaluating the fat volume retention rate. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to Table of Contents or the online Instructions to Authors www.springer.com/00266.

IL-10 induces MC3T3-E1 cells differentiation towards osteoblastic fate in murine model.

Interleukin-10 (IL-10) displays well-documented anti-inflammatory effects, but its effects on osteoblast differentiation have not been investigated. In this study, we found IL-10 negatively regulates microRNA-7025-5p (miR-7025-5p), the down-regulation of which enhances osteoblast differentiation. Furthermore, through luciferase reporter assays, we found evidence that insulin-like growth factor 1 receptor (IGF1R) is a miR-7025-5p target gene that positively regulates osteoblast differentiation. In vivo studies indicated that the pre-injection of IL-10 leads to increased bone formation, while agomiR-7025-5p injection delays fracture healing. Taken together, these results indicate that IL-10 induces osteoblast differentiation via regulation of the miR-7025-5p/IGF1R axis. IL-10 therefore represents a promising therapeutic strategy to promote fracture healing.

Circulating Exosomal miR-20b-5p Inhibition Restores Wnt9b Signaling and Reverses Diabetes-Associated Impaired Wound Healing.

At present, developing therapeutic strategies to improve wound healing in individuals with diabetes remains challenging. Exosomes represent a promising nanomaterial from which microRNAs (miRNAs) can be isolated. These miRNAs have the potential to exert therapeutic effects, and thus, determining the potential therapeutic contributions of specific miRNAs circulating in exosomes is of great importance. In the present study, circulating exosomal miRNAs are identified in diabetic patients and assessed for their roles in the context of diabetic wound healing. A significant upregulation of miR-20b-5p is observed in exosomes isolated from patients with type 2 diabetes mellitus (T2DM), and this miRNA is able to suppress human umbilical vein endothelial cell angiogenesis via regulation of Wnt9b/ß-catenin signaling. It is found that the application of either miR-20b-5p or diabetic exosomes to wound sites is sufficient to slow wound healing and angiogenesis. In diabetic mice, it is found that knocking out miR-20b-5p significantly enhances wound healing and promotes wound angiogenesis. Together, these findings thus provide strong evidence that miR-20b-5p is highly enriched in exosomes from patients with T2DM and can be transferred to cells of the vascular endothelium, where it targets Wnt9b signaling to negatively regulate cell functionality and angiogenesis.

A porous collagen-GAG scaffold promotes muscle regeneration following volumetric muscle loss injury.

Volumetric muscle loss (VML) is a segmental loss of skeletal muscle which commonly heals with fibrosis, minimal muscle regeneration, and loss of muscle strength. Treatment options for these wounds which promote functional recovery are currently lacking. This study was designed to investigate whether the collagen-GAG scaffold (CGS) promotes functional muscle recovery following VML. A total of 66 C57/Bl6 mice were used in a three-stage experiment. First, 24 animals were split into three groups which underwent sham injury or unilateral quadriceps VML injury with or without CGS implantation. Two weeks post-surgery, muscle was harvested for histological and gene expression analysis. In the second stage, 18 mice underwent bilateral quadriceps VML injury, followed by weekly functional testing using a treadmill. In the third stage, 24 mice underwent sham or bilateral quadriceps VML injury with or without CGS implantation, with tissue harvested six weeks post-surgery for histological and gene expression analysis. VML mice treated with CGS demonstrated increased remnant fiber hypertrophy versus both the VML with no CGS and uninjured groups. Both VML groups showed greater muscle fiber hypertrophy than non-injured muscle. This phenomenon was still evident in the longer-term experiment. The gene array indicated that the CGS promoted upregulation of factors involved in promoting wound healing and regeneration. In terms of functional improvement, the VML mice treated with CGS ran at higher maximum speeds than VML without CGS. A CGS was shown to enhance muscle hypertrophy in response to VML injury with a resultant improvement in functional performance. A gene array highlighted increased gene expression of multiple growth factors following CGS implantation. This suggests that implantation of a CGS could be a promising treatment for VML wounds.

The Role of Hypoxia and Hypoxia Signaling in Skeletal Muscle Physiology.

Hypoxia and hypoxia signaling play an integral role in regulating skeletal muscle physiology. Environmental hypoxia and tissue hypoxia in muscles cue for their appropriate physiological response and adaptation, and cause an array of cellular and metabolic changes. In addition, muscle stem cells (satellite cells), exist in a hypoxic state, and this intrinsic hypoxic state correlates with their quiescence and stemness. The mechanisms of hypoxia-mediated regulation of satellite cells and myogenesis are yet to be characterized, and their seemingly contradicting effects reported leave their exact roles somewhat perplexing. This review summarizes the recent findings on the effect of hypoxia and hypoxia signaling on the key aspects of muscle physiology, namely, stem cell maintenance and myogenesis with a particular attention given to distinguish the intrinsic versus local hypoxia in an attempt to better understand their respective regulatory roles and how their relationship affects the overall response. This review further describes their mechanistic links and their possible implications on the relevant pathologies and therapeutics.

Nanosheet Promotes Chronic Wound Healing by Localizing Uncultured Stromal Vascular Fraction Cells.

Objective: To develop an efficacious and efficient method for treating chronic wounds using "nanosheet" that improves the survival and localization of transplanted cells without prior seeding to optimally derive the regenerative potentials of uncultured stromal vascular fraction (SVF) cells. Approach: We propose a method whereby the wound is covered by uncultured SVF cells using the nanosheet [porous poly(d, l,-lactic acid)] (PDLLA) films) designed to hold cells in a single-cell layer. A chronic wound model was created on 12-month-old db/db mice by inflecting a full-thickness skin excision on their dorsum and was subsequently given either no treatment or a treatment with SVF cells alone (with Tegaderm dressing), nanosheet alone, or nanosheet with SVF cells. Results: The placement of the nanosheet improved the grafted cell retention rate at day 10 timepoint by 5 folds, and the wound area was the smallest in the wounds treated with SVF cells plus nanosheet in comparison to the other groups. Collagen deposition and epidermal growth factor were significantly higher in the wound beds treated with SVF cells with the nanosheet, offering some mechanistic insights. Innovation: Porous poly(d, l,-lactic acid acid) (PDLLA) films or "nanosheet" printed on the nanoscale (1-100 nm in thickness) as a cellular scaffold for cytotherapy for the treatment of chronic wounds. Conclusion: The use of the nanosheet is an effective way to improve the transplanted SVF cell retention and accelerate the overall wound closure.

Acellular collagen-glycosaminoglycan matrix promotes functional recovery in a rat model of volumetric muscle loss.

Aim: Volumetric muscle loss (VML) is a composite loss of skeletal muscle, which heals with fibrosis, minimal muscle regeneration, and incomplete functional recovery. This study investigated whether collagen-glycosaminoglycan scaffolds (CGS) improve functional recovery following VML. Methods: 15 Sprague-Dawley rats underwent either sham injury or bilateral tibialis anterior (TA) VML injury, with or without CGS implantation. Results: In rats with VML injuries treated with CGS, the TA exhibited greater in vivo tetanic forces and in situ twitch and tetanic dorsiflexion forces compared with those in the non-CGS group at 4- and 6-weeks following injury, respectively. Histologically, the VML with CGS group demonstrated reduced fibrosis and increased muscle regeneration. Conclusion: Taken together, CGS implantation has potential augment muscle recovery following VML.

Volumetric muscle loss (VML) is a large injury to skeletal muscle. VML heals with scarring, little muscle regeneration, and incomplete strength recovery. The current treatment for VML involves transferring muscle from one part of the body to the injury site. However, this is limited by weakness of the donor site and incomplete recovery of muscle function. Therefore, other treatments have been developed to aid in muscle healing. One such treatment involves using three dimensional templates, known as scaffolds, to aid in muscle regeneration. Our goal is to determine whether a collagen­glycosaminoglycan scaffold (CGS), which is already used for other medical purposes, can improve healing of VML injuries in rats. CGS placement in rat muscle injuries resulted in decreased scarring, increased muscle regeneration, and increased strength recovery compared with the non-CGS group.

VEGFA Promotes Skeletal Muscle Regeneration in Aging.

Aging is associated with loss of skeletal muscle regeneration. Differentially regulated vascular endothelial growth factor (VEGF)A with aging may partially underlies this loss of regenerative capacity. To assess the role of VEGFA in muscle regeneration, young (12-14 weeks old) and old C57BL/6 mice (24,25 months old) are subjected to cryoinjury in the tibialis anterior (TA) muscle to induce muscle regeneration. The average cross-sectional area (CSA) of regenerating myofibers is 33% smaller in old as compared to young (p < 0.01) mice, which correlates with a two-fold loss of muscle VEGFA protein levels (p = 0.02). The capillary density in the TA is similar between the two groups. Young VEGFlo mice, with a 50% decrease in systemic VEGFA activity, exhibit a two-fold reduction in the average regenerating fiber CSA following cryoinjury (p < 0.01) in comparison to littermate controls. ML228, a hypoxia signaling activator known to increase VEGFA levels, augments muscle VEGFA levels and increases average CSA of regenerating fibers in both old mice (25% increase, p < 0.01) and VEGFlo (20% increase, p < 0.01) mice, but not in young or littermate controls. These results suggest that VEGFA may be a therapeutic target in age-related muscle loss.

Melatonin Promotes BMSCs Osteoblastic Differentiation and Relieves Inflammation by Suppressing the NF-κB Pathways.

Bone mesenchymal stem cells (BMSCs) play an important role in maintaining the dynamic balance of bone metabolism. Recent studies have reported that a decrease in the osteogenic function of MSCs is strongly associated with osteoporosis. Melatonin is a neuroendocrine hormone produced in the pineal gland and is essential in the physiological regulation. This study is aimed at exploring the effect of melatonin on MSCs osteoblastic differentiation and elucidate the underlying mechanisms. We isolated BMSCs from rat bone marrow and demonstrated that melatonin improved osteogenic differentiation of BMSCs by the alizarin red staining and ALP staining. We then showed that melatonin enhanced osteogenic gene expression in BMSCs, including ALP, Col 1, OCN, OPN, and RUNX2. We further revealed that melatonin inhibited the inflammatory response of BMSCs by suppressing the NF-κB signaling pathways. In light of this, we found that the NF-κB pathway-specific activator TNF-α activated the NF-κB pathway, inhibited osteogenic differentiation, and induced inflammatory response in BMSCs. Melatonin was found to reverse the inhibitory effect of TNF-α on osteogenic differentiation and inflammation in BMSCs. Taken together, these findings indicated that melatonin may have therapeutic potential to be used for the treatment of osteoporosis.

A Whole-Course-Repair System Based on Neurogenesis-Angiogenesis Crosstalk and Macrophage Reprogramming Promotes Diabetic Wound Healing.

Diabetic wound (DW) therapy is currently a big challenge in medicine and strategies to enhance neurogenesis and angiogenesis have appeared to be a promising direction. However, the current treatments have failed to coordinate neurogenesis and angiogenesis simultaneously, leading to an increased disability rate caused by DWs. Herein, a whole-course-repair system is introduced by a hydrogel to concurrently achieve a mutually supportive cycle of neurogenesis-angiogenesis under a favorable immune-microenvironment. This hydrogel can first be one-step packaged in a syringe for later in situ local injections to cover wounds long-termly for accelerated wound healing via the synergistic effect of magnesium ions (Mg2+ ) and engineered small extracellular vesicles (sEVs). The self-healing and bio-adhesive properties of the hydrogel make it an ideal physical barrier for DWs. At the inflammation stage, the formulation can recruit bone marrow-derived mesenchymal stem cells to the wound sites and stimulate them toward neurogenic differentiation, while providing a favorable immune microenvironment via macrophage reprogramming. At the proliferation stage of wound repair, robust angiogenesis occurs by the synergistic effect of the newly differentiated neural cells and the released Mg2+ , allowing a regenerative neurogenesis-angiogenesis cycle to take place at the wound site. This whole-course-repair system provides a novel platform for combined DW therapy.

Aerobic exercise and scaffolds with hierarchical porosity synergistically promote functional recovery post volumetric muscle loss.

Volumetric muscle loss (VML), which refers to a composite skeletal muscle defect, most commonly heals by scarring and minimal muscle regeneration but substantial fibrosis. Current surgical interventions and physical therapy techniques are limited in restoring muscle function following VML. Novel tissue engineering strategies may offer an option to promote functional muscle recovery. The present study evaluates a colloidal scaffold with hierarchical porosity and controlled mechanical properties for the treatment of VML. In addition, as VML results in an acute decrease in insulin-like growth factor 1 (IGF-1), a myogenic factor, the scaffold was designed to slowly release IGF-1 following implantation. The foam-like scaffold is directly crosslinked onto remnant muscle without the need for suturing. In situ 3D printing of IGF-1-releasing porous muscle scaffold onto VML injuries resulted in robust tissue ingrowth, improved muscle repair, and increased muscle strength in a murine VML model. Histological analysis confirmed regeneration of new muscle in the engineered scaffolds. In addition, the scaffolds significantly reduced fibrosis and increased the expression of neuromuscular junctions in the newly regenerated tissue. Exercise training, when combined with the engineered scaffolds, augmented the treatment outcome in a synergistic fashion. These data suggest highly porous scaffolds and exercise therapy, in combination, may be a treatment option following VML.