Long-term outcomes of sphincter pharyngoplasty in patients with cleft palate.

OBJECTIVE: The purpose of this study was to evaluate long-term outcomes of sphincter pharyngoplasties, including speech outcomes, revision surgeries, and postoperative incidence of obstructive sleep apnea (OSA). DESIGN: Retrospective matched-cohort study SETTING: Two craniofacial centers in Los Angeles, CA PATIENTS: Patients (n = 166) with cleft lip and palate (CLP) or isolated cleft palate (iCP) who underwent sphincter pharyngoplasty from 1992 to 2022 were identified. An age- and diagnosis-matched control group of 67 patients with CLP/iCP without velopharyngeal insufficiency (VPI) was also identified. INTERVENTIONS: The pharyngoplasty group underwent sphincter pharyngoplasty, whereas the non-VPI group had no history of VPI surgery or sphincter pharyngoplasty. MAIN OUTCOME MEASURES: Postoperative speech outcomes, revision surgeries, and incidence of OSA were evaluated. Multivariable regression was used to evaluate independent predictors of OSA. RESULTS: Among the patients in the pharyngoplasty cohort, 63.9% demonstrated improved and sustained speech outcomes after a single pharyngoplasty, with a median postoperative follow-up of 8.8 years (interquartile range [IQR], 3.6-12.0 years). One-third of the patients who underwent pharyngoplasty required a revision surgery, with a median time to primary revision of 3.9 years (IQR, 1.9-7.0 years). OSA rates increased significantly among the pharyngoplasty cohort, from 3% before surgery to 14.5% after surgery (p < 0.001). The average time from sphincter pharyngoplasty to OSA diagnosis was 4.4 ± 2.4 years. Multivariable analysis results indicated that sphincter pharyngoplasty surgery was independently associated with a fourfold increase in OSA (p = 0.03). CONCLUSIONS: Although sphincter pharyngoplasty remains successful in improving long-term speech outcomes, persistent OSA is a sequela that should be monitored beyond the immediate postoperative period.

United States Health Policies on Gender-Affirming Care in 2022.

BACKGROUND: Within the United States, access to gender-affirming operations covered by health insurance has increased dramatically over the past decade. However, the perpetually changing landscape and inconsistencies of individual state health policies governing private and public insurance coverage present a lack of clarity for reconstructive surgeons and other physicians attempting to provide gender-affirming care. This work systematically reviewed the current U.S. health policies for both private insurance and Medicaid on a state-by-state basis. METHODS: Individual state health policies in effect as of August of 2022 on gender-affirming care were reviewed using the LexisNexis legal database, state legislature publications, and Medicaid manuals. Primary outcomes were categorization of policies as protective, restrictive, or unclear for each state. Secondary outcomes included analyses of demographics covered by current health policies and geographic differences. RESULTS: Protective state-level health policies related to gender-affirming care were present in approximately half of the nation for both private insurance (49.0%) and Medicaid (52.9%). Explicitly restrictive policies were found in 5.9% and 17.6% of states for private insurance and Medicaid, respectively. Regionally, the Northeast and West had the highest rates of protective policies, whereas the Midwest and South had the highest rates of restrictive policies on gender-affirming care. CONCLUSIONS: State-level health policies on gender-affirming care vary significantly across the United States with regional associations. Clarity in the current and evolving state-specific health policies governing gender-affirming care is essential for surgeons and physicians caring for transgender and gender-diverse individuals.

Bone-Anchored Maxillary Protraction for Adolescents with Cleft Palate and Class III Malocclusion: A Case Series.

To describe the long-term treatment course of bone-anchored maxillary protraction (BAMP) and evaluate orthognathic surgical indications after BAMP.Retrospective case series.Craniofacial/Cleft Palate Program at the Orthopaedic Institute for Children in Los Angeles, CA.Twelve male patients with cleft palate (CP), unilateral cleft lip and palate (UCLP), or bilateral cleft lip and palate (BCLP) and Class III malocclusion treated with BAMP (mean age: 11.4 ± 2.6 years) were included.BAMP treatment was performed by placement of bone-anchored maxillary and mandibular plates connected with intraoral Class III dental elastics or maxillary plates connected to a facemask.We retrospectively assessed BAMP treatment variables, including age at surgery, revision surgeries, and treatment duration. The primary goal was correction to class I occlusion.Twelve patients underwent BAMP treatment for an average of 4.4 ± 2.4 years. Two patients were corrected to class I occlusion at the time of this report. Le Fort I advancement was no longer required in two patients (16.7%), it was required for nine patients (75.0%) and was completed for one patient following BAMP treatment (8.3%).This preliminary report demonstrated that BAMP treatment may be associated with a minimal reduction in the requirement for Le Fort I advancement at skeletal maturity. Future studies with larger sample sizes are necessary to confirm this association.

Duration of Feminizing Hormone Therapy on Facial Fat Volumes.

BACKGROUND: Gender-affirming feminizing hormone therapy induces body fat redistribution. However, the amount and timing of facial fat changes in response to feminizing hormone therapy are unknown, albeit relevant to counseling and surgical planning for facial gender-affirming surgery. In this work, we assessed the influence of feminizing hormone therapy duration on malar and temporal fat volume. METHODS: Malar and temporal fat volumes were compared using computed tomography in transfeminine patients (age 20-29 years, body mass index [BMI] 18.5-24.9) treated with feminizing hormone therapy for <2 years versus ≥2 years. Patients with prior surgical or non-surgical facial soft-tissue interventions were excluded. Multivariable linear regressions evaluated the contribution of hormone therapy duration to malar and temporal fat volumes. RESULTS: 45 patients were included with 30 patients (66.7%) treated with feminizing hormone therapy for ≥2 years and 15 patients (33.3%) treated for <2 years (median[interquartile range, IQR]: 44.5[33.5-65.6] vs. 15.0[11.0-18.0] months, p<0.001). Patients treated with hormone therapy for ≥2 years demonstrated a 1.6-fold greater malar fat volume (5.5[4.2-6.3] vs. 3.4[2.3-4.2] cm 3,p<0.001) and 1.4-fold greater temporal fat volume (2.8[2.4-3.6] cm 3 vs. 2.0[1.7-2.4] cm 3, p=0.01) compared to those treated for <2 years. When accounting for other contributory variables such as BMI, skull size, and total soft-tissue depth in multivariable linear regression models, hormone therapy duration ≥2 years independently predicted higher malar (ß=0.51, p<0.001) and temporal (ß=0.32, p=0.02) fat volumes. CONCLUSIONS: Feminizing hormone therapy increases malar and temporal fat volumes by approximately 2 cm 3 and 0.8 cm 3 for each area, respectively, after 2 years of treatment.

Functional outcomes of nerve allografts augmented with mesenchymal stem cells and surgical angiogenesis in a rat sciatic nerve defect model.

BACKGROUND: Motor function recovery following acellular nerve allograft (ANA) repair remains inferior to autologous nerve reconstruction. We investigated the functional recovery of ANAs after combined mesenchymal stem cell (MSC) delivery and surgical angiogenesis in a rat sciatic nerve defect model. METHODS: In 100 Lewis rats, unilateral sciatic nerve defects were reconstructed with (I) autografts, (II) ANAs, (III) ANAs wrapped with a superficial inferior epigastric artery fascial (SIEF) flap, combined with either (IV) undifferentiated MSCs or (V) Schwann cell-like differentiated MSCs. The tibialis anterior muscle area was evaluated during the survival period using ultrasonography. Functional recovery, histomorphometry, and immunofluorescence were assessed at 12 and 16 weeks. RESULTS: At 12 weeks, the addition of surgical angiogenesis and MSCs improved ankle contractures. The SIEF flap also significantly improved compound muscle action potential (CMAP) outcomes compared with ANAs. Autografts outperformed all groups in muscle force and weight. At 16 weeks, ankle contractures of ANAs remained inferior to autografts and SIEF, whereas the CMAP amplitude was comparable between groups. The muscle force of autografts remained superior to all other groups, and the muscle weight of ANAs remained inferior to autografts. No differences were found in histomorphometry outcomes between SIEF groups and ANAs. Vascularity, determined by CD34 staining, was significantly higher in SIEF groups compared with ANAs. CONCLUSIONS: The combination of surgical angiogenesis and MSCs did not result in a synergistic improvement in functional outcomes. In a short nerve gap model, the adipofascial flap may provide sufficient MSCs to ANAs without additional ex vivo MSC seeding.

Dynamic Seeding versus Microinjection of Adipose-Derived Mesenchymal Stem Cells to Acellular Nerve Allograft Reconstructions.

BACKGROUND: Functional recovery following acellular nerve allograft (ANA) reconstructions remains inferior to autologous nerve grafting, but have demonstrated improved outcomes with the addition of adipose-derived mesenchymal stem cells (MSC). Controversy exists regarding the optimal cell delivery method to enhance ANA reconstructions. We investigated the functional recovery of ANAs after dynamic seeding versus microinjection of MSCs. METHODS: Forty Lewis rats underwent reconstruction of a 10-mm sciatic nerve defect. Animals were divided into four groups: reversed autograft, ANA alone, ANA dynamically seeded, or ANA injected with MSCs. During the survival period, ultrasound measurements of the tibialis anterior (TA) muscle cross-sectional area were performed. At 12 weeks, functional recovery was evaluated using measurements of ankle contracture, compound muscle action potential (CMAP), maximum isometric tetanic force (ITF), muscle mass, histomorphometry, and immunofluorescence. RESULTS: The dynamic seeding and microinjection groups demonstrated higher cross-sectional TA muscle area recovery than autografts and ANAs alone at week 8 and week 4 and 8, respectively. The ankle contracture and CMAP amplitude recovery were superior in autografts and both seeding methods compared to ANAs alone. The microinjection group demonstrated significantly higher ITF, muscle mass, and number of axons compared to ANAs alone. Both seeding methods showed higher CD34 densities compared to ANAs alone. No significant differences between dynamic seeding and microinjection were observed for both functional and histological outcomes. CONCLUSIONS: The addition of MSCs to ANAs demonstrated earlier motor regeneration compared to autografts and ANAs alone. Both seeding methods improved functional outcomes in the rat sciatic nerve defect model. CLINICAL RELEVANCE STATEMENT: Future clinical applications of stem cell-based nerve reconstructions are dependent on determining optimum delivery methods, which are technically feasible, reproducible, cost-efficient, and timely.

An enhanced recovery after surgery protocol for facial feminization surgery reduces perioperative opioid usage, pain, and hospital stay.

BACKGROUND: Prescription drug misuse in transgender individuals is estimated to be three times higher than that of the general population in the United States, suggesting that opioid-reduction strategies deserve significant consideration in gender-affirming surgeries. In this work, we describe the implementation of an enhanced recovery after surgery (ERAS) protocol to reduce opioid use after facial feminization surgery. METHODS: A total of 79 patients who underwent single-stage facial feminization surgery before (n = 38) or after (n = 41) ERAS protocol implementation were included. Primary outcomes assessed were perioperative opioid consumption (morphine equivalent dose/kilogram, MED/kg), average patient-reported pain scores, and length of hospital stay. Comparisons between groups and multivariable linear regression analyses were conducted to define the contribution of the ERAS protocol to each of the three primary outcomes. RESULTS: Age, body mass index, mental health diagnoses, and length of surgery did not differ between pre-ERAS and ERAS groups. Compared to pre-ERAS patients, patients treated under the ERAS protocol consumed less opioids (median [interquartile range, IQR], 0.8 [0.5-1.1] versus 1.5 [1.0-2.1] MED/kg, p < 0.001), reported lower pain scores (2.5 ± 1.8 versus 3.7 ± 1.6, p = 0.002), and required a shorter hospital stay (median [IQR], 27.3 [26.3-49.8] versus 32.4 [24.8-39.1] h, p < 0.001). When controlling for other contributing variables such as previous gender-affirming surgeries, mental health diagnoses, and length of surgery using multivariable linear regression analyses, ERAS protocol implementation independently predicted reduced opioid use, lower pain scores, and shorter hospital stay after facial feminization surgery. CONCLUSIONS: The current work details an ERAS protocol for facial feminization surgery that reduces perioperative opioid consumption, patient-reported pain scores, and hospital stays.

Sarcopenia Best Predicts Complications in Free Flap Breast Reconstruction.

Breast reconstruction remains a major component of the plastic surgeon's repertoire, especially free-flap breast reconstruction (FFBR), though this is a high-risk surgery in which patient selection is paramount. Preoperative predictors of complication remain mixed in their utility. We sought to determine whether the sarcopenia score, a validated measure of physiologic health, outperforms the body mass index (BMI) and modified frailty index (mFI) in terms of predicting outcomes. Methods: All patients with at least 6-months follow-up and imaging of the abdomen who underwent FFBR from 2013 to 2022 were included in this study. Appropriate preoperative and postoperative data were included, and sarcopenia scores were extracted from imaging. Complications were defined as any unexpected outcome that required a return to the operating room or readmission. Statistical analysis and regression were performed. Results: In total, 299 patients were included. Patients were split into groups, based on sarcopenia scores. Patients with lower sarcopenia had significantly more complications than those with higher scores. BMI and mFI both did not correlate with complication rates. Sarcopenia was the only independent predictor of complication severity when other factors were controlled for in a multivariate regression model. Conclusions: Sarcopenia correlates with the presence of severe complications in patients who undergo FFBR in a stronger fashion to BMI and the mFI. Thus, sarcopenia should be considered in the preoperative evaluation in patients undergoing FFBR.

Convergence of Calcium Channel Regulation and Mechanotransduction in Skeletal Regenerative Biomaterial Design.

Cells are known to perceive their microenvironment through extracellular and intracellular mechanical signals. Upon sensing mechanical stimuli, cells can initiate various downstream signaling pathways that are vital to regulating proliferation, growth, and homeostasis. One such physiologic activity modulated by mechanical stimuli is osteogenic differentiation. The process of osteogenic mechanotransduction is regulated by numerous calcium ion channels-including channels coupled to cilia, mechanosensitive and voltage-sensitive channels, and channels associated with the endoplasmic reticulum. Evidence suggests these channels are implicated in osteogenic pathways such as the YAP/TAZ and canonical Wnt pathways. This review aims to describe the involvement of calcium channels in regulating osteogenic differentiation in response to mechanical loading and characterize the fashion in which those channels directly or indirectly mediate this process. The mechanotransduction pathway is a promising target for the development of regenerative materials for clinical applications due to its independence from exogenous growth factor supplementation. As such, also described are examples of osteogenic biomaterial strategies that involve the discussed calcium ion channels, calcium-dependent cellular structures, or calcium ion-regulating cellular features. Understanding the distinct ways calcium channels and signaling regulate these processes may uncover potential targets for advancing biomaterials with regenerative osteogenic capabilities.

Association of Patient-Reported Anxiety and Pain After Alveolar Bone Grafting.

OBJECTIVE: To evaluate the role of psychosocial well-being on perioperative pain and opioid use among patients with cleft lip and palate (CLP) undergoing alveolar bone grafting (ABG). DESIGN: Retrospective review. SETTING: Tertiary level craniofacial clinic. PARTICIPANTS: 34 patients with CLP (median age: 11.7 years), including 25 (73.5%) unilateral CLP and 9 (26.5%) bilateral CLP, who underwent ABG from 2015 to 2022. INTERVENTIONS: ABG using iliac crest bone graft. Patients were prospectively administered four patient-reported psychosocial instruments from the Patient-Reported Outcomes Measurement Information System. MAIN OUTCOME MEASURES: Perioperative opioid use in morphine equivalent dosage/kilogram, patient-reported pain scores, and length of hospital stay after ABG. RESULTS: Patient-reported anxiety (r = 0.41, p = 0.02) and depressive symptoms (r = 0.35, p = 0.04) correlated to higher perioperative opioid usage. Multivariable regression models including psychosocial scores, total acetaminophen usage, length of surgery, and other simultaneous surgeries were developed for total opioid usage, patient-reported pain, and length of hospital stay. Patient-reported anxiety was independently predictive of higher perioperative opioid use (ß=0.36, p = 0.01) and higher pain scores (ß=0.39, p = 0.02), but not length of hospital stay. CONCLUSIONS: We identified an association for patient-reported anxiety and perioperative opioid use and pain in a CLP cohort undergoing ABG. Future considerations in preoperative patient and family consultation may be indicated in patients self-reporting higher anxiety in an effort to minimize perioperative opioid usage.

Modulating Temporospatial Phosphate Equilibrium by Nanoparticulate Mineralized Collagen Materials Induces Osteogenesis via PiT-1 and PiT-2.

The temporospatial equilibrium of phosphate contributes to physiological bone development and fracture healing, yet optimal control of phosphate content has not been explored in skeletal regenerative materials. Nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) is a synthetic, tunable material that promotes in vivo skull regeneration. In this work, the effects of MC-GAG phosphate content on the surrounding microenvironment and osteoprogenitor differentiation are investigated. This study finds that MC-GAG exhibits a temporal relationship with soluble phosphate with elution early in culture shifting to absorption with or without differentiating primary bone marrow-derived human mesenchymal stem cells (hMSCs). The intrinsic phosphate content of MC-GAG is sufficient to stimulate osteogenic differentiation of hMSCs in basal growth media without the addition of exogenous phosphate in a manner that can be severely reduced, but not eliminated, by knockdown of the sodium phosphate transporters PiT-1 or PiT-2. The contributions of PiT-1 and PiT-2 to MC-GAG-mediated osteogenesis are nonredundant but also nonadditive, suggestive that the heterodimeric form is essential to its activity. These findings indicate that the mineral content of MC-GAG alters phosphate concentrations within a local microenvironment resulting in osteogenic differentiation of progenitor cells via both PiT-1 and PiT-2.

Safety of Allogeneic Mesenchymal Stem Cell Seeding of NeuraGen Nerve Guides in a Rabbit Model.

Mesenchymal stem cells (MSCs) stimulate nerve and tissue regeneration and are primed for clinical translation. Application of autologous MSCs is limited by requirements for expedient harvesting procedures, proliferative expansion to increase number of cells, and reduced regenerative potential due to aging or pathological conditions. Because MSCs are immune privileged, allogeneic MSCs may serve as "off-the-shelf" cell-based reconstructive treatments to support nerve repair. Therefore, we examined the safety and immune response parameters of allogeneic MSCs seeded on NeuraGen® Nerve Guides (NNGs) in a rabbit model. NNGs with or without allogeneic rabbit MSCs were applied to rabbit sciatic nerves. Randomly assigned treatment included group I (no surgery control, n = 3) or groups II and III (sciatic nerve wrapped with unseeded or allogeneic MSC-seeded NNGs; n = 5/group). Rabbits were euthanized after 2 weeks to monitor functional recovery by histological evaluation of sciatic nerves and tibialis anterior (TA) muscle. Host reactions to allogeneic MSCs were analyzed by assessment of body and tissue weight, temperature, as well as hematological parameters, including white blood cell count (WBC), spleen histology, and CD4+ and CD8+ T lymphocytes. Histological analyses of nerves and spleen were all unremarkable, consistent with absence of overt systemic and local immune responses upon allogeneic MSC administration. No significant differences were observed in WBC or CD4+ and CD8+ T lymphocytes across unseeded and seeded treatment groups. Thus, allogenic MSCs are safe for use and may be considered in lieu of autologous MSCs in translational animal studies as the basis for future clinical nerve repair strategies. Impact statement Autologous mesenchymal stem cells (MSC) have been reported to enhance nerve regeneration when used in conjunction with nerve graft substitutes. However, autologous stem cell sources delay treatment and may be susceptible to age- or disease-related dysfunctions. In this study, we investigated the safety of allogeneic MSCs and the optimal number of cells for nerve conduit delivery in a rabbit model. When compared with unseeded nerve conduits, allogeneic MSC-seeded conduits did not induce a systemic or local immune response. The findings of this study will ultimately facilitate the clinical translation of a universal donor cell-based treatment option for nerve defects.

Osteoprotegerin-eluting nanoparticulate mineralized collagen scaffolds improve skull regeneration.

Custom synthesis of extracellular matrix (ECM)-inspired materials for condition-specific reconstruction has emerged as a potentially translatable regenerative strategy. In skull defect reconstruction, nanoparticulate mineralized collagen glycosaminoglycan scaffolds (MC-GAG) have demonstrated osteogenic and anti-osteoclastogenic properties, culminating in the ability to partially heal in vivo skull defects without the addition of exogenous growth factors or progenitor cell loading. In an effort to reduce catabolism during early skull regeneration, we fabricated a composite material (MCGO) of MC-GAG and recombinant osteoprotegerin (OPG), an endogenous anti-osteoclastogenic decoy receptor. In the presence of differentiating osteoprogenitors, MCGO demonstrated an additive effect with endogenous OPG limited to the first 14 days of culture with total eluted and scaffold-bound OPG exceeding that of MC-GAG. Functionally, MCGO exhibited similar osteogenic properties as MC-GAG, however, MCGO significantly reduced maturation and resorptive activities of primary human osteoclasts. In a rabbit skull defect model, MCGO scaffold-reconstructed defects displayed higher mineralization as well as increased hardness and microfracture resistance compared to non-OPG functionalized MC-GAG scaffolds. The current work suggests that MCGO is a development in the goal of reaching a materials-based strategy for skull regeneration.

COVID-19 Pandemic Associated With Increased Self-reported Depressive Symptoms in Patients With Congenital Craniofacial Diagnoses.

OBJECTIVE: The current study investigated the influence of the coronavirus (COVID-19) pandemic on patients with congenital craniofacial diagnoses. METHODS: Patients (n = 66) with craniofacial diagnoses aged between 8 and 17 were prospectively evaluated with longitudinal psychosocial assessments using the anger, anxiety, depressive symptoms, and peer relationships instruments within the pediatric Patient-Reported Outcomes Measurement Information System (PROMIS). The COVID-19 cohort (n = 33) included patients with assessments within 2 years prior to the pandemic (t0) and during the pandemic (t1; March 2020 to March 2021). An age-matched comparison cohort (n = 33) with similar demographics and diagnoses included patients assessed twice over 3 years prior to the pandemic. RESULTS: All PROMIS measures were in the average range clinically for both groups across time points. However, the COVID-19 group reported a significant increase in depressive symptoms during the pandemic (t1) compared to pre-pandemic (t0) scores (48.2 ± 10.1 vs 44.3 ± 9.4, P = .04, d = -0.37), while the comparison group did not demonstrate any differences in psychosocial functioning between t0 and t1. For the COVID-19 cohort, only the pandemic timeframe (r = 0.21, P = .03) was significantly associated with increased depressive symptom scores, and no other sociodemographic or medical variables were associated with depressive symptoms. CONCLUSIONS: Self-reported depressive symptoms increased during the COVID-19 pandemic in patients with congenital craniofacial diagnoses. Longitudinal studies are needed to elucidate whether such changes will be persistent or compound known variables associated with psychosocial functioning.

Dynamic seeding versus microinjection of mesenchymal stem cells for acellular nerve allograft: an in vitro comparison.

BACKGROUND: Mesenchymal stem cell (MSC)-supplemented acellular nerve allografts (ANA) are a potential strategy to improve the treatment of segmental nerve defects. Prior to clinical translation, optimal cell delivery methods must be defined. While two techniques, dynamic seeding and microinjection, have been described, the seeding efficiency, cell viability, and distribution of MSCs in ANAs are yet to be compared. METHODS: Sciatic nerve segments of Sprague-Dawley rats were decellularized, and MSCs were harvested from the adipose tissue of Lewis rats. Cell viability was evaluated after injection of MSCs through a 27-gauge needle at different flow rates (10, 5, and 1 µL/min). MSCs were dynamically seeded or longitudinally injected into ANAs. Cell viability, seeding efficiency, and distribution were evaluated using LIVE/DEAD and MTS assays, scanning electron microscopy, and Hoechst staining. RESULTS: No statistically significant difference in cell viability after injection at different flow rates was seen. After cell delivery, 84.1 ± 3.7% and 87.8 ± 2.8% of MSCs remained viable in the dynamic seeding and microinjection group, respectively (p = 0.41). The seeding efficiency of microinjection (100.4%±5.6) was significantly higher than dynamic seeding (48.1%±8.6) on day 1 (p = 0.001). Dynamic seeding demonstrated a significantly more uniform cell distribution over the course of the ANA compared to microinjection (p = 0.02). CONCLUSION: MSCs remain viable after both dynamic seeding and microinjection in ANAs. Higher seeding efficiency was observed with microinjection, but dynamic seeding resulted in a more uniform distribution. In vivo studies are required to assess the effect on gene expression profiles and functional motor outcomes.

The effect of mesenchymal stem cells and surgical angiogenesis on immune response and revascularization of acellular nerve allografts in a rat sciatic defect model.

BACKGROUND: Increasing evidence demonstrates an interplay between neoangiogenesis and immune cells. We investigated the immune response and revascularization of acellular nerve allografts (ANA) after combined stem cell delivery and surgical angiogenesis in a rat model. METHODS: Unilateral sciatic nerve defects in 60 Lewis rats were repaired with (I) autografts, (II) ANAs, and (III) ANAs wrapped within a pedicled superficial inferior epigastric artery fascial flap to induce surgical angiogenesis, combined with seeding of either (IV) undifferentiated mesenchymal stem cells (uMSCs) or (V) MSCs differentiated into Schwann cell-like cells. Immune cell phenotyping was performed on days 7 and 14. The vascular volume of nerves was measured by microcomputed tomography at 12 and 16 weeks. RESULTS: On day 7, helper T cells (CD4+) were significantly increased in groups IV and V compared to group I. Regulatory T cells (CD4+CD25+) were significantly higher in groups III-IV, and cytotoxic T cells (CD8+) were significantly reduced in groups IV and V compared to group II, respectively. Group II demonstrated the highest levels of natural killer cells (CD161+) compared to groups III-V. On day 14, group IV demonstrated the highest CD4/CD8 ratio. Vascular volume was significantly higher in groups III-V compared to group II at 12 weeks and groups IV and V compared to group II at 16 weeks. The CD4/CD8 ratio demonstrated a positive correlation to vascular volumes at 12 weeks. CONCLUSION: Early favorable immune responses were observed in ANAs treated with surgical angiogenesis with or without stem cell delivery and demonstrated improved vascularity at longer follow-up.

ß-Catenin Limits Osteogenesis on Regenerative Materials in a Stiffness-Dependent Manner.

Targeted refinement of regenerative materials requires mechanistic understanding of cell-material interactions. The nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) scaffold is shown to promote skull regeneration in vivo without additive exogenous growth factors or progenitor cells, suggesting potential for clinical translation. This work evaluates modulation of MC-GAG stiffness on canonical Wnt (cWnt) signaling. Primary human bone marrow-derived mesenchymal stem cells (hMSCs) are differentiated on two MC-GAG scaffolds (noncrosslinked, NX-MC, 0.3 kPa vs conventionally crosslinked, MC, 3.9 kPa). hMSCs increase expression of activated ß-catenin, the major cWnt intracellular mediator, and the mechanosensitive YAP protein with near complete subcellular colocalization on stiffer MC scaffolds. Overall Wnt pathway inhibition reduces activated ß-catenin and osteogenic differentiation, while elevating BMP4 and phosphorylated Smad1/5 (p-Smad1/5) expression on MC, but not NX-MC. Unlike Wnt pathway downregulation, isolated canonical Wnt inhibition with ß-catenin knockdown increases osteogenic differentiation and mineralization specifically on the stiffer MC. ß-catenin knockdown also increases p-Smad1/5, Runx2, and BMP4 expression only on the stiffer MC material. Thus, while stiffness-induced activation of the Wnt and mechanotransduction pathways promotes osteogenesis on MC-GAG, activated ß-catenin is a limiting agent and may serve as a useful target or readout for optimal modulation of stiffness in skeletal regenerative materials.

Maximum Isometric Tetanic Force Measurement of the Tibialis Anterior Muscle in the Rat.

Traumatic nerve injuries result in substantial functional loss and segmental nerve defects often necessitate the use of autologous interposition nerve grafts. Due to their limited availability and associated donor side morbidity, many studies in the field of nerve regeneration focus on alternative techniques to bridge a segmental nerve gap. In order to investigate the outcomes of surgical or pharmacological experimental treatment options, the rat sciatic nerve model is often used as a bioassay. There are a variety of outcome measurements used in rat models to determine the extent of nerve regeneration. The maximum output force of the target muscle remains the most relevant outcome for clinical translation of experimental therapies. Isometric force measurement of tetanic muscle contraction has previously been described as a reproducible and valid technique for evaluating motor recovery after nerve injury or repair in both rat and rabbit models. In this video, we will provide a step-by-step instruction of this invaluable procedure for assessment of functional recovery of the tibialis anterior muscle in a rat sciatic nerve defect model using optimized parameters. We will describe the necessary pre-surgical preparations in addition to the surgical approach and dissection of the common peroneal nerve and tibialis anterior muscle tendon. The isometric tetanic force measurement technique will be detailed. Determining the optimal muscle length and stimulus pulse frequency is explained and measuring the maximum tetanic muscle contraction is demonstrated.

The role of vascularization in nerve regeneration of nerve graft.

Vascularization is an important factor in nerve graft survival and function. The specific molecular regulations and patterns of angiogenesis following peripheral nerve injury are in a broad complex of pathways. This review aims to summarize current knowledge on the role of vascularization in nerve regeneration, including the key regulation molecules, and mechanisms and patterns of revascularization after nerve injury. Angiogenesis, the maturation of pre-existing vessels into new areas, is stimulated through angiogenic factors such as vascular endothelial growth factor and precedes the repair of damaged nerves. Vascular endothelial growth factor administration to nerves has demonstrated to increase revascularization after injury in basic science research. In the clinical setting, vascularized nerve grafts could be used in the reconstruction of large segmental peripheral nerve injuries. Vascularized nerve grafts are postulated to accelerate revascularization and enhance nerve regeneration by providing an optimal nutritional environment, especially in scarred beds, and decrease fibroblast infiltration. This could improve functional recovery after nerve grafting, however, conclusive evidence of the superiority of vascularized nerve grafts is lacking in human studies. A well-designed randomized controlled trial comparing vascularized nerve grafts to non-vascularized nerve grafts involving patients with similar injuries, nerve graft repair and follow-up times is necessary to demonstrate the efficacy of vascularized nerve grafts. Due to technical challenges, composite transfer of a nerve graft along with its adipose tissue has been proposed to provide a healthy tissue bed. Basic science research has shown that a vascularized fascial flap containing adipose tissue and a vascular bundle improves revascularization through excreted angiogenic factors, provided by the stem cells in the adipose tissue as well as by the blood supply and environmental support. While it was previously believed that revascularization occurred from both nerve ends, recent studies propose that revascularization occurs primarily from the proximal nerve coaptation. Fascial flaps or vascularized nerve grafts have limited applicability and future directions could lead towards off-the-shelf alternatives to autografting, such as biodegradable nerve scaffolds which include capillary-like networks to enable vascularization and avoid graft necrosis and ischemia.

An expandable embryonic stem cell-derived Purkinje neuron progenitor population that exhibits in vivo maturation in the adult mouse cerebellum.

The directed differentiation of patient-derived induced pluripotent stem cells into cell-type specific neurons has inspired the development of therapeutic discovery for neurodegenerative diseases. Many forms of ataxia result from degeneration of cerebellar Purkinje cells, but thus far it has not been possible to efficiently generate Purkinje neuron (PN) progenitors from human or mouse pluripotent stem cells, let alone to develop a methodology for in vivo transplantation in the adult cerebellum. Here, we present a protocol to obtain an expandable population of cerebellar neuron progenitors from mouse embryonic stem cells. Our protocol is characterized by applying factors that promote proliferation of cerebellar progenitors. Cerebellar progenitors isolated in culture from cell aggregates contained a stable subpopulation of PN progenitors that could be expanded for up to 6 passages. When transplanted into the adult cerebellum of either wild-type mice or a strain lacking Purkinje cells (L7cre-ERCC1 knockout), GFP-labeled progenitors differentiated in vivo to establish a population of calbindin-positive cells in the molecular layer with dendritic trees typical of mature PNs. We conclude that this protocol may be useful for the generation and maturation of PNs, highlighting the potential for development of a regenerative medicine approach to the treatment of cerebellar neurodegenerative diseases.