Disrupting the intrinsic growth potential of a suture contributes to midfacial hypoplasia

Development and Characterization of a Novel Composite Hydrogel Biomaterial for Improved Mucoperiosteal Wound Repair

Mucoperiosteal wound healing, as it occurs after pediatric cleft palate surgery, can be challenging due to the limitations of current treatments such as tissue flaps secured with sutures and fibrin glue. In this study, we characterized the in vitro performance of a novel composite hydrogel biomaterial designed to be employed as an in situ wound filler and enhance mucoperiosteal wound healing. We evaluated a range of photopolymerizable formulations containing methacrylated gelatin (GelMA), glycol chitosan, and bioglass microparticles. Our aim was to identify one or more formulations with an appropriate balance of properties against a set of functional requirements that we established for this application. To test the formulations against these criteria, we measured photopolymerization kinetics, mechanical properties, degradation rate, in vitro biocompatibility, and ex vivo tissue adhesion. All formulations polymerized in less than 90 s using violet light. In addition, we found that GelMA-based hydrogels were more adhesive to mucoperiosteal tissue than clinical standard fibrin glue. Inclusion of small amounts of bioglass in the formulation increased mechanical compatibility with mucoperiosteal tissue, enhanced cytoconductivity, and promoted cell proliferation. Taken together, our results support the suitability of these photopolymerized composite hydrogels as in situ mucoperiosteal wound fillers. Overall, this study lays the groundwork for investigating the in vivo, pre-clinical effectiveness of these composite hydrogels in improving mucoperiosteal wound healing outcomes.

Orthognathic Surgery Rates in Furlow Double-Opposing Z-Plasty Versus Straight-Line Repair: A Review of Three Decades of Experience

OBJECTIVE

The influence of different surgical techniques on maxillary growth remains unclear. This study investigates the long-term impact of Furlow double-opposing Z-plasty versus straight-line repair (SLR) techniques on midface growth and subsequent orthognathic surgery.

DESIGN

Retrospective cohort study.

SETTING

Tertiary children's hospital.

PATIENTS/PARTICIPANTS

This study evaluated patients who underwent primary palatoplasty with Furlow or SLR techniques from 1994-2023. Patients were >14 years old at their most recent follow-up.

INTERVENTIONS

No interventions were performed.

MAIN OUTCOME MEASURE(S)

Primary outcomes were orthognathic surgery and orthognathic surgery recommendation rates to correct midface hypoplasia (MFH). Cephalometrics at the time of orthognathic surgery recommendation were traced to validate MFH.

RESULTS

In total, 1857 patients underwent palatoplasty, of which 335 met inclusion criteria (49 SLR, 286 Furlow). Average age at last follow-up was 18.5±2.6 years. Patients who underwent Furlow versus SLR showed no significant difference in orthognathic surgery rates (p=0.428) or recommendation for orthognathic surgery rates (p=0.900). Patients recommended to undergo orthognathic surgery had more negative ANB angles (p<0.001) and smaller SNA angles (p<0.001) than patients not recommended for orthognathic surgery, demonstrating maxillary hypoplasia. Upon multivariate regression, patients with Veau III and IV clefts had an increased need for orthognathic surgery, p=0.047 and p=0.008, respectively.

CONCLUSIONS

Our findings suggest that higher cleft severity contributes to future orthognathic surgery. However, palatoplasty technique did not influence orthognathic surgery rates. Our results provide valuable data when surgeons are considering the impact of palatoplasty technique on sagittal growth restriction.

Mll4 regulates postnatal palate growth and midpalatal suture development

MLL4, also known as KMT2D, is a histone methyltransferase that acts as an important epigenetic regulator during various organogenesis programs. Mutations in the MLL4 gene are the major cause for Kabuki syndrome, a human developmental disorder that involves craniofacial birth defects, including anomalies in the palate. The purpose of this study was to investigate the role of Mll4 and the underlying mechanisms in the development and growth of the palate. We generated a novel conditional knockout (cKO) mouse model with tissue-specific deletion of Mll4 in the palatal mesenchyme. By using micro-computed tomography (CT), histology, cell mechanism assays, and gene expression analysis approaches, we examined the development and growth of the palate in the Mll4 -cKO mice. Gross intra-oral examination at adult stages showed that Mll4 -cKO mice had defects along the midline of the palate, which included disrupted rugae pattern and widened midpalatal suture. Micro-CT-based skeletal analysis in the adult mice revealed that the overall palate width was decreased in the Mll4 -cKO mice. By using whole-mount and histological staining approaches at perinatal stages, we identified that the midline defects started to appear as early as 1 day prior to birth, manifesting initially as a widened midpalatal suture, accompanied by increased cell apoptosis in the suture mesenchyme cells. Genome-wide analysis of mRNA expression in the midpalatal suture tissue showed that Mll4 is essential for timely expression of major genes for cartilage development, such as Col2a1 and Acan , at birth. These results were validated through immunofluorescence staining, confirming that the expression of chondrogenic markers Sox9 and Col2a1 were markedly decreased, whereas that of the osteogenic marker Runx2 remained unchanged, in the midpalatal suture of the Mll4 -cKO mice. Indeed, time-course histological analysis during postnatal palate growth revealed retardation in the development of the suture cartilage in the Mll4 -cKO mice. In parallel, time-course micro-CT analysis during postnatal palatogenesis confirmed a transverse growth deficit in the palate of the Mll4 -cKO mice. Taken together, our results show that Mll4 is essential for timely occurrence of key cellular and molecular events that lead to proper midpalatal suture development and palate growth.

Speech Outcomes after Delayed Hard Palate Closure and Synchronous Secondary Alveolar Bone Grafting in Patients with Cleft Lip, Alveolus and Palate

Background  The best timing of closure of the hard palate in individuals with cleft lip, alveolus, and palate (CLAP) to reach the optimal speech outcomes and maxillary growth is still a subject of debate. This study evaluates changes in compensatory articulatory patterns and resonance in patients with unilateral and bilateral CLAP who underwent simultaneous closure of the hard palate and secondary alveolar bone grafting (ABG). Methods  A retrospective study of patients with nonsyndromic unilateral and bilateral CLAP who underwent delayed hard palate closure (DHPC) simultaneously with ABG at 9 to 12 years of age from 2013 to 2018. The articulatory patterns, nasality, degree of hypernasality, facial grimacing, and speech intelligibility were assessed pre- and postoperatively. Results  Forty-eight patients were included. DHPC and ABG were performed at the mean age of 10.5 years. Postoperatively hypernasal speech was still present in 54% of patients; however, the degree of hypernasality decreased in 67% ( p  < 0.001). Grimacing decreased in 27% ( p  = 0.015). Articulation disorders remained present in 85% ( p  = 0.375). Intelligible speech (grade 1 or 2) was observed in 71 compared with 35% of patients preoperatively ( p  < 0.001). Conclusion  This study showed an improved resonance and intelligibility following DHPC at the mean age of 10.5 years, however compensatory articulation errors persisted. Sequential treatments such as speech therapy play a key role in improvement of speech and may reduce remaining compensatory mechanisms following DHPC.

Tendon-associated gene expression precedes osteogenesis in mid-palatal suture establishment

Orthodontic maxillary expansion relies on intrinsic mid-palatal suture mechanobiology to induce guided osteogenesis, yet establishment of the mid-palatal suture within the continuous secondary palate and causes of maxillary insufficiency remain poorly understood. In contrast, advances in cranial suture research hold promise to improve surgical repair of prematurely fused cranial sutures in craniosynostosis to potentially restore the obliterated signaling environment and ensure continual success of the intervention. We hypothesized that mid-palatal suture establishment is governed by shared principles with calvarial sutures and involves functional linkage between expanding primary ossification centres with the midline mesenchyme. We characterized establishment of the mid-palatal suture from late embryonic to early postnatal timepoints. Suture establishment was visualized using histological techniques and multimodal transcriptomics. We identified that mid-palatal suture formation depends on a spatiotemporally controlled signalling milieu in which tendon-associated genes play a significant role. We mapped relationships between extracellular matrix-encoding gene expression, tenocyte markers, and novel suture patency candidate genes. We identified similar expression patterns in FaceBase-deposited scRNA-seq datasets from cranial sutures. These findings demonstrate shared biological principles for suture establishment, providing further avenues for future development and understanding of maxillofacial interventions.

Rapid Maxillary Expansion Treatment in Patients with Cleft Lip and Palate: A Survey on Clinical Experience in the European Cleft Centers

Cleft lip and palate patients require complex interdisciplinary treatment, including maxillary expansion and secondary alveolar bone grafting. However, the evidence on these treatment procedures and outcomes is lacking. Therefore, this study aimed to survey the subjective observations of European maxillofacial surgeons and orthodontists on the maxillary expansion and bone grafting treatment protocols and the associated complications. An online questionnaire was sent to 131 centers. The questions assessed the participants' demographic data, maxillary expansion and alveolar bone grafting protocols, and the associated complications. Descriptive statistics and a t-test were used to analyze the data. The response rate was 40.5%. The average age for maxillary expansion was 9-10 years. The secondary alveolar bone grafting was planned 5-10 months after the expansion. The most common complications were asymmetric expansion, relapse, and fistula formation. The protocols and materials used vary widely among centers. Anatomical alterations and developmental processes, like tooth eruption adjacent to the cleft, should be seriously considered for treatment planning. This survey showed that there is still a lack of consensus on these treatment procedures. Further clinical trials should focus on long-term outcome evaluation to identify treatment components for optimal alveolar bone substitution and transversal maxillary expansion treatment in patients with clefts.

Full-Thickness Oral Mucoperiosteal Defects: Challenges and Opportunities

Regenerative engineering strategies for the oral mucoperiosteum, as may be needed following surgeries, such as cleft palate repair and tumor resection, are underdeveloped compared with those for maxillofacial bone. However, critical-size tissue defects left to heal by secondary intention can lead to complications, such as infection, fistula formation, scarring, and midface hypoplasia. This review describes current clinical practice for replacing mucoperiosteal tissue, including autografts and allografts. Potentially paradigm-shifting experimental regenerative engineering strategies for mucoperiosteal wound healing, such as hybrid grafts and engineered matrices, are also discussed. Throughout the review, the advantages and disadvantages of each replacement or regeneration strategy are outlined in the context of clinical outcomes, quality of life for the patient, availability of materials, and cost of care. Finally, future directions for research and development in the area of mucoperiosteum repair are proposed, with an emphasis on identifying globally available and affordable solutions for promoting mucoperiosteal regeneration. Impact statement Unassisted oral mucoperiosteal wound healing can lead to severe complications such as infection, fistulae, scarring, and developmental abnormalities. Thus, strategies for promoting wound healing must be considered when mucoperiosteal defects are incident to oral surgery, as in palatoplasty or tumor resection. Emerging mucoperiosteal tissue engineering strategies, described in this study, have the potential to overcome the limitations of current standard-of-care donor tissue grafts. For example, the use of engineered mucoperiosteal biomaterials could circumvent concerns about tissue availability and immunogenicity. Moreover, employment of tissue engineering strategies may improve the equity of oral wound care by increasing global affordability and accessibility of materials.

Midface Growth Potential in Unoperated Clefts: A Systematic Review and Meta-Analysis

ABSTRACT

Competing hypotheses for the development of midface hypoplasia in patients with cleft lip and palate include both theories of an intrinsic restricted growth potential of the midface and extrinsic surgical disruption of maxillary growth centers and scar growth restriction secondary to palatoplasty. The following meta-analysis aims to better understand the intrinsic growth potential of the midface in a patient with cleft lip and palate unaffected by surgical correction. A systematic review of studies reporting cephalometric measurements in patients with unoperated and operated unilateral cleft lip and palate (UCLP), bilateral cleft lip and palate (BCLP), and isolated cleft palate (ICP) abstracted SNA and ANB angles, age at cephalometric analysis, syndromic diagnosis, and patient demographics. Age and Region-matched controls without cleft palate were used for comparison. SNA angle for unoperated UCLP (84.5 ± 4.0°), BCLP (85.3 ± 2.8°), and ICP (79.2 ± 4.2°) were statistically different than controls (82.4 ± 3.5°), (all P ≤ 0.001). SNA angles for operated UCLP (76.2 ± 4.2°), BCLP (79.8 ± 3.6°), and ICP (79.0 ± 4.3°) groups were statistically smaller than controls (all P ≤ 0.001). SNA angle in unoperated ICP (n = 143) was equivalent to operated ICP patients (79.2 ± 4.2° versus 79.0 ± 4.3° P = 0.78). No unoperated group mean SNA met criteria for midface hypoplasia (SNA < 80). Unoperated UCLP/BLCP exhibit a more robust growth potential of the maxilla, whereas operated patients demonstrate stunted growth compared to normal phenotype. Unoperated ICP demonstrates restricted growth in both operated and unoperated patients. As such, patients with UCLP/BCLP differ from patients with ICP and the factors affecting midface growth may differ.Level of Evidence: IV.

How Deviation of Nasal Septum Affects Nasal Appearance in Unilateral Cleft Patients: A Study Using Cone-Beam Computed Tomography

AIM

To quantitatively evaluate the relationship between nasal appearance and nasal septum deviation in unilateral complete cleft patients using cone-beam computed tomography.Method: Cone-beam computed tomography images of 180 patients with unilateral cleft lip/palate from June 2014 to June 2017 were used in the study. None of the subjects had undergone septoplasty. The data were compared between the 2 groups to elucidate the relationship between nasal appearance and deviated nasal septum in unilateral complete cleft patients.

RESULTS

The mean age of a total of 180 patients (126 males and 54 females) was 14.58 years, with a standard deviation of 7.10 years, ranged from 6 years old to 49 years old. Columella nasi symmetry parameters show slight positive significant association with angle of nasal septal deviation on transerve plan (r = 0.250, P < 0.001), TRSD (r = 0.323, P < 0.001) and coronal range of nasal septal deviation (r = 0.294, P < 0.001), and moderate positive significant association with coronal angle about septal deviation (r = 0.404, P < 0.001).

CONCLUSIONS

Columella nasi symmetry affected by septal deviation, whereas there is lack of evidence to say symmetry of nasal tip and base affected by septal deviation. The symmetry of nasal tip and alar base are not just determined by nasal septum deviation. The nasal septum deviation show difference in different cleft type.

A Meta-Analysis of Palatal Repair Timing

ABSTRACT

Developing midface hypoplasia is common after palatoplasty and has been hypothesized to be influenced by the timing of hard palate repair. This meta-analysis assesses the risk of developing midface hypoplasia based on age at hard palate repair. A Pubmed PRISMA systematic review and meta-analysis was completed for literature focused on palatoplasty and midface hypoplasia published between 1970 and 2019. Cephalometric data were extracted and categorized by age at hard palate repair: <6, 7 to 12, 13 to 18, 19 to 24, and 25 to 83 months. Analysis of these groups and a control were compared using independent T-tests and Spearman correlation coefficients. SNA angles for each group were 77.9 ± 3.1° (<6 months), 77.7 ± 4.2° (7-12 months), 78.7 ± 4.2° (13-18 months), 75.1 ± 4.2° (19-24 months), 75.5 ± 4.8° (25-83 months), and were statistically different than the control group 82.4 ± 3.5° (P < 0.0001). Hard palate repair at 13 to 18 months had a statistically significant greater SNA angle than all other groups except for the repair at <6 months group (P = 0.074). As age at hard palate closure increased beyond 18 months, the SNA decreased, corresponding to a more hypoplastic maxilla (Spearman's correlation coefficient -0.381, P = 0.015). Analysis suggests that younger age at the time of repair is less likely to create in midface hypoplasia in adulthood. Minimizing midface hypoplasia in cleft palate patients by optimizing algorithms of care is a practical way to decrease the burden of disease on patients, families and medical systems. Further studies are needed to evaluate the role of technique on outcomes.Level of Evidence: IV.

Craniofacial Growth Analysis of Individuals With and Without Cleft Lip and Palate in Colombia

INTRODUCTION

Craniofacial growth is a dynamic and unpredictable process influenced by genetic and environmental factors, presenting phenotypic and gender differences.

OBJECTIVE

Evaluate the differences in craniofacial growth and development in a group of Colombian individuals with complete unilateral and bilateral cleft lip and palate (CLP) and without CLP, classified by gender and age.

SETTING AND SAMPLE POPULATION

Five hundred forty-one profile radiographs of 126 patients with unilateral CLP, 126 with bilateral CLP, and 289 without CLP. All patients of affected groups had a history of CLP correction surgery without nasoalveolar molding with orthopedic and orthodontic treatments.

MATERIALS AND METHODS

This cross-sectional study was performed comparing 8 cephalometric measurements on radiographs, 5 linear/3 angular. Analysis was performed by median and interquartile range for all cephalometric measurements. Comparison between the groups was performed using Kruskal-Wallis and Mann-Whitney U, with a 95% confidence.

RESULTS

Significant differences between the groups of patients with and without CLP, between types of clefts and genders. The skeletal structures of patients with CLP were smaller than those of control but improved with growth. Patients with unilateral CLP presented flat profiles and predominant class III malocclusions, while patients with bilateral CLP, at early ages, were class II and in the prepubertal stage, the values were progressively negative until the end of the growth period, suggesting class III. Patients with CLP presented posteroinferior rotation of the mandible, vertical measurements increased, and deflection of the cranial base.

CONCLUSION

Given their growth alterations, patients with CLP benefit from orthopedic and orthodontic treatment.

The Likelihood of Orthognathic Surgery After Orofacial Cleft Repair

ABSTRACT

Midface hypoplasia is one of the most significant sequelae of cleft lip and/or palate surgery. A complete understanding of the rate of orthognathic surgery across varying cleft phenotypes is a powerful tool for educating patients and families as to the treatment course that the patient will incur during their lifetime. Understanding the average rates of orthognathic intervention also can act to develop metrics for outcome evaluation with different treatment protocols. Attempting to identify the average rates of orthognathic intervention, the authors conducted a systematic review and meta-analysis by combining studies from 1987 to 2016 describing the frequency of orthognathic intervention on the different cleft phenotypes as the primary outcome. Secondary outcomes included identification of surgical protocol, age of patient at orthognathic intervention, and the method by which patients were evaluated for orthognathic intervention. The rate of orthognathic surgery was 38.1% for bilateral cleft lip and palate (BCLP), 30.2% for unilateral cleft lip and palate (UCLP), 4.4% for isolated cleft palate (ICP), and 1.8% for patients with isolated cleft lip (ICL). 71% (n = 10) reported using lateral cephalograms for orthognathic surgery evaluation and only one of those studies reported specific objective cephalometric measurements for orthognathic intervention. Our findings demonstrated that BCLP possessed the highest rate of orthognathic intervention followed by UCLP, ICP, and ICL. ICP and ICL both possessed low rates of orthognathic intervention. By sharing our findings, the authors hope to provide a useful tool for informing patients' families as to their risk of needing orthognathic intervention.

Pattern of Morphological Variability in Unrepaired Unilateral Clefts With and Without Cleft Palate May Suggest Intrinsic Growth Deficiency

In individuals with cleft lip and palate (CLP) an iatrogenic effect of operations on subsequent maxillary growth is well-known. Much less is known about the association between occurrence of CLP and intrinsic growth deficiency of the maxillofacial complex. The aim of this study was to compare morphological variability in subjects with unilateral cleft lip and alveolus/palate and unaffected controls using geometric morphometric methods. The research hypothesis was that if subjects with unrepaired unilateral CLP have intrinsic growth deficiency, the pattern of their craniofacial growth variation may differ from that in unaffected individuals. Lateral cephalograms were available of three groups of the same ethnic background (Proto-Malayid): (a) non-syndromic unrepaired unilateral complete cleft lip, alveolus, and palate (UCLP), N = 66, mean age 24.5 years (b) non-syndromic unrepaired unilateral complete cleft lip and alveolus (UCLA), N = 177, mean age 23.7 years, and (c) NORM (N = 50), mean age 21.2 years without a cleft. Using geometric morphometrics shape variability in groups and shape differences between groups was analyzed. Principal component analysis (PCA) was used to examine shape variability, while differences between groups and sexes were evaluated with canonical variate analysis. Sexual dimorphism was evaluated with discriminant function analysis (DA). Results showed that in comparison to NORM subjects, shape variability in UCLA and UCLP is more pronounced in the antero-posterior than in vertical direction. Pairwise comparisons of the mean shape configurations (NORM vs. UCLA, NORM vs. UCLP, and UCLA vs. UCLP) revealed significant differences between cleft and non-cleft subjects. The first canonical variate (CV1, 68.2% of variance) demonstrated that differences were associated with maxillary shape and/or position and incisor inclination, while in females, the CV1 (69.2% of variance) showed a combination of differences of “maxillary shape and/or position and incisor inclination” and inclination of the cranial base. Shape variability demonstrated considerable differences in subjects with UCLA, UCLP, and NORM. Moreover, in subjects with a cleft, within-sample variability was more pronounced in the antero-posterior direction, while in non-cleft subjects, within-sample variability was more pronounced in the vertical direction. These findings may suggest that subjects with unilateral clefts have intrinsic growth impairment affecting subsequent facial development.

Molecular Basis for Craniofacial Phenotypes Caused by Sclerostin Deletion

Some genetic disorders are associated with distinctive facial features, which can aid in diagnosis. While considerable advances have been made in identifying causal genes, relatively little progress has been made toward understanding how a particular genotype results in a characteristic craniofacial phenotype. An example is sclerosteosis/van Buchem disease, which is caused by mutations in the Wnt inhibitor sclerostin (SOST). Affected patients have a high bone mass coupled with a distinctive appearance where the mandible is enlarged and the maxilla is foreshortened. Here, mice carrying a null mutation in Sost were analyzed using quantitative micro-computed tomographic (µCT) imaging and histomorphometric analyses to determine the extent to which the size and shape of craniofacial skeleton were altered. Sost^-/- mice exhibited a significant increase in appositional bone growth, which increased the height and width of the mandible and reduced the diameters of foramina. In vivo fluorochrome labeling, histology, and immunohistochemical analyses indicated that excessive bone deposition in the premaxillary suture mesenchyme curtailed overall growth, leading to midfacial hypoplasia. The amount of bone extracellular matrix produced by Sost^-/- cells was significantly increased; as a consequence, osteoid seams were evident throughout the facial skeleton. Collectively, these analyses revealed a remarkable fidelity between human characteristics of sclerosteosis/van Buchem disease and the Sost^-/- phenotype and provide clues into the conserved role for sclerostin signaling in modulating craniofacial morphology.

Functional stability analyses of maxillofacial skeleton bearing cleft deformities

The symmetrically stable craniofacial bony structure supports the complex functions and delicate contour of the face. Congenital craniofacial deformities are often accompanied by bony defects and have been repetitively correlated with compromised dento-maxillary stability, but neither the extent nor the pattern of cleft-related maxillary instability has been explored in detail. Furthermore, it is largely unknown if the bony defect and related instability are correlated with secondary maxillary deformity common among patients with orofacial clefts. With the aid of finite element modeling, we studied the detailed relationship between cleft-related bony defect and maxillary stability under occlusal loading. Craniofacial models were generated based on cone-beam computed tomography data and loaded with mimicked bite forces along the axial axis of each tooth. Our data showed that all cleft models exhibited more asymmetrical deformations under mastication compared with the normal. Models with palatal cleft demonstrated greater asymmetry, greater dental arch contraction, and less maxillary protrusion compared to models with alveolar cleft only. For unilateral cleft models, alveolus on non-cleft side tended to be more protruded and lifted than the cleft side. For bilateral cleft models, the most prominent feature was the seriously contracted alveolar arch and curved and pitched premaxillae. These findings indicated cleft type-specific pattern of maxillary instability, which were largely in accordance with dentoalveolar morphological features among patients. Collectively, our study elucidated the detailed relationship between cleft bony defect and the pattern of maxillary instability, and suggested a prototype for studying the abnormal maxillary and dental arch growth among patients with craniofacial deformities.

WNT-activated bone grafts repair osteonecrotic lesions in aged animals

The Wnt pathway is a new target in bone therapeutic space. WNT proteins are potent stem cell activators and pro-osteogenic agents. Here, we gained insights into the molecular and cellular mechanisms responsible for liposome-reconstituted recombinant human WNT3A protein (L-WNT3A) efficacy to treat osteonecrotic defects. Skeletal injuries were coupled with cryoablation to create non-healing osteonecrotic defects in the diaphysis of the murine long bones. To replicate clinical therapy, osteonecrotic defects were treated with autologous bone graft, which were simulated by using bone graft material from syngeneic ACTB-eGFP-expressing mice. Control osteonecrotic defects received autografts alone; test sites received autografts treated ex vivo with L-WNT3A. In vivo µCT monitored healing over time and immunohistochemistry were used to track the fate of donor cells and assess their capacity to repair osteonecrotic defects according to age and WNT activation status. Collectively, analyses demonstrated that cells from the autograft directly contributed to repair of an osteonecrotic lesion, but this contribution diminished as the age of the donor increased. Pre-treating autografts from aged animals with L-WNT3A restored osteogenic capacity to autografts back to levels observed in autografts from young animals. A WNT therapeutic approach may therefore have utility in the treatment of osteonecrosis, especially in aged patients.

Linking suckling biomechanics to the development of the palate

Skulls are amongst the most informative documents of evolutionary history but a complex geometry, coupled with composite material properties and complicated biomechanics, have made it particularly challenging to identify mechanical principles guiding the skull’s morphogenesis. Despite this challenge, multiple lines of evidence, for example the relationship between masticatory function and the evolution of jaw shape, nonetheless suggest that mechanobiology plays a major role in skull morphogenesis. To begin to tackle this persistent challenge, cellular, molecular and tissue-level analyses of the developing mouse palate were coupled with finite element modeling to demonstrate that patterns of strain created by mammalian-specific oral behaviors produce complementary patterns of chondrogenic gene expression in an initially homogeneous population of cranial neural crest cells. Neural crest cells change from an osteogenic to a chondrogenic fate, leading to the materialization of cartilaginous growth plate-like structures in the palatal midline. These growth plates contribute to lateral expansion of the head but are transient structures; when the strain patterns associated with suckling dissipate at weaning, the growth plates disappear and the palate ossifies. Thus, mechanical cues such as strain appear to co-regulate cell fate specification and ultimately, help drive large-scale morphogenetic changes in head shape.

Mechanical Stress Changes the Complex Interplay Between HO-1, Inflammation and Fibrosis, During Excisional Wound Repair

Mechanical stress following surgery or injury can promote pathological wound healing and fibrosis, and lead to functional loss and esthetic problems. Splinted excisional wounds can be used as a model for inducing mechanical stress. The cytoprotective enzyme heme oxygenase-1 (HO-1) is thought to orchestrate the defense against inflammatory and oxidative insults that drive fibrosis. Here, we investigated the activation of the HO-1 system in a splinted and non-splinted full-thickness excisional wound model using HO-1-luc transgenic mice. Effects of splinting on wound closure, HO-1 promoter activity, and markers of inflammation and fibrosis were assessed. After seven days, splinted wounds were more than three times larger than non-splinted wounds, demonstrating a delay in wound closure. HO-1 promoter activity rapidly decreased following removal of the (epi)dermis, but was induced in both splinted and non-splinted wounds during skin repair. Splinting induced more HO-1 gene expression in 7-day wounds; however, HO-1 protein expression remained lower in the epidermis, likely due to lower numbers of keratinocytes in the re-epithelialization tissue. Higher numbers of F4/80-positive macrophages, αSMA-positive myofibroblasts, and increased levels of the inflammatory genes IL-1β, TNF-α, and COX-2 were present in 7-day splinted wounds. Surprisingly, mRNA expression of newly formed collagen (type III) was lower in 7-day wounds after splinting, whereas, VEGF and MMP-9 were increased. In summary, these data demonstrate that splinting delays cutaneous wound closure and HO-1 protein induction. The pro-inflammatory environment following splinting may facilitate higher myofibroblast numbers and increase the risk of fibrosis and scar formation. Therefore, inducing HO-1 activity against mechanical stress-induced inflammation and fibrosis may be an interesting strategy to prevent negative effects of surgery on growth and function in patients with orofacial clefts or in patients with burns.