Research Spotlight

Aman, H., T. Shokri, L. V. Reddy and Y. Ducic (2019). “Secondary Management of Midface Fractures.” Facial Plast Surg 35(6): 640-644.

Full text of this article.

Secondary reconstruction of posttraumatic facial deformities has been consistently described as one of the most challenging procedures performed. Ideal primary reconstruction cannot always be achieved, and often it is complicated by severe comminution or inadequate surgical management. It also can arise because of a lack of definitive surgical repair or excessive delay of initial treatment. Complications leading to secondary deformities can occur even when craniofacial injuries are treated by experienced surgeons. Following proper surgical principles, meticulous perioperative planning, and anticipation of potential functional and aesthetic sequelae limit many of those complications. Herein, we discuss secondary procedures in traumatic midface injuries.

Zhang, Q., Q. Zhang, S. Yang, P. C. Dechow, H. Zhu, H. Y. Yeh and Q. Wang (2019). “Divided zygoma in Holocene human populations from Northern China.” Am J Hum Biol 31(6): e23314.

Full text of this article.

OBJECTIVES: Divided zygoma (DZ) occurs in contemporaneous human populations, with the highest incidences in people from East Asia and Southern Africa. The present study examines the prevalence and variation of this condition in the Holocene populations of Northern China for the first time. METHODS: In this study, 1145 skulls from various human populations living in Northern China from the Neolithic Age to recent dynasties (5000-300 years BP) were examined. Specifically, cranial measurements and a CT scan were conducted to quantify craniofacial morphology. RESULTS: Fifteen skulls were identified with DZ, revealing an overall prevalence of 1.3% in the collection, while it was determined to be higher in North Asian and Northeast Asian regional groups. In skulls with unilateral DZ, the superior division of the zygoma was generally slender, while the inferior division of the zygoma was more robust. In skulls with bilateral DZ, the maxillae were generally more laterally extended. Moreover, unilateral DZ skulls displayed differences in cortical bone thickness between two sides of the facial skeleton. DISCUSSION: In context, the distribution pattern within these data points toward a greater prevalence of the DZ phenotype in North and Northeast Asian regional groups, suggesting a hypothesis that the DZ trait is more frequent in populations characterized by flat and broad faces. Accordingly, further studies into the DZ condition will deepen our understanding of developments in plasticity, variation, and recent evolution of the human cranium.

Wang, Y., Q. Yan, Y. Zhao, X. Liu, S. Lin, P. Zhang, L. Ma, Y. Lai, X. Bai, C. Liu, C. Wu, J. Q. Feng, D. Chen, H. Cao and G. Xiao (2019). “Focal adhesion proteins Pinch1 and Pinch2 regulate bone homeostasis in mice.” JCI Insight 4(22).

Full text of this article.

Mammalian focal adhesion proteins Pinch1 and Pinch2 regulate integrin activation and cell-extracellular matrix adhesion and migration. Here, we show that deleting Pinch1 in osteocytes and mature osteoblasts using the 10-kb mouse Dmp1-Cre and Pinch2 globally (double KO; dKO) results in severe osteopenia throughout life, while ablating either gene does not cause bone loss, suggesting a functional redundancy of both factors in bone. Pinch deletion in osteocytes and mature osteoblasts generates signals that inhibit osteoblast and bone formation. Pinch-deficient osteocytes and conditioned media from dKO bone slice cultures contain abundant sclerostin protein and potently suppress osteoblast differentiation in primary BM stromal cells (BMSC) and calvarial cultures. Pinch deletion increases adiposity in the BM cavity. Primary dKO BMSC cultures display decreased osteoblastic but enhanced adipogenic, differentiation capacity. Pinch loss decreases expression of integrin beta3, integrin-linked kinase (ILK), and alpha-parvin and increases that of active caspase-3 and -8 in osteocytes. Pinch loss increases osteocyte apoptosis in vitro and in bone. Pinch loss upregulates expression of both Rankl and Opg in the cortical bone and does not increase osteoclast formation and bone resorption. Finally, Pinch ablation exacerbates hindlimb unloading-induced bone loss and impairs active ulna loading-stimulated bone formation. Thus, we establish a critical role of Pinch in control of bone homeostasis.

Swidi, A. J., A. E. Griffin and P. H. Buschang (2019). “Mandibular alignment changes after full-fixed orthodontic treatment: a systematic review and meta-analysis.” Eur J Orthod 41(6): 609-621.

Full text of this article.

BACKGROUND: Although post-treatment mandibular alignment has been extensively investigated, the findings remain controversial. OBJECTIVES: The objective was to assess mandibular alignment changes, as measured by the irregularity index, of patients who underwent full-fixed orthodontic treatment and were followed up at least 1 year after retention. SEARCH METHODS: MEDLINE, EMBASE, and Cochrane library, in addition, the reference lists of included studies, were screened. The search was conducted up to April 2018. SELECTION CRITERIA: The study designs included both interventional and observational studies of orthodontic patients who received either extraction or non-extraction treatment. DATA COLLECTION AND ANALYSIS: The interventional studies were assessed using the Cochrane Collaboration’s risk of bias assessment tool. The quality of the observational studies was evaluated using National Institution of Health quality assessment tools. The first two authors independently applied the eligibility criteria, extracted the data, and assessed the risk of bias. Any conflicts were resolved with consensus discussion with the third author. RESULTS: The search retrieved 11 326 articles, 170 of which were assessed for eligibility. There were 44 studies included in the qualitative assessments and 30 in the meta-analyses. The studies included 1 randomized control trial (RCT) and 43 observational studies. The RCT was judged to have a high risk of bias and all of the observational studies had either fair or poor quality. The meta-analysis was based on studies judged to be of fair quality, including a total of 1859 patients. All meta-analyses were performed using random-effect models. The standardized mean difference between post-treatment and post-retention irregularity was 1.22 (95% CI, 1.04-1.40) and 0.85 (95% CI, 0.63-1.07) after extraction and non-extraction treatments, respectively. There was a substantial heterogeneity for the extraction (I2 = 75.2%) and non-extraction (I2 = 70.1%) studies. The follow-up duration (1-10 versus 10-20 years) explained 33% of the heterogeneity, with longer follow-up studies showing more irregularity. LIMITATIONS: The quality of evidence provided by the studies was low. There was a risk of publication bias, and the search was limited to English language. CONCLUSIONS AND IMPLICATIONS: Post-treatment mandibular irregularity increases are limited. Irregularity increases are slightly greater in patients treated with mandibular premolars extractions, and in patients followed up over longer periods of time. REGISTRATION: The study protocol was not registered.

Song, A., W. Dai, M. J. Jang, L. Medrano, Z. Li, H. Zhao, M. Shao, J. Tan, A. Li, T. Ning, M. M. Miller, B. Armstrong, J. M. Huss, Y. Zhu, Y. Liu, V. Gradinaru, X. Wu, L. Jiang, P. E. Scherer and Q. A. Wang (2019). “Low- and high-thermogenic brown adipocyte subpopulations coexist in murine adipose tissue.” J Clin Invest Nov 25. pii: 129167. [Epub ahead of print].

Full text of this article.

Brown adipose tissue (BAT), as the main site of adaptive thermogenesis, exerts beneficial metabolic effects on obesity and insulin resistance. BAT has been previously assumed to contain a homogeneous population of brown adipocytes. Utilizing multiple mouse models capable of genetically labeling different cellular populations, as well as single-cell RNA sequencing and 3D tissue profiling, we discovered a new brown adipocyte subpopulation with low thermogenic activity coexisting with the classical high-thermogenic brown adipocytes within the BAT. Compared with the high-thermogenic brown adipocytes, these low-thermogenic brown adipocytes had substantially lower Ucp1 and Adipoq expression, larger lipid droplets, and lower mitochondrial content. Functional analyses showed that, unlike the high-thermogenic brown adipocytes, the low-thermogenic brown adipocytes have markedly lower basal mitochondrial respiration, and they are specialized in fatty acid uptake. Upon changes in environmental temperature, the 2 brown adipocyte subpopulations underwent dynamic interconversions. Cold exposure converted low-thermogenic brown adipocytes into high-thermogenic cells. A thermoneutral environment had the opposite effect. The recruitment of high-thermogenic brown adipocytes by cold stimulation is not affected by high fat diet feeding, but it does substantially decline with age. Our results revealed a high degree of functional heterogeneity of brown adipocytes.