A unique form of collective epithelial migration is crucial for tissue fusion in the secondary palate and can overcome loss of epithelial apoptosis

Tissue fusion is an oft-employed process in morphogenesis which often requires the removal of the epithelia intervening multiple distinct primordia to form one continuous structure. In the mammalian secondary palate, a midline epithelial seam (MES) forms between two palatal shelves and must be removed to allow mesenchymal confluence. Abundant apoptosis and cell extrusion in this epithelial seam support their importance in its removal. However, by genetically disrupting the intrinsic apoptotic regulators BAX and BAK within the MES, we find a complete loss of cell death and cell extrusion, but successful removal of the MES, indicating that developmental compensation enables fusion. Novel static and live imaging approaches reveal that the MES is removed through a unique form of collective epithelial cell migration in which epithelial trails and islands stream through the mesenchyme to reach the oral and nasal epithelial surfaces. These epithelial trails and islands begin to express periderm markers while retaining expression of the basal epithelial marker ΔNp63, suggesting their migration to the oral and nasal surface is concomitant with their differentiation to an epithelial intermediate. Live imaging reveals anisotropic actomyosin contractility within epithelial trails that drives their peristaltic movement, and genetic loss of non-muscle myosin IIA-mediated actomyosin contractility results in dispersion of epithelial collectives and dramatic failure of normal MES migration. These findings demonstrate redundancy between cellular mechanisms of morphogenesis and reveal a crucial role for a unique form of collective epithelial migration during tissue fusion.

Orofacial clefts

Orofacial clefting is an umbrella term for common human malformations. The most common of these malformations result from failure of tissue fusion events during formation of the embryonic face. Single-gene causes of orofacial clefting are rare and often associated with other clinical features in the form of a recognizable syndromal diagnosis. Isolated orofacial clefting is most likely caused by gene–environment interactions but the exact nature of these interactions is not yet known

Outcomes of treatment of haemorrhoidal disease with KLS Martin maXium marClamp® CUT IQ thermal tissue fusion instrument based on offset electrode technology compared to the Milligan-Morgan procedure with bipolar coagulation for the excision of grade III and IV haemorrhoids

Introduction. The study compared the effects of surgical treatment of grade III and IV haemorrhoids achieved with a conventional operative technique and by using a thermal tissue fusion instrument based on offset electrode technology. A total of 60 patients with grade III and IV haemorrhoids were operated on in the Department of General and Oncologic Surgery, Municipal Hospital in Siemianowice Śląskie, and in the On-Clinic Medical Centre in Chorzów, between October 2011 and September 2015. Aim. The aim of the study was to compare the outcomes of treatment of haemorrhoidal disease using KLS Martin maXium marClamp® CUT IQ thermal tissue fusion instrument based on offset electrode technology and the Milligan-Morgan surgical procedure with bipolar coagulation for the excision of grade III and IV haemorrhoids. Material and methods. The patients were divided into two groups: Group 1 – patients operated on using KLS Martin maXium marClamp® CUT IQ thermal tissue fusion instrument based on offset electrode technology. Group 2 – patients operated on using the conventional Milligan-Morgan technique with electrocoagulation. The evaluated parameters included the length of hospital stay after surgery, duration of the surgical procedure, level of pain on the postoperative days 1 and 2 rated on a 10-point VAS scale, and postoperative wound healing time. Results. A reduction in postoperative pain, shorter procedure duration and hospital stay, and more rapid postoperative wound healing were observed in Group 1 compared to Group 2. Conclusions. In our study material, the application of a thermal tissue fusion instrument using offset electrode technology in surgeries to remove grade III and IV haemorrhoids, compared to the conventional Milligan-Morgan procedure with electrocoagulation, brought the following results: – less postoperative pain, – shorter duration of surgical procedure, – reduced length of hospital stay, – faster healing of postoperative wound.

In-frame deletion of SPECC1L microtubule binding domain results in embryonic tissue movement and fusion defects

Embryonic morphogenesis of the neural tube, palate, ventral body wall and optic fissure require precise sequence of tissue movement and fusion, which if incomplete, leads to anencephaly/exencephaly, cleft palate, omphalocele and coloboma, respectively. These are genetically heterogeneous birth defects, so there is a continued need to identify etiologic genes. Patients with autosomal dominant SPECC1L mutations show syndromic malformations, including hypertelorism, cleft palate and omphalocele. These SPECC1L mutations cluster in the second coiled-coil domain (CCD2), which facilitates association with microtubules. To study SPECC1L function in mice, we first generated a null allele (Specc1lΔEx4) lacking the entire SPECC1L protein. Homozygous mutants for these truncations died perinatally without cleft palate or exencephaly. Given the clustering of human mutations in CCD2, we hypothesized that targeted perturbation of CCD2 may be required. Indeed, homozygotes for in-frame deletions involving CCD2 (Specc1lΔCCD2) resulted in ~50% exencephaly and ~50% cleft palate. Interestingly, these two phenotypes are never observed in the same embryo. Examination of embryos with and without exencephaly revealed that the oral cavity was narrower in exencephalic embryos, which allowed palatal shelves to elevate despite their defect. In contrast to an evenly distributed subcellular expression pattern, mutant SPECC1L-ΔCCD2 protein showed abnormal subcellular localization, decreased overlap with microtubules, increased actin bundles, and dislocated non-muscle myosin II to the cell cortex. Thus, we show that perturbations of CCD2 in the context of full SPECC1L protein affects tissue fusion dynamics, indicating that human SPECC1L CCD2 mutations are gain-of-function. Improper SPECC1L subcellular localization appears to disrupt connections between actomyosin and microtubule networks, which in turn may affect cell alignment and coordinate movement during tissue morphogenesis.

Mesenchymal Stem Cells Combined with Tissue Fusion Technology Promoted Wound Healing in Porcine Bowel Anastomosis

Objective. To evaluate the possible biological effect of allogenic mesenchymal stem cells (MSCs) combined with tissue fusion technology on the anastomosis. Methods. Sixteen pigs were divided into a 7 d group and 14 d group, each of which was further subdivided into an MSC-treated group and a control group. Five anastomoses per animal were established using LigaSure ForceTriad (Covidien, MA, USA), a tissue sealing system. Cell migration and tissue-specific differentiation potency, in addition to potential cytokine and genetic changes, were investigated. Results. There were no significant between-group differences in postoperative complications and anastomosis burst pressure. The number of proliferating cell nuclear antigen- (PCNA-) positive cells was significantly higher in the MSC-treated group as compared with that in the control group (P=0.021). Labeled MSCs were found in the mucosal layer, villus, and lamina propria, as well as in the lamina muscularis mucosae, where they exhibited characteristics of smooth muscle cells. Conclusions. Grafted MSCs significantly promoted epithelial and connective cell proliferation and maintained their cell migration capacity and differentiation potential in the fused anastomotic tissues, without causing severe postoperative complications.