Microvascular autologous submandibular gland transplantation in severe cases of keratoconjunctivitis sicca

Salivary Gland Transplantation as a Promising Approach for Tear Film Restoration in Severe Dry Eye Disease

With increased awareness of dry eye disease (DED), a multitude of therapeutic options have become available. Nevertheless, the treatment of severe DED remains difficult. In a patient whose DED is related to the loss of lacrimal function without severe destruction of the salivary glands, autologous transplantation of the latter as functioning exocrine tissue to rebuild a stable tear film is an attractive idea. All three major and minor salivary glands have been used for such transplantation. Due to the complications associated with and unfavorable prognosis of parotid duct and sublingual gland transplantation, surgeons now prefer to use the submandibular gland (SMG) for such procedures. The transplantation of the SMG not only has a high survival rate, but also improves dry eye symptoms and signs for more than 20 years post-surgery. The regulation of the secretion of the transplanted SMG is critical because the denervated SMG changes its mechanism of secretion. Innovative procedures have been developed to stimulate secretion in order to prevent the obstruction of the Wharton's duct and to decrease secretion when postoperative "epiphora" occurs. Among the minor salivary glands, the transplantation of the labial salivary glands is the most successful in the long-term. The measurement of the flow rates of minor salivary glands and donor-site selection are critical steps before surgery.

Surgical Procedures in the Treatment of Dry Eye Disease

Dry eye disease (DED) is a multifactorial disease affecting 5% to 50% in different populations. The most severe cases of DED are often caused by aqueous deficient dry eye disease (ADDE) due to lacrimal gland (LG) hypofunction. Many patients with severe ADDE do not experience adequate symptom relief from topical treatment, severely reducing their quality of life. The focus of this review is to describe the surgical interventions presently being used or investigated when topical treatment with eye drops is insufficient. The conventional surgical approach is to proceed to punctal occlusion or partial or total tarsorrhaphy. However, novel surgical procedures have been reported to have higher efficacy and patient satisfaction than conventional treatments. These procedures include amniotic membrane transplantation, transposition or transplantation of the salivary glands, and cell-based injections into the LG, each with strengths and weaknesses. Further development of these treatment modalities might prove pivotal in treating dry eye patients in the future.

Characteristics and management of vascular compromise after an organ transplantation surgery of the head and neck region: Analysis of 220 submandibular glands with autologous transplantation

BACKGROUND

Microvascular submandibular gland transplantation (SMGT) for severe dry eye disease (DED) has rarely been reported in the literature. The aim of this study was to report a case series of SMGT with the special focus on monitoring and management of postoperative vascular compromise.

METHODS

Using a retrospective single-cohort study design, the investigators enrolled a sample of DED patients undergoing SMGT in a Chinese university hospital during 1999 and 2021. The main outcomes were baseline and surgical data, post-operative manifestations, and surgical results. Descriptive, uni- and bivariate statistics were computed with the significant P < 0.05.

RESULTS

During the study period, 220 DED patients (55.9% female) with a mean age of 32.66±14.47 years underwent SMGT. Vascular compromises occurred in 27 grafted glands (12.3%; 22 venous compromises and 5 arterial compromises) at a median of 27 h(range, 3.3 to 288 h) after surgery. Harden texture and swelling of the covering skin flap of the donor indicated venous compromises, while some specific sign was absent for arterial compromise. The accompanying vein of the facial artery (FAV) as a donor's vein was associated with less vascular compromise compared to the anterior facial vein (AFV). Timely reexploration was performed in 25 glands (92.6%), with a salvaged rate of 48%, and more venous compromises were salvaged compared to artery compromises (54.6% vs. 0%, P = 0.047). Temporary hypersecretion on postoperative 2-5 days was noticed in the grafted glands with no or salvaged vascular compromise (Schirmer's test, 35 mm/5 min and 37 mm/5 min, respectively, P = 0.749), while they were absent for the 15 surgically failed grands (Schirmer's test 0 mm/5 min, P<0.001).

CONCLUSIONS

Vascular compromise appears to be a common complication of SMGT. Postoperative hypersecretion of the grafted glands may indicate good circulation, and the use of FAV as the donor's vein could help to decrease the risk of vascular compromise.

Novel Local Chimeric Flap Based on Tunnelized Facial Artery Myomucosal Island Flap and Submandibular Gland Flap for Reconstructions After Oral Squamous Cell Carcinoma Surgery

The reconstruction of oral tongue and floor of mouth defects after resections of squamous cell carcinoma is a challenging task in reconstructive surgery aiming for appropriate restoration of oral function and quality of life improvement. In this study, the authors introduce the innovative reconstruction technique of medium-sized defects consisting of tunnelized facial artery myomucosal island flap and submandibular gland flap as the local chimeric flap pedicled on facial vessels. A retrospective case series evaluation of 4 patients suffering from oral cavity cancer (stages III and IVa), who underwent transoral tumor excision with neck dissection and immediate reconstruction in the time period September 2020 to July 2021, was conducted. No flap losses or flap-related complications were identified. No recurrences occurred during the follow-up at 11.0±4.5 months (range: 6-16 mo, median=11 mo). Tunnelized facial artery myomucosal island flap and submandibular gland flap local chimeric flap expands the reconstruction options of medium-sized defects after ablative oral cancer surgery in carefully selected patients primarily not suitable for free flap reconstructions.

[Role and mechanism of muscarinic acetylcholine receptor in the regulation of submandibular gland secretion]

Muscarinic acetylcholine receptors (mAChRs), including M1-M5 subtypes, are classic receptors in regulating water, ion, and solute transport in salivary gland. Our work focuses on the studies on the expression pattern and function of mAChR in the submandibular gland (SMG), and the underlying mechanism involved in the mAChR-regulated secretion, together with the effect of parasympathectomy on the salivary secretion. Microvascular autotransplantation of SMG into the temporal fossa provides a continuous and endogenous source of fluids, and is currently an effective method for treating severe keratoconjunctivitis sicca. By using RT-PCR, Western blotting, and immunofluorescence, our data demonstrated that the expression of M1 and M3 subtypes were decreased in latent period in rabbit SMG autotransplantation model, whereas carbachol stimulation promoted the salivary secretion, as well as M1 and M3 expressions. By contrast, mAChRs were hypersensitive in epiphora SMGs, whereas atropine gel and botulinum toxin A application significantly inhibited the hypersecretion in both animal models and patients. Furthermore, the possible intracellular signal molecules involved in the mAChR-modulated salivary secretion were explored. Activation of mAChR upregulated the expression of aquaporin 5 (AQP5), the main transporter that mediated water secretion through transcellular pathway, and led to AQP5 trafficking from lipid rafts to non-lipid microdomain. Extracellular signal-regulated kinase 1/2 (ERK1/2) was involved in the mAChR-regulated AQP5 content. mAChR activation also modulated the expression, distribution, and function of tight junction proteins, and increased paracellular permeability. ERK1/2/β-arrestin2/clathrin/ubiquitin signaling pathway was responsible for the mAChR-regulated downregulation of tight junction molecule claudin-4. Cytoskeleton filamentous actin (F-actin) was also involved in the distribution and barrier function of epithelial tight junctions. Besides, endothelial tight junctions were opened by mAChR agonist-evoked salivation in the mice. Furthermore, parasympathetic denervation increased resting salivary secretion in the long terminrats and minipigs. Taken together, our work demonstrated that mAChR regulated saliva secretion via transcellular and paracellular pathways in SMG epithelium as well as tight junction opening in SMG endothelium. Modulation of mAChR might be a promising strategy to ameliorate SMG dysfunction.

Vascularization of the maxilla by a branch of the submandibular artery

Vascular variations are common. A cervicofacial anatomical dissection carried out at the anatomy laboratory allowed us to document a rare vascular variation. The facial artery did not give rise to branches that led to the submandibular gland; an artery arising directly from the external carotid artery vascularized the submandibular gland and gave rise to the ascending palatine artery that led to the maxilla. We did not find cases in the literature where an artery emanated directly from the external carotid artery to vascularize the submandibular gland and that gave rise to an ascending palatine artery leading to the maxilla. Knowledge of the variations of the arterial vascularisation of the submandibular gland is important for submandibulectomies and transfers of the gland.

Preganglionic Parasympathetic Denervation Rabbit Model for Innervation Studies

PURPOSE

Tear secretion from the main lacrimal gland (LG) is mainly regulated by parasympathetic nerves. We performed several innervation studies to investigate lacrimation.

METHODS

In male rabbits, we performed a retrograde dye-tracing study of LG innervation, evaluated preganglionic parasympathetic denervation, and administered glial cell-derived neurotrophic factor (GDNF) in the surgical area after parasympathetic denervation.

RESULTS

Accumulation of fluorescent dye was observed in the pterygopalatine ganglion cells on the same side as the dye injection into the main LG. Fewer stained cells were observed in the cervical and trigeminal ganglia. After parasympathetic denervation surgery, tear secretion was decreased, and fluorescein and rose bengal staining scores were increased at day 1 after surgery and remained increased for 3 months on the denervated side only. Most of the effects in rabbits with parasympathetic denervation were not recovered by administration of GDNF.

CONCLUSIONS

The main LG is primarily innervated by parasympathetic nerves to stimulate tear secretion. After preganglionic parasympathetic denervation, lacrimation was decreased, resulting in dry eyes, and this was maintained for at least 3 months. Administration of GDNF only minimally altered the effects of denervation.

Autonomic reinnervation and functional regeneration in autologous transplanted submandibular glands in patients with severe keratoconjunctivitis sicca

Autologous submandibular gland (SMG) transplantation has been proved to ameliorate the discomforts in patients with severe keratoconjunctivitis sicca. The transplanted glands underwent a hypofunctional period and then restored secretion spontaneously. This study aims to investigate whether autonomic nerves reinnervate the grafts and contribute to the functional recovery, and further determine the origin of these nerves. Parts of the transplanted SMGs were collected from the epiphora patients, and a rabbit SMG transplantation model was established to fulfill the serial observation on the transplanted glands with time. The results showed that autonomic nerves distributed in the transplanted SMGs and parasympathetic ganglionic cells were observed in the stroma of the glands. Low-dense and unevenly distributed cholinergic axons, severe acinar atrophy and fibrosis were visible in the patients’ glands 4–6 months post-transplantation, whereas the cholinergic axon density and acinar area were increased with time. The acinar area or the secretory flow rate of the transplanted glands was statistically correlated with the cholinergic axon density in the rabbit model, respectively. Meanwhile, large cholinergic nerve trunks were found to locate in the temporal fascia lower to the gland, and sympathetic plexus concomitant with the arteries was observed both in the adjacent fascia and in the stroma of the glands. In summary, the transplanted SMGs are reinnervated by autonomic nerves and the cholinergic nerves play a role in the morphological and functional restoration of the glands. Moreover, these autonomic nerves might originate from the auriculotemporal nerve and the sympathetic plexus around the supplying arteries.

Regenerated nerves play a role in restoring the function of transplanted submandibular glands (SMGs) in treating dry eye syndrome. Dry eye syndrome, or keratoconjunctivitis sicca (KCS), is a leading cause of patients visiting ophthalmologists, and one effective treatment in severe cases is transplanting SMGs (to the temporal area). Autonomic nerves have an important function in maintaining the secretory function of salivary glands, and a team headed by Yan Zhang and Guang-Yan Yu at Peking University, China investigated whether those nerves underwent reinnervation (restoration of nerve control) with transplanted SMGs in KCS patients and in a rabbit model. The authors found that in both the patients and rabbit model, the transplanted SMGs were reinnervated and the regenerated nerves played a role in restoring the glands’ function. The findings offer new insights into managing SMG transplantation.

Botulinum Toxin Conjugated With Silk Fibroin and 4-Hexylresorcinol

PURPOSE

The objective of this study was to evaluate whether silk fibroin (SF) incorporated into 4-hexylresorcinol (4HR) could increase botulinum toxin-A (BTX-A) activity.

MATERIAL AND METHODS

In total, 30 rats were used for this study. The animals were divided into 6 groups according to the injected materials (SA: saline only; SF; 4HR; B2: 2 units of BTX-A; B2 + SF + 4HR: combination of B2, SF, and 4HR; B5: 5 units of BTX-A). Serial sonography was used for the evaluation of muscle thickness after injection. Immunohistochemical staining was used for the evaluation of myosin type II (myo2) and Bcl-2 protein expression.

RESULTS

The relative thickness of the masseter muscle in B2 group was 66.14% ± 4.55% to the preinjection level; in B2 + SF + 4HR group was 54.59% ± 4.83%, and in B5 group was 56.19% ± 8.28%. Any BTX-injected group showed significantly lower value of the relative muscle thickness compared to SA, SF, or 4HR group (P < 0.001 for all). The difference of relative muscle thickness between B2 group and B2 + SF + 4HR group was statistically significant (P < 0.001). The intensity of myo2 immunostaining in B5, B2, and B2 + SF + 4HR group was significantly higher than those in the other groups (P < 0.05).

CONCLUSIONS

When 2 units of BTX was incorporated to SF and 4HR, combination formula showed similar activity to those of 5 units of BTX.

Decreased interaction between ZO-1 and occludin is involved in alteration of tight junctions in transplanted epiphora submandibular glands

Tight junctions (TJs) in salivary epithelium play an important role in regulating saliva secretion. Autologous transplantation of submandibular glands (SMGs) is an effective method to treat severe dry eye syndrome. However, epiphora occurs in some patients 6 months after transplantation. We previously found that the acinar TJs are enlarged in rabbit SMGs after long-term transplantation, but the exact TJ components involved in the epiphora are still unknown. Here, we found that the mRNA and protein expression of ZO-1 and occludin were increased in the transplanted SMGs obtained from epiphora patients, while other TJs were unchanged. The intensity of ZO-1 and occludin at the apicolateral membranes as well as occludin in the cytoplasm were increased in epiphora SMGs, but the interaction between ZO-1 and occludin was decreased as evidenced by both co-immunoprecipitation assay and co-immunofluorescence staining. Mechanically, the expression of casein kinase 2α (CK2α) and CK2β, which was reported to affect occludin modification and the interaction of occludin with ZO-1 in previous literatures, were increased in epiphora glands. Moreover, activation of muscarinic acetylcholine receptor (mAChR) by carbachol directly decreased the interaction between ZO-1 and occludin and increased the acinar TJ width in the freshly isolated human SMGs, whereas these effects were abolished by pretreatment with CK2 inhibitor. Taken together, our findings suggest that decreased interaction between ZO-1 and occludin might contribute to the epiphora occurred in the transplanted SMGs, and mAChR together with the intracellular molecule CK2 might be responsible for the alteration of TJs in epiphora glands.

Muscarinic acetylcholine receptor-mediated tight junction opening is involved in epiphora in late phase of submandibular gland transplantation

Submandibular gland (SMG) autotransplantation is an effective therapy for treating severe dry eye syndrome. However, epiphora occurs in more than 40% of patients 6 months after operation. We previously found that muscarinic acetylcholine receptor (mAChR) plays a crucial role in regulating SMG secretion partially through the modulation on tight junction (TJ)-based paracellular pathway. Therefore, the present study aimed to investigate the possible involvement of mAChR and TJ in a rabbit long-term model of SMG transplantation. We found that SMG secretion was significantly increased on postoperative days 90 and 180, which imitated epiphora observed in the patients with SMG transplantation. Although the mRNA expression and fluorescence intensity of M1 and M3 mAChR subtypes were reversed to control levels on postoperative days 30, 90, and 180, the content of β-arrestin2, but not β-arrestin1, was gradually decreased after transplantation, which suggests that mAChR may be hypersensitive in late phase of SMG transplantation. The width of acinar TJs was enlarged and fluorescence intensity of F-actin in peri-apicolateral membranes were remarkably increased on postoperative days 90 and 180. Topical treatment with atropine gel significantly reduced SMG secretion, TJ width, as well as F-actin intensity in peri-apicolateral membranes on postoperative days 180. Moreover, in a perfused rabbit SMG, carbachol increased salivary secretion, enlarged TJ width, and induced F-actin rearrangement, whereas these responses were inhibited by atropine pretreatment. Taken together, our findings suggest that the hypersensitive mAChR may contribute to epiphora in late phase of SMG transplantation through modulating TJ-based paracellular permeability.

Free thyroid transfer: Short-term results of a novel procedure to prevent post-radiation hypothyroidism

Background

The incidence of radiation‐induced hypothyroidism (RIH) in patients with head and neck cancer is >50%. The purpose of this study was to assess the long‐term efficacy of free thyroid transfer (FTT) for prevention of RIH in patients with head and neck cancer.

Methods

Hemithyroid dissection was completed in 10 patients with advanced head and neck cancer undergoing ablation, radial forearm free flap (RFFF) reconstruction, and postoperative radiotherapy (RT). The hemithyroid was anastomosed to the donor site vessels in the forearm. Thyroid laboratory testing and technetium (Tc) scans were performed 6 weeks and 12 months postoperatively to establish functional integrity.

Results

FTT was successfully performed in 9 of 10 recruited patients. Postoperative Tc scans demonstrated strong Tc uptake in the forearm donor site at 6 weeks and 12 months in all patients who underwent transplantations.

Conclusion

FTT is feasible with maintenance of function, and may represent a novel strategy for prevention of RIH. © 2016 Elsevier Head & Neck Published by Wiley Periodicals, Inc. Head Neck39: 1234–1238, 2017

An Experimental Study on Botulinum Toxin Type A for the Treatment of Excessive Secretion after Submandibular Gland Transplantation in Rabbits

Objectives. To investigate whether botulinum toxin type A (BTXA) could control excessive secretion after submandibular gland (SMG) transplantation in rabbits and its possible mechanisms. Methods. A new SMG transplantation model was established in rabbit. 30 successfully constructed models were randomly assigned to five groups including control group and four experimental groups. Secretion outputs were used to analyze the effect of BTXA injection on excessive secretion. Hematoxylin and eosin (HE) staining, transmission electron microscopy (TEM), Western blot, and immunofluorescence were performed to analyze its possible mechanisms. Results. After BTXA injection, a significant decrease of excessive secretion after SMG transplantation was found in 2 and 4 weeks groups, but no significant effect on 12 and 24 weeks groups. HE and TEM results showed that BTXA led to morphological and ultrastructural changes of acinar cells of transplanted SMG. Western blot results suggested that BTXA decreased the aquaporin-5 (AQP5) protein expression after BTXA injection for 2 and 4 weeks. Immunofluorescence results showed that AQP5 protein was mainly expressed in the cytoplasm after BTXA injection for 2 and 4 weeks, which might indicate that BTXA promoted AQP5 expression from the cell membrane to cytoplasm. Conclusion. BTXA could effectively control excessive secretion after SMG transplantation in rabbits.

S100 and p65 expression are increased in the masseter muscle after botulinum toxin-A injection

Background

The purpose of this study was to compare the expression levels of p65 and S100 in the rat masseter muscle after the injection of different concentrations of botulinum toxin-A (BTX-A).

Methods

We injected either 5 or 10 U of BTX-A into both masseter muscle of rats. As a control group, the same volume of saline was injected. After 14 days, the animals were sacrificed. Subsequently, a biopsy and immunohistochemical staining of the samples were performed using a p65 or S100 antibody.

Results

The cross-sectional area of each myofibril was significantly reduced by BTX-A injection (P < 0.001). The expression of p65 and S100 increased significantly with increasing concentrations of BTX-A (P < 0.001).

Conclusions

The injection of BTX-A into the masseter muscle induced muscle atrophy. Subsequently, p65 and S100 expression in myoblasts were increased for the protection of muscle cells.