Regeneration of nerve fibres in the maxillary sinus mucosa after experimental surgery. An immunocytochemical double-labelling study in the rabbit

Nerve fibre regeneration in the maxillary sinus mucosa after surgery was studied in 10 New Zealand White rabbits. Four and 8 weeks following unilateral removal of the mucosa, the animals were fixed by perfusion, and the nose-sinus complexes were frozen and cut on a cryostat equipped with a tungsten-hardened knife. A double-labelling immunocytochemical procedure was developed with commercially available antibodies to protein gene product (PGP) 9.5 and tyrosine hydroxylase (TH) or neuropeptide Y (NPY). The study revealed that the maxillary sinus mucosa in rabbit is reinnervated at 4 and 8 weeks postoperatively. Furthermore, the regenerated lamina propria showed increased TH immunoreactivity (TH-IR) and NPY-IR, compared with the contralateral, non-operated side. Many of the fibres were seen in close proximity to newly formed vessels. These findings add further to the explanation of the altered vasoreactivity found earlier in regenerated sinus mucosa 1 month after surgery. This study also showed that demineralization of the nose-sinus complexes is not necessary if a hardened metal knife is used.

Microvasculature, blood flow, and vasoreactivity in rabbit sinus mucosa after surgery

OBJECTIVES

To study the circulatory integrity of the sinus mucosa following surgery, the vascular anatomy, blood flow, and vasoconstrictor response of the regenerated microcirculatory network were analyzed.

STUDY DESIGN

Forty-six New Zealand White rabbits were operated on unilaterally with either a modified radical operation (MRO) or middle meatal antrostomy (MMA), using the nonoperated sinus for control purposes. After surgery, the animals were left to heal for 1 month.

METHODS

Vascular casts were prepared with a low-viscosity methyl methacrylate resin and studied by scanning electron microscopy. Blood flow was measured by means of radiolabeled microspheres (tin 113 [113Sn]). The vasoconstrictor response to oxymetazoline at increasing concentrations was measured with laser Doppler flowmetry.

RESULTS

The number of vessels increased significantly in the regenerated mucosa. The vascular casts displayed a rich microcirculation with local signs of angiogenesis. However, there was no difference in blood flow between the operated cavities and their control sides. Following MRO the regenerated mucosa was more sensitive to the vasoconstrictor effect of oxymetazoline, compared with the control side. This difference was not evident in the MMA-operated sinuses.

CONCLUSIONS

In this model, surgery does not seriously interfere with the sinus blood flow, although the regenerated mucosa did display an altered vasoreactivity. These findings should be considered in relation to the effects of surgery intended to limit local inflammation and to ensure the ventilation of the sinuses.

Effects of surgery on mucosal pathologic changes following experimental sinusitis in rabbit

In the present investigation, the regenerative capacity of the infected maxillary sinus mucosa following surgical procedures was studied in a rabbit model. Sinusitis was induced by occluding the ostium with and without the addition of Staphylococcus aureus or Bacteroides fragilis, or by provoking a prolonged bacterial infection with both pathogens. The surgical procedures performed were 1) widening of the natural sinus ostium (middle meatal antrostomy; MMA) and 2) removal of sinus mucosa without ostial interference (modified radical operation; MRO). The histologic features of the entire nose-sinus complex were studied, graded semiquantitatively, and compared with findings in untreated sinusitis, or after surgery only. Whereas MMA and MRO both led to a decrease of the inflammatory features of the sinus mucosa in induced sinusitis, persistent local histopathology was observed in the ostial region following MMA surgery. This indicates the importance of local pathologic changes resulting from interactions of bacterial colonization, inflammation, and surgery in chronic sinusitis.

Endoscopic and Caldwell-Luc approaches in chronic maxillary sinusitis: a comparative histopathologic study on preoperative and postoperative mucosal morphology

The aim of the present investigation was to study the histopathologic mucosal changes occurring in chronic maxillary sinusitis both preoperative and postoperative to functional endoscopic sinus (FES) surgery and the Caldwell-Luc (C-L) operation. Correlations were also sought between the histopathologic parameters and endoscopic findings, as well as patient symptoms. Sixty sinuses with the FES surgery and 55 sinuses with the C-L procedure were studied. The histologic parameters were graded semiquantitatively and compared preoperatively and postoperatively. The C-L operation reduced almost all parameters, whereas after the FES operation only edema and inflammatory cells were significantly reduced. Fibrosis increased postoperatively with both methods. The number of inflammatory cells was closely correlated to a thickened antral mucosa and to purulent secretion. No valid correlations were found when comparing histology with patient symptoms. All in all, histologic considerations suggest that asthmatic patients with severe sinonasal polyposis might benefit from the C-L procedure.

Regeneration of maxillary sinus mucosa following surgical removal. Experimental study in rabbits

A rapid regeneration of the epithelium takes place in the maxillary sinus in rabbits after experimental operative removal of the mucosa. Two weeks postoperatively the previously denuded areas have reepithelialized. The subepithelial glands, however, do not seem to regenerate. The normal sinus mucosa contains numerous serous glands in the lamina propria, but in the regenerated mucosa these glands are replaced by dense connective tissue. Atypical glands and polyp formations are sometimes encountered, but goblet cells are sparse. Furthermore, the sinus cavity on the operated side is reduced in size compared with the nonoperated side because of fibrosis and periosteal reactions including bone degradation and neogenesis. This study indicates that although the mucosa is reepithelialized within 2 weeks, the regeneration of the lamina propria is incomplete, and reactive cellular processes such as bone remodeling, fibroblast proliferation, and formation of polyps and "atypical glands" are characteristic of regenerating mucosa.

Cellular regeneration and recovery of the maxillary sinus mucosa. An experimental study in rabbits

Unilateral maxillary sinusitis was induced in 30 New Zealand White rabbits with Streptococcus pneumoniae or Bacteroides fragilis. In another group of 15 rabbits without infection, the sinus mucosa was surgically removed in defined areas. In both series, the sinuses were serially sectioned for histological analysis of the cellular regenerative capacity. In maxillary sinusitis induced by Bacteroides fragilis, an inflammatory and also reparative process involving all mucosal layers including the underlying periosteum was seen. The more superficial trauma as found in pneumococcal sinusitis eventually led to restitution ad integrum. Following surgical removal, the denuded sinus-lining was reepithelized by a flattened ciliated epithelium on a lamina propria displaying fibrosis and lacking serous glands. The restoration of the rabbit maxillary sinus mucosa after surgical trauma thus leads to structural abnormalities of the epithelium as well as the lamina propria, and these changes are likely to interfere with the normal function of the sinus mucosa.