Facile fabrication of selegiline-loaded alginate hydrogel for neuroprotection and functional recovery in a rat model of spinal cord injury through localized spinal delivery

Abstract

Objectives: Spinal cord injury (SCI) is a highly disabling and fatal disorder with no effective treatment to date. Selegiline, a selective MAO-B inhibitor, has shown new neuroprotective and neurorescuing effects with various beneficial effects on neuron-associated disorders. These effects have triggered investigations into its impact on different neuron-associated disorders and SCI. Thus, in continuation of the previous studies, this study evaluates the local therapeutic effects of selegiline-loaded alginate hydrogel on SCI by analyzing apoptotic factors, histological factors, and improvements in locomotor function and neuropathic pain.

Materials and methods: Hydrogels were fabricated via cross-linking gelation method and characterized by FT-IR and SEM analysis. Selegiline release from hydrogels was evaluated by UV spectroscopy, and hydrogel biocompatibilities were verified through an MTT assay. Afterward, 36 rats were divided into six groups: sham, negative group, treated with empty hydrogel, and three selegiline-treated groups (2.5, 5, and 10 mg/kg). After 28 days, the locomotor activity, the expression of Bax and Bcl2 (apoptosis index), and GFAP changes in the lesion site were assessed using Basso, Beattie, and Bresnahan (BBB) scale, western blot technique, and immunohistochemical assay, respectively.

Results: Hydrogel tests showed the suitability of hydrogels and sustained selegiline release from them. Rats treated with selegiline-loaded hydrogels showed significant locomotor improvement and reduced apoptosis indices in SCI-induced rats (P≤0.05). Additionally, GFAP immunohistochemistry analysis indicated notable histological improvements.

Conclusion: Findings suggest that selegiline-loaded hydrogels can improve SCI through apoptosis inhibition and neurorescuing effects. Further clinical studies are warranted to validate these findings in human SCI.

Keywords: Alginate hydrogel; Apoptosis; Functional recovery; Selegiline; Spinal cord Injury.

Figure 1

Summary of the process, method, and results of this study

Figure 2

Cell viability of L929 cells after 72 hr of confronting with empty alginate hydrogel and hydrogels containing different doses of selegiline

Figure 3

FT-IR spectra of the Sodium alginate, selegiline, and the final formulation

Figure 4

Two images of the microstructure of selegiline-loaded alginate hydrogel captured by scanning electron microscope (SEM)

Figure 5

Release profile of different hydrogels

Figure 6

Basso, Beattie, and Bresnahan (BBB) scores of different groups throughout the experiment

Figure 7

(a) Shows the duration (in seconds) that different rat groups tolerate heat-induced pain on different days of the experiment, and (b) shows the sensitivity of different rat groups to cold-induced pain on different days of the experiment, measured as a score explained in the methods section

Figure 8

(a) Bax expression in different rat groups, (b) Bcl2 expression in different rat groups, and (c) Bax/Bcl2 ratio (apoptotic index) in different rat groups Groups are labeled below each bar of the charts

Figure 9

Serum levels of TNF-α in different rat groups, measured by ELISA Groups are labeled below each bar of the chart

Figure 10

Immunohistochemical analysis of GFAP expression in the lesion site of the spinal tissue in different rat groups. Darker areas indicate higher GFAP expression Groups are labeled below each image. GFAP: Glial fibrillary acidic protein