Comparative study of autologous stromal vascular fraction and adipose-derived stem cells for erectile function recovery in a rat model of cavernous nerve injury

Abstract

The abilities of intracavernous injection of autologous stromal vascular fraction (SVF) and adipose-derived stem cells (ADSCs) to facilitate recovery of erectile function in a rat model of cavernous nerve (CN) injury were compared. Forty male Sprague-Dawley rats were randomly divided into four groups: sham and control groups (intracavernous injection of phosphate-buffered saline), SVF group (intracavernous injection of SVF), and ADSC group (intracavernous injection of ADSCs). Rats in the latter three groups underwent bilateral CN injury prior to injection. The evaluation of erectile function and histomorphometric studies were performed 4 weeks after injection. The ratio of maximal intracavernous pressure to mean arterial pressure was significantly lower in the control group than in the sham group (0.18 vs. 0.56, p < .001). Intracavernous injection of SVF (0.36, p = .035) significantly improved erectile function compared with that in the control group, whereas the ADSC group (0.35, p = .052) showed marginally significant improvement. The smooth muscle/collagen ratio, smooth muscle content, number of neuronal nitric-oxide synthase-positive nerve fibers, and expression of von Willebrand factor were significantly higher in the SVF and ADSC groups than in the control group. Expression of endothelial nitric-oxide synthase was significantly increased in the SVF group. The increases in the smooth muscle/collagen ratio and von Willebrand factor expression were larger in the SVF group than in the ADSC group. Intracavernous injection of SVF or ADSCs was equally effective in recovering penile erection in a rat model of CN injury.

Keywords: Adipose; Culture; Endothelial cell; Neuropathy; Rat model; Smooth muscle cells.

Figure 1.

Study design. Abbreviations: ADSC, adipose-derived stem cell; CN, cavernous nerve; PBS, phosphate-buffered saline; SVF, stromal vascular fraction.

Figure 2.

Representative flow cytometry histograms. (A): Representative flow cytometry histograms of stromal vascular fraction. (B): Representative flow cytometry histograms of adipose-derived stem cells (ADSCs). (C): Appearance of ADSCs after 3 weeks of induction of adipogenic, osteogenic, and chondrogenic differentiation. Magnification, ×100 in adipogenesis and osteogenesis and ×400 in chondrogenesis. Abbreviations: APC, allophycocyanin; FITC, fluorescein isothiocyanate; PE, phycoerythrin.

Figure 3.

Intracavernous pressure/mean arterial pressure ratios. (A): Maximal intracavernous pressure/mean arterial pressure ratios. (B): Total intracavernous pressure/mean arterial pressure ratios. NS indicates p > .05 between the SVF and ADSC groups. ∗, p < .05; ∗∗∗, p < .001 compared with the control group. Abbreviations: ADSC, adipose-derived stem cell; ICP, intracavernous pressure; MAP, mean arterial pressure; NS, not significant; sec, second; SVF, stromal vascular fraction.

Figure 4.

Smooth muscle/collagen ratio and smooth muscle content. (A): Graph showing the smooth muscle/collagen ratio obtained by quantitative image analysis of Masson’s trichrome staining data (top). Bottom: Representative photomicrographs of corpus cavernosum tissue stained with Masson’s trichrome stain. Original magnification, ×20. (B): Graph showing smooth muscle content as the ratio of the area stained positive for ASMA to the total area within the tunica albuginea (top). Bottom: Representative photomicrographs of smooth muscle content in the corpus cavernosum tissue. Original magnification, ×200. NS indicates p > .05 between the SVF and ADSC groups. ∗∗, p < .01; ∗∗∗, p < .001 compared with the control group; ††, p < .01 between the SVF and ADSC groups. Abbreviations: ADSC, adipose-derived stem cell; ASMA, α smooth muscle actin; NS, not significant; SVF, stromal vascular fraction.

Figure 5.

Neuronal nitric-oxide synthase. Top: Graph showing cavernous nerve function as the ratio of the area stained positive for neuronal nitric-oxide synthase to the total area within dorsal nerves. Bottom: Representative photomicrographs of neuronal nitric-oxide synthase-positive area in the dorsal nerve. Original magnification, ×400. NS indicates p > .05 between the SVF and ADSC groups. ∗∗∗, p < .001 compared with the control group. Abbreviations: ADSC, adipose-derived stem cell; nNOS, neuronal nitric-oxide synthase; NS, not significant; SVF, stromal vascular fraction.

Figure 6.

Endothelial cell content. (A): Graph showing endothelial cell content as ratio of the area stained positive for endothelial nitric-oxide synthase to the total area within the tunica albuginea (top). Bottom: Representative photomicrographs of endothelial cell content in the corpus cavernosum tissue. Original magnification, ×400. (B): Graph showing endothelial cell content as the ratio of the area stained positive for von Willebrand factor to the total area within the tunica albuginea (top). Bottom: Representative photomicrographs of endothelial cell content in the corpus cavernosum tissue. Original magnification, ×20. NS indicates p > .05 compared with the control group, or between the SVF and ADSC groups. ∗∗, p < .01; ∗∗∗, p < .001 compared with the control group; †, p < .05 between the SVF and ADSC groups. Abbreviations: ADSC, adipose-derived stem cell; eNOS, endothelial nitric-oxide synthase; NS, not significant; SVF, stromal vascular fraction; vWF, von Willebrand factor.