Table 1.

List of studies reporting beneficial effects of transplanting mesenchymal cells via different routes to restore spermatogenesis after chemoablation

Study	Highlights
Vahdati et al. [66]	The study evaluated the regenerative effect of bone marrow derived stem cells (CD29+/CD73+/CD45-) on spermatogenesis of busulphan treated infertile hamster. Following 60 days after efferent duct injection of bone marrow stem cells, histological evaluation of testis showed presence ofspermatogonia, primary spermatocytes, spermatids and sperm in seminiferous tubules compared to negative controls.
Maghen et al. [67]	The study evaluated the role of human umbilical cord blood MSCs in regeneration of testicular niche. In addition to supporting the expression of murine germ cells and putative SSCs in vitro, the in vivo potential was evaluated by transplantation of MSCs into azoospermic mouse model. Transplanted cells majorly localized into interstitial space. Following transplantation, partial reconstruction of seminiferous tubule architecture was observed.
Abd Allah et al. [68]	The study evaluated the effect of transplantation of human cord blood derived mesenchymal cells (CD34-) and hematopoietic stem cells (CD34+) by local injection into testis of busulphan treated recipient mice. Testicular histoarchitecture was found normal and sperm were present in lumen in mesenchymal cells transplanted group compared to the HSC transplanted group. l
Ghasemzadeh-Hasankolaei et al. [69]	The study evaluated the fate of autologous bone marrow MSCs (isolated and labelled with PKH26) after transplantation into testes of busulphan treated Wistar rats. Transplanted bone marrow MSCs were studied at 3 time points (4,6 and 8 weeks) after transplantationand were found to survive post transplantation as studied by PKH26 expression. Some transplanted cells homed at germinal epithelium and expressed germ cell markers DAZLand STELLAindicating differentiation to spermatogonia.
Rahmanifar et al. [70]	The study aimed to evaluate the seminiferous tubules of azoospermic rats following bone marrow derived MSCs transplantation. The recipient mice were prepared by busulphan treatment. Following efferent duct injection of MSCs, the transplanted tubules showed spermatogenesis with presence of germinal cells like spermatogonia, primary spermatocytes, spermatids and sperm.
Anand et al. [25, 26]	The study showed that VSELs survive busulphan treatment in the testis and resume spermatogenesis when mesenchymal/Sertoli cells are transplanted through the intertubular route.
Chen et al. [71]	In vivo differentiation potential of human cord blood mesenchymal stem cells was evaluated following transplantation into busulphan treated mice seminiferous tubules. Transplanted tubules exhibited improved histology compared to busulphan treated tubules.
Yang et al. [72	The study investigated the potential of human umbilical cord MSCs (CD31−/CD73+/CD105+) to promote spermatogenesis regeneration in busulphan treated testis following interstitial injections. Three weeks after injection, there was an increased expression of meiotic markers namely, Dazl, Vasa, Stra8, Scp3, Cyclin A1, Tnp2, Pgk2, Miwi, Tex18 and Akap3. Protein level expression of MIWI, VASAa and SCPwas also increased compared to controls.
Sabbaghi et al. [73]	Rat bone marrow MSCs (5-10 × 106 cells) were cultured and transplanted via rete testis into torsioned azoospermic testis. Germ cell specific markers (OCT4, VASAand c-KIT) were monitored for the differentiation of MSCs after transplantation.
Aziz et al. [74]	Bone marrow derived MSCs were transplanted into busulphan treated rats. Results showed that MSCs have potential for in vivo transdifferentiation into spermatids and spermatocytes.