Mesenchymal Stem Cells in Regenerative Medicine, Possible Applications in The Restoration of Spermatogenesis: A Review

Document Type : Review Article


1 Department of Urology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

2 Stem Cell Technology Research Center, Burn and Wound Healing Research Center, Comparative and Experimental Medicine Center, Shiraz University of Medical Sciences, Shiraz, Iran

3 Department of Oncology, Cross Cancer Institute, University of Alberta, Edmonton, Canada


Infertility is a common clinical condition and about half of the major causes are due to male-related infertility. Pathogenesis
of this abnormality is generally undefined; so establishing a proper treatment option is relatively uncertain. In recent
years, several evidences demonstrated that mesenchymal stem cells (MSCs) can be a hope for innovative and efficient
treatment of male infertility. This study reviews possible applications of MSCs in the restoration of spermatogenesis
in male infertility of both humans and animals to suggest new avenues for future clinical practices. Articles published
in “PubMed” and “Google Scholar” from January 1, 2000, to August 1, 2023, were investigated by searching items of
“mesenchymal stem cells”, “cell therapy”, “cell transplantation”, and, “regenerative medicine” keywords, in addition
to the “urology”, “andrology”, “reproductive medicine”, “male infertility”, “azoospermia”, and “spermatogenesis”. The
results obtained from the transplantation of MSCs in the treatment of male infertility seemed encouraging and they
revealed the safety and efficacy of these cells to recover spermatogenesis; eventhough further stem cell research
is still required before recruiting clinical application of MSCs in the treatment of human male infertility. Undertaking more
well-defined, standardized, and reproducible protocols and enrolling larger sample sizes during a longer follow-up
period can benefit the relevance of MSC transplantation in the restoration of spermatogenesis and treatment of male
infertility. It seems that developing and utilizing stem cell transplantations, exosomes, scaffold delivery systems, and
three dimensional (3D) culture methods may open a new window to getting more benefits from cell therapy in the
treatment of men infertility.


Main Subjects

  1. Pourmoghadam Z, Aghebati-Maleki L, Motalebnezhad M, Yousefixa B, Yousefi M. Current approaches for the treatment of male infertility with stem cell therapy. J Cell Physiol. 2018; 233(10): 6455-6469.
  2. Tamburrino L, Traini G, Marcellini A, Vignozzi L, Baldi E, Marchiani S. Cryopreservation of human spermatozoa: functional, molecular and clinical aspects. Int J Mol Sci. 2023; 24(5): 4656.
  3. Mahabadi JA, Sabzalipour H, Bafrani HH, Gheibi Hayat SM, Nikzad H. Application of induced pluripotent stem cell and embryonic stem cell technology to the study of male infertility. J Cell Physiol. 2018; 233(11): 8441-8449.
  4. Martin-Inaraja M, Ferreira M, Taelman J, Eguizabal C, Chuva De Sousa Lopes SM. Improving in vitro culture of human male fetal germ cells. Cells. 2021; 10(8): 2033.
  5. Kaboodkhani R, Mehrabani D, Karimi-Busheri F. Achievements and challenges in transplantation of mesenchymal stem cells in otorhinolaryngology. J Clin Med. 2021; 10(13): 2940.
  6. Fazeli Z, Abedindo A, Omrani MD, Ghaderian SMH. Mesenchymal stem cells MSCs) therapy for recovery of fertility: a systematic review. Stem Cell Rev Rep. 2018; 14(1): 1-12.
  7. Nayernia K, Lee JH, Drusenheimer N, Nolte J, Wulf G, Dressel R, et al. Derivation of male germ cells from bone marrow stem cells. Lab Invest. 2006; 86(7): 654-663.
  8. Hosseini-Asl SK, Mehrabani D, Karimi-Busheri F. Therapeutic effect of mesenchymal stem cells in ulcerative colitis: a review on achievements and challenges. J Clin Med. 2020; 9(12): 3922.
  9. Zhankina R, Baghban N, Askarov M, Saipiyeva D, Ibragimov A, Kadirova B, et al. Mesenchymal stromal/stem cells and their exosomes for restoration of spermatogenesis in non-obstructive azoospermia: a systemic review. Stem Cell Res Ther. 2021; 12(1): 229.
  10. Rahmanifar F, Tamadon A, Mehrabani D, Zare S, Abasi S, Keshavarz S, et al. Histomorphometric evaluation of treatment of rat azoosper-mic seminiferous tubules by allotransplantation of bone marrow-derived mesenchymal stem cells. Iran J Basic Med Sci. 2016; 19(6): 653-661.
  11. Lewis SE. Should sperm DNA fragmentation testing be included in the male infertility work-up? Reprod Biomed Online. 2015; 31(2): 134-137.
  12. Esteves SC, Roque M, Bedoschi GM, Conforti A, Humaidan P, Alviggi C. Defining low prognosis patients undergoing assisted reproductive technology: POSEIDON criteria-the why. Front Endocrinol (Lausanne). 2018; 9: 461.
  13. Cioppi F, Rosta V, Krausz C. Genetics of azoospermia. Int J Mol Sci. 2021; 22(6): 3264.
  14. Shojaeian A, Mehri-Ghahfarrokhi A, Banitalebi-Dehkordi M. Monophosphoryl lipid A and retinoic acid combinations increased germ cell differentiation markers expression in human umbilical cordderived mesenchymal stromal cells in an in vitro ovine acellular testis scaffold. Int J Mol Cell Med. 2020; 9(4): 288-296.
  15. Shojaeian A, Mehri-Ghahfarrokhi A, Rahmati-Dehkordi S, Banitalebi- Dehkordi M. Evaluation of isolation method in remaining of differentiation potential of perivascular human umbilical cord mesenchymal stem cells toward male germ cell-like. J Shahrekord Univ Med Sci. 2021; 23(2): 81-86.
  16. Gauthier-Fisher A, Kauffman A, Librach CL. Potential use of stem cells for fertility preservation. Andrology. 2020; 8(4): 862-878.
  17. Hosseinzadeh Shirzeily M, Pasbakhsh P, Amidi F, Mehrannia K, Sobhani A. Comparison of differentiation potential of male mouse adipose tissue and bone marrow derived-mesenchymal stem cells into germ cells. Iran J Reprod Med. 2013; 11(12): 965-976.
  18. Ghatreh Samani K, Eliyasi Dashtaki M, Alaei S, Saki G. Differentiation potential of adipose tissue-derived mesenchymal stem cells into germ cells with and without growth factors. Andrologia. 2021; 53(1): e13892.
  19. Ghorbanlou M, Abdanipour A, Shirazi R, Malekmohammadi N, Shokri S, Nejatbakhsh R. Indirect co-culture of testicular cells with bone marrow mesenchymal stem cells leads to male germ cell-specific gene expressions. Cell J. 2019; 20(4): 505-512.
  20. Dissanayake D, Patel H, Wijesinghe PS. Differentiation of human male germ cells from Wharton’s jelly-derived mesenchymal stem cells. Clin Exp Reprod Med. 2018; 45(2): 75-81.
  21. Mutee’Khudair A, Alzaharna MM, Sharif FA. Trans differentiating human adipose-derived mesenchymal stem cells into male germ-like cells utilizing Rabbit Sertoli cells: an experimental study. Int J Reprod Biomed. 2023; 21(3): 213-228.
  22. Salvatore G, Dolci S, Camaioni A, Klinger FG, De Felici M. Reprogramming human female adipose mesenchymal stem cells into primordial germ cell-like cells. Stem Cell Rev Rep. 2023; 19(7): 2274-2283.
  23. Shirzeyli MH, Tayyebiazar A, Aliakbari F, Ghasemi F, Eini F, Shirzeyli FH, et al. Comparison of the efficacy of bone morphogenetic protein-4 on in vitro differentiation of murine adipose and bone marrow mesenchymal stem cells into primordial germ cells. Res Pharmaceut Sci. 2022; 17(2): 123-133.
  24. Kumar K, Das K, Kumar A, Singh P, Madhusoodan AP, Dutt T, et al. Supplementation of retinoic acid alone in MSC culture medium induced germ cell-like cell differentiation. J Anim Reprod Biotechnol. 2023; 38(2): 54-61.
  25. Ebrahimi S, Shams A, Maghami P, Hekmat A. Differentiation of mouse bone marrow mesenchymal stem cells into germ-like cells by retinoic acid, titanium nanotubes-coated fibrin formation, and ultraviolet radiation as inductions in vitro. Res Square. 2022; 1-21. Available from: (06 Nov 2023).
  26. Önen S, Köse S, Yersal N, Korkusuz P. Mesenchymal stem cells promote spermatogonial stem/progenitor cell pool and spermatogenesis in neonatal mice in vitro. Sci Rep. 2022; 12(1): 11494.
  27. Ge W, Sun YC, Qiao T, Liu HX, He TR, Wang JJ, et al. Murine skin-derived multipotent papillary dermal fibroblast progenitors show germline potential in vitro. Stem Cell Res Ther. 2023; 14(1): 17.
  28. Abdollahifar MA, Azad N, Faraji Sani M, Raoofi A, Abdi S, Aliaghaei A, et al. Impaired spermatogenesis caused by busulfan is partially ameliorated by treatment with conditioned medium of adipose tissue derived mesenchymal stem cells. Biotech Histochem. 2022; 97(2): 107-117.
  29. Abdelaziz MH, Salah El-Din EY, El-Dakdoky MH, Ahmed TA. The impact of mesenchymal stem cells on doxorubicin-induced testicular toxicity and progeny outcome of male prepubertal rats. Birth Defects Res. 2019; 111(13): 906-919.
  30. Karimaghai N, Tamadon A, Rahmanifar F, Mehrabani D, Raayat Jahromi A, Zare S, et al. Spermatogenesis after transplantation of adipose tissue-derived mesenchymal stem cells in busulfan-induced azoospermic hamster. Iran J Basic Med Sci. 2018; 21(7): 660-667.
  31. Hajihoseini M, Mehrabani D, Vahdati A, Hosseini SE, Tamadon A, Dianatpour M, et al. Spermatogenesis after transplantation of adipose tissue-derived stem cells in azoospermic guinea pigs: a histological and histomorphometric study. Galen Med J. 2018; 7: e1000.
  32. Guo XB, Zhai JW, Xia H, Yang JK, Zhou JH, Guo WB, et al. Protective effect of bone marrow mesenchymal stem cell-derived exosomesagainst the reproductive toxicity of cyclophosphamide is associated with the p38MAPK/ERK and AKT signaling pathways. Asian J Androl. 2021; 23(4): 386-391.
  33. Meligy FY, Abo Elgheed AT, Alghareeb SM. Therapeutic effect of adipose- derived mesenchymal stem cells on Cisplatin induced testicular damage in adult male albino rat. Ultrastruct Pathol. 2019; 43(1): 28-55.
  34. Kadam P, Ntemou E, Onofre J, Van Saen D, Goossens E. Does cotransplantation of mesenchymal and spermatogonial stem cells improve reproductive efficiency and safety in mice? Stem Cell Res Ther. 2019; 10(1): 310.
  35. Atalla S, Saleh H, Gawad SA, Mohamed H. Histological study on the effect of adipose tissue-derived mesenchymal stem cells on the testis of chemically induced castration model by calcium chloride in adult albino rats. Egypt J Histol. 2017; 40(4): 486-498.
  36. Zhang ZY, Xing XY, Ju GQ, Zhong L, Sun J. Mesenchymal stem cells from human umbilical cord ameliorate testicular dysfunction in a male rat hypogonadism model. Asian J Androl. 2017; 19(5): 543-547.
  37. Hassan AI, Alam SS. Evaluation of mesenchymal stem cells in treatment of infertility in male rats. Stem Cell Res Ther. 2014; 5(6): 131.
  38. Zhao XH, Qiu JH, Cai WQ, Li S, Li W. Preparation of infertile male rabbits by local electron beam irradiation for intratesticular transplantation of autologous bone marrow stem cells. Acta Cir Bras. 2013; 28(2): 148-153.
  39. Hsiao CH, Ji AT, Chang CC, Chien MH, Lee LM, Ho JH. Mesenchymal stem cells restore the sperm motility from testicular torsion-detorsion injury by regulation of glucose metabolism in sperm. Stem Cell Res Ther. 2019; 10(1): 270.
  40. Cai YT, Xiong CL, Liu TS, Shen SL, Rao JP, Qiu F. Secretions released from mesenchymal stem cells improve spermatogenesis restoration of cytotoxic treatment with busulfan in azoospermia mice. Andrologia. 2021; 53(8): e14144.
  41. Ibrahim HF, Safwat SH, Zeitoun TM, El Mulla KF, Medwar AY. The therapeutic potential of amniotic fluid-derived stem cells on busulfaninduced azoospermia in adult rats. Tissue Eng Regen Med. 2021; 18(2): 279-295.
  42. Lu J, Liu Z, Shu M, Zhang L, Xia W, Tang L, et al. Human placental mesenchymal stem cells ameliorate chemotherapy-induced damage in the testis by reducing apoptosis/oxidative stress and promoting autophagy. Stem Cell Res Ther. 2021; 12(1): 199.
  43. Deng C, Xie Y, Zhang C, Ouyang B, Chen H, Lv L, et al. Urine-derived stem cells facilitate endogenous spermatogenesis restoration of busulfan-induced nonobstructive azoospermic mice by paracrine exosomes. Stem Cells Dev. 2019; 28(19): 1322-1333.
  44. Qian C, Meng Q, Lu J, Zhang L, Li H, Huang B. Human amnion mesenchymal stem cells restore spermatogenesis in mice with busulfaninduced testis toxicity by inhibiting apoptosis and oxidative stress. Stem Cell Res Ther. 2020; 11(1): 290.
  45. Mehrabani D, Hassanshahi MA, Tamadon A, Zare S, Keshavarz S, Rahmanifar F, et al. Adipose tissue-derived mesenchymal stem cells repair germinal cells of seminiferous tubules of busulfan-induced azoospermic rats. J Hum Reprod Sci. 2015; 8(2): 103-110.
  46. El-Fiky BA. Fertility in induced azoospermic mice. J Biosci Appl Res. 2016; 2(9): 626-633.
  47. Wang YJ, Yan J, Zou XL, Guo KJ, Zhao Y, Meng CY, et al. Bone marrow mesenchymal stem cells repair cadmium-induced rat testis injury by inhibiting mitochondrial apoptosis. Chem Biol Interact. 2017; 271: 39-47.
  48. Luo Y, Xie L, Mohsin A, Ahmed W, Xu C, Peng Y, et al. Efficient generation of male germ-like cells derived during co-culturing of adiposederived mesenchymal stem cells with Sertoli cells under retinoic acid and testosterone induction. Stem Cell Res Ther. 2019; 10(1): 91.
  49. Payehdar A, Hosseini E, Mehrabani D, Forouzanfar M. healing effect of conditioned medium of adipose tissue-derived mesenchymal stem cells on histomorphometric changes of mice testis in busulfan induced-azoospermia model. Intern Med Today. 2017; 23(3): 235-240.
  50. Cakici C, Buyrukcu B, Duruksu G, Haliloglu AH, Aksoy A, Isık A, et al. Recovery of fertility in azoospermia rats after injection of adipose-tissue- derived mesenchymal stem cells: the sperm generation. Biomed Res Int. 2013; 2013: 529589.
  51. Zhankina R, Afshar A, Farrar Z, Khoradmehr A, Baghban M, Suleiman M, et al. Restoration of spermatogenesis in azoospermic mice by bone marrow mesenchymal stromal/stem cells conditioned medium. Res Square. 2021; 1-23. Available from: https://assets.researchsquare. com/files/rs-169243/v1/dabe80f7-a71d-4a42-b108-ccfc11ab5608. pdf?c=1631877385 (06 Nov 2023).
  52. Zhang D, Liu X, Peng J, He D, Lin T, Zhu J, et al. Potential spermatogenesis recovery with bone marrow mesenchymal stem cells in an azoospermic rat model. Int J Mol Sci. 2014; 15(8): 13151-13165.
  53. Badawy AA, El-Magd MA, AlSadrah SA, Alruwaili MM. Altered expression of some miRNAs and their target genes following mesenchymal stem cell treatment in busulfan-induced azoospermic rats. Gene. 2020; 737: 144481.
  54. Kadam P, Ntemou E, Baert Y, Van Laere S, Van Saen D, Goossens E. Co-transplantation of mesenchymal stem cells improves spermatogonial stem cell transplantation efficiency in mice. Stem Cell Res Ther. 2018; 9(1): 317.
  55. Mozafar A, Mehrabani D, Vahdati A, Hosseini E, Forouzanfar M. Histomorphometric evaluation of allogeneic transplantation of bone marrow mesenchymal stem cells in azoospermic mice model. Indonesian Biomed J. 2018; 10(2): 171-178.
  56. Vahdati A, Fathi A, Hajihoseini M, Aliborzi G, Hosseini E. The regenerative effect of bone marrow-derived stem cells in spermatogenesis of infertile hamster. World J Plast Surg. 2017; 6(1): 18-25.
  57. Hajihoseini M, Vahdati A, Hosseini SE, Mehrabani D, Tamadon A. Induction of spermatogenesis after stem cell therapy of azoospermic guinea pigs. Vet Arh. 2017; 87(3): 333-350.
  58. Ghasemzadeh-Hasankolaei M, Batavani R, Eslaminejad MB, Sayahpour, F. Transplantation of autologous bone marrow mesenchymal stem cells into the testes of infertile male rats and new germ cell formation. Int J Stem Cells. 2016; 9(2): 250-263.
  59. Zhou XY, Ma YZ, Wang XH, Liu DJ, Ren Y, Ji XP. Bone marrow mesenchymal stem cells to repair the reproductive system of male azoospermia rats. Zhonghua Nan Ke Xue. 2015; 21(8): 692-697.
  60. Tamadon A, Mehrabani D, Rahmanifar F, Jahromi AR, Panahi M, Zare S, et al. Induction of spermatogenesis by bone marrow-derived mesenchymal stem cells in busulfan-induced azoospermia in hamster. Int J Stem Cells. 2015; 8(2): 134-145.
  61. Zahkook SA, Atwa A, Shahat M, Mansour AM. Bakry S. Mesenchymal stem cells restore fertility in induced azoospermic rats following chemotherapy administration. J Reprod Infertil. 2014; 5(2): 50-57.
  62. Monsefi M, Fereydouni B, Rohani L, Talaei T. Mesenchymal stem cells repair germinal cells of seminiferous tubules of sterile rats. Iran J Reprod Med. 2013; 11(7): 537-544.
  63. Wang F, Liu C, Zhang SS, Liu WS , Hua JL. Transplantation of goat bone marrow mesenchymal stem cells (gMSCs) help restore spermatogenesis in endogenous germ cells-depleted mouse models. J Integr Agric. 2013; 12(3): 483-494.
  64. Aziz MTA, Mostafa T, Atta H, Asaad S, Fouad HH, Mohsen G, et al. In vitro and in vivo lineage conversion of bone marrow stem cells into germ cells in experimental azoospermia in rat. Stem Cell Studies. 2011; 1(1): e15.
  65. Lue Y, Erkkila K, Liu PY, Ma K, Wang C, Hikim AS, et al. Fate of bone marrow stem cells transplanted into the testis: potential implication for men with testicular failure. Am J Pathol. 2007; 170(3): 899-908.
  66. Van Saen D, Goossens E, De Block G, Tournaye H. Bone marrow stem cells transplanted to the testis of sterile mice do not differentiate into spermatogonial stem cells and have no protective effect on fertility. Fertil Steril. 2009; 91 Suppl 4: 1549-1552.
  67. Mashiach J, Zohni K, Lopez L, Filice M, Garcia M, Wyse B, et al. Human umbilical cord perivascular cells prevent chemotherapeutic druginduced male infertility in a mouse model. F S Sci. 2021; 2(1): 24-32.
  68. Chen H, Tang QL, Wu XY, Xie LC, Lin LM, Ho GY, et al. Differentiation of human umbilical cord mesenchymal stem cells into germ-like cells in mouse seminiferous tubules. Mol Med Rep. 2015; 12(1): 819-828.
  69. Abd Allah SH, Pasha HF, Abdelrahman AA, Mazen NF. Molecular effect of human umbilical cord blood CD34-positive and CD34-negative stem cells and their conjugate in azoospermic mice. Mol Cell Biochem. 2017; 428(1-2): 179-191.
  70. Yang RF, Liu TH, Zhao K, Xiong CL. Enhancement of mouse germ cell-associated genes expression by injection of human umbilical cord mesenchymal stem cells into the testis of chemical-induced azoospermic mice. Asian J Androl. 2014; 16(5): 698-704.
  71. Kadam P, Van Saen D, Goossens E. Can mesenchymal stem cells improve spermatogonial stem cell transplantation efficiency? Andrology. 2017; 5(1): 2-9.
  72. Sherif IO, Sabry D, Abdel-Aziz A, Sarhan OM. The role of mesenchymal stem cells in chemotherapy-induced gonadotoxicity. Stem Cell Res Ther. 2018; 9(1): 196.
  73. Elbaghdady HAM, Alwaili MA, El-Demerdash RS. Amelioration of cadmium- induced testes’ damage in rats by the bone marrow mesenchymal stem cells. Ecotoxicol Environ Saf. 2018; 148: 763-769.
  74. Iqbal F, Szaraz P, Librach M, Gauthier-Fisher A, Librach CL. Angiogenic potency evaluation of cell therapy candidates by a novel application of the in vitro aortic ring assay. Stem Cell Res Ther. 2017; 8: 184.
  75. Sabbaghi Mehrjardi MA, Bahrami AR, Feizzade B, Kalantar SM, Moghaddam Matin M, Kalantari M, et al. Trial evaluation of bone marrow derived mesenchymal stem cells MSCs) transplantation in revival of spermatogenesis in testicular torsion. Middle East Fertil Soc J. 2012; 17(4): 243-249.
  76. Aghamir SM, Salavati A, Yousefie R, Tootian Z, Ghazaleh N, Jamali M, et al. Does bone marrow-derived mesenchymal stem cell transfusion prevent antisperm antibody production after traumatic testis rupture? Urology. 2014; 84(1): 82-86.
  77. Ibrahim D, Abozied N, Abdel Maboud S, Alzamami A, Alturki NA, Jaremko M, et al. Therapeutic potential of bone marrow mesenchymal stem cells in cyclophosphamide-induced infertility. Front Pharmacol. 2023; 14: 1122175.
  78. Hussein YM, Hussein RM, Amin AI, Mohamed AS, Hussein HS. Evaluation of mesenchymal stem cells and vitamin E in treatment of infertile male albino rats. Int J Multidisciplinary Curr Res. 2015; 3(5): 932-951.
  79. Hsiao CH, Ji AT, Chang CC, Cheng CJ, Lee LM, Ho JH. Local injection of mesenchymal stem cells protects testicular torsion-induced germ cell injury. Stem Cell Res Ther. 2015; 6(1): 113.
  80. Choi WY, Jeon HG, Chung Y, Lim JJ, Shin DH, Kim JM, et al. Isolation and characterization of novel, highly proliferative human CD34/CD73- double-positive testis-derived stem cells for cell therapy. Stem Cells Dev. 2013; 22(15): 2158-2173.
  81. Ramesh M, Mojaverrostami S, Khadivi F, Rastegar T, Abbasi Y, Bashiri Z. Protective effects of human amniotic membrane derived mesenchymal stem cells (hAMSCs) secreted factors on mouse spermatogenesis and sperm chromatin condensation following unilateral testicular torsion. Ann Anat. 2023; 249: 152084.
  82. Zavattaro M, Felicetti F, Faraci D, Scaldaferri M, Dellacasa C, Busca A, et al. Impact of allogeneic stem cell transplantation on testicular and sexual function. Transplant Cell Ther. 2021; 27(2): 182.e1-182.e8.
  83. Jacobsen FM, Fode M, Sønksen J, Ohl DA, Jensen CFS. Successful extraction of sperm cells after autologous bone marrow transplant: a case report. Scand J Urol. 2019; 53(2-3): 174-175.
  84. Couto PS, Shatirishvili G, Bersenev A, Verter F. First decade of clinical trials and published studies with mesenchymal stromal cells from umbilical cord tissue. Regen Med. 2019; 14(4): 309-319.
  85. Can A, Celikkan FT, Cinar O. Umbilical cord mesenchymal stromal cell transplantations: A systemic analysis of clinical trials. Cytotherapy. 2017; 19(12): 1351-1382.
  86. Zhao Y, Tang F, Xiao Z, Han G, Wang N, Yin N, et al. Clinical study of neuroregen scaffold combined with human mesenchymal stem cells for the repair of chronic complete spinal cord injury. Cell Transplant. 2017; 26(5): 891-900.
  87. Vij SC, Sabanegh E Jr, Agarwal A. Biological therapy for non-obstructive azoospermia. Expert Opin Biol Ther. 2018; 18(1): 19-23.