ANNALS OF MEDICAL AND BIOMEDICAL SCIENCES. 2019; 5 (1): 8-12 ISSN 2059-9447 8 | Page DAYO ROTIMI OMOTOSO 1 , ADENIRAN OLUWADA- MILARE AKINOLA 2 , OOREOLUWAPO OLOLADE DARAMOLA 3 1 Department of Anatomy, College of Health Sciences, Igbinedion University, Okada, Edo State, Nigeria; 2 Department of Physiology, College of Health Sci- ences, University of Medical Sciences, Ondo City, Ondo State, Nigeria; 3 Department of Physiology, College of Health Sciences, Igbinedion University, Okada, Edo State, Nigeria Received 21 May 2019 Accepted 18 August 2019 Introduction Medicinal plants refer to plants that have parts or the entire plant with constituent chemical components that can be ap- plied for therapeutic purposes [1, 2]. One of these plants which represent an important component of natural plant biodiversity in many tropical and temperate regions is Ag- eratum conyzoides Linn (Asteraceae) (commonly called goat weed). A. conyzoides L. is a tropical medicinal plant with an age-long history of varying ethno-pharmacological applications [3, 4]. Numerous studies have also docu- mented diverse pharmacological applications and biologi- cal activities of extracts of A. conyzoides L including anti- proliferative, anti-inflammatory, anti-oxidant and so on [5, 6]. Basically, proliferation of cells is a vital biological pro- cess which is regulated by inter-related factors to ensure normal tissue growth and development. The maturation of tissues is usually attained when there is a balance between cell proliferation and death. However, studies have linked tissue pathology and aberrant cell proliferation that results from genomic mutations and mutant gene expression [7, 8, 9]. A major self-regenerating tissue with immense ability to proliferate is the liver. Correspondence to: Dr. Dayo Rotimi Omotoso Email: dayohmts@gmail.com ABSTRACT Objective: Medicinal plant studies have documented diverse pharmacological applications and biological activities of different parts of such plants but still with insufficient knowledge about molecular mechanisms of applications and activities. This study was therefore carried out to assess the expression of molecular mark- ers of cell cycle and proliferation (Ki-67 and p53 pro- teins) in hepatic tissue of rats exposed to aqueous leaf extracts of A. conyzoides L. and possible effects of ex- posure on hepatic tissue proliferative ability. Methods: This study involved 20 male Wistar rats (170-180g) divided into four groups (A-D), groups A was non-treated control while groups B-D were admin- istered aqueous extracts of A. conyzoides L. at dose rate of 100, 300 and 500 mg/kg b.wt. orally for 28 days. After the treatment period, animals were sacrificed, liver tissues were harvested and processed, tissue sec- tions produced were stained with histological staining (H & E) techniques and immunohistochemically stained for cell proliferation (Ki-67) and tumor sup- pressor (p53) protein with HRP-DAB staining tech- nique (using monoclonal antibody). Stained sections were analyzed using image-J software. Data obtained were statistically analyzed using IBM-SPSS (version 20) and compared using T-test and analysis of variance (ANOVA). Results: The result of this study showed significant decrease (p<0.05) in the Ki-67 protein expression level but no significant difference in the p53 protein expres- sion level in hepatic tissues of all treatment groups rel- ative to the non-treated group. Conclusion: The aqueous extracts of A. conyzoides L. exhibit significant down-regulatory effect on the ex- pression of cell proliferation (Ki-67) protein in hepatic tissues of study animals and this may indicate promi- nent anti-proliferative activity of the extracts. KEY WORDS: Ki-67, p53 Liver Rats Ageratum conyzoides The hepatic tissue is largely composed of hepatocytes which possess rapid proliferative ability that in turn ac- counts for hepatic regenerative ability following partial hepatectomy or tissue necrosis due to hepatotoxin exposure Immunoexpression of cell proliferation (Ki-67) and tumor suppressor (p53) proteins in hepatic tissue exposed to aqueous extracts of Ageratum conyzoides Linn using rat model