Time-dependent neovasculogenesis and regeneration of different bladder wall components in the bladder acellular matrix graft in rats.
OBJECTIVE
To determine the time-dependent regeneration of different cellular components in the bladder acellular matrix graft (BAMG) and the involvement of hematopoietic stem cells in BAMG vascular regeneration.


METHODS
Thirty-three male Sprague Dawley rats underwent partial cystectomy and the acellular matrices were grafted to the remaining host bladder. At 4, 7, 14, 30, 60, 90, and 180 d after grafting, animals were sacrificed and their bladders were excised and paraffin-embedded. Tissue sections were stained for determination of CD3, CD20, CD34, CD31, CD68, smooth muscle cell (SMC) alpha-actin, and neurofilament protein as well as elastin fibers and collagen typing. Cystometric evaluation of grafted bladders was also performed 3 mo after procedure.


RESULTS
In acellular matrices, there was no expression of cellular markers and type-1 collagen fibers were predominant. One month after surgery, all grafted matrices were completely lined with urothelium. Polymorphonuclear cells and lymphocytes densely infiltrated BAMG during the first 2 wk after grafting; however the inflammation resolved by the first post-surgical mo. CD34+ endothelial progenitor cells (EPCs) were found in all grafts 4 d after surgery. The number of CD34+ cells increased continuously and peaked 2 mo after grafting. The increment in number of CD31+ microvessels in grafted matrices followed that of CD34+ cells and reached 144.5% of control values at third post-surgical mo. The mean number of CD34+ and CD31+ cells returned to control ranges by 6 mo after grafting. Expression of SMC alpha-actin was first visualized on day 4 and alpha-actin intensity reached to control values 6 mo after grafting. Neural elements appeared 1 wk after grafting and just 60% of normal intensity was achieved by the sixth post-surgical mo; however complete nerve bundles were found in all grafted matrices after 1 mo. Cystometric studies revealed higher bladder capacity and compliance but lower maximum intravesical pressure in grafted bladders in comparison with controls, 3 mo after surgery.


CONCLUSIONS
Our results demonstrate the effective cellular regeneration in BAMG and propose a considerable role for the CD34+ EPCs in the neo-vasculogenesis of the grafts.
Kajbafzadeh
Abdol-Mohammad
AM
Pediatric Urology Research Center, Children's Hospital Medical Center, Tehran University of Medical Sciences, Tehran, Iran. kajbafzd@sina.tums.ac.ir
Payabvash
Seyedmehdi
S
Salmasi
Amirali Hassanzadeh
AH
Sadeghi
Zhina
Z
Elmi
Azadeh
A
Vejdani
Kaveh
K
Tavangar
Seyed Mohammad
SM
Tajik
Parvin
P
Mahjoub
Fatemeh
F
D000199:Actins / Q000378:metabolism; D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D002452:Cell Count; D002474:Cell-Free System / Q000637:transplantation*; D015653:Cystectomy; D003556:Cystitis / Q000473:pathology; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D008214:Lymphocytes / Q000473:pathology; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism; D018919:Neovascularization, Physiologic; D020556:Neutrophil Infiltration; D011184:Postoperative Period; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration; D013234:Stem Cells / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D001743:Urinary Bladder / Q000473:pathology / Q000503:physiopathology / Q000601:surgery* / Q000637:transplantation*
D000199:Actins; D018952:Antigens, CD34