<PAGE>

                                                                   Exhibit 10.12

                           COMMERCIAL LEASE AGREEMENT

STATE OF GEORGIA

COUNTY OF FULTON

      THIS LEASE AGREEMENT, is, made and entered into this 1st day of Nov, 1999
by and between Charles P. Garrison (hereinafter referred to as "Lessor") and
Georgia Tissue Bank (hereinafter referred to as "Lessee");

                              W I T N E S S E T H:

      1. Premises. Lessor, for and in consideration of the rents, covenants,
agreements and stipulations hereinafter mentioned, reserved and contained to be
paid, kept and performed by Lessor, has leased and rented and by these presents
does lease and rent unto Lessee, and Lessee hereby agrees to lease and take upon
the terms and conditions which hereinafter appear, the following described
property (hereinafter called "premises"), to-wit;

            The entire building which is represented by the attached floor plan
            at Exhibit A representing a 9.275 square building known as 120-138
            Hammond Drive, and the parking spaces and common areas appurtenant
            thereto.

      2. Term. To have and to hold the same for a term beginning on the 1st day
of November, 1999 and terminating at 12:00 Midnight on October 31, 2002, unless
sooner terminated as hereinafter provided.

      3. Rental. Lessee agrees to pay to Lessor promptly on the 1st day of each
month in advance during the term of this lease a monthly rental of $12,365. Said
monthly rental payments shall be payable to Lessor at such location as Lessor
shall from time to time specify. If the rental is not received by the 10th day
of the month, a 5% delinquency penalty is due.

                                                             Schedule 3.11(b)(i)


                                      -1-
<PAGE>

      The monthly rental payment for any partial month shall be prorated based
upon the number of days.

      The monthly lease payments shall be increased as follows:

            November, 2000 through October, 2001 - $12,860

            November, 2001 through October, 2002 - $13,374

      4. Utility Bills. Lessee shall be responsible for and pay all utilities,
including but not limited to water, sewer, gas, electricity, fuel, telephone,
light and heat bills for the leased premises; and Lessee shall pay all charges
for janitorial, garbage collection services or other sanitary services rendered
to the leased premises or used by Lessee in connection therewith. If Lessee
fails to pay any of said utility bills or charges for garbage collection or
other sanitary services, Lessor may pay the same; and such payment may be added
to the rental of the premises next due as additional rent.

      5. Use of the Premises. Premises shall be used for General office space
and/or Laboratory/Medical Facility purposes and no other. Premises shall not be
used for any illegal purposes nor in any manner to create any nuisance or
trespass nor in any manner to vitiate the insurance or increase the rate of
insurance on premiums.

      6. Abandonment of Leased Premises. Lessee agrees not to abandon or vacate
the leased premises during the period of this lease and agrees to use said
premises for the purposes herein leased until the expiration hereof.

      7. Repairs by Lessor. Lessor agrees to keep in good repair the roof,
foundations and exterior walls of the premises (exclusive of all glass and
exclusive of all exterior doors) and underground utility and sewer pipes outside
the exterior walls of the building, except repairs rendered necessary by the
negligence of Lessee or Lessee's agents, employees or invitees. Lessor gives
Lessee exclusive control over the premises and shall be under no obligation to
inspect said premises. Lessee shall promptly report in writing to Lessor any
defective condition known to Lessee which Lessor is required to repair; and
failure to so


                                      -2-
<PAGE>

report such defects shall make Lessee responsible to Lessor for any liability
incurred by Lessor by reason of such defects.

      If Lessor does not within 45 days of written request by Lessee, make
required repairs, Lessee may contract to have such repairs made, provided any
repairs exceeding $7,500 may not be made without Lessor's express written
consent. If Lessor does not pay for such repairs upon presentment of an invoice
after completion of the repairs, Lessee may set-off such amounts against
Lessee's rent obligations.

      8. Repairs by Lessee. Lessee accepts the leased premises in their present
condition and as suited for the uses intended by Lessee. Lessee shall,
throughout the initial term of this lease and all renewals hereof, at Lessee's
expense, maintain in good order and repair the leased premises, including the
building and other improvements located thereon except those repairs expressly
required to be made by Lessor. Lessee further agrees to care for the grounds
around the building, including the mowing of grass, paving, care of shrubs and
general landscaping. Lessee agrees to return said premises to Lessor at the
expiration of prior to termination of this lease in as good condition and repair
as when first received, natural wear and tear, damage by storm, fire, lighting,
earthquake or other casualty alone excepted. Elevators, if any, are accepted by
Lessee as in satisfactory operating condition on this date; and Lessee shall, as
Lessee's own expense, maintain said elevators in good operating condition during
the term of this lease and any extensions hereof.

      9.1 Taxes and Association Fee. Lessee shall pay as additional rental
during the term of this lease and any extension or renewal thereof, the
association fees and the taxes (including but not limited to ad valorem taxes,
special assessments and any other governmental charges) attributable to the
premises for each tax year. In the event the premises are less than the entire
property, the association fee and taxes for any such year applicable to the
premises shall be determined by proration on the basis that the rental floor
area of the premises bears to the total rentable floor area of the entire
property. Lessee's pro rata portion of the association fee and taxes, as
provided herein, shall be payable on a monthly basis based upon the prior year's
actual association fees or taxes. Such estimated amounts shall be adjusted
annually.


                                      -3-
<PAGE>

      9.2 Insurance. Lessee shall, upon demand, pay as additional rental during
the term of this lease and any extension or renewal thereof the property and
casualty insurance on the premises for each tax year.

      9.3 Mutual Waiver of Subrogation. The Landlord agrees that he will have
inserted in each property and casualty policy or policies of insurance, which he
may be required to carry (if any), a provision substantially as follows: "It is
hereby stipulated that this insurance shall not be invalidated should the
insured waive in writing prior to a loss any or all right of recovery against
any party for loss occurring to the property described herein" and Landlord
hereby waives, during the term of this lease, any or all rights of recovery
against the Tenant, its officers, employees, and agents for loss occurring to
the premises to the extent that indemnification would be due under such
insurance protection.

      Likewise, the Tenant agrees that he will have inserted in each property
and casualty policy or policies of insurance, which it may be required to carry,
(if any), a provision substantially as follows: "It is hereby stipulated that
this insurance shall not be invalidated should the insured waive in writing
prior to a loss any or all right of recovery against any party for loss
occurring to the property described herein" and Tenant does hereby waive, during
the term of this Lease, any and all rights of recovery against the Landlord, its
officers, employees, and agents to the extent that indemnification would be due
under such insurance protection.

      10. Destruction of or Damages to Premises. If premises are totally
destroyed by storm, fire, lightning, earthquake or other casualty, this lease
shall terminate as of the date of such destruction; and rental shall be
accounted for as between Lessor and Lessee as of that date. If premises are
damaged but not wholly destroyed by any such casualties, rental shall abate in
such proportion as use of the premises has been destroyed; and Lessor shall
restore premises to substantially the same condition as before damage as
speedily as practicable, whereupon full rental shall recommence.

      Notwithstanding the foregoing, if Lessor has not within 6 months restored
the premises to substantially the same condition as before damage, the Lessee
may terminate this lease without being treated as in default.


                                      -4-
<PAGE>

      11.1 Indemnity. Lessee agrees to indemnify and save harmless Lessor
against all claims for damages to persons or property by reason of the use or
occupancy of the leased premises and all expenses incurred by Lessor because
thereof, including reasonable attorney's fees and court costs.

      11.2 Indemnity. Lessor agrees to indemnify and save harmless Lessee
against all claims for damages to persons or property by reason of the use or
occupancy by Lessor or Lessor's agents of the leased premises and all expenses
incurred by Lessee because thereof, including reasonable attorney's fees and
court costs.

      12. Governmental Orders. Lessee agrees, at Lessee's own expense, to
promptly comply with all requirements of any legally constituted public
authority made necessary by reason of Lessee's occupancy of said premises.
Lessor agrees to promptly comply with any such requirements if not made
necessary by reason of Lessee's occupancy. However, it is mutually agreed
between Lessor and Lessee that, if in order to comply with such requirements,
the cost to Lessor or Lessee, as the case may be, shall exceed a sum equal to
one year's rent, then Lessor or Lessee who is obligated to comply with such
requirements is privileged to terminate this lease by giving written notice of
termination to the other party via Certified Mail, Return Receipt Requested,
which termination shall become effective sixty (60) days after receipt of such
notice and which notice shall eliminate the necessity of compliance with such
requirement by party giving such notice unless the party receiving such notice
of termination shall, before such termination becomes effective, pays to the
party giving notice all costs of compliance in excess of one year's rent or
secures the payment of said sum in a manner satisfactory to the party giving
notice.

      13. Condemnation. If the whole of the leased premises or such portion
thereof as will make the premises unusable for the purposes herein leased shall
be condemned by any legally constituted authority for any public use or purpose,
then in either of said events the term hereby granted shall cease from the date
when possession thereof is taken by public authorities; and rental shall be
accounted for as between Lessor and Lessee as of said date. Such termination,
however, shall be without prejudice to the rights of either Lessor or Lessee to
recover compensation and damage caused by condemnation from the condemnor. It is


                                      -5-
<PAGE>

further understood and agreed that neither Lessee nor Lessor shall have any
rights in any award made to the other by any condemnation authority
notwithstanding the termination of the lease as herein provided.

      14. Assignment and Subletting. Lessee may sublease portions of the leased
premises to others provided such sublessee's operation is a part of the general
operation of Lessee and under the supervision and control of Lessee and provided
such operation is within the purposes for such said premises shall be used.
Except as provided in the preceding sentence, Lessee shall not assign this lease
or any interest hereunder or sublet premises or any part thereof or permit the
use of premises by any party other than Lessee without the prior written consent
of Lessor (not to be unreasonably withheld) endorsed hereon. At the option of
Lessor, Assignee or Lessee shall become directly liable to Lessee for all
obligations of Lessee hereunder; but no sublease or assignment by Lessee shall
relieve Lessee of any liability hereunder.

      15. Removal of Fixtures. If Lessee is not in default under this lease,
Lessee may remove all fixtures and equipment which Lessee owns, provided Lessee
repair all damage to premises caused by such removal and provided that Lessee,
at Lessee's expense, return the space to standard office space comparable to
other office space within the leased premises.

      16. Cancellation of Lease by Lessor. It is mutually agreed that, in the
event Lessee shall default in the payment of rent, including additional rent
herein reserved, when due and fails to cure said default within five (5) days
after written notice thereof from Lessor; or if Lessee shall be in default in
performing any of the terms or provisions of this lease other than the provision
requiring the payment of rent and fails to cure such default within thirty (30)
days after the date of receipt of written notice of default from Lessor; or if
Lessee is adjudicated bankrupt; or if a permanent receiver is appointed for
Lessee's property and such receiver is not removed within sixty (60) days after
written notice form Lessor to Lessee to obtain such removal; or if, whether
voluntarily or involuntarily, Lessee takes advantage of any debtor relief
proceedings under any present or future law, whereby the rent or any part
thereof is or is proposed to be reduced or payment thereof deferred; or if
Lessee makes an assignment for the benefit of creditors; or if Lessee's effects
should be levied upon or


                                      -6-
<PAGE>

attached under process against Lessee and not satisfied or dissolved within
thirty (30) days after written notice from Lessor to Lessee to obtain
satisfaction thereof; then and in any of said events, Lessor (at Lessor's
option) may at once or within six (6) months thereafter (but only during
continuance of such default or condition), terminate this lease by written
notice to Lessee, whereupon this lease shall end. After an authorized assignment
or subletting of the entire premises covered by this lease, the occurring of any
of the foregoing defaults or events shall affect the lease only if caused by or
happening to the assignee or sublessee. Any notice provided in this Paragraph
may be given by Lessor or Lessor's Attorney. Upon such termination by Lessor,
Lessee will at once surrender possession of the premises to Lessor and remove
all of Lessee's effects therefrom; and Lessor may forthwith re-enter the
premises, repossess same and remove all persons and effect therefrom using such
force as may be necessary without being guilty of trespass, forcible entry,
detainer or other tort.

      17. Re-entry by Lessor. Lessor, as Lessee's agent, may (at Lessor's
option), without terminating this lease upon Lessee's breaching this lease,
enter upon and rent the premises at the best price obtainable by reasonable
effort without advertisement and by private negotiations and for any term Lessor
deems proper. Lessee shall be liable to Lessor for the deficiency, if any,
between Lessee's rent hereunder and the price obtained by Lessor on reletting.

      18. Exterior Signs. Lessee shall place no signs upon the outside walls or
roof of the leased premises except with the written consent of Lessor. Any and
all signs placed on the premises by Lessee shall be maintained in compliance
with rules and regulations governing such signs; and Lessee shall be responsible
to Lessor for any damages caused by installation, use or maintenance of said
signs. Lessee agrees to repair all damage incident to the removal of said signs
upon removal of same.

      19. Entry for Carding. Etc.. Lessor may card premises "For Rent" or "For
Sale" ninety (90) days before the termination of this lease. Lessor or his
agents may enter the premises at reasonable hours to exhibit same to prospective
purchasers or tenants and to make repairs required of Lessor under the terms
hereof.


                                      -7-
<PAGE>

      20. Effect of Termination of Lease. No termination of this lease prior to
the normal ending thereof by lapse of time or otherwise shall affect Lessor's
right to collect rent for the period prior to termination thereof.

      21. Mortgagee's Rights. Lessee's rights shall be subject to any bona fide
mortgage or deed to secure debt which is now or may hereafter be placed upon the
premises by Lessor.

      22. No Estate in Land. This lease shall create the relationship of
landlord and tenant between the parties hereto; and no estate shall pass out of
Lessor. Lessee has only a usufruct not subject to levy and sale and not
assignable by Lessee except by Lessor's consent (not to be unreasonably
withheld).

      23. Holding Over. If Lessee remains in possession of premises after the
expiration of the term hereof with Lessor's acquiescence an without any express
agreement of the parties, Lessee shall be a tenant at will at the rental rate in
effect at the end of this lease; and there shall be no renewal of this lease by
operation of law.

      24. Attorney's Fees and Homestead. If any rent owing under this lease is
collected by or through an attorney at law, Lessee agrees to pay reasonable
attorney's fees incurred by Lessor. Lessee waives all homestead rights and
exemptions which Lessee may have under the law as against any obligation owing
under this lease. Lessee hereby assigns to Lessor all Lessee's homestead and
exemption.

      25. Rights Cumulative. All rights, powers and privileges conferred
hereunder upon parties hereto shall be cumulative but not restrictive to those
given by law.

      26. Service of Notice. Lessee hereby appoints as Lessee's agent to receive
service of all dispossessory or distraint proceedings and notices hereunder and
all notices required under this lease, the person in charge of the leased
premises at the time or the person occupying said premises, and if no person is
in charge of or occupying said premises, then such service or notice may be made
by attaching the same on the main entrance to said


                                      -8-
<PAGE>

premises. A copy of all notices under this lease shall also be sent to Lessee's
last-known address if different from said premises.

      27. Waiver of Rights. No failure of Lessor to exercise any power given
Lessor hereunder or to insist upon strict compliance by Lessee with Lessee's
obligations hereunder and no custom or practice of the parties at variance with
the terms hereof shall constitute a waiver of Lessor's right to demand exact
compliance with the terms hereof.

      28. Time of Essence. Time is of the essence of this lease agreement.

      29. Definitions. "Lessor" as used herein shall include first party and
first party's heirs, representatives, assigns, and successors in title to the
premises. "Lessee" shall include second party and second party's heirs and
representatives and, if this lease shall be validly assigned or sublet, shall
include also Lessee assignees or sublessees as to the premises covered by such
assignment or sublease. "Lessor" and "Lessee" shall include male and female,
singular and plural, corporation, partnership or individual as may fit the
particular parties.

      30. Security Deposit. Upon execution of this lease, Lessee shall pay a
security deposit in the amount of Twelve Thousand Three Hundred Sixty-Five
Dollars ($12,365.00) to Lessor. Upon termination of this lease and surrender of
the premises by Lessee to Lessor, the security deposit shall be returned to
Lessee, provided that Lessor may hold the security deposit for a period of
thirty (30) days following surrender of possession and may deduct from the
amount refunded any rental due and payable, the costs of repairing any damage or
replacing any damaged portion of the premises and costs of cleaning the premises
if Lessee fails to do so prior to surrender of possession.

      31. Special Stipulations. In so far as the following stipulations conflict
with any of the foregoing provisions, the following shall control:

N/A
--------------------------------------------------------------------------------


                                      -9-
<PAGE>

      32. Entire Agreement. This lease contains the entire agreement between the
parties hereto; and no representations, inducements, promises or agreements,
oral or otherwise between the parties and not embodied herein shall be of any
force or effect.

      33. Lease Contingent Upon Simultaneous Closing. This lease is void unless
simultaneous with the execution of this lease, the contracts dated November __,
1999 between NTBN-GTB, Inc., Georgia Tissue Bank, Inc. and Dr. Charles P.
Garrison are also consummated.


                                      -10-
<PAGE>

      IN WITNESS WHEREOF, the parties have hereunto executed this lease
agreement as of the day and year first above written.

AS TO LESSOR:

SIGNED, SEALED AND DELIVERED              /s/ Charles P. Garrison, M.D.
IN THE PRESENCE OF:                       --------------------------------------
                                          CHARLES P. GARRISON, M.D.


-----------------------------------
WITNESS

/s/ W. Courtney Lafon                      [SEAL]
-----------------------------------   W. Courtney Lafon
NOTARY PUBLIC                              NOTARY
                                           EXPIRES
                                           GEORGIA
                                        AUG. 27, 2002
                                           PUBLIC
                                        FULTON COUNTY

AS TO LESSEE:                             GEORGIA TISSUE BANK, INC.

SIGNED, SEALED AND DELIVERED              /s/ Jamie M. Groom
IN THE PRESENCE OF:                       --------------------------------------
                                          By: Jamie M. Groom, PRESIDENT

/s/ [ILLEGIBLE]
-----------------------------------
WITNESS


/s/ Marsha D. Foreman                    [SEAL]            Marsha D. Foreman
-----------------------------------   NOTARY PUBLIC      Commission # CC747340
NOTARY PUBLIC                       STATE OF FLORIDA     Expires July 12, 2002
                                                              BONDED THRU
                                                      ATLANTIC BONDING CO., INC.

Guaranty of Lease

      All provisions of the above lease and any extension thereto, are fully
guaranteed by Regeneration Technologies, Inc.

                                         REGENERATION TECHNOLOGIES, INC.


SIGNED, SEALED AND DELIVERED              /s/ Jamie M. Groom
IN THE PRESENCE OF:                       --------------------------------------
                                          By: Jamie M. Groom, PRESIDENT

/s/ [ILLEGIBLE]
-----------------------------------
WITNESS


/s/ Marsha D. Foreman                    [SEAL]            Marsha D. Foreman
-----------------------------------   NOTARY PUBLIC      Commission # CC747340
NOTARY PUBLIC                       STATE OF FLORIDA     Expires July 12, 2002
                                                              BONDED THRU
                                                      ATLANTIC BONDING CO., INC.


                                      -11-